he axial coordination reactions of tetraphenylporphinatocobalt (Ⅲ) chloride(Co TPPC1) with various imidazoles RIm ( HIm . imidazole; Melm , 2-methylimida-zole) were investigated in acetone and dichloromethand so...he axial coordination reactions of tetraphenylporphinatocobalt (Ⅲ) chloride(Co TPPC1) with various imidazoles RIm ( HIm . imidazole; Melm , 2-methylimida-zole) were investigated in acetone and dichloromethand solvents at different temper-atures. The reaction mechanisms were proposed and the differences between experi-mental results in the two solvents h ave been interpreted using the proposed mecha-nisms and rate equations for the first time , and the reaction scheme for the axial re-action of the metalloporphyrin has been developed. Hydrogen bonding plays an im-portant role in the reactions. The effects of various imidazoles for these reactionsand the solvents are reported. The comparison between iron and cobalt porphyrinsin the kinetics are discussed.展开更多
Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configura...Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configuration of metal-N_(4)sites and their catalytic performance.Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge.Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin(Co-N4)to construct penta-coordinated cobalt porphyrin(Co-N_(5))renders cobalt a higher electron density,thereby favoring the rate-determining O_(2)adsorption/activation and reducing the oxygen electroreduction barrier.Therefore,a well-defined Co-N_(5)site is rationally introduced into the azo-linked polymer framework for a fundamental structure-catalytic performance correlation study.As-prepared Co-N_(5)catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N_(4)counterpart,discloses a markedly higher power density(141.4 mW cm^(−2)),and possesses better long-term durability(over 160 h cycles)in a Zn-air battery.Moreover,such a Co-N_(5)catalyst also showcases potential applications for CO_(2)reduction with high CO_(2)-to-CO conversion faradic efficiency and better selectivity than the Co-N_(4)counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction.This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metalporphyrin-based catalysts and offers atomic understanding of the structure-performance correlation on single atom catalysts for future catalyst design.展开更多
The fluorescence kinetic characteristics of binary complex Ti-3,5-dibromosalicylfluorone (Ti-3,5-DBSAF) was studied by stopped-flow fluorescence kinetic method, the results showthat its rate equation is R=k.[Ti4+].[H4...The fluorescence kinetic characteristics of binary complex Ti-3,5-dibromosalicylfluorone (Ti-3,5-DBSAF) was studied by stopped-flow fluorescence kinetic method, the results showthat its rate equation is R=k.[Ti4+].[H4R] [H3+ O]-1, refering to Eigen-Tamm mechanism, the reasonable mechanism is derivated. The possibile geometric structure of the binary complex was alsodiscussed.展开更多
文摘he axial coordination reactions of tetraphenylporphinatocobalt (Ⅲ) chloride(Co TPPC1) with various imidazoles RIm ( HIm . imidazole; Melm , 2-methylimida-zole) were investigated in acetone and dichloromethand solvents at different temper-atures. The reaction mechanisms were proposed and the differences between experi-mental results in the two solvents h ave been interpreted using the proposed mecha-nisms and rate equations for the first time , and the reaction scheme for the axial re-action of the metalloporphyrin has been developed. Hydrogen bonding plays an im-portant role in the reactions. The effects of various imidazoles for these reactionsand the solvents are reported. The comparison between iron and cobalt porphyrinsin the kinetics are discussed.
基金financially supported by the National Natural Science Foundation of China(grant nos.52073137 and 51763018).
文摘Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configuration of metal-N_(4)sites and their catalytic performance.Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge.Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin(Co-N4)to construct penta-coordinated cobalt porphyrin(Co-N_(5))renders cobalt a higher electron density,thereby favoring the rate-determining O_(2)adsorption/activation and reducing the oxygen electroreduction barrier.Therefore,a well-defined Co-N_(5)site is rationally introduced into the azo-linked polymer framework for a fundamental structure-catalytic performance correlation study.As-prepared Co-N_(5)catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N_(4)counterpart,discloses a markedly higher power density(141.4 mW cm^(−2)),and possesses better long-term durability(over 160 h cycles)in a Zn-air battery.Moreover,such a Co-N_(5)catalyst also showcases potential applications for CO_(2)reduction with high CO_(2)-to-CO conversion faradic efficiency and better selectivity than the Co-N_(4)counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction.This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metalporphyrin-based catalysts and offers atomic understanding of the structure-performance correlation on single atom catalysts for future catalyst design.
文摘The fluorescence kinetic characteristics of binary complex Ti-3,5-dibromosalicylfluorone (Ti-3,5-DBSAF) was studied by stopped-flow fluorescence kinetic method, the results showthat its rate equation is R=k.[Ti4+].[H4R] [H3+ O]-1, refering to Eigen-Tamm mechanism, the reasonable mechanism is derivated. The possibile geometric structure of the binary complex was alsodiscussed.
