Research Article Synthesis of Imine-Naphthol Tripodal

Research ArticleSynthesis of Imine-Naphthol Tripodal Ligand and Study ofIts Coordination Behaviour towards Fe(III) Al(III) and Cr(III)Metal Ions

Kirandeep Kaur and Minati Baral

Department of Chemistry National Institute of Technology Kurukshetra Haryana 136119 India

Correspondence should be addressed to Minati Baral minatibnitkkrgmailcom

Received 23 May 2014 Accepted 24 July 2014 Published 8 September 2014

Academic Editor Spyros P Perlepes

Copyright copy 2014 K Kaur and M Baral This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

A hexadentate Schiff base tripodal ligand is synthesized by the condensation of tris (2-aminoethyl) amine with 2-hydroxy-1-naphthaldehyde and characterized by various spectroscopic techniques like UV-VIS IR NMR MASS and elemental analysisThe solution studies by potentiometric and spectrophotometric methods are done at 25 plusmn 1∘C 120583 = 01M KCl to calculate theprotonation constants of the ligand and formation constants of metal complexes formed by the ligand with Fe(III) Al(III) andCr(III) metal ionsThe affinity of the ligand towards Fe(III) is compared with deferiprone (a drug applied for iron intoxication) andtransferrin (the main Fe(III) binding protein in plasma) Structural analysis of the ligand and the metal complexes was done usingsemiempirical PM6 method Electronic and IR spectra are calculated by semiempirical methods and compared with experimentalone

1 Introduction

Studies of multidentate ligands have experienced a tremen-dous upsurge because such ligands mimic the environmentof metal ions in biological systems [1] These ligands providevarious coordinating sites to the guest metal ions whichcan fulfill the primary valency and result in novel structuralmotifsMultidentate ligands can have cyclic linear branchedand tripodal nature [2] Cyclic ligands offer high selectivitybut slower metalation kinetics Linear and branched ligandsshow faster metalation kinetics but less selectivity and easydemetalationThe tripods show the advantages of both types

Due to such advantages and also for the ease of for-mation work has been done on the synthesis of tripodalligand(s) especially the Schiff base tripodal ligand(s) More-over the tren based Schiff bases have drawn special interestas they offer a number of applications chemosensing andfluorosensing in chelation therapy for the treatment of metaloverload clinical diagnosis and chemotherapy [3ndash5] Themetal complexation of such ligands has been extensivelystudied with trivalent metal ions such as Fe(III) Cr(III)and Al(III) and is found to form uncharged complexes

with high thermodynamic stability and kinetic inertness [6ndash13] The coordination chemistry with Fe(III) with tripodsystems has been explored with respect to their potentialapplication in iron overload treatment [14ndash17] The searchto develop new effective chelators for the treatment ofaluminium intoxication [18 19] leads to the complexationstudy of Al(III) with tripodal chelators Removal of Cr(III) isalso extremely necessary as it leads to formation of Cr(VI)a highly toxic form and known to have mutagenic andcarcinogenic properties [20 21] Such tripodal chelators areknown to form strong complexes with Cr(III) and hence canbe explored for Cr(III) removal

Considering the extensive usage of tripodal multidentatechelating systems we in our present work report the synthesisof a novel multidentate imine-naphthol based tripodal ligandalong with spectroscopic details and discussion of keto-enoltautomerism shown by the ligand (Figure 1) The coordina-tion behaviour of the ligand with the three trivalent metalions Fe(III) Cr(III) and Al(III) studied by potentiometricand spectrophotometric methods is also reported The pro-tonation constants of the ligand and formation constantsof the metal complexes are determined Some theoretical

Hindawi Publishing CorporationBioinorganic Chemistry and ApplicationsVolume 2014 Article ID 915457 10 pageshttpdxdoiorg1011552014915457

2 Bioinorganic Chemistry and Applications

NN

NOH

OH

HO

N

(a)

1619

1611

(b)

Figure 1 (a)Molecular structure of trenhynaph (b) least strain energy structure of ligand obtained from semiempirical PM6method showingpresence of hydrogen bonding

studies carried out to shed light on the structural elucidationand binding modes in the complexes by using semiempiricalmethod are also reported

2 Experimental

21 Materials and Measurements All chemicals and sol-vents were of analytical grade available commercially Potas-sium hydroxide and hydrochloric acid were obtained fromFisher Scientific 2-Hydroxynaphthaldehyde and Tris (2-amino ethyl) amine (tren) were obtained from SigmaAldrich Anhydrous ferric chloride aluminium sulphateand chromium chloride were procured from Qualigens FineChemicals (Fisher Scientific) Tetrahydrofuran and dimethylsulfoxide were purchased from Merck Chemicals were usedas purchased without purification Solvents were dried usingstandard methods [22]

Melting points (MP) were determined on a microsil(India) MP apparatus and are uncorrected They are givenin degree centigrade (∘C) Electronic spectra were taken onHitachi spectrophotometer U 0080D Infrared (IR) spectrawere recorded on a Perkin-Elmer RX 1 FT-IR spectrometerusing KBr discs 1H and 13C NMR spectra were recorded ona Bruker Avance II 400 NMR spectrometer at SAIF PanjabUniversity Chandigarh using tetramethylsilane (TMS) as aninternal referenceThe chemical shifts are mentioned in partsper million (ppm) The mass spectrum was performed onWaters Micromass Q-TOF Micro with electron spray ioniza-tion (EI) technique at SAIF Panjab University ChandigarhC H N S andO analysis was carried out on EUROEA 3000Potentiometric studies were carried on Sension 02 pHmeter

22 Synthesis of 1-[(E)-2-[Bis[2-[(2-hydroxy-1-naphthyl)meth-yleneamino]ethyl]amino]ethyl iminomethyl]naphthalen-2-ol(trenhynaph) In a round bottom flask 10mL of THF wastaken added to it 3 g (00174mol) of 2-hydroxynaphthalde-hyde and the contents were stirred till complete dissolutionA solution of 00846 g of tren in 10mL of THF was addeddropwise Solution was allowed to stir for 1 hr Very thickand bright yellow coloured precipitates were obtainedwhich were filtered washed with diethyl ether and dried

in vacuum Yield (228 g 76) MP (185ndash189)∘C colour(yellow) IR (KBr pellet cmminus1) 3055 (Ar=CndashH) 2940(ndashCH2 asymmetric) 2821(ndashCH

2 symmetric) 1622(ndashC=N)

1350(ndashCndashO) 764(=CndashH OOP) 1H NMR (DMSO-D6 120575

ppm) 300 (t 119869 = 1248 6H H-12) 375 (t 119869 = 464 6HH-13) 668 (d 119869 = 932 3H H = 3) 713 (d 119869 = 146 3H H= 6) 732 (t 119869 = 149 3H H = 7) 753 (d 119869 = 772 3H H =5) 760 (d 119869 = 916 3H H = 4) 798 (t 119869 = 882 3H H =8) 904 (d 119869 = 976 3H H = 11) 1411 (d 119869 = 384 3H H= 14) 13C NMR (DMSO-D

6 120575 ppm) 17726 15905 13676

13414 12858 12753 12507 12533 12187 11858 105773893 4018 mass spectrum (ESI) molecular ion [M+2] peak119898119911 = 6104 [M+1] peak 119898119911 = 6093 anal calcd forC39H36O3N4(60827) C77 H9 N92 O79 found C7723

H936 N935 O798

23 Titration Procedure Potentiometric titrations were car-ried out in order to find out the protonation constant of theligand and formation constant of the metal complexes Thetemperature for the experiment was maintained at 25 plusmn 1∘CA titration cell which has double glass walls was used andattached to circulatory bath to maintain the consistency oftemperature Sension 02 pHmeter in combination with glasselectrode was used to measure the pHThe whole equipmentset was calibrated according to the standard methods [23]

Doubly distilled deoxygenated and deionized water wasused to prepare all the solutions used in the experiment KOHsolution (01M) was prepared in 5 95 ratio of DMSOwaterHCl solution (01M) was prepared in water Ionic strengthof the solution was maintained 01M by adding 1MKClsolution The solution of ligand of strength 001M wasprepared in DMSO and solution of metal 001M in waterThe final concentration of ligand and metal in titration cellwas maintained at 0001M The ratio of DMSOwater in theresulting titration cell was maintained at 5 95 by addingappropriate solutions Following titrations in which metalto ligand ratios CMCL (0 1) and CMCL (1 1) were carriedout The data obtained from the experiment is fed intothe least square fitting program HYPERQUAD 2006 andmanual fitting of experimental and theoretical data was done

Bioinorganic Chemistry and Applications 3

Tren2-Hydroxy-1-naphthaldehyde

Stirring 3 hrs rtTHF

trenhynaph

3NN

NN

O

NH2N

NH2

NH2

+ HOHO OH

OH

Figure 2 Scheme for the synthesis of trenhynaph

to obtain the protonation constant of the ligand and theformation constants of metal complexes The whole titrationprocedure is carried out twice to confirm the results

Spectrophotometric titrations were carried out in thesame conditions as for potentiometric titrations In thesestudies a dilute solution of ligands (1times10minus5M) andmetal ion(1 times 10minus5M) was made acidic by adding appropriate amountof 01MHCl at an ionic strength of 01MKCl and titratedagainst standard 01MKOH solution After each addition ofthe base sufficient time was given to attain the equilibriumwhen a constant value of pHwas attained and then an aliquotof the solution was taken out to take the spectra Transfer ofthe solutions was done very carefully to minimize the errordue to volume loss Computer program pHAb was used todetermine the protonation constants of ligand and formationconstants of metal complexes

24 Theoretical Studies Whole theoretical study was per-formed on the machine Pentium (R) IV having windowsXP environment 320GHz CPU using computational pro-gram HYPERCHEM version 75 [24] and CACHe worksystem Pro version 75085 [25] The minimum strain energyof the molecule and the metal complexes was obtainedthroughmolecularmechanicsmethod usingMM+ force fieldThe initial structure obtained was reoptimized by semiem-pirical method using PM6 self-consistent field (SCF) atRestricted Hartree-Fock Polak-Ribiere method Semiempiri-cal ZINDO1 method was applied to calculate the vibrationalspectra ZINDO using INDOS parameters is used for cal-culating electronic spectra after reoptimizing geometry withMOPAC PM5

3 Results and Discussions

31 Synthesis and Characterization The ligand trenhynaphwas synthesized by condensation of triamine (tren) and alde-hyde (2-hydroxynaphthaldehyde) as per the scheme shownin the Figure 2 It is bright yellow in colour and found to besoluble completely in DMSO and DMSOwater ratio above5 95 It is also partially soluble in methanol and ethanol butinsoluble in other solvents like chloroform ether acetonitrileacetone and so forth

2 2

1

2

345

6

78 9

10

11

1213

14

Keto formEnol form

N

N

O

H H

O

N

N

Scheme 1 Keto-enol forms of trenhynaph

The ligand was characterised on the basis of elementalanalysis UV-VIS IR 1HNMR 13CNMR andMASS spectraIt has been studied earlier that the presence of ortho hydroxylgroup in Schiff bases favours the existence of intramolecularhydrogen bonds and the tautomerism which accounts for theformation of either phenol-amine or keto-amine tautomer(Scheme 1) For the Schiff bases of salicylaldehyde withamines (ndashNH) form is found to be less stable The salicy-laldimines exist predominantly in ndashOH tautomeric form incrystalline state and the reason behind this is the loss of ringaromaticity [26] But 2-hydroxynaphthylidenes derivativesshow the presence of both the tautomers ie keto-amineand enolimine In naphthalimides (ndashNH) form is expectedto be more stable due to resonance and delocalization in theretained aromatic structure [27 28]

Matijevic-Sosa et al investigated a number of 2-hydroxy-1-naphthaldehyde Schiff bases through various spectro-scopic techniques like IR one and two dimensional homo-heteronuclear 1H and 13C NMR It was established thatin solution (DMSO) the (ndashNH) tautomer predominateswhile the IR spectra of solid samples (KBr) suggest thatthe Schiff bases exist in solid state as (ndashOH) isomer [2930] Considering these previous observations we investigatedthe spectra of our ligand and found that the above sametrend is being followed in our case also IR spectra suggestthe predominance of the (ndashOH) isomer and 1H and 13CNMR (DMSO-d

6) suggest the (ndashNH) tautomer Electronic

spectrum of trenhynaph exhibits three peaks Peaks obtained


0

10

20

200 300

(a) (b)

Wavelength (nm)

250 300 350 40005

10

15

20

Abso

rban

ceWavelength (nm)

times104

Mol

ar ab

sorp

tivity

(mol

minus1

cmminus1)

Figure 3 (a) Theoretical electronic spectra of ligand trenhynaphby ZINDO using INDOS parameters after reoptimizing geometrywith MOPAC PM5 and (b) experimental electronic spectra of theligand (1 times 10minus5M in DMSOH

2

O 595)

at 2549 nm and 31599 nm can be attributed to the 120587 rarr120587lowast transitions due to naphthyl ring and 36599 nm 119899 rarr120587lowast transitions associated with the imine bond Figure 3(b)

Similarly the calculated electronic spectra also give threepeaks Figure 3(a) Although the calculated electronic signalsare not the same as the theoretical one still they follow thesame trend as that of the experimental one

IR spectra show a strong band at 1622 cmminus1 which can beattributed to ] (ndashC=N) and they confirm the condensation ofamine and aldehyde The sharp peak obtained at 1350 cmminus1which can be due to the ] (ndashCndashO) suggests in solid statethat it exists as ndashOH tautomer Aromatic =CndashH stretchingis obtained at 3055 cmminus1 and =CndashH out of plain bendingis obtained at 764 cmminus1 The low intensity peaks obtainedat 2940 cmminus1 and 2821 cmminus1 can be assigned to asymmetricstretching vibrations and symmetric stretching vibrations ofthe methylene (ndashCH

2) group of parent tren moiety The IR

spectrum of the ligand is also obtained theoretically by usingsemiempirical ZINDO1 methodThe theoretical values werenot in quantitative agreement with the experimental valuesbut the trend of the peaks follows the same pattern as inTable 1

Skeletal structure of the ligand is revealed by NMRspectra of the ligand The 1H NMR spectra show peaksat 30039 ppm (t 6H) and 37633 ppm (t 6H) which canbe attributed to the methylene protons shown in Scheme 1by numbers 12 and 13 respectively The signal obtained at90615 ppm (d 3H) shows the presence of imine protonnumber 11The peak obtained at 6698 (d 3H) 76177 (d 3H)7547 (d 3H) 71334 (t 3H) 73272 (t 3H) and 79926 (d3H) corresponds to the proton numbers 3 4 5 6 7 and 8respectively as shown Scheme 1 A peak at 141123 ppm (d3H) is also obtained corresponding to the proton of iminenitrogenwhen ligand exists in keto-imine form Similarly 13CNMR spectra also show the presence of signal at 17726 ppmwhich corresponds to the carbonyl carbon C2 The signalsobtained at 10577 12187 13676 13414 12507 12858 1183112753 and 12533 correspond to the carbon atom numbers 13 4 5 6 7 8 9 and 10 respectively The signal at 15905 ppm

minus4 minus2 0 2 4 6 82

4

6

8

10

12

(III)

(IV)

(II)

(I)

pH

a

Figure 4 Potentiometric titration curves (I) 1times10minus3M trenhynaph(L) 1times10minus3M[trenhynaph][M(III)] (1 1 molar ratio) [(II)-Al (III)-Cr (IV)-Fe] 119879 = 25 plusmn 1∘C 01MKCl and ldquo119886rdquo is the moles of baseadded per mole of ligandcomplex

corresponds to carbon atom number 11 Peaks for methylenecarbon atoms are obtained at 3893 and 4018

Mass spectrum of the ligand shows molecular ion peak at119898119911 6093 which was expected at 60827 The base peak with100 intensity is obtained at119898119911 4552 which corresponds tothe fragment C

28H30N4O2(4542) Onemore important peak

at119898119911 2811 corresponds to the fragment C13H23N3

32 Ligand Protonation Constant The formation of metalcomplexes is viewed as competition between the protons ofligand moiety and metal ions hence protonation constantswere evaluated experimentally which are required to beused as input data to calculate the formation constants ofthe metal complexes Potentiometric studies to investigatethe protonation constants were carried out in DMSOwater(5 95) mixture at 120583 = 01MKCl and 25 plusmn 1∘C Thepotentiometric curves between pH and ldquo119886rdquo where ldquo119886rdquo is themoles of base added per mole of ligand present are shown inFigure 4 Up to the volume of 119886 = 0 only the excess of acidis being consumed After 119886 = 0mL drastic increase in pH isobserved and this indicates the deprotonation of the ligandInflection point at 119886 = 3 indicates the release of three molesof protons from the ligand

The potentiometric data on quantitative analysis by usingthe software Hyperquad 2006 [31] gave the acceptable best fitfor the three protonation constants for the tripod The fol-lowing are the proposed reactions which are being followedby the ligand during its protonation process

LH119899minus1+H 999445999468 LH

119899 119870

119899=

[LH119899]

[LH119899minus1] [H]

(1)

where L(ligand) 119899 = 1 2 3If we examine our ligand structure it is found that the

tripodal ligand(s) in its fully protonated form have sevenprotons which can be deprotonated by the addition of


Table 1 Experimental and theoretical IR spectral data of ligand

IR ] (ndashC=N) ] (ndashCndashO) ] (Ar=CndashH) 120575 (=CndashH) ] (ndashCH2) ] (ndashCH2) ] (ndashC=N)(OOP) Asymmetric Symmetric

Experimental (cmminus1) 1622 1350 3055 764 2940 2821 1622Theoretical (cmminus1) 1683 1384 3105 772 2967 2853 1683

Table 2 Protonation constants (logK) of the ligand and trenhynaph at 119879 = 25 plusmn 1∘C and 120583 = 01MKCl in DMSOH2O (595) calculatedusing Hyperquad 2006 [31]

Equilibrium logKAssignments Potentiometry Spectrophotometry

L + H 999445999468HL OndashH 903 plusmn 001 904 plusmn 005

HL + H 999445999468H2L OndashH 802 plusmn 003 801 plusmn 006

H2L + H 999445999468 H3L OndashH 712 plusmn 002 713 plusmn 009

base These seven protons include three protons of tertiaryimine nitrogen and three protons of naphtholic oxygen andone proton associated with tertiary amine of tren cappingBut under the present investigation only three protonationconstants can be calculated which corresponds to the protonsof naphtholic oxygen Table 2 The protonation constant forthe three protons of imine nitrogen cannot be calculatedbecause when an aromatic alcohol system forms a Schiffbase the imine nitrogen possesses very low basicity withlogKa of 153 and 284 [32] It is found to be so due to thendashI effect of the substituted aromatic naphthol group whichreduces the electron density of imine nitrogen The apicalnitrogen atom is also very acidic with pKa lt 15 [8] So theligand is considered to be triprotic LH

3and the calculated

protonation constants correspond to the naphtholic protonsThe protonation constant values are found to be lower thannaphthol it may be caused by the intramolecular hydrogenbonding supported by the least strain energy structure of theligand (Figure 1)

Protonation constants of the ligand were also calcu-lated by spectrophotometric method In this method a pHversus absorbance measurement was carried out at ligandconcentration (1 times 10minus5M) 25 plusmn 1∘C and constant ionicstrength 01MKClThe absorbance spectra of the ligandwererecorded within the pH range (317ndash990) and are shown inFigure 5(a) No appreciable changes in the electronic spectrawere observed below the experimental pH 317 and abovepH 990 and spectra overlapped with each other The stateof equilibrium between various protonated and deprotonatedspecies was examined from the spectral changes like shiftingof peaks and formation of isosbestic points The whole rangeof spectral data as shown in the Figure 5(a) was includedin the calculations by nonlinear least square fitting programpHAb which gave best fit for three species whose protonationconstants agreed well with the potentiometric results

The solution remained yellow in the entire pH rangeThe ligand exhibited three peaks with maxima at 2549 nm31599 nm can be attributed to the 120587 rarr 120587lowast transitionsdue to naphthyl ring and 36599 nm 119899 rarr 120587lowast transitionsassociated with the imine bond Peak obtained at 2549 nmshowed a bathochromic and hyperchromic shift A new peakappeared at 275 which showed a concomitant hyperchromic

shift Another peak at 31599 nm due to 120587 rarr 120587lowast transitionsassociated with naphthyl ring showed lowering of intensitywith increasing pH Absorption band at 36599 nm experi-ences a bathochromic and hyperchromic shift The shiftingof the peaks to longer wavelength can be explained by thefact that on deprotonation formation of naphtholate iontakes place which can stabilize the 120587lowast excited state dueto charge delocalization bring the lowest excited closer tothe highest ground state and thus permit a lower energy(longer wavelength) for transition Since the imine bond is inconjugation with the ring the peak at 36599 nm also experi-ences red shift

From the diagram the speciation diagram obtained byusing HYSS program [33] it can be inferred that at initialstages the ligand remains 100 in its fully protonated formLH3 Figure 6(a) The dominance of the LH

3species starts

to decrease as the pH increases With the increase in pH thedeprotonation of the ligand starts to form species LH

2 LH

and L After pHsim5 LH2begins to form and exists up to pHsim9

though in very low amount LH is formed predominantly inthe pH range 7ndash9 Fully deprotonated species of the ligandL shows its formation at pHsim75 and becomes predominantafter pH 9

33 Metal Complex Formation Figure 4 shows the potentio-metric titration curves of the ligand in presence of M(III)where M = Fe Al and Cr in 1 1 metal-ligand ratio Themetal ligand curves are showing considerable changes withrespect to the curves of the ligand which qualitatively impliesthat the metal complexation has occurred and the shapeof the curve also gives an idea about the good affinity ofligand towards metal ions The potentiometric curve forFe(III) lies below the curve for Cr(III) and Al(III) indicatingbetter complexation with Fe(III) The break point obtainedat the value 119886 = 4 corresponds to the release of fourmoles of protons of the ligand prior to deprotonation fromhydroxyl group Further addition of KOH increases pH andanother inflection point is obtained at 119886 = 7 indicatingoverall release of seven protons from the ligands AbovepHsim95 the solution becomes turbid due to the appear-ance of precipitate which may be caused by hydrolysis of


250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce

300 400 500 600Wavelength (nm)

(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)

Figure 5 pH dependent electronic spectra as a function of absorbance and wavelength for (a) trenhynaph (b) 1 1 solution of Fe(III) (c)Cr(III) and (d) Al(III) and trenhynaph [trenhynaph] = [M(III)] = 1 times 10minus5M 119879 = 25 plusmn 1∘C 01M KCl in DMSOH

2

O (5 95)

the metal complexes Taking these observations in consid-eration a number of models were tried in the programHyperquad 2006 to calculate the formation constantThe bestfit was obtained while considering the species MLH

3 MLH

2

MLH ML and MLHminus1

for Fe(III) Cr(III) and MLH3and

ML and MLHminus1

for Al(III) Table 3 The following equationsshow the equilibrium reactions for the overall formationconstants

M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)

where L(ligand) M(Fe(III)Cr(III)Al(III)) 119899 = 0 1 2 3 minus1Spectrophotometric method was also employed to cal-

culate the formation constant in order to support poten-tiometric outcomes The spectrophotometric titrations werecarried out in DMSOH

2O (595) solution with ligand

and metal concentration of 1 times 10minus5M at 25 plusmn 1∘C and

ionic strength 01MKCl The electronic spectra of ligandin presence of equimolar metal ions Fe(III) Al(III) andCr(III) were recorded in the pH range 2ndash10 and significantspectral changes observed in different pH ranges are givenin Figures 5(a) 5(b) and 5(c) Shifting of the ligand peakswas observed along with the formation of isosbestic pointswith gradual increase of pH In Fe(III)-trenhynaph metalcomplex one of the characteristic absorption bands (120587 rarr120587lowast) for the naphthyl ring observed at 2549 nm experiences

a red shift along with the appearance of new low intensitypeak located at 277 nm The other peak with maxima at31599 nm was observed with lowering in intensity The peakassociatedwith 119899 rarr 120587lowast transition centered at 36597 nmalsoshowed a red shift with a hyperchromic effect Formation ofisosbestic points at 280 300 370 and 440 nm due to shiftingof the peaks indicates the involvement of hydroxyl group ofnaphthyl ring and the imine nitrogen in complexation Anadditional band due to metal ligand charge transfer band


Table 3 Overall (log120573) for the metal complexes formed by the ligand at 119879 = 25 plusmn 1∘C and 120583 = 01MKCl by potentiometry andspectrophotometry

log120573 MLH3 MLH2 MLH ML MLHminus1

Fe(III) A 3979 plusmn 002 3539 plusmn 004 3191 plusmn 009 2937 plusmn 001 1728 plusmn 001

B 3978 plusmn 006 3538 plusmn 007 3190 plusmn 010 2936 plusmn 002 1726 plusmn 009

Cr(III) A 3868 plusmn 005 3354 plusmn 001 2698 plusmn 009 2094 plusmn 006 854 plusmn 003


Al(III) A 3410 plusmn 007 mdash mdash 2049 plusmn 006 983 plusmn 009

B 3411 plusmn 009 mdash mdash 2047 plusmn 007 981 plusmn 008

4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)

Figure 6 Species distribution curves computed from the (a) protonation constants for trenghynaph and (b) formation constants for[trenhynaph Fe(III)] (c) Cr(III) and (d) Al(III)

is also observed for the Fe(III) complex located at 540 nminferring a hexacoordinated environment Similar spectralvariations are observed for chromium and aluminium metalions suggesting similar modes of coordination as for iron

Species distribution curve obtained from the programHYSS using the calculated formation constant values isshown in Figures 6(b) 6(c) and 6(d) It indicates that theformation of the complex occurs at pHsim2 for Fe(III) Cr(III)and Al(III) The very first species formed is MLH

3 further

increase in the pH leads to the formation of MLH2 MLH

ML and MLHminus1

for Fe(III) Cr(III) and ML and MLHminus1

for Al(III) MLH3type of complex may be formed due to

the interaction of weakly basic amine nitrogen atoms In thiscomplex species the metal ion is face capped by the ligandThe three remaining coordinating sites may be occupied bywater molecules to satisfy the primary valency of the metalion The Fe(III)L species began to form at pH = 3 whilefor chromium it appeared after pH = 4 and for aluminium


MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N

Figure 7 Suggested coordination modes of ligand with Fe(III) Cr(III) and Al(III)

it was formed after pH = 5 which support the bettercomplexation with Fe(III) metal ion The various probablecoordination modes are shown in Figure 7 Addition of morebases will result in the replacement of water molecules by thenaphtholic hydroxyl groups to form the subsequent speciesMLH2MLH andMLThe formation of the speciesMLH

minus1is

due to the deprotonation ofML But there is no deprotonatingsite in ML Thus the formation of MLH

minus1may possibly be

due to the deprotonation of water molecules linked with theimine linkage resulting in the breaking of Schiff base [34]

Results obtained for the ligand under present investiga-tion are compared with two similar (N

3O3) type ligands

ciscis-135-tris[(2-hydroxy-benzylidene)aminomethyl]cyclo-hexane (L1) ciscis-135-tris[1-(2-hydroxyphenyl) ethylide-neaminomethyl]cyclohexane (L2) deferiprone (medicallyapplied for the iron intoxication) and transferrin (themain Febinding protein in plasma) The pFe values for ligands L1 L2deferiprone and transferrin at pH = 74 are 2014 and 1641193 and 203 respectively [9] These values are calculatedusing [L]total = 5 times 10

minus4M [Fe(III)]total = 5 times 10minus5M

deprotonation constants of the ligand and the formationconstant of metal complexes The ligand in the currentinvestigation has pM = 2182 at the same concentrationof ligand and metal This indicates that our ligand hasbetter complexation ability for Fe(III) at pH 74 than ligandsL1 L2 deferiprone and transferrin So the ligand can beexplored for their potential application for iron overloadchelation therapy For the metal ions Fe(III) Al(III) andCr(III) at pH = 74 the pM values are 2182 1493 and 1528respectively The highest value is obtained for Fe(III) Theligand selectively binds with Fe(III) ions at pH 74 To checkwhether this selectivity order is followed for whole pH rangegraphs between pH and pM drawn Figure 8 Curves showthat the selectivity for Fe(III) ions remains greater than theother metals for the whole pH range

In order to validate the formation of the above saidcomplexes for the threemetal ions the structural investigationof all the species formed in solution (MLH

3 MLH

2 MLH

ML and MLHminus1) was performed using PM6 semiempirical

method The energy value thus obtained also supports thatthe most stable species formed is ML type for the three metalions under study (Table 4) Among three metal ions ML typeof complex is found to be themost stable for ironmetal Bondlengths bond angles total energy and heat of formationfor ML type of complex of the all metal ions are calculatedand it is found that the metal complexes possess distortedoctahedral geometry (Figures 9(a) 9(b) and 9(c) Table 4)

20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26

Fe(III)-L Cr(III)-L Al (III)-L

pM

pH

Figure 8 pH versus pM graph pM was calculated for [L] = 5 times10minus4 and [M] = 5 times 10minus5 using protonation constant of ligands and

complexation constants 12057311119899

4 Conclusions

The solution studies of trenhynaph by potentiometric andspectrophotometric methods revealed that three protonationconstants can be assigned to hydroxyl group of naphtholmoiety The formation constants of its metal complexes withFe(III) Cr(III) and Al(III) were determined in solutionunder similar adopted experimental conditions showing theformation of ML as the single major species at physiologicalpH The calculated log120573 values are 2937 2094 and 2049for Fe(III)-L Cr(III)-L and Al(III)-L respectively Nineunit higher log120573 values for Fe(III)-L indicate the admirableaffinity of the ligand towards Fe(III) than Cr(III) and Al(III)rendering it asmore potent iron chelators at physiological pHFurther the pM values at pH = 74 for Fe(III) complex withtrenhynaph are found to be 2 to 3 units more as compared tostructurally similar chelators deferiprone (medically applieddrug for the iron intoxication) and transferrin (the mainFe binding protein in plasma) indicating higher selectivityof the ligand towards iron in its trivalent state The highbinding affinity of the ligand towards Fe(III) metal ion can beutilized for the removal of Fe(III) in iron overload chelation


Table 4 The calculated total energies for the various metal complexes formed in solution and structural parameters of MndashL type complexthrough semiempirical PM6 method

Species Fe(III) Cr(III) Al(III) PropertiesE (eV) E (eV) E (eV) Fe(III)ndashL Cr(III)ndashL Al(III)ndashL

MLH3

minus4204531 minus25176750 minus24199876 Bond length(MndashN) (A∘) 2133 2129 2143

MLH2

minus10326754 minus98326785 mdash Bond length(MndashO) (A∘) 2021 2042 2078

MLH minus58324516 minus51305612 mdash Bond length(MndashN) (A∘) 2133 2129 2143

ML minus95298324 minus92461048 minus83481312 Δ119867119891

(kcalmol) minus16743 minus14215 minus12893

MLHminus1

minus8904563 minus7206745 minus9603451 Bond angleltOMN (∘) 9134 9199 9201

(a) (b) (c)

Figure 9 Least strain structures of ML type metal complexes for (a) Fe(III) (b) Cr(III) and (c) Al(III) using semiempirical PM6 method atHatree-Fock algorithms

therapy Also the noticeable electronic spectral changes ofthe complex at pHsim7 with the variation in pH support theligand for potential application as an optical sensor towardsFe(III) metal ion in biological systems Hence synthesis ofsuch ligands and their derivatives will open up a perspectivetowards the development of new optical biosensors

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Council of Scientific andIndustrial Research Human Resource Development GroupPUSA New Delhi India for financial support and NationalInstitute of Technology Kurukshetra India for providinginfrastructure and research facilities

References

[1] M Gelinsky R Vogler and H Vahrenkamp ldquoTripodal pseu-dopeptides with three histidine or cysteine donors synthesis

and zinc complexationrdquo Inorganic Chemistry vol 41 no 9 pp2560ndash2564 2002

[2] A E Martell and R D Hancock Metal Complexes in AqueousSolution Plenum New York NY USA 1996

[3] W A Quinn M A Saeed D R Powell and M A HossainldquoAn anthracene-based tripodal chemosensor for anion sensingrdquoInternational Journal of Environmental Research and PublicHealth vol 7 no 5 pp 2057ndash2070 2010

[4] P A Gale ldquoStructural and molecular recognition studies withacyclic anion receptorsrdquo Accounts of Chemical Research vol 39no 7 pp 465ndash475 2006

[5] R Grazina L Gano J Sebestık and M Amelia Santos ldquoNewtripodal hydroxypyridinone based chelating agents for Fe(III)Al(III) and Ga(III) synthesis physico-chemical properties andbioevaluationrdquo Journal of Inorganic Biochemistry vol 103 no 2pp 262ndash273 2009

[6] E T Clarke and A E Martell ldquoPotentiometric and spec-trophotometric determination of the stabilities of In(III)Ga(III) and Fe(III) complexes of N119873101584011987310158401015840-tris(35-dimethyl-2-hydroxybenzyl)-147-triazacyclononanerdquo Inorganica ChimicaActa vol 186 no 1 pp 103ndash111 1991

[7] R M Kirchner C Mealli M Bailey et al ldquoThe variablecoordination chemistry of a potentially heptadentate ligandwith a series of 3d transition metal ions The chemistry andstructures of [M(py

3

tren)]2+ where M(II) Mn Fe Co Ni Cu


and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3

rdquoCoordinationChemistry Reviews vol 77 pp 89ndash163 1987

[8] P Caravan and C Orvig ldquoTripodal aminophenolate ligandcomplexes of aluminum(III) Gallium(III) and Indium(III) inwaterrdquo Inorganic Chemistry vol 36 no 2 pp 236ndash248 1997

[9] B K Kanungo M Baral S K Sahoo and S E MuthuldquoSynthesis spectroscopic and theoretical studies of two noveltripodal imine-phenol ligands and their complexation withFe(III)rdquo Spectrochimica Acta A Molecular and BiomolecularSpectroscopy vol 74 no 2 pp 544ndash552 2009

[10] A D Garnovskii A L Nivorozhkin and V I Minkin ldquoLigandenvironment and the structure of Schiff base adducts and tetra-coordinated metal-chelatesrdquo Coordination Chemistry Reviewsvol 126 no 1-2 pp 1ndash69 1993

[11] V Alexander ldquoDesign and synthesis of macrocyclic ligandsand their complexes of lanthanides and actinidesrdquo ChemicalReviews vol 95 no 2 pp 273ndash342 1995

[12] E ADertz J Xu andKN Raymond ldquoTren-based analogues ofbacillibactin structure and stabilityrdquo Inorganic Chemistry vol45 no 14 pp 5465ndash5478 2006

[13] C Orvig D J Berg and S J Rettig ldquoHeptadentate ligandsfor the lanthanidesThe first structurally characterized exampleof a lanthanide heptadentate ligand complex [tris (3-aza-4-methyl-6-oxohept-4-en-1-yl)amine]ytterbium(III)rdquo Journal ofthe American Chemical Society vol 113 no 7 pp 2528ndash25321991

[14] D Imbert F Thomas P Baret et al ldquoSynthesis and iron(III)complexing ability of CacCAM a new analog of enterobactinpossessing a free carboxylic anchor arm Comparative studieswith TRENCAMrdquo New Journal of Chemistry vol 24 no 5 pp281ndash288 2000

[15] D Imbert P Baret D Gaude et al ldquoHydrophilic and lipophiliciron chelators with the same complexing abilitiesrdquo Chemistryvol 8 no 5 pp 1091ndash1100 2002

[16] M A Santos S M Marques and S Chaves ldquoHydroxypyridi-nones as ldquoprivilegedrdquo chelating structures for the design ofmedicinal drugsrdquoCoordination Chemistry Reviews vol 256 no1-2 pp 240ndash259 2012

[17] R Peng F Wang and Y Sha ldquoSynthesis of 5-dialkyl(aryl)ami-nomethyl-8-hydroxyquinoline dansylates as selective fluores-cent sensors for Fe3+rdquo Molecules vol 12 no 5 pp 1191ndash12012007

[18] J B Cannata-Andıa and J L Fernandez-Martın ldquoThe clinicalimpact of aluminium overload in renal failurerdquo NephrologyDialysis Transplantation vol 17 no 2 pp 9ndash12 2002

[19] J L Fernandez-Martin A Canteros A Alles P Massariand J Cannata-Andia ldquoAluminum exposure in chronic renalfailure in Iberoamerica at the end of the 1990s overview andperspectivesrdquoTheAmerican Journal of the Medical Sciences vol320 no 2 pp 96ndash99 2000

[20] A Corval K Kuldova Y Eichen Z Pikramenou J MLehn and H P Trommsdorff ldquoPhotochromism and thermo-chromism driven by intramolecular proton transfer in dinitro-benzylpyridine compoundsrdquoThe Journal of Physical Chemistryvol 100 no 50 pp 19315ndash19320 1996

[21] D G Barceloux and D Barceloux ldquoChromiumrdquo Clinical Toxi-cology vol 37 no 2 pp 173ndash194 1999

[22] H C Lukaski ldquoChromium as a supplementrdquo Annual Review ofNutrition vol 19 pp 279ndash302 1999

[23] B S Furniss A J Hannaford PW G Smith and A R TatchellVOGELrsquoS Textbook of Practical Organic Chemistry PrenticeHall 5th edition 2008

[24] Instructional manual for portable pHISE meter Sension2HACH Company

[25] Hyperchem manual for Hyperchem Release 7 for windowsJanuary 2002

[26] User guide manual for chache version 601 Fujitsu limited2003

[27] T Inabe ldquoProton transfer in N-salicylideneanilines Anapproach to controlling the charge transport in molecularmaterialsrdquo New Journal of Chemistry vol 15 pp 129ndash136 1991

[28] T Inabe I Lineau T Mitani Y Maruyama and S TakedaldquoProton Transfer in N-(2-Hydroxy-1-naphthylmethylene)-1-pyrenamine and N Nrsquo- Bis (2-hydroxy-1-naphthyl methylene)-p-phenylenediamine Crystalsrdquo Bulletin of Chemical Society ofJapan vol 67 no 3 pp 612ndash621 1994

[29] JMatijevic-SosaM Vinkovic andD Vikic-Topic ldquoNMR spec-troscopy of 2-hydroxy-1-naphthylidene Schiff bases with chloroandhydroxy substituted anilinemoietyrdquoCroaticaChemicaActavol 79 no 3 pp 489ndash495 2006

[30] S Bilge Z Kilic Z Hayvali T Hokelek and S Safran ldquoIntra-molecular hydrogen bonding and tautomerism in Schiff basespart VI Syntheses and structural investigation of salicy-laldimine and naphthaldimine derivativesrdquo Journal of ChemicalSciences vol 121 no 6 pp 989ndash1001 2009

[31] User guide Hyperquad 2006[32] A Golcu M Tumer H Demirelli and R A Wheatley

ldquoCd(II) andCu(II) complexes of polydentate Schiff base ligandssynthesis characterization properties and biological activityrdquoInorganica Chimica Acta vol 358 no 6 pp 1785ndash1797 2005

[33] User guide Hyperquad Simulation and Speciation 2009[34] S K Sahoo S E Muthu M Baral and B K Kanungo ldquoPoten-

tiometric and spectrophotometric study of a newdipodal ligandNN1015840-bis2-[(2-hydroxybenzyli-dine)amino]ethylmalonamidewith Co(II) Ni(II) Cu(II) and Zn(II)rdquo Spectrochimica ActaA Molecular and Biomolecular Spectroscopy vol 63 no 3 pp574ndash586 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


NN

NOH

OH

HO

N

(a)

1619

1611

(b)

Figure 1 (a)Molecular structure of trenhynaph (b) least strain energy structure of ligand obtained from semiempirical PM6method showingpresence of hydrogen bonding

studies carried out to shed light on the structural elucidationand binding modes in the complexes by using semiempiricalmethod are also reported

2 Experimental

21 Materials and Measurements All chemicals and sol-vents were of analytical grade available commercially Potas-sium hydroxide and hydrochloric acid were obtained fromFisher Scientific 2-Hydroxynaphthaldehyde and Tris (2-amino ethyl) amine (tren) were obtained from SigmaAldrich Anhydrous ferric chloride aluminium sulphateand chromium chloride were procured from Qualigens FineChemicals (Fisher Scientific) Tetrahydrofuran and dimethylsulfoxide were purchased from Merck Chemicals were usedas purchased without purification Solvents were dried usingstandard methods [22]

Melting points (MP) were determined on a microsil(India) MP apparatus and are uncorrected They are givenin degree centigrade (∘C) Electronic spectra were taken onHitachi spectrophotometer U 0080D Infrared (IR) spectrawere recorded on a Perkin-Elmer RX 1 FT-IR spectrometerusing KBr discs 1H and 13C NMR spectra were recorded ona Bruker Avance II 400 NMR spectrometer at SAIF PanjabUniversity Chandigarh using tetramethylsilane (TMS) as aninternal referenceThe chemical shifts are mentioned in partsper million (ppm) The mass spectrum was performed onWaters Micromass Q-TOF Micro with electron spray ioniza-tion (EI) technique at SAIF Panjab University ChandigarhC H N S andO analysis was carried out on EUROEA 3000Potentiometric studies were carried on Sension 02 pHmeter

22 Synthesis of 1-[(E)-2-[Bis[2-[(2-hydroxy-1-naphthyl)meth-yleneamino]ethyl]amino]ethyl iminomethyl]naphthalen-2-ol(trenhynaph) In a round bottom flask 10mL of THF wastaken added to it 3 g (00174mol) of 2-hydroxynaphthalde-hyde and the contents were stirred till complete dissolutionA solution of 00846 g of tren in 10mL of THF was addeddropwise Solution was allowed to stir for 1 hr Very thickand bright yellow coloured precipitates were obtainedwhich were filtered washed with diethyl ether and dried

in vacuum Yield (228 g 76) MP (185ndash189)∘C colour(yellow) IR (KBr pellet cmminus1) 3055 (Ar=CndashH) 2940(ndashCH2 asymmetric) 2821(ndashCH

2 symmetric) 1622(ndashC=N)

1350(ndashCndashO) 764(=CndashH OOP) 1H NMR (DMSO-D6 120575

ppm) 300 (t 119869 = 1248 6H H-12) 375 (t 119869 = 464 6HH-13) 668 (d 119869 = 932 3H H = 3) 713 (d 119869 = 146 3H H= 6) 732 (t 119869 = 149 3H H = 7) 753 (d 119869 = 772 3H H =5) 760 (d 119869 = 916 3H H = 4) 798 (t 119869 = 882 3H H =8) 904 (d 119869 = 976 3H H = 11) 1411 (d 119869 = 384 3H H= 14) 13C NMR (DMSO-D

6 120575 ppm) 17726 15905 13676

13414 12858 12753 12507 12533 12187 11858 105773893 4018 mass spectrum (ESI) molecular ion [M+2] peak119898119911 = 6104 [M+1] peak 119898119911 = 6093 anal calcd forC39H36O3N4(60827) C77 H9 N92 O79 found C7723

H936 N935 O798

23 Titration Procedure Potentiometric titrations were car-ried out in order to find out the protonation constant of theligand and formation constant of the metal complexes Thetemperature for the experiment was maintained at 25 plusmn 1∘CA titration cell which has double glass walls was used andattached to circulatory bath to maintain the consistency oftemperature Sension 02 pHmeter in combination with glasselectrode was used to measure the pHThe whole equipmentset was calibrated according to the standard methods [23]

Doubly distilled deoxygenated and deionized water wasused to prepare all the solutions used in the experiment KOHsolution (01M) was prepared in 5 95 ratio of DMSOwaterHCl solution (01M) was prepared in water Ionic strengthof the solution was maintained 01M by adding 1MKClsolution The solution of ligand of strength 001M wasprepared in DMSO and solution of metal 001M in waterThe final concentration of ligand and metal in titration cellwas maintained at 0001M The ratio of DMSOwater in theresulting titration cell was maintained at 5 95 by addingappropriate solutions Following titrations in which metalto ligand ratios CMCL (0 1) and CMCL (1 1) were carriedout The data obtained from the experiment is fed intothe least square fitting program HYPERQUAD 2006 andmanual fitting of experimental and theoretical data was done




trenhynaph

3NN

NN

O

NH2N

NH2

NH2

+ HOHO OH

OH







2 2

1

2

345

6

78 9

10

11

1213

14

Keto formEnol form

N

N

O

H H

O

N

N







0

10

20

200 300

(a) (b)

Wavelength (nm)

250 300 350 40005

10

15

20

Abso

rban

ceWavelength (nm)

times104

Mol

ar ab

sorp

tivity

(mol

minus1

cmminus1)


2

O 595)








4

6

8

10

12

(III)

(IV)

(II)

(I)

pH

a








LH119899minus1+H 999445999468 LH

119899 119870

119899=

[LH119899]


(1)













3and the calculated






3species starts


2 LH





250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce


(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)


2

O (5 95)


3 MLH

2



ML and MLHminus1


M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)
















4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




trenhynaph

3NN

NN

O

NH2N

NH2

NH2

+ HOHO OH

OH







2 2

1

2

345

6

78 9

10

11

1213

14

Keto formEnol form

N

N

O

H H

O

N

N







0

10

20

200 300

(a) (b)

Wavelength (nm)

250 300 350 40005

10

15

20

Abso

rban

ceWavelength (nm)

times104

Mol

ar ab

sorp

tivity

(mol

minus1

cmminus1)


2

O 595)








4

6

8

10

12

(III)

(IV)

(II)

(I)

pH

a








LH119899minus1+H 999445999468 LH

119899 119870

119899=

[LH119899]


(1)













3and the calculated






3species starts


2 LH





250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce


(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)


2

O (5 95)


3 MLH

2



ML and MLHminus1


M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)
















4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

10

20

200 300

(a) (b)

Wavelength (nm)

250 300 350 40005

10

15

20

Abso

rban

ceWavelength (nm)

times104

Mol

ar ab

sorp

tivity

(mol

minus1

cmminus1)


2

O 595)








4

6

8

10

12

(III)

(IV)

(II)

(I)

pH

a








LH119899minus1+H 999445999468 LH

119899 119870

119899=

[LH119899]


(1)













3and the calculated






3species starts


2 LH





250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce


(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)


2

O (5 95)


3 MLH

2



ML and MLHminus1


M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)
















4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of











3and the calculated






3species starts


2 LH





250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce


(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)


2

O (5 95)


3 MLH

2



ML and MLHminus1


M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)
















4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


250 300 350 400 450 500

05

10

15

20

25Ab

sorb

ance

Wavelength (nm)

pH (317ndash990)

(a)

300 400 500 600 700

05

10

15

20

450 500 550 600 650010015020025030035040045050

pH (474ndash988)

Abso

rban

ce

Wavelength (nm)

(b)

05

10

15

20

pH (372ndash998)

Abso

rban

ce


(c)

pH (356ndash954)


05

10

15

20

25

Abso

rban

ce

(d)


2

O (5 95)


3 MLH

2



ML and MLHminus1


M + L + 119899H = MLH119899 120573

11119899=

[MLH119899]

[M] [L] [H]119899 (2)
















4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










4 6 8 100

10

20

30

40

50

60

70

80

90

100

LH2LH

LH3 LH

Form

atio

n re

lativ

e to

L (

)

pH

(a)

2 3 4 5 6 7 8 90

20

40

60

80

100

FeLH3

FeL

FeLHFeLH2Form

atio

n re

lativ

e to

Fe (

)

pH

FeLHminus1

(b)

CrL

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Cr (

)

CrLH3

CrLHCrLH

2

CrLHminus1

(c)

AlLHminus1

AlLAlLH3

2 3 4 5 6 7 8 9pH

0

20

40

60

80

100

Form

atio

n re

lativ

e to

Al (

)

(d)




3 further


ML and MLHminus1





MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


MLH3 MLH2 MLH ML

M M MM

NN N NN

O

N N N

O

N

O O

N

O

N

O

N

OOO

N

OO

N N

O

N



minus1is





3O3) type ligands





3 MLH

2 MLH



20 25 30 35 40 45 50 55 60 65 70 75 80 85 9010

12

14

16

18

20

22

24

26


pM

pH



4 Conclusions





MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




MLH3


MLH2





MLHminus1


(a) (b) (c)





Acknowledgments


References









3



and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


and Zn and (py3

tren) NCH2

CH2

C(H)(C5

H4

N)3






































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Synthesis of Imine-Naphthol Tripodal