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Computational studies of peripheral ring twisting in meso ‐ N ‐methyl pyridyl‐substituted porphyrins
Author(s) -
Monaco Regina R.,
Zhao Ming
Publication year - 1993
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560460604
Subject(s) - coplanarity , mndo , chemistry , ring (chemistry) , porphyrin , intercalation (chemistry) , pyridinium , stereochemistry , molecular orbital , computational chemistry , crystallography , molecule , medicinal chemistry , photochemistry , organic chemistry , geometry , mathematics
Semiempirical molecular orbital calculations for the porphyrins tetrakis(4‐ N ‐methyl pyridyl)porphine (H 2 TMpyP‐4) and tetrakis(2‐ N ‐methyl pyridyl)porphine using the MNDO and AM ‐1 Hamiltonians suggest that twisting one or more of the pyridinium rings results, at considerable energy expense, in highly nonplanar macrocycle configurations as the exocyclic ring(s) approach coplanarity. The results imply that the mechanism of intercalation of H 2 TMpyP‐4 into DNA cannot require twisting the exocyclic rings anywhere close to coplanarity with the central porphine core, but involves, instead, the inherent flexibility of DNA itself. © 1993 John Wiley & Sons, Inc.