运用杂化密度泛函B3LYP方法,在6-31G*水平上优化得到了一种Mg _(12) B _(24)团簇的笼状稳定结构,其IR最强吸收峰位于205.23 cm^(-1),Raman谱的最强峰位于242.63 cm^(-1).Mg _(12) B _(24)团簇笼状结构中B原子主要是sp杂化轨道参与成键,M...运用杂化密度泛函B3LYP方法,在6-31G*水平上优化得到了一种Mg _(12) B _(24)团簇的笼状稳定结构,其IR最强吸收峰位于205.23 cm^(-1),Raman谱的最强峰位于242.63 cm^(-1).Mg _(12) B _(24)团簇笼状结构中B原子主要是sp杂化轨道参与成键,Mg原子主要是s轨道参与成键.团簇中B原子层堆积了大量的电子,表明MgB 2的超导作用主要发生在B原子层;B原子层电子存在较强的离域性,也为超导电性提供了条件;Mg原子起了提供电子的作用.展开更多
The bicyclic cryptand 1,4,7, 10,13,16,21, 24-octaaza-bigcyclo [8, 8,8] hexacosan-3, 8, 12, 17, 20, 25-hex-one (COBH) bearing diaminoethane groups along the eight-atom bridges was synthesized. The structure consists of...The bicyclic cryptand 1,4,7, 10,13,16,21, 24-octaaza-bigcyclo [8, 8,8] hexacosan-3, 8, 12, 17, 20, 25-hex-one (COBH) bearing diaminoethane groups along the eight-atom bridges was synthesized. The structure consists of discrete neutral macrobicyclic units; the two cycles share the two tertiary amine nitrogen atoms, which exhibit an endo-cndo conformation. Three identical branches formed by 1, 2-diaminoethane link the two tertiary amine groups. The protonation reactions of cryptand (COBH) and its complex formation with copper (II) were investigated by potentiometry in water and in a DMSO/water (80:20 in mass ratio) mixture as solvents. The cryptand acts as a his-base through its two N-bridgehead and exhibits a strong cooperativity that favors the first protonation and makes the second one difficult (△pK= 5.0). An inward rotation of the amide groups to form hydrogen bonds accounts for this cooperativity. The interaction of COBH with copper (II) leads to several binuclear complex proton contents.展开更多
文摘运用杂化密度泛函B3LYP方法,在6-31G*水平上优化得到了一种Mg _(12) B _(24)团簇的笼状稳定结构,其IR最强吸收峰位于205.23 cm^(-1),Raman谱的最强峰位于242.63 cm^(-1).Mg _(12) B _(24)团簇笼状结构中B原子主要是sp杂化轨道参与成键,Mg原子主要是s轨道参与成键.团簇中B原子层堆积了大量的电子,表明MgB 2的超导作用主要发生在B原子层;B原子层电子存在较强的离域性,也为超导电性提供了条件;Mg原子起了提供电子的作用.
基金the National Natural Science Foundation of China (No.29875018) and the Natural Science Foundation of Gansu Province (ZS991-A25-
文摘The bicyclic cryptand 1,4,7, 10,13,16,21, 24-octaaza-bigcyclo [8, 8,8] hexacosan-3, 8, 12, 17, 20, 25-hex-one (COBH) bearing diaminoethane groups along the eight-atom bridges was synthesized. The structure consists of discrete neutral macrobicyclic units; the two cycles share the two tertiary amine nitrogen atoms, which exhibit an endo-cndo conformation. Three identical branches formed by 1, 2-diaminoethane link the two tertiary amine groups. The protonation reactions of cryptand (COBH) and its complex formation with copper (II) were investigated by potentiometry in water and in a DMSO/water (80:20 in mass ratio) mixture as solvents. The cryptand acts as a his-base through its two N-bridgehead and exhibits a strong cooperativity that favors the first protonation and makes the second one difficult (△pK= 5.0). An inward rotation of the amide groups to form hydrogen bonds accounts for this cooperativity. The interaction of COBH with copper (II) leads to several binuclear complex proton contents.
