Fine-Tuning of Electronic Structure of Cobalt(II) Ion in Nonplanar Porphyrins and Tracking of a Cross-Hybrid Stage: Implications for the Distortion of Natural Tetrapyrrole Macrocycles

Abstract

The core size of the porphyrin macrocycles was closely related to their stability of the different electron structure in the central metal ion. Cobalt(II) ions can undergo a conversion in electron configurations upon N4 core contraction of 0.05 Å in nonplanar porphyrins, and these ions still maintain low spin forms after and before conversion. The structural fine-tuning can induce the appearance of a cross-hybrid stage [d(x(2)-y(2))sp(2) ↔ d(z(2))sp(2)] based on quadrilateral coordination of the planar core. The results indicate that the configuration conversion plays a key role in electron transfer in redox catalysis involving cobalt complexes. The electronic properties of six monostrapped cobalt(II) porphyrins were investigated by spectral, paramagnetic, and electrochemical methods. The macrocyclic deformations and size parameters of Co-containing model compounds were directly obtained from their crystal structures.

Optimal Size Matching and Minimal Distortion Energy: Implications for Natural Selection by the Macrocycle of the Iron Species in Heme

“…For zinc complexes 7 ‐Zn to 3 ‐Zn, the spectral shifts show a continuous trend because of the invariability of the zinc(II) ion . For complexes 7 ‐M to 3 ‐M [M = Fe III Cl, Co II ],, the continuity of the spectral shift trend is interrupted, as previously reported. The differential spectroscopic method can be used to track changes in the electronic structures of metal ions in nonplanar porphyrins.…”

“…An inspection of the plot shows that the structures of the three metal ions in the model porphyrins can be changed and their diameters are mutually independent of each other. It has been shown that changing the macrocycle core size can directly change the electronic structures of iron(III), and cobalt(II) , . A similar effect is seen for nickel(II); the conversion point is between n C = 4 and 5 (Figure , labeled ☆), which is in agreement with the position derived from the spectral deviation (Figure ).…”

“…In recent studies, a relationship between macrocyclic distortion and the electronic activities of metals was established for several series of ruffle‐, saddle‐, and dome‐type porphyrins (Figure , a–d) . We found that macrocyclic distortion ( A mC ) directly affects the core size (Figure , a–b), which induces changes in the electronic configuration of the central metal ions (Figure , b–c) such as iron(III),, cobalt(II),, copper(II), and zinc(II) . In the conversion process, an electron (or electron pair) in a 3d orbital is activated (Figure , c–d), which guarantees the potential catalytic abilities of these metal complexes (Figure , d–e).…”

The Kirkendall Effect for Engineering Oxygen Vacancy of Hollow Co3O4 Nanoparticles toward High‐Performance Portable Zinc–Air Batteries

“…These nanoparticles have been proved to be unique hollow structures by transmission electron microscope (TEM) images (Figure d). The high‐resolution TEM and selected‐area electron‐diffraction (SAED) images (Figure e) reveal typical polycrystalline features of the hollow particles, which is derived from the irregular vacancy diffusion, identifying the particle as Co 3 O 4 nanoparticle (JCPDS No. 42‐1467).…”

Going with the Electron Flow: Heme Electronic Structure and Electron Transfer in Cytochrome c

“…Studies of model systems provide predictions of how ruffling will impact cobalt porphyrin electronic structure. In one study, Wang and Zhou found that enhancing Co(II) porphyrin ruffling increases the amount of spin density in the Co(II) d(z 2 ) orbital, which has implications for the interaction with substrate and reaction pathways. In another example, Grinstaff showed that highly distorted halogenated iron porphyrins catalyze alkane oxidation .…”