Indian Journal of Chemistry Vol. 38A, June 1999, pp. 613 - 617

Synthesis and characterisation of complexes of cobalt (II), nickel (II), copper (II) and zinc (II) with schiff bases_derived from cinnamaldehyde and 4-arnino-3-ethyl-5-

mercapto-s-triazole and 4-amino-5-mercapto-3-n-propyl-s-triazole

A Kumar, G Singh, R N Handa & S N Dubey*

Depart ment of Chemistry , Kurukshet ra Universi ty, Kurukshetra 136 I 19, Haryana, Indi a

and P J Squattri to

Department of Chemi stry, Cent ral Michigan University, Moun t Pleasant , Mi chi gan 48859, USA

Rl'Cl'il 'l't/ 5 Augus! 1998; revised 8 March 1999

Complexes of Com ), Ni(ll) , Cu(l l) and ZnCH) with schiff bases deri ved from condensation of cinnamaldehyde with 4-amino-3-ethyl-5-mercapto-s-triazole and 4-amino-5-mercapto-3-n-propy l-s-t ri a z o I e ha ve been prepared. The se co 01-

plexe s have bee n charac terized on the basis of elemental analyses and IR , NMR, electronic spectral data, magnetic and thermal studies.

There is growing interest in the studies on the metal complexes of schiff bases derived from tri­azoles which are biologically important ligands t

-9

.

The ligands resulting from the condensation of 4-amino-5-mercapto-3-trifluoromethyl-s-triazole with benzaldehyde and 2-hydroxy-l-naphthaldehyde have been reported to form complexes with some metal ion 10 . Literature survey has revealed that no attempt has been made to study the bivalent cobalt, nickel , copper and zinc complexes with the above mentioned schiff bases . It was, therefore, thought of interest to study the synthesis and characterization of some cin­namalideneamino-s-triazoles complexes of Co (II), Ni (II), Cu (II) and Zn (II) metal ions .

Experimental

All the chemicals and solvents used were of AR grade. Ci!lnamaldehyde was obtained from Sisco­Chern Industries. The metal acetates were purchased

from Albright and Wilson (MGF) Ltd, England . Metal contents were estimated using standard methods 1t

•

IR spectra of the compounds were recorded on a Beckman IR-20 spectrophotometer in the region, 4000-250 cm- I

. IH NMR spectra were recorded on a Perkin-Elmer 90 MHz spectrometer. The diffused refluctance spectra (200-! 800 nm) were recorded at ITT, Madras. Magnetic susceptibility measurements and thennal studies were made at room temperature using vibrating sample magnetometer (Model J 55) at University of Roorkee, Roorkee. The magnetometer was calibrated using a standard nickel pallet and Hg[Co (CNS)4]'

Reactions of various schiff bases with different metal ions, viz., Co (II), Ni (II), Cu (II) and Zn (II) were carried out in hot ethanolic solution of metal acetates in I : I and I :2molar ratios. The~solid prod­ucts obtained were found to be stable in air and non­hygroscopic . The analytical data (Table I) indicated complexes with general fonnulae, (MLOAc) .nH20 and ML2.nH20 In I: 1 and 1 :2 molar ratios

R 2 C,U" !! - C,H, I M = Co(Il), Ni(ll) and Zn(ll)

l l)

"

n

614 INDIAN J CHEM, SEC. A, JUNE 1999

Table I-Analytical and physical data for the complexes

Compd

C13HI4N4S (CEMn

Co (C 13H 13N4S) OAc.3H20

Co (CISHI6N4S02).3H20

Co (CI3HI3N4S) 2.2H20

Ni (C I3 HI3N4S) OAc.3H20

Ni (CISHI6N4S02).3H20

Ni (CI3HI3N4S) 2.2H20

Cu (CI3H 13N4S) OAc.H20

Cu (ClsHI6N4S0) .H20

Cu (CI3HI3N4S) 2

Zn (CI3HI3N4S) OAc.3H20

Zn (CISHI6N4S02).3H20

Zn (CI3HI3N4S) 2.2H20

CI2H12N4S (CMP1)

Co (CI4HISN4S) OAc.3H20

Co (CI6H 18N4S02).3H20

Co (CI4HISN4S) 2.2H20

Ni (CI4HI5N4S) OAc.3H20

Ni (CI6HI8N4S02).3 H20

Ni (CI4HISN4S) 2.2H20

Cu (CI4HISN4S) OAc H20

CU (CI6HI8N4S02) .H20

Cu (CI4H IS N4S) 2

Zn (CI4HISN4S) OAc.3H20

Zn (CI6HI8N4S02).3 H20

Zn (CI4HISN4S) 2.2H20

Colour

Light yellow

Purple

Light purple

Light green

Light green

Green

Dirty green

'Light yellow

Light yellow

Light yellow

Light purple

Light purple

Light green

Light green

Yellowish 'green

Dirty green

Light yellow

Light yellow

M

14.20 (13.73)

10.OS (9.67) 14.20

(13 .69)

9.80 (9.64) 16.S0

(lS.98)

11.28 (11.00) IS .70

(lS .OI)

11.14 (10.62)

13 .70 (13 .29)

9.80 (9.24) 13.70

(l3 .2S)

9.40 (9.21 ) IS.24

(lS .43)

10.78 (10.49) 14.66

(14.54)

10.42 (10.16)

respectively (OAc = CH)COO-, n = 1 for Cu (II), n = 3 for Co (II), Ni (II) and Zn (II) in I I ratio and n = 2 for Co (II), Ni (II) and Zn (II) in I : 2 ratio) . With Cu (II) in I : 2 ratio , . the complex was found to be anhy­drous . The presence of coordinated water in these complexes was confirmed by thermal analysis of the cOl]1pounds. The complexes are insoluble in water and common organic solvents and do not melt but decompose at

C

60.21 (60.46) 42.30

(41.96)

SI .70 (SI.23) 42.08

(41.98)

SI.44 (SI.2S) 4S.48

(4S.27)

S3 .90 (S4.02) 41.50

(41.34)

SO.4S (SO.70) 62.05

(61. 76) 43 .90

(43 .35)

52.S3 (S2.75) 43.90

(43.37)

52.45 (52.77) 46.80

(46.6S)

S5 .20 (S5.48) 43 .08

(42.72)

S2.40 (S2.22)

Found (Calcd.), % H

5.30 (S.42) S.50

(5 .1 2)

S.06 (4.92) 5.40

(5 .13)

5.04 (4.92) 4.31

(4.S2)

4.90 (4.50) 4.90

(5.05)

4.90 (4.87) S.70

(5.88) 5.37

(5.41 )

5.80 (5.33) 5.20

(S.42)

5.71 (5.34) 4.75

(4.85)

4.90 (4.95) 5.70

(5.34)

7.98 (S.28)

N

21.4S (21.70) 12.87 (l 3.0S)

18.S9 ( 18.39) 13 .20 (1 3.06)

18.70 (1 8.39) 14.26 (1 4.08)

19.4S (1 9.38) 12.60 (l2 .86)

18.40 (18 .20) 20.78 (20.58) 12.80 (12.64)

17. 12 (17 .58) 12.43 (12.65)

17.97 (17.59) 13.68 (13 .60)

18.67 (18.49) 12.81 (12.46)

17.22 (17.40)

S

12.60 (12.40)

7.S0 (7.46)

10.79 ( IO.SI )

7.30 (7.46)

10.90 (10.51 )

8.S0 (8.04)

10.78 (11.08)

7.40 (7.3S)

10.35 (10.40) 11.80

(I 1.76) 7.42

(7.22)

10.30 (10.04)

7.20 (7.23 )

10.08 (l O. OS)

7.90 (7.77)

10.90 (10.56)

6.97 (7.12)

9.65 (9.94)

higher temperature e xhibiting their poly­meric nature (I).

Preparation of ligands 4-Amino-3-ethyl-5-mercapto-s-triazole and 4 -

amino - 5 - mercapto - 3 - n - propyl - s - triazole were prepared by known method 12 . 4-

Cinnamalideneamino - 3-ethyl - 5-mercapto­s-triazole (CEMT) was prepared by condens­lllg cinnamaldehyde (8 .74 ml) and 4-amino-

NOTES 615

Table 2-IH NMR spectral data (0 ppm) of CEMT and CMIT and their Zn (II) complexes

Compd SH Aromatic Alkyl -CH=N- CH3COO

CEMT 4.70s 6.80-7.40 3.40 q (2H, -CH2CH3) 9.7 1.80 I (3H, -CH2CH3)

4.4-4.6 broad peak (-CH=CH-)

Zn (CEMD OAc.3H2O 7.10-7.57 3.49 q (2H, -CH2CH3) 9.95 2.4 s (3H, CH3COO) 2.01 I (3H, -CH2CH3)

4.3-4.45 broad peak (-CH=CH-)

Zn (CEMD 2.2H20 7.14-7.54 3.26 q (2H, -CH2CH3) 10.14 1.99 I (3H, -CH2CH3)

4.3-4.5 broad peak (-CH=CH-)

CMIT 4.59 s 6.72-7.38 3.20 I (2H, -CH2CH2CH3) 9.4 2.34 q (3H, -CH2CH2CH3)

1.14 I (3H, -CH2CH2CH3)

4.4-4.6 broad peak (-CH=CH-)

Zn (CMPT) OAc.3H20 6.80-7.45 3.25 I (2H, -CH2CH2CH3) 9.83 2.7 s (3H, CH3COO) 2.28 q (3H, -CH2CH2CH3)

1.40 I (3H, -CH2CH2CH3)

4.4-4.55 broad peak (-CH=CH-)

Zn (CMPT) 2.2H2O 7.20-8.09 3.50 I (2H, -CH2CH2CH3) 10.01

2.60 q (3H, -CH2CH2CH3)

1.39 I (3H, -CH2CH2CH3)

4.4-4.6 broad peak (-CH=CH-)

3-ethyl-5-mercapto-s-triazole (lOg) in hot 40 ml ethanolic solution. Piperidene (1 ml) was also added to the reaction mixture. A light yellow solid started separating out after half an hour of refluxing. The product was filtered and washed with ethanol. The light yellow crystals were obtained on crystallization from ethanol (m.p.,. 177°; yield, 82%).

was washed with water. ethanol and ether and finally dried in vacuo. The yield 'of the complexes varied from 70-80%. The complexes obtained were solid and non-hygroscopic.

4-Cinnamalideneamino-5-mercapto-3-n-propyl-s­triazole (CMPT) was prepared by refluxing a mixture of cinnamaldehyde (8.0 ml) and 4-amino-5-mercapto-3-n-propyl-s-triazole (lOg) for 3 h using 50 ml etha­nol as solvent on water bath . Piperidine (2 ml) was also added to the mixture. The schiff base formed as yellow crystals was crystallized from ethanol (mp 142°; yield, 78%).

Preparation of metal complexes Wann aqueous ethanolic solution of the metal

acetate was treated with ethanolic solution of the schiff bases in I: I and 1:2 molar ratios . The pre­cipitate formed was allowed to settle. The precipitate

Results and discussion The analytical and physical data of the compounds

are given in Table 1. The results of elemental analy­ses of the complexes (Table I) correspond to stoichi­ometries for metal : ligand in I : I and 1 : 2 molar ratios. The IR band at 3300-3150 cm-! in the com­plexes is assigned to the v (OH) vibration of coordi­nated water molecules . A strong band at 1660-1630 cm-! in the spectra of the free ligands assigned to v (-N=CH). is iowered by 30-35 cm-! in the spectra of the complexes. indicating coordination through azomethine nitrogen of schiff bases i3.!4. The ligands. 4-cinnamalideneamino-3-ethyl-5-mercapto-s-triazole (CEMT) and 4-cinnamaliden'earnino-5-mercapto-3-n­propyl-s-triazole (CMPT). show characteristic vSH bands at 2620 and 2660 cm-! respectively. The

616 INDIAN 1 CHEM, SEC. A, JUNE 1999

deprotonation of thiol group and complexation through sulphur is indicated by the absence of bands at 2620 and 2660 em-I in the spectra of complexes_ Metal-sulphur ba.nd '5, '6 formation is further con­fimled by a band at -425-380 em-I in the far IR re­gion . A new band appe~s at :'8 I 0 cm-I, which may be attributed to v (C-S), indicating the coordination through sulphur atom. Formation of metal-nitrogen ' bond '7, '8 is confirmed by presence of IWband in the region 540-490 cm-I. A band in the 1740-1700 cm-I

region is assigned to v (OOCCH) in 1 : I (metal : ligand) complexes. The above findings indicated the bidentate (N and S den or atoms) nature of ligands.

The electronic spectra- of the Co (II) com­plexes are indicated by the absorption bands in the regiQns 7000-10,000 and 18,000-20,000 em-I v I and v, tran s i ti ons , [4T lg (F) ~4T2g (F) (VI) a nd 4TIJ: (F) ~4TI !: (P) ( V3)}, suggest octahe­dral geometryl9, e.g., Co (CIJiI5N4Sh-2H20 for which absorption bands at 9200 and 18700 cm- I for VI and V.l transitions respectively were observed. The mag­netic moment values for the Co (II) complexes at room temperature were found to be in the range of 2.2-2.8 BM, indicating d7 low spin six coordinated complexes, e.g., the magnetic moment values for CO(C I3 HI 3N4S h. 2H 20 and CO(C I3 H 13 N4S) OAc .3H 20 were found to be 2 .73 and 2 .77 BM respectively.

Ni(II) complexes , indicated three absorption bands in the regions 7000- I 3,000, 13,000-19,000 and 20,000-27,000 em-I for v" V2 and V3 transitions CA2!: (F) ~3T21: (F) (VI)' 3A2g (F) ~3Tlg (F) (V2) and 3A 2~ (F) ~3TI !: (P) (V3)]. The electronic spec­trum of Ni (CI3HI3N4S) OAc.3H20 showed three bands at 8800, 16400 and 22500 em-I for v" V2 and V3 transitions respectively indicating octahedral ge­ometr/o. The magnetic moment values for the Ni (II) complexes at room temperature . were found to be in the range21 (2.8-3.5 BM) expected for six­coordinated geometry having cf system, e.g., Ni (C 13H13N4Sh-2H20 showed magnetic moment value of 3.21 BM.

In Cu (II) complexes, a single broad band observed around 18,000 em-I was assigned to the transition 2 Eg ---7 3T2!:, which is characteristic of square planar ge­ometryI9.2 1. Cu (II) complexes exhibited magnetic moment value in the range of 1.70-2.20 BM, e.g., Cu (C I3H1,N4S) OAc.H20 showed magnetic mbment of 1.83 BM.

Zinc (II) complexes are diamagnetic as expected for dlo configuration. Elemental analyses, IR, 'H NMR and thermal studies suggest octahedral geome­try for Zn (II) complexes.

The 'H NMR spectra of CMPT and its 1: 1 and 1:2 zinc complexes were recorded in TFA (Table 2). The signal due to SH proton of ligand appeared at 0 4.7 ppm and disappeared in the spectra of the corre­sponding zinc (II) complexes. The signal at 0 9.9 ppm due to azomethine proton (-N=CH-) is shifted down­field in the spectra of its I : I and 1 : 2 zinc (II) com­plexes and observed at 0 10.24 and 10.32 ppm, re­spectively. This indicates chelation of the ligand through sulphur and nitrogen atoms.

EPR spectrum of Cu (CI3HI3N4S) 2 has also been studied_ The gil and g.l values were found to be 2.2 and 2.037 respectively. The gave was calculated to be 2.08_ The higher value of gil as compared to g.l indi­cates the presence of unpaired electron in d 2 2

X - y

orbital.

Thermal behaviour of the complexes are almost the same, hence only that of Cu (CI3HI3N4S) 2 is being discussed in detail. The anhydrous copper (II) com­plex was stable up to 200°C and then starts decom­posing partially giving metal-triazole at 350°C with a mass loss of two cinnamalidene moieties, 39.98% on the TG curve (theoret. 40.17%). The organic parts decompose completely in the temperature range 375-550°C as indicated by the DTA and TG curve with a mass loss of 83.5% (theoret. 83.45%). The formation of copper sulphide takes place at 550°C. Finally, CuO is obtained as the end-product at 650°C with a mass loss of·13.01 % (theoret. 12.77%).

Acknowledgement One of the authors AK is thankful to the UGC,

New Delhi, for financial assitance_

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317. 2 lha Raj Ranjan & Sircar D K, Jha Usha Chirn Acta Turc, 23

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r

NOTES 617

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8 Ashok K Sen. Gurrneet Singh. Kiran Singh. Raj K Noren, 15 Gajeendragad M R & Aggarwal U. Aust J Chern, 28 (1975) Ram N Handa & Surendra N Dubey, Indian J Chern, 36A 763. (1997) 89l. 16 Suzuki I, Bull Japan chern Soc, 35 (1962) 186, 1449.

9 Ashok K Sen, Gurmeet Singh, Kiran Singh, Ram N Handa. 17 Prabhakaran C P & Patel C C, J inorg nucl Chern, 31 (1969) Surendr!l N Dubey & Philip J Squattrito, Proc Indian Acad 3316. Sci (Chern Sci), 110 (1998) 75 . 18 Gluchinsky P, Mochler G M & Sinn E. Acta Spectro Chirn,

10 Dubey S N & Kaushik Beena, Synth react inorg rnet org (1967) 1287. Chern, 14 (1987) 181. 19 Lever A B P, Inorganic electronic spectroscopy, 2nd Edn

II Vogel A I. A textbook of quantitative inorganic analysis, 4th (Elsevier, Amsterdam) 1989. Edn (Longmans Green. London) 1978. 20 Figgis. B N & Lewis J, Ch.6, Modem coordination chern is-

12 Dhaka K S, Mohan J, Chadha V K & Pujru;i H K, Indian J try (Interscience, New Yark) 1960. Chern, 12 (1974) 288. 21 Weeks J & Flacker J P, Inorg Che~, 7 (1968) 2548.