Hybrid Orbital Deformation (HOD) Effect and Spectral Red-Shift Property of Nonplanar porphyrin

Abstract

A series of 5,15-meso,meso-strapped nonplanar porphyrins with different degrees of ruffling distortion, as a model system, have been synthesized and characterized. The spectral red-shift of the nonplanar porphyrins was experimentally demonstrated to mainly originate from the hybrid orbital deformation (HOD) effect due to the distortion in the tetrapyrrole macrocycle, which confirmed previous explanations to the red-shift phenomenon.

Inactivation of the Heme Degrading Enzyme IsdI by an Active Site Substitution That Diminishes Heme Ruffling

“…2). The red shift of absorption maxima is commonly observed for distorted model heme compounds (32–34). However, these model compounds typically involve non-ferrous metal centers or porphyrin ligands with peripheral substituents different from those of protoheme IX that are required to achieve heme distortion.…”

“…However, these model compounds typically involve non-ferrous metal centers or porphyrin ligands with peripheral substituents different from those of protoheme IX that are required to achieve heme distortion. Consequently, these models differ from protoheme IX in several respects in addition to the extent of heme distortion, a situation that prevents unambiguous assignment of these spectroscopic differences to differences in heme distortion alone (32–34). For the forms of IsdI studied here, heme distortion is achieved without metal ion substitution or porphyrin ring side-chain substitution, so the shifts in the absorption maxima of the cyanide derivatives of these proteins can be attributed primarily to heme distortion.…”

Electronic properties of the highly ruffled heme bound to the heme degrading enzyme IsdI

“…1B and Table S1) is commonly observed for distorted model heme compounds, but attribution of this observation to heme ruffling, perturbation from side-chain substitutions or shortening of pyrrole-N to metal bond length has been debated (45)(46)(47). This latter possibility can be ruled out for the IsdIFe 3þ CN complex because the crystal structure indicates no change in this bond distance upon binding cyanide.…”

Theoretical study of electronic structure and absorption spectra of diacid and zinc species of series of meso-phenylporphyrins

“…Zinc porphyrin series. For zinc porphyrins, only the electronic and conformational effects are analyzed in this article; the influence of the hybrid orbital deformation (HOD) effect [10] has been ignored because of the negligible out-of-plane distortion. For both types of adjusted porphyrin models employed, ad-porphyrins II and IV, the central Zn 2+ ion remained untouched.…”

“…As a general phenomenon, the spectral shift has attracted much attention and has been ascribed to the change of electronic structure induced by several factors, such as the electronic effect of substituent, out-of-plane distortion, and the change of bond length and bond angle-called in-plane nuclear reorganization (IPNR) by DiMagno and co-workers [6,7]. The combined action of several factors, frequently, confounds the identification of the primary cause of spectral shift; therefore, this has given rise to certain debates in the past decades [6][7][8][9][10].…”