Theoretical Analysis of Core Size Effect in Metalloporphyrins

Abstract

Density functional theory has been applied to a series of unsubstituted planar metalloporphyrins (MPs) to elucidate how geometry and frequencies correlate with the metal-nitrogen distance, referred to as the core size. Different transition metals can invoke expansion or contraction of the porphyrin core due to electronic effects resulting from the amount of d-electron pairing as well as occupancy of the d(x(2)(-y(2))) orbital. A full vibrational analysis consisting of all in-plane and out-of-plane frequencies was carried out, and the resulting modes were plotted against core size for a linear analysis and grouped within symmetry blocks. The modes were separated according to planarity, and all modes with a large slope and best fit greater than 0.8 were considered sensitive to metal-nitrogen distances. All planar skeletal modes above 1450 cm(-1), including the pyrolle ring deformations, are found to be core-size sensitive. The most significant out-of-plane modes sensitive to core size are gamma(8) and gamma(9), which are infrared active and grouped within the A(2u) symmetry block. The present work also opens possible quantitative applications for the correlation of spectroscopic properties of MPs and heme proteins with actual structural parameters.

Nanopatterning of Surfaces with Monometallic and Heterobimetallic 1D Coordination Polymers: A Molecular Tectonics Approach at the Solid/Liquid Interface

“…only 0.01 kcal mol -1 higher) to the C 1 geometry ( Figure S6). 29 Such ruffled geometry adopted by the porphyrin core in tecton T-Ni is in agreement with already reported data for Ni(II)-porphyrin meso-subsituted with alkyl groups. 30 We can anticipate that on the basis of the STM images hereafter discussed (vide infra), we believe that the geometry of molecule T and T-Ni onto the HOPG surface could not correspond to the energy C 1 and C s minima found in the gas phase and discussed above, in particular as far as the alkyl chains and planarity of the molecule are concerned.…”

Revealing substituent effects on the electronic structure and planarity of Ni-porphyrins

“…Calculations were performed using the split-valence 6-31G* basis set [92–96] and the hybrid B3LYP functional [97]. This approach was earlier shown to give geometries in a good agreement with experiments (see, e.g., [53]), and is subsequently referred to as B3LYP/6-31G*. The solvent effects were estimated at the B3LYP/6-31G* level of theory using the self-consistent reaction field IEF-PCM method [98] (UA0 model) with water, benzene, and acetonitrile as solvents (dielectric constants ε = 78.39, 2.247, and 36.64, respectively).…”

“…Effects of the central metal on structural properties of unsubstituted metalloporphyrins (MPs), including Ni-porphyrins, were studied previously by Kozlowski and co-workers [53–58]. In the 2009 DFT study of chemical bonding and aromaticity of a series of MPs [28] the D 4h structure was shown to be a global minimum for NiP.…”

Spectro-Electrochemical Investigation of the bc1 Complex from the Yeast Saccharomyces cerevisiae using Surface Enhanced B-Band Resonance Raman Spectroscopy

“…Calculations predict, that the ν 4 mode consists of 36% of (C α −C β ) stretching and deformation of the pyrrole half ring, the latter plays a crucial role for the sensitivity to the oxidation state. (Kozlowski, Bingham et al 2008) Likewise the modes ν 2 , ν 3 and ν 10 originate from C−C stretching, namely ν(C β −C β ) , ν(C α −C m ) sym and ν(C α −C m ) asym , respectively. (Spiro, Czernuszewicz et al 1989;Hu 1993) 4In comparison to the ν 4 mode the contribution of the ν 3 mode is rather small.…”