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Electronic structure of Ni(II) porphyrins and phthalocyanine studied by soft X-ray absorption spectroscopy

Krasnikov, S. A.; Preobrajenski, Alexei LU ; Sergeeva, N. N.; Brzhezinskaya, M. M.; Nesterov, M. A.; Cafolla, A. A.; Senge, M. O. and Vinogradov, A. S. (2007) In Chemical Physics 332(2-3). p.318-324
Abstract
Investigations of chemical bonding and electronic structure features for polycrystalline Ni(II) phthalocyanine (NiPc), Ni(II) tetrabenzoporphyrin (NiTBP), Ni(II) 2,3,7,8,12,13,17,18-octaethylporphyrin (NiOEP), Ni(II) 5,10,15,20-tetraisobutylporphyrin (NiTiBuP), Ni(II) 5,15-diphenylporphyrin (NidPP) and Ni(II) 5,15-diisobutylporphyrin (NidiBuP) have been performed by means of high-resolution soft X-ray absorption spectroscopy. It has been found that the low-lying unoccupied electron states in nickel porphyrins are mainly generated by the NiN4 quasi-molecule: the lowest empty state is the weakly antibonding molecular orbital (MO) of sigma b(1g), symmetry with nearly pure Ni 3d(x2-y2) character, while the next empty state is the e(g) MO,... (More)
Investigations of chemical bonding and electronic structure features for polycrystalline Ni(II) phthalocyanine (NiPc), Ni(II) tetrabenzoporphyrin (NiTBP), Ni(II) 2,3,7,8,12,13,17,18-octaethylporphyrin (NiOEP), Ni(II) 5,10,15,20-tetraisobutylporphyrin (NiTiBuP), Ni(II) 5,15-diphenylporphyrin (NidPP) and Ni(II) 5,15-diisobutylporphyrin (NidiBuP) have been performed by means of high-resolution soft X-ray absorption spectroscopy. It has been found that the low-lying unoccupied electron states in nickel porphyrins are mainly generated by the NiN4 quasi-molecule: the lowest empty state is the weakly antibonding molecular orbital (MO) of sigma b(1g), symmetry with nearly pure Ni 3d(x2-y2) character, while the next empty state is the e(g) MO, which has a hybridized Ni 3d pi-N 2p pi character and reflects pi chemical bonding (pi-back-donation) between nickel and neighbouring nitrogen atoms of the pyrrole rings. The differences observed in the Ni 2p spectra of nickel porphyrins and phthalocyanines indicate a limited usefulness of the NiN4 quasi-molecule and a need for its extension to the whole porphyrin (phthalocyanine) macrocycle. As a result, the differences in the Ni 2p spectra of the complexes and in their electronic structure are associated with a torsion of the opposite pyrrole ring planes (NiOEP, NiTiBuP) and the presence of N atoms in meso positions (NiPc). These conclusions are further confirmed by a comparative analysis of the Ni 2p and N Is absorption spectra for NiPc and NiOEP. (c) 2007 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
x-ray absorption, electronic structure, phthalocyanine, porphyrin, spectroscopy, NEXAFS
in
Chemical Physics
volume
332
issue
2-3
pages
318 - 324
publisher
Elsevier
external identifiers
  • wos:000244549500021
  • scopus:33846839181
ISSN
0301-0104
DOI
10.1016/j.chemphys.2006.12.015
language
English
LU publication?
yes
id
b96471d3-1712-41ba-8a31-690e17a4fe50 (old id 672846)
date added to LUP
2007-12-12 09:28:42
date last changed
2017-08-27 05:24:49
@article{b96471d3-1712-41ba-8a31-690e17a4fe50,
  abstract     = {Investigations of chemical bonding and electronic structure features for polycrystalline Ni(II) phthalocyanine (NiPc), Ni(II) tetrabenzoporphyrin (NiTBP), Ni(II) 2,3,7,8,12,13,17,18-octaethylporphyrin (NiOEP), Ni(II) 5,10,15,20-tetraisobutylporphyrin (NiTiBuP), Ni(II) 5,15-diphenylporphyrin (NidPP) and Ni(II) 5,15-diisobutylporphyrin (NidiBuP) have been performed by means of high-resolution soft X-ray absorption spectroscopy. It has been found that the low-lying unoccupied electron states in nickel porphyrins are mainly generated by the NiN4 quasi-molecule: the lowest empty state is the weakly antibonding molecular orbital (MO) of sigma b(1g), symmetry with nearly pure Ni 3d(x2-y2) character, while the next empty state is the e(g) MO, which has a hybridized Ni 3d pi-N 2p pi character and reflects pi chemical bonding (pi-back-donation) between nickel and neighbouring nitrogen atoms of the pyrrole rings. The differences observed in the Ni 2p spectra of nickel porphyrins and phthalocyanines indicate a limited usefulness of the NiN4 quasi-molecule and a need for its extension to the whole porphyrin (phthalocyanine) macrocycle. As a result, the differences in the Ni 2p spectra of the complexes and in their electronic structure are associated with a torsion of the opposite pyrrole ring planes (NiOEP, NiTiBuP) and the presence of N atoms in meso positions (NiPc). These conclusions are further confirmed by a comparative analysis of the Ni 2p and N Is absorption spectra for NiPc and NiOEP. (c) 2007 Elsevier B.V. All rights reserved.},
  author       = {Krasnikov, S. A. and Preobrajenski, Alexei and Sergeeva, N. N. and Brzhezinskaya, M. M. and Nesterov, M. A. and Cafolla, A. A. and Senge, M. O. and Vinogradov, A. S.},
  issn         = {0301-0104},
  keyword      = {x-ray absorption,electronic structure,phthalocyanine,porphyrin,spectroscopy,NEXAFS},
  language     = {eng},
  number       = {2-3},
  pages        = {318--324},
  publisher    = {Elsevier},
  series       = {Chemical Physics},
  title        = {Electronic structure of Ni(II) porphyrins and phthalocyanine studied by soft X-ray absorption spectroscopy},
  url          = {http://dx.doi.org/10.1016/j.chemphys.2006.12.015},
  volume       = {332},
  year         = {2007},
}