Synthesis Of Serial Nonplanar Zinc Porphyrins And The Fixation To Dioxygen

Oxygen is one of the most economical and environmental protection oxidants. Simulation of the natural conversion process is an important way of oxygen utilization.The adsorption and activation of molecular oxygen to metal porphyrin complexes has played an important role in simulating and understanding the catalytic oxidation performance of hemoglobin.In this paper,zinc porphyrin was selected as the research object,the electronic structure of the metal zinc is regulated by adjusting the twist of the porphyrin ring to realize the fixation and activation of molecular oxygen.In the study, a series of zinc porphyrins whose distortion could be adjusted were synthesized, and the oxygen content of 1-Zn complex was obtained.The saddle type porphyrins and their zinc complexes were synthesized by using propionate as solvent in the paper.During the process of synthesis,two short alkyl chains were bridged on the 5,10- and 15,20- two groups ortho-position meso site of porphyrin macrocycle, this method was used to force the macrocycle deformed. Two binding chain was distributed on the same side of the macrocycle which was adoped a saddle-type deformation.The twist of the saddle type zinc porphyrin ring could be adjusted by the variation of the length of the bundling chain. The structures of model compouds were characterized by means of single crystal diffraction?X-ray?,nuclear magnetic resonance?NMR?, high resolution mass spectrometry?HR-MS?, ultraviolet absorption spectrum?UV-vis?,infrared spectrum?IR?, cyclic voltammetry?CV? and electron spin resonance?EPR? in detail.The degree of deformation directly affected the core size of the macrocycle.This change allowed the 1-Zn to have the ability to bond molecular oxygen. The deformation of macrocycle promoted the N4 core to shrink significantly.With the number of carbon atoms in strapped alkyl chains decreased,the molecular energy level of porphyrin also changed obviously. The deformation induced by the linkers could cause a spectral red shift of >30 nm compared with the absorption spectrum of regular porphyrins. The obvious shift indicates that there was considerablemacrocyclic deformation that increased the ground state of the molecule.This could only derive from the adjustment of macrocyclic deformation to electronic structure of zinc.The N4 unit coordination electrons exchanged with the electron pair of zinc?II? in d orbit and enlarged the splitting of energy levels of d orbitals under strong core deformation.The exchange interaction not only made the d-z effect of Zn-O₂ achived, but also made the adsorption of molecular oxygen to zinc ion become possible.At last,the Zinc porphrin formed a stable superoxide complexes,and the d-? effect also made molecular oxygen activated. The fixation of dioxygen can be reasonably explained by the Dewar-Chatt-Duncanson model in this paper. The result of single crystal diffraction and mass spectrometry provided direct support for the above analysis.Both of these effects tended to decrease the Zn-O bond order and increase that of the O-O bond.These research results indicate that this type of saddle porphyrin has the potential to be used as a new model system of heme.