Porphyrins: What Happens when Nitrogens Are Replaced by Phosphorus? Dr. Aleksey Kuznetsov, Visiting Professor, Department of Chemistry, UFSCar E-mail:

Porphyrins:

What Happens when Nitrogens Are

Replaced by Phosphorus?

Dr. Aleksey Kuznetsov, Visiting Professor,

Department of Chemistry, UFSCar

E-mail: [email protected]

2

ContentsContents

What are porphyrins and why are we interested in them?

Geometric and electronic features of metalloporphyrins

Motivation: what exactly is interesting for us and why?

What happens when all pyrrole N’s are replaced with P’s: NiP example

Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms,

MP(P)4 (M= Sc, Ti, Fe, Ni, Cu, Zn)

Comparative DFT study of the M-L binding energies (M = Sc, Ti, V, Cr, Mn, Fe,

Co, Ni, Cu, and Zn; L = porphine, P, and P4-substituted porphine, P(P)4)

Follow-up work

3

Motivation: What Are Porphyrins and Why Are We Interested in Them?

Motivation: What Are Porphyrins and Why Are We Interested in Them?

Molecular structures of the various iron tetrapyrrole macrocycles. Adapted from M.-S. Liao, J. D. Watts and M.-J. Huang, J. Phys. Chem. A, 2005, 109, 7988-8000.

Metalloporphyrins and Related Compounds

(a) chromophores (b) electron transfer agents

Biological Functions:

O2 transport and storage

light energy collection/transport

solar energy ⇒ chemical energy

conversion (photosynthetic reaction

centers)

electron transfer (cytochromes) etc.

Technological Applications:

catalysis

phototherapy

molecular electronics

artificial photosynthesis

sensitizers for dye-sensitized solar

cells (inexpensive, effective, and

environmentally friendly

chromophores) etc. 4

5

Structures of protoheme (iron protoporphyrin IX), chlorophyll b, and cofactor F430. Adapted from J. A. Shelnutt, X.-Z. Song, J.-A. Ma, S.-J. Jia, W. Jentzen and C. J. Medforth, Chem. Soc. Rev., 1998, 27, 31-41.

6

Geometric and Electronic Features of MetalloporphyrinsGeometric and Electronic Features of Metalloporphyrins

Four pyrrole rings; flat or nearly flat shape

7

Nearly degenerate HOMOs and degenerate LUMOs

8

Under D4h symmetry, tetrapyrrole species can undergo two nearly degenerate

electronic transitions: * HOMO (a1u) → LUMO (eg)

* HOMO-1 (a2u) → LUMO (eg).

The accidental degeneracy (high symmetry!) of these transitions strong mixing

two linear combinations: a higher energy in-phase combination (strongly allowed

Soret B-band) and a lower energy out-of-phase combination (weakly allowed Q-

band).

T. Miyahara, H. Nakatsuji, J. Hasegawa, A. Osuka, N. Aratani and A. Tsuda, J. Chem. Phys., 2002, 117, 11196-11207

9

Aromaticity

Representations of -electron delocalization for a porphyrin core. Adapted from Y. Zhu and R. B. Silverman, J. Org. Chem., 2007, 72, 233-239.

Computed NICS values for free porphyrin base (left), its dianion (center), and the Mg complex (right). The dashed lines indicate the delocalized systems. Adapted from M. K. Cyrański, T. M. Krygowski, M. Wisiorowski, N. J. R. v. E. Hommes and P. v. R. Schleyer, Angew. Chem. Int. Ed., 1998, 37, 177-180.

10

Conformational Flexibility of Porphyrins and Their Derivatives

Heme distortions. Left: out-of-plane distortions (red) are doming (dom) A2u, ruffling (ruf) B1u, saddling (sad) B2u, waving (wax, way) Egx,y and propellering (pro) A1u. Right: positive (red) and negative (blue) in-plane distortions involving meso-stretching (mst) B2g, N-pyrrole stretching (nst) B1g, pyrrole translation (trx, try) Eux,y, breathing (bre) A1g, and pyrrole rotation (rot) A2g. The reference D4h structure is shown in black. Adapted from D. E. Bikiel, F. Forti, L. Boechi, M. Nardini, F. J. Luque, M. A. Marti and D. A. Estrin, J. Phys. Chem. B, 2010, 114, 8536–8543.

11

Sterically demanding/electron-withdrawing or donating

substituents in - or meso-positions; annulation

Central metaloxidation

Alteration of the conjugated system

Replacement of N(s) with

heteroatom(s)

Macrocycle “strapping” via covalent linkage

Degree of reduction Cation-

radical formation

Axial ligands

N-substitution

Factors capable of affecting the porphyrin macrocycle geometry (distortions from planarity) and electronic structure/delocalization

(Senge, M. O. Chem. Commun. 2006, 243)

12

Tuning the size, shape, charge, and properties of porphyrins by

replacing pyrrole nitrogen(s) with other elementsreplacing pyrrole nitrogen(s) with other elements.

Numerous efforts devoted to the modification of the porphyrin core

with C, Si, or O-Se atoms.

Replacement of just 1 or 2 pyrrole nitrogens by P studied in several

porphyrins and their derivatives.

No studies of free porphyrins or their metal complexes with all

4 pyrrole nitrogens replaced with phosphorus atoms (P4-

porphyrins, or P(P)4) have been performed.

Motivation: What Is Interesting for Us? Motivation: What Is Interesting for Us?

13

D. Delaere, M.T. Nguyen, A density functional study of the ground state electronic

structure of phosphorus-porphyrins, Chem. Phys. Lett. 376 (2003) 329-337.

Y. Matano, T. Nakabuchi, H. Imahori, Synthesis, structures, and aromaticity of

phosphole-containing porphyrins and their metal complexes, Pure Appl. Chem. 82

(2010) 583-593.

Y. Matano, H. Imahori, Phosphole-containing calixpyrroles, calixphyrins, and

porphyrins: synthesis and coordination chemistry, Acc. Chem. Res. 42 (2009) 1193-

1204.

T. Nakabuchi, Y. Matano, H. Imahori, Remarkable effects of P-perfluorophenyl

group on the synthesis of core-modified phosphaporphyrinoids and

phosphadithiasapphyrin, Org. Lett. 12 (2010) 1112-1115.

T. Nakabuchi, M. Nakashima, S. Fujishige, H. Nakano, Y. Matano, H. Imahori,

Synthesis and reactions of phosphaporphyrins: reconstruction of -skeleton triggered

by oxygenation of a core phosphorus atom, J. Org. Chem. 75 (2010) 375-389.

Y. Matano, M. Nakashima, T. Nakabuchi, H. Imahori, S. Fujishige, H. Nakano,

Monophosphaporphyrins: oxidative -extension at the peripherally fused carbocycle

of the phosphaporphyrin ring, Org. Lett. 10 (2008) 553-556.

14

Y. Matano, T. Nakabuchi, S. Fujishige, H. Nakano, H. Imahori, Redox-coupled

complexation of 23-phospha-21-thiaporphyrin with group 10 metals: a convenient

access to stable core-modified isophorin-metal complexes, J. Am. Chem. Soc. 130

(2008) 16446-16447.

Y. Matano, T. Nakabuchi, T. Miyajima, H. Imahori, H. Nakano, Synthesis of

phosphorus-containing hybrid porphyrin, Org. Lett. 8 (2006) 5713-5716.

Y. Matano, T. Miyajima, N. Ochi, T. Nakabuchi, M. Shiro, Y. Nakao, S. Sakaki, H.

Imahori, Syntheses, structures, and coordination chemistry of phosphole-containing

hybrid calixphyrins: promising macrocyclic P,N2,X-mixed donor ligands for

designing reactive transition-metal complexes, J. Am. Chem. Soc. 130 (2008) 990-

1002.

Y. Matano, T. Miyajima, T. Nakabuchi, H. Imahori, N. Ochi, S. Sakaki, Phosphorus-

containing hybrid calixphyrins: promising mixed-donor ligands for visible and

efficient palladium catalysts, J. Am. Chem. Soc. 128 (2006) 11760-11761.

N. Ochi, Y. Nakao, H. Sato, Y. Matano, H. Imahori, S. Sakaki, New palladium(II)

complex of P,S-containing hybrid calixphyrin. Theoretical study of electronic

structure and reactivity for oxidative addition, J. Am. Chem. Soc. 131 (2009) 10955–

10963.

15

Design of new compounds with potential applications in:

Catalysis

Alternative Energetics (Solar Energy Conversion)

Electronics

Optics

Medicine?

Motivation: Why Is It Interesting? Motivation: Why Is It Interesting?

16

Questions:

(i) Structures of P4-porphyrins and their metal complexes?

(ii) Charge distribution in P4-porphyrins?

(iii) Stabilities of metallo-P4-porphyrins?

(iv) Substituents effects?

(v) Annulation effects?

(vi) Comparison with tetrapyrroles?

Motivation: What Is Interesting for Us-2?

Motivation: What Is Interesting for Us-2?

17

18

What Happens when ALL Pyrrole N’s Replaced with P’s?What Happens when ALL Pyrrole N’s Replaced with P’s?

∡Cm-Ni-C

m', o:

146.5

∡Cm-Ni-C

m', o:

167.50.79

-0.71

-0.11

0.26

Barbee, J.; Kuznetsov, A. E. Comp. Theoret. Chem. 981, 73, 2012.

19

20

Questions addressed in the research:

(i) What structures will P(P)4 compound and its metal complexes adopt?

(ii) How will be charges distributed in the metal-P(P)4 compounds compared to

tetrapyrrole species?

(iii) How will the complete replacement of nitrogens affect the ground spin state?

(iv) How different will be the MP(P)4 electronic properties compared to their MP

counterparts?

21

Labeling scheme used in the study

Structural FeaturesStructural Features

22

ScIIP(P)4 FeIIP(P)4

NiIIP(P)4ZnIIP(P)4

23

Important Points:

All the neutral and cationic MP(P)4 species possess general prominent structural

feature: pronounced bowl-like shape, compared to generally planar or slightly

distorted from planar shapes of the tetrapyrrole counterparts.

The only bond distance which changes significantly from Sc to Zn is the M-P

bond distance.

The P5-P4-P3-M dihedral angle can be taken as the measure of the bowl-like

distortion in the MP(P)4 compounds.

P5-P4-P3-M: ca. 46-48o (Sc) → -4o (Zn).

24

The changes in the M-P bond distances and in the P5-P4-P3-M dihedral angles are

generally in line with electronegativies of the transition metals under consideration

(Sc: 1.36; Ti: 1.54; Fe: 1.83; Ni: 1.91; Cu: 1.90; Zn: 1.65) and thus with their

polarization abilities, but not with their cationic radii.

The cationic MP(P)4 species have structures very similar to the neutral counterparts.

The general structural feature of the MP(P)4 species can be explained by the

pyramidalization of the P-atom bonds.

25

Summary of the structural differences between MP(P)4 and MP:

(i) M-P bond distances: longer than M-N bond distances by ca. 0.16 Å.

(ii) P-Cbond distances: generally longer than N-Cbond distances by ca. 0.4 Å.

(iii) C-P-C bond angles: generally smaller than C-N-C bond angles by ca. 10-15o.

(iv) In MP Cm-M-Cm' angles differ from 180o only in ScIIP and ScIIIP and very

insignificantly in TiIIP, whereas in all MP(P)4 these angles differ from 180o very

strongly, by ca. 35 – 60o.

(v) P5-P4-P3-M dihedral angles: vary broadly, but N5-N4-N3-M dihedral angles are

different from 0o only for ScIIP, ScIIIP, and TiIIP.

(vi) C-C bond distances: generally not influenced by N-replacement with P-atoms.

26

Species NBO charges, e

M P C C Cm H

ScIIP(P)4

(C1, 2A)

0.79 0.42,

0.50

-0.35,

-0.39

-0.23 -0.18

0.24

TiIIP(P)4

(C2, 3B)

0.36 0.54

-0.37

-0.22 -0.16

0.23

FeIIP(P)4

(C1, 3A)

0.20 0.55,

0.62

-0.37,

-0.38

-0.22 -0.17 0.24

NiIIP(P)4

(C2, 1A)

-0.19 0.68

-0.38

-0.22

-0.17

0.24

CuIIP(P)4

(C1, 2A)

0.24 0.54

-0.37 -0.22 -0.17 0.24

ZnIIP(P)4

(C2, 1A)

0.61 0.45

-0.35 -0.22

-0.17 0.24

Species NBO charges, e

M N C C Cm H

ScIIP

(C2, 2B)

1.81 -0.71,

-0.73

0.15,

0.16

-0.24 -0.26

0.24

TiIIP

(D2h, 3B2g)

1.48 -0.68

0.16

-0.25 -0.25

0.24

FeIIP

(D4h, 3B1g)

1.18 -0.60,

-0.62

0.16 -0.24 -0.23 0.24

NiIIP

(D2d, 1A1)

0.93 -0.56

0.16 -0.24

-0.23

0.24

CuIIP

(D4h, 2B1g)

1.11 -0.61 0.16 -0.24 -0.23 0.24

ZnIIP

(D4h, 1A1g)

1.28 -0.65

0.17 -0.25

-0.23 0.24

Electronic Features: ChargesElectronic Features: ChargesTable 1. Gas-phase calculated NBO charges for the neutral MP(P)4 species, M = Sc, Ti, Fe, Ni, Cu, Zn.

Table 2. Gas-phase calculated NBO charges for the neutral MP species, M = Sc, Ti, Fe, Ni, Cu, Zn.

27

Summary of electronic features:

Positive charges on metals in MP(P)4: generally noticeably lower than charges on

metals in MP; explanation: nitrogen and phosphorus electronegativity differences

(3.04 vs. 2.19).

The unusually small Ni2+ radius, 0.69 Å,

its unusually high polarization ability

very significant charge transfer from the phosphorus centers to Ni2+

noticeable negative charge on the Ni center, -0.19e.

28

The positive charge buildup on the P-atoms, opposite to the negative charge on

nitrogens in the MP tetrapyrrole counterparts of MP(P)4,

different reactivity patterns of the MP(P)4 compounds and their potential novel

applications.

The significant negative charges accumulated on the C-atoms in MP(P)4 compared

to the positive charge in MP: clearly explained by the lower P electronegativity

(2.19) compared to C (2.55); N electronegativity, 3.04, is significantly higher than

P.

29

(HOMO/LUMO)a // Optical gapb

Sc Ti Fe Ni Cu Zn

MIIP(P)4

: 1.45

: 1.97//

2.48

: 1.35

: 1.95//

2.34

: 2.59

: 1.74//

2.59

2.57//

3.04

: 1.38

: 2.67//

2.77

1.97//

2.91

MIIP

: 1.30

: 2.66//

2.85

: 1.32

: 2.74//

3.08

: 3.12

: 2.37//

3.45

3.13//

3.52

: 3.08

: 3.11//

3.52

3.07//

3.55

Table 3. Gas-phase calculated HOMO/LUMO gaps (eV) and optical gaps (eV) for the neutral MP(P)4 and MP species, M = Sc, Ti, Fe, Ni, Cu, Zn.

Electronic Features: Orbital GapsElectronic Features: Orbital Gaps

30

For ScIIP(P)4 and TiIIP(P)4 IPv/IPad values higher

than for ScIIP and TiIIP; starting from FeIIP IPv/IPad values higher for the MP species than for their MP(P)4 counterparts.

Electronic Features:

Ionization Potentials

Electronic Features:

Ionization Potentials

31

EAv/EAad values for MP(P)4 noticeably higher

than for their MP counterparts, due to significant stabilization of the MP(P)4 LUMOs compared to

their MP counterparts.

Electronic Features: Electron

Affinities

Electronic Features: Electron

Affinities

32

(i) The HOMOs of MP(P)4 have noticeable M contributions (exceptions: ZnIIP(P)4,

ScIIIP(P)4, TiIVP(P)4, and FeIIIP(P)4).

(ii) The LUMOs of MIIP(P)4 in general have compositions qualitatively similar to the

LUMOs of the MIIP counterparts, except ScIIP and FeIIP.

(iii) The HOMOs of ScIIP(P)4 and TiIIP(P)4 have compositions similar to the HOMOs

of their MIIP counterparts.

Electronic Features: Compositions of Frontier OrbitalsElectronic Features: Compositions of Frontier Orbitals

33

(iv) The HOMOs of FeIIP(P)4 (-HOMO), NiIIP(P)4, CuIIP(P)4 (-HOMO), and

ZnIIP(P)4 have significant contributions from the metal and phosphorus atoms

compared to zero contributions of the metal and nitrogen atoms in the HOMOs of their

MIIP counterparts.

(v) There are noticeable composition differences for the HOMOs of the cationic

MP(P)4 species compared to their MP counterparts: significant contributions of the

phosphorus atoms compared with zero contributions of the nitrogen atoms in the MP

species.

34

Conclusions and PerspectivesConclusions and Perspectives

(i) Complete substitution of the pyrrole nitrogens by phosphorus does not change the

calculated ground spin states and ordering of spin states.

(ii) All MP(P)4 possess a pronounced bowl-like shape. The cationic species have

structures very similar to their neutral counterparts.

(iii) The positive NBO charges on the metals in MP(P)4 are generally noticeably lower

than charges on the metals in MP. The significant positive charge is calculated to

accumulate on the P-atoms.

(iv) Both the calculated HOMO/LUMO gaps and optical gaps for the MP(P)4 species

are noticeably smaller than for their MP counterparts

35

(i) How will counterions affect structures and properties of cationic MP(P)4 species?

(ii) How will annulation with different rings affect MP(P)4 species?

(iii) How strongly can MP(P)4 species interact with each other or with other (small)

molecules?

Conclusions and PerspectivesConclusions and Perspectives

36

The results of this study were presented as online e-presentation at the Virtual Conference on Computational Chemistry VCCC-2014. Mauritius, 1-31 August, 2014, and selected as one of three best e-presentations.

37

Follow-up study:

Comparative DFT study of the M-L binding energies (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn; L = porphine, P, and P4-substituted

porphine, P(P)4). Aleksey E. Kuznetsov

38Figure 1. Gas-phase calculated binding energies, Ebind (eV), for the MP(P)4 (red signs) and MP (green signs) compounds in their ground states. ZPE energies not included.

39

I. Computational study on how the modification of the ligand, from P(P)42- to Pc(P)4

2-,

Pc = phthalocyanine, would affect structural and electronic properties (HOMO/LUMO

gaps, optical gaps, ionization potentials, electron affinities) and M-Ligand binding

energies of MP(P)4 derivatives for the metals of the first transition row (Sc, Ti, V, Cr,

Mn, Fe, Co, Ni, Cu, Zn).

More Follow-Up WorkMore Follow-Up Work

40

II. Computational study of effects of counterions (Cl-, N3-, CH3COO-) and modification

of the ligand (from P(P)42- to P(P)4(C6H4)4

2-, which is actually annulation of P(P)42- with

four benzene rings) on structural and electronic properties (HOMO/LUMO gaps,

optical gaps, ionization potentials, electron affinities) and M-Ligand binding energies

of metallotetraphosphaporphyrin derivatives.


41

III. Preliminary computational studies of stacks, or dimers, of neutral MP(P)4 species

are currently in progress. The calculated binding energies of these dimers are usually

about several kcal/mol. It is of high interest to understand why the coordination type

shown is preferred over other types of bonding.

Calculated gas-phase structures of the neutral dimers (stacks) of MP(P)4, M = (a) Sc (C1, 3A), (b) Ni (C1, 1A), and (c) Zn (C1, 1A).


42

IV. Computational studies of complexes C60-MP(P)4, M = Zn, Ni, similar to structure

shown below.


Junzi Liu, Yong Zhang, and Wenjian Liu, J. Chem. Theory Comput., 2014, 10 (6), pp 2436–2448

43

V. Computational studies of O2 and N2 activation by MP(P)4 species.


Victoria E. J. Berryman, Matthew G. Baker, and Russell J. Boyd, J. Phys. Chem. A 2014, 118, 4565−4574

44

Thank You for Your Attention!!!Thank You for Your Attention!!!

Questions?

45

Computational DetailsComputational Details

The studies performed with the Gaussian 09 package.

All the calculations done using the split-valence 6-31G* basis set and the hybrid

B3LYP functional. This approach proved to give geometries in good agreement

with experiments and shown to produce the ordering of spin states of metallo-

porphyrin complexes reasonably well. The energy differences (in kcal/mol) obtained

with the zero-point corrections given in parentheses.

The MP(P)4 species studied both in the gas phase and with implicit solvent effects,

using the self-consistent reaction field IEF-PCM method (the UFF default model,

with the electrostatic scaling factor = 1.0), with H2O, C6H5CH3, and CH3CN as

solvents (dielectric constants ε = 78.3553, 2.2706, and 35.688, respectively).

For further demonstration of the reliability of the B3LYP/6-31G* approach, global

minimum search calculations on MP(P)4 repeated using two GGA functionals, PBE

and PW91, in the gas phase, with the 6-31G* basis set.

46

Computational DetailsComputational Details

Time-dependent DFT calculations of the optical gaps performed using the TD-

B3LYP approach: with the gas-phase B3LYP/6-31G* optimized geometries, the 6-

31G* basis set, and number of the states chosen to be 30.

The vertical ionization potentials (IPs) and electron affinities (EAs), IPsv/EAsv,

obtained in single-point calculations from the energies of systems with N and N±1

electrons; the latter calculated using geometries of the N-electron systems. The

adiabatic IPs and EAs (IPad/EAad) obtained from the energies of the systems with N

and N±1 electrons, the latter calculated using optimized geometries of the N±1

electron species.

For the charge analysis, the Natural Bond Orbital (NBO) analysis scheme used.

For HOMO and LUMO compositions: total densities of states (DOS) and fragment

densities of states (projected DOS, PDOS) calculated. For the fragment densities of

states calculations, the MP(P)4 and MP species ‘split’ into the following fragments:

M, P/N, and (C+H) remainder of the ligands.

47

Species Bond length, Å, and angles, deg.

M-P P-C C-C C-C C-Cm Cm-M-Cm' C-P-C P-M-P P5-P4-P3-M

MIIP(P)4

ScIIP(P)4

(C1, 2A)

2.43,

2.53

1.77,

1.80

1.43,

1.45

1.37,

1.39

1.40,

1.42

119.36

92.39,

95.39

107.76,

137.97

46.42

TiIIP(P)4

(C2, 3B)

2.32

1.78

1.44

1.38

1.41

123.24 92.31

130.73

32.97

FeIIP(P)4

(C2, 3B)

2.15,

2.20

1.78,

1.79

1.43,

1.45

1.37,

1.39

1.40,

1.42

141.79 93.01,

93.34

166.03,

169.73

9.74

NiIIP(P)4

(C2, 1A)

2.12

1.78

1.44

1.38

1.41

146.47

92.94

174.13 4.15

CuIIP(P)4

(C2, 2A)

2.24 1.79 1.44 1.38 1.41 144.94 91.55 178.18 -1.29

ZnIIP(P)4

(C2, 1A)

2.37 1.79 1.45 1.37 1.41 144.55 91.39 173.83 -4.36

Table 1. Gas-phase calculated (B3LYP/6-31G* level of theory) principal structural parameters of the neutral MIIP(P)4, M = Sc, Ti, Fe, Ni, Cu, Zn, and cationic MIII/IVP(P)4 species, M = ScIII,

TiIV, FeIII.

48

ZnIIP(P)4

(C2, 1A)

2.37 1.79 1.45 1.37 1.41 144.55 91.39 173.83 -4.36

MIII/IVP(P)4

ScIIIP(P)4

(C1, 1A)

2.43,

2.55,

2.56

1.77,

1.79

1.44,

1.45

1.38 1.40,

1.41

119.26

92.32,

95.00

105.18,

136.25

47.69

TiIVP(P)4

(C1, 3A)

2.35,

2.36

1.79

1.43

1.39

1.40,

1.41

122.03,

122.04

93.12,

93.34

124.53,

126.02

36.72

FeIIIP(P)4

(C2, 4A)

2.19

1.79 1.43 1.39 1.41 139.50,

139.51

92.80,

92.81

165.20,

165.24

10.38

Table 1. Gas-phase calculated (B3LYP/6-31G* level of theory) principal structural parameters of the neutral MIIP(P)4, M = Sc, Ti, Fe, Ni, Cu, Zn, and cationic MIII/IVP(P)4 species, M = ScIII,

TiIV, FeIII (continuation).

49

Ground state (symmetry, spin)/

Energy gap between the ground state and the next spin state,E0 (E)

Sc Ti Fe Ni Cu Zn

MIIP(P)4

C2, 2B/

22.1 (21.5)

C2, 3B/

8.2 (8.5)

C2, 3B/

16.6 (15.2)

C2, 1A/

24.7 (18.1)

C2, 2A/

32.7 (30.7)

C2, 1A/

17.6 (16.9)

MIII/IVP(P)4

C1, 1A/

20.8 (18.8)

C1, 3A/

4.3 (3.3)

C2, 4A/

12.0 (12.4)

Table 1. Ground state (symmetry, spin) and energy gap between the ground state and the next

spin state for the neutral MIIP(P)4, M = Sc, Ti, Fe, Ni, Cu, Zn, and cationic MIII/IVP(P)4 species,

M = ScIII, TiIV, FeIII (gas-phase calculated, B3LYP/6-31G* level of theory).

Ground States and Low-Lying StatesGround States and Low-Lying States

50


Energy gap with the next lower-lying spin state,E0 (E)

Sc Ti Fe Ni Cu Zn

MIIP

C2, 2B/

35.6 (33.1)

D2h, 3B2g/

2.8 (2.4)

D4h, 3B1g/

8.1 (6.8)

D2d, 1A1/

8.0 (7.0)

D4h, 2B1g/

42.7 (39.2)

D4h, 1A1g/

42.1 (38.4)

MIII/IVP

C1, 1A/

37.5 (35.2)

C1, 3A/

3.2 (4.1)

D4h, 4B3g/

13.5 (12.1)


spin state for the neutral MIIP, M = Sc, Ti, Fe, Ni, Cu, Zn, and cationic MIII/IVP species, M = ScIII,

TiIV, FeIII (gas-phase calculated, B3LYP/6-31G* level of theory).

Important: the complete substitution of the pyrrole nitrogens by phosphorus atoms does not change the calculated ground spin state of the compound and also generally does not change the ordering of spin states. This situation is retained for both neutral and cationic species.

51


Energy gap between the ground state and the next spin state, E0 (E)

Sc Ti Fe Ni Cu Zn

MIIP(P)4

C2, 2B/

22.1 (21.5)//

18.4 (17.8)//

18.4 (18.0)

C2, 3B/

8.2 (8.5)//

5.6 (5.4)//

5.4 (5.3)

C2, 3B/

16.6 (15.2)//

16.7 (16.9)//

16.6 (16.0)

C2, 1A/

24.7 (18.1)//

23.9 (22.7)//

25.2 (24.7)

C2, 2A/

32.7 (30.7)//

33.3 (30.4)//

33.2 (30.4)

C2, 1A/

17.6 (16.9)//

14.0 (13.4)//

14.0 (13.5)



M = ScIII, TiIV, FeIII (gas-phase, [B3LYP/6-31G*]//[PW91/6-31G*]//[PBE/6-31G*] levels of

theory).

Ground States and Low-Lying States:

Effects of Other Functionals

Ground States and Low-Lying States:

Effects of Other Functionals

52

C2, 2B/

22.1 (21.5)//

18.4 (17.8)//

18.4 (18.0)

C2, 3B/

8.2 (8.5)//

5.6 (5.4)//

5.4 (5.3)

C2, 3B/

16.6 (15.2)//

16.7 (16.9)//

16.6 (16.0)

C2, 1A/

24.7 (18.1)//

23.9 (22.7)//

25.2 (24.7)

C2, 2A/

32.7 (30.7)//

33.3 (30.4)//

33.2 (30.4)

C2, 1A/

17.6 (16.9)//

14.0 (13.4)//

14.0 (13.5)

MIII/IVP(P)4

C1, 1A/

20.8 (18.8)//

15.1 (14.5)//

15.1 (14.5)

C1, 3A/

4.3 (3.3)//

3.1 (2.6)//

3.3 (2.7)

C2, 4A/

12.0 (12.4)//

5.3 (5.1)//

5.6 (5.5)

- - -



M = ScIII, TiIV, FeIII (gas-phase, [B3LYP/6-31G*]//[PW91/6-31G*]//[PBE/6-31G*] levels of

theory) (continuation).

Important:

(i) Other density functionals did not influence the ground spin state of both neutral and cationic MP(P)4 compounds and did not affect significantly the energy gaps

between the ground state and the next low-lying spin state.

(ii) All the three implicit solvents used did not change noticeably the relative energies of MP(P)4 spin states or isomers. Thus, it was justified to consider the gas-phase

calculated neutral and cationic species in the discussion.

53

Contributions of the specific atoms in %a

M//P(N)//C+H

Orbital Sc Ti Fe Ni Cu Zn

MIIP(P)4

HOMO : 14//0//78

: 0//53//42

: 26//0//72

: 0//51//45

: 14//33//52

: 32//0//58

21//31//48 : 14//36//50

: 0//0//98

0//48//47

LUMO : 12//15//73

: 12//0//79

: 25//0//69

: 11//0//80

: 0//36//70

: 16//0//78

0//23//72 : 0//20//78

: 0//17//81

0//16//82

MIII/IVP(P)4

HOMO 0//53//43

: 0//50//47

: 0//0//98

: 0//47//47

: 0//36//57

- - -

LUMO 16//0//78

: 21//0//74

: 0//48//49

: 0//22//76

: 30//0//67

- - -

Table 9. Contributions of the specific atoms in % to the HOMO and LUMO of the neutral MP(P)4 and MP species, M = Sc, Ti, Fe, Ni, Cu, Zn, at the B3LYP/6-31G* level of theory.

54

LUMO 16//0//78

: 21//0//74

: 0//48//49

: 0//22//76

: 30//0//67

- - -

MIIP

HOMO : 13//0//81

: 0//21//76

: 36//0//62

: 0//23//76

: 0//0//100

: 74//0//24

0//0//100 : 0//0//100

: 0//0//100

0//0//100

LUMO : 11//0//83

: 11//0//82

: 17//0//78

: 10//0//83

: 0//12//85

: 0//0//83

0//12//86 : 0//12//88

: 0//12//87

0//12//88

MIII/IVP

HOMO 0//0//100

: 0//0//97

: 0//0//95

: 0//0//100

: 0//0//100

- - -

LUMO 15//0//79

: 34//0//64

: 0//14//85

: 54//35//10

: 105//0//0

- - -

Table 9. Contributions of the specific atoms in % to the HOMO and LUMO of the neutral MP(P)4 and MP species, M = Sc, Ti, Fe, Ni, Cu, Zn, at the B3LYP/6-31G* level of theory.

55

Figure 2. Relative stabilities of spin states of the MP(P)4 (a) and MP (b) species (in eV). The ground state is set to 0 eV. Spin multiplicity 2S+1 is indicated in the chart.

56

Figure 2. Relative stabilities of spin states of the MP(P)4 (a) and MP (b) species (in eV). The ground state is set to 0 eV. Spin multiplicity 2S+1 is indicated in the chart.

57

Examples of sandwich complexes of transition metals (TM) and organic

molecules (metallocenes):

Os Cr Mn

2. Novel Sandwich Compounds2. Novel Sandwich Compounds

Motivation: What Are Sandwich Compounds and Why Are They Interesting?

Motivation: What Are Sandwich Compounds and Why Are They Interesting?

58

(i) Design of 1D-complexes (wires) with more than 1 metal atom between

two (aromatic) ligands.

(ii) Design of complexes with metal clusters containing both organic and

inorganic ligands.

(iii)What new properties sandwich complexes with metal clusters could have?

(iv) Possibilities to design 2D/3D-complexes containing metal clusters, and

their potential applications.

Motivation: What Specifically Is Interesting for Us?

Motivation: What Specifically Is Interesting for Us?

59

Multiple metal centers in a single molecular unit

cooperative effects

molecular electronics

catalysis

magnetic and optical materials

polymers

medicine

nanodevices, etc.

Potentially useful properties:

•facile redox behavior

•easy derivatization

•electron conductivity

60

Theoretical design of sandwich complexes containing TM clusters and

various organic and inorganic ligands:

(i) What would be the largest n at which a sandwiched TMn cluster is still

stable?

(ii) Complexes with both the same and different (mixed) TMn clusters?

(iii) Multiple-decker systems containing several layers of TMn clusters and

ligands? What would be the maximum number of metal cluster layers/

ligand layers (‘decks’) at which a system is still stable?

Research TasksResearch Tasks

61

Summary of the Preliminary WorkSummary of the Preliminary Work

Theoretical design of a series of sandwich complexes [M3L2(CO)3]q (M = Cu, Ag, Au;

L = C7H7, P5, P6, As5, As6; q = 3+, 1-, …).

Inspired by the works of Peng Jin, Fengyu Li, and Zhongfang Chen (Theoretical

Design of Novel Trinuclear Sandwich Complexes with Central M3 Triangles (M =

Ni, Pd, Pt), J. Phys. Chem. A 2011, 115, 2402–2408) and Jesús Muñiz, Enrique

Sansores, and Roger Castillo (Theoretical study on the electronic structure and

reactivity of the series of compounds [Au3X3M2], with X = H, F, Cl, Br, I and M =

Li, Na, K, Rb, Cs: the quest for novel catalytic nano-materials, Theor. Chem. Acc.

2013, 132, 1373.

62

Jin, P.; Li, F.; Chen, Z. J. Phys. Chem. A 2011, 115, 2402.

63

Collaborative projects at the Department of Chemistry at UFSCar:

I. Investigation of Ru-diphosphine/pyrimidine complexes possessing potential

anti-Mycobacterium tuberculosis activity and cytotoxicity; collaboration with the

research group of Professor Alzir Batista.

One publication within this joint project was submitted to Journal of the Brazilian

Chemical Society:

Anti-Mycobacterium tuberculosis activity and cytotoxicity of ruthenium diphosphine/

pyrimidine-2-thiolate complexes, Benedicto A. V. Lima, Rodrigo S. Correa, Angelica

E. Graminha, Aleksey Kusnetsov, Javier Ellena, Fernando R. Pavan, Clarice Q.F.

Leite, Alzir A. Batista.

Collaborative WorkCollaborative Work

64

65

Another publication within this joint project is currently in preparation.3 isomeric complexes with different orientations of Cl and CO are studied:tc-[RuCl(CO)(dppb)(bipy)]PF6 (1) cc-[RuCl(CO)(dppb)(bipy)]PF6 (2) ct-[RuCl(CO)(dppb)(bipy)]PF6 (3)

Subject of computational study: relative energies of complexes, charges, HOMO compositions. B3LYP with different basis sets is used.

Ru

Cl

CO

P

PN

N

66

II. Investigation of electrochemically reduced graphene oxide; collaboration with

the research group of Professor Ernesto Pereira.

Currently, the computational studies of the graphene sheet model are performed with

the goal to show that the corrugated graphene is more stable than the flat graphene.

C42 model is used, with the PBEPBE/3-21+G* theoretical approach.

67

III. Investigation of Au nanoparticles passivated with (X-C4H9)2 ligands, X = S,

Se, Te; collaboration with the research group of Professor Emerson Camargo.

The goal of the project: to clarify the reason of nonlinear dependence of ligand

oxidation percentage on the X nature.

The DFT approach with different functionals and different basis sets, and with

different nanoparticle models is being used.

68Au20(Se2C4H18)2, 1A;

BE 32.8 kcal/mol

Au20(Te2C4H18)2, 1A; BE 43.0 kcal/mol

Au20(S2C4H18)2, 1A; BE 27.9 kcal/mol

69

The outside collaborative project covers the topic of assignment of the ET mechanism

in cytochrome bc1:

On the use of properly calibrated 1D tunneling models in biological electron

transfer: resolution of the Hopfield-Dutton-Gray paradox and assignment of the

ET mechanism in cytochrome bc1. Aleksey E. Kuznetsov, Judith C. Hempel, Shahar

Keinan, William A. Cramer, and David N. Beratan. Manuscript in preparation;

collaboration with the research group of Professor David N. Beratan (Duke

University, USA) and with Dr. Shahar Keinan (University of North Carolina, Chapel

Hill, USA).

70

Also, in 2014 I participated in the joint project grant application under Chamada de

Propostas do Programa para Pesquisas em eScience provided to FAPESP

(rejected), and submitted my own proposal for the financial support offered by the

CNPq, Call ‘CHAMADA UNIVERSAL MCTI/CNPQ Nº 14/2014’, “Porphyrin

Derivatives with All Pyrrole Nitrogens Replaced with Phosphorus Atoms: New

Chemistry and New Potential Applications“ (rejected).

Last semester I was teaching the graduate course “Introduction to Computational

Chemistry”, and this semester I will be teaching the graduate course “Quantum

Chemistry: Theoretical Basis and Practical Applications”.

Documents

Porphyrins: What Happens when Nitrogens Are Replaced by Phosphorus? Dr. Aleksey Kuznetsov, Visiting Professor, Department of Chemistry, UFSCar E-mail: