The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods
Shen, Yong LU and Ryde, Ulf LU
(2004)
In Journal of Inorganic Biochemistry
98(5).
p.878-895
- Abstract
- The metallation of tetrapyrroles is believed to proceed via a sitting-atop (SAT) complex, in which some of the pyrrole nitrogen atoms are still protonated and the metal ion resides above the ring plane. No crystal structure of such a complex has been presented, but NMR and extended X-ray absorption fine structure (EXAFS) data has been reported for Cu2+ in acetonitrile. We have used density functional calculations to obtain reasonable models for SAT complexes of porphyrins with Mg2+, Fe2+, and Cu2+. The results show that there are many possible SAT complexes with 1-5 solvent molecules, one or two metal ions, and cis or trans protonation of the porphyrin ring. Many of these have similar energies and their relative stabilities vary with the... (More)
- The metallation of tetrapyrroles is believed to proceed via a sitting-atop (SAT) complex, in which some of the pyrrole nitrogen atoms are still protonated and the metal ion resides above the ring plane. No crystal structure of such a complex has been presented, but NMR and extended X-ray absorption fine structure (EXAFS) data has been reported for Cu2+ in acetonitrile. We have used density functional calculations to obtain reasonable models for SAT complexes of porphyrins with Mg2+, Fe2+, and Cu2+. The results show that there are many possible SAT complexes with 1-5 solvent molecules, one or two metal ions, and cis or trans protonation of the porphyrin ring. Many of these have similar energies and their relative stabilities vary with the metal ion. A complex with two cis pyrrolenine nitrogens atoms and 2-4 solvent molecules coordinated to Cu2+ fits the NMR and EXAFS data best. However, we cannot fully exclude the possibility that what is observed is rather a mixture of a doubly protonated porphyrin and the copper porphyrin. Mg2+ has a lower affinity for porphyrin and stronger affinity for water, so a complex with five water molecules and only one bond to porphyrin seems to be most stable. For Fe2+, a cis structure with two first-sphere water molecules and four interactions to the porphyrin seems to be most likely. (C) 2004 Elsevier Inc. All rights reserved. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/139663
- author
- Shen, Yong
LU
and Ryde, Ulf
LU
- organization
- publishing date
- 2004
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Sitting-atop complex, Haem, Chlorophyll, Porphyrin distortion, Ligand exchange, Density functional theory
- in
- Journal of Inorganic Biochemistry
- volume
- 98
- issue
- 5
- pages
- 878 - 895
- publisher
- Elsevier
- external identifiers
-
- wos:000221678300025
- pmid:15134934
- scopus:2342556417
- pmid:15134934
- ISSN
- 1873-3344
- DOI
- 10.1016/j.jinorgbio.2004.01.004
- language
- English
- LU publication?
- yes
- additional info
- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Theoretical Chemistry (S) (011001039), Inorganic chemistry (ceased) (LUR000010)
- id
- 8a032a0b-47f0-47d4-bd4b-942044f05afd (old id 139663)
- date added to LUP
- 2016-04-01 16:08:22
- date last changed
- 2023-01-24 02:30:27
@article{8a032a0b-47f0-47d4-bd4b-942044f05afd,
abstract = {{The metallation of tetrapyrroles is believed to proceed via a sitting-atop (SAT) complex, in which some of the pyrrole nitrogen atoms are still protonated and the metal ion resides above the ring plane. No crystal structure of such a complex has been presented, but NMR and extended X-ray absorption fine structure (EXAFS) data has been reported for Cu2+ in acetonitrile. We have used density functional calculations to obtain reasonable models for SAT complexes of porphyrins with Mg2+, Fe2+, and Cu2+. The results show that there are many possible SAT complexes with 1-5 solvent molecules, one or two metal ions, and cis or trans protonation of the porphyrin ring. Many of these have similar energies and their relative stabilities vary with the metal ion. A complex with two cis pyrrolenine nitrogens atoms and 2-4 solvent molecules coordinated to Cu2+ fits the NMR and EXAFS data best. However, we cannot fully exclude the possibility that what is observed is rather a mixture of a doubly protonated porphyrin and the copper porphyrin. Mg2+ has a lower affinity for porphyrin and stronger affinity for water, so a complex with five water molecules and only one bond to porphyrin seems to be most stable. For Fe2+, a cis structure with two first-sphere water molecules and four interactions to the porphyrin seems to be most likely. (C) 2004 Elsevier Inc. All rights reserved.}},
author = {{Shen, Yong and Ryde, Ulf}},
issn = {{1873-3344}},
keywords = {{Sitting-atop complex; Haem; Chlorophyll; Porphyrin distortion; Ligand exchange; Density functional theory}},
language = {{eng}},
number = {{5}},
pages = {{878--895}},
publisher = {{Elsevier}},
series = {{Journal of Inorganic Biochemistry}},
title = {{The structure of sitting-atop complexes of metalloporphyrins studied by theoretical methods}},
url = {{https://lup.lub.lu.se/search/files/135492489/66_sat.pdf}},
doi = {{10.1016/j.jinorgbio.2004.01.004}},
volume = {{98}},
year = {{2004}},
}