A series of chiral salen\|Co(Ⅱ) complexes have been synthesized and characterized, and they are for the first time used as the catalyst for asymmetric borohydride reduction of aromatic ketone. Enantiometric exesses u...A series of chiral salen\|Co(Ⅱ) complexes have been synthesized and characterized, and they are for the first time used as the catalyst for asymmetric borohydride reduction of aromatic ketone. Enantiometric exesses up to 28.2% have been achieved at the room temperature. The influence of substituent on enantioselectivity of the reactions was studied.展开更多
Low discharge capacity and poor cycle stability are the major obstacles hindering the operation of Li-O_(2)batteries with highenergy-density.These obstacles are mainly caused by the cathode passivation behaviours and ...Low discharge capacity and poor cycle stability are the major obstacles hindering the operation of Li-O_(2)batteries with highenergy-density.These obstacles are mainly caused by the cathode passivation behaviours and the accumulation of by-products.Promoting the discharge process in solution and accelerating the decomposition of discharge products and by-products are able to alleviate above problems to some extent.Herein,chiral salen-Co(Ⅱ)complex,(1R,2R)-(-)-N,N-bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanediaminocobalt(Ⅱ)(Co(Ⅱ))as a multi-functional redox mediator was introduced into electrolyte to induce solution phase formation of Li_(2)O_(2)and catalyze the oxidation of Li_(2)O_(2)and main by-products Li_(2)CO3.Due to the Co(Ⅱ)has the solvation effect towards Li+,it can drive solution phase formation of Li_(2)O_(2),to prevent electrode from passivation and then increase the discharge capacity with a high Li_(2)O_(2)yield of 96.09%.Furthermore,the Co(Ⅱ)possesses suitable redox couple potentials,and it does so while simultaneously boosting the oxidization of Li_(2)O_(2)and the decomposition of Li_(2)CO3,reducing charge overpotential,and promoting cycle lifespan.Thereby,a cell with Co(Ⅱ)achieved a long cycling stability at low charge plateau(3.66 V)over 252 cycles with a specific capacity of 500 mAh·gcarbon^(−1).展开更多
文摘A series of chiral salen\|Co(Ⅱ) complexes have been synthesized and characterized, and they are for the first time used as the catalyst for asymmetric borohydride reduction of aromatic ketone. Enantiometric exesses up to 28.2% have been achieved at the room temperature. The influence of substituent on enantioselectivity of the reactions was studied.
基金the National Key Research and Development Program of China(No.2017YFA0206703)the National Natural Science Foundation of China(No.22075270)+2 种基金the National Natural Science Foundation of China(No.21903019)the Top Young Talents Program in University of Hebei Province(No.BJ2020014)the numerical calculations in this paper have been done on the supercomputing system in the Supercomputing Center of University of Science and Technology of China.
文摘Low discharge capacity and poor cycle stability are the major obstacles hindering the operation of Li-O_(2)batteries with highenergy-density.These obstacles are mainly caused by the cathode passivation behaviours and the accumulation of by-products.Promoting the discharge process in solution and accelerating the decomposition of discharge products and by-products are able to alleviate above problems to some extent.Herein,chiral salen-Co(Ⅱ)complex,(1R,2R)-(-)-N,N-bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanediaminocobalt(Ⅱ)(Co(Ⅱ))as a multi-functional redox mediator was introduced into electrolyte to induce solution phase formation of Li_(2)O_(2)and catalyze the oxidation of Li_(2)O_(2)and main by-products Li_(2)CO3.Due to the Co(Ⅱ)has the solvation effect towards Li+,it can drive solution phase formation of Li_(2)O_(2),to prevent electrode from passivation and then increase the discharge capacity with a high Li_(2)O_(2)yield of 96.09%.Furthermore,the Co(Ⅱ)possesses suitable redox couple potentials,and it does so while simultaneously boosting the oxidization of Li_(2)O_(2)and the decomposition of Li_(2)CO3,reducing charge overpotential,and promoting cycle lifespan.Thereby,a cell with Co(Ⅱ)achieved a long cycling stability at low charge plateau(3.66 V)over 252 cycles with a specific capacity of 500 mAh·gcarbon^(−1).
