Conformational equilibria of solvent N,N-dimethylpropionamide in the bulk and in the coordination sphere of the manganese(II) ion
Conformational equilibria of solvent N,N-dimethylpropionamide in the bulk and in the coordination sphere of the manganese(II) ion
复制标题
溶剂 N,N-二甲基丙酰胺在本体和锰 (II) 离子配位层中的构象平衡
DOI：
10.1039/b302143b
复制
发表时间：
2003
影响因子：
3.3
通讯作者：
S. Ishiguro
中科院分区：
文献类型：
--
作者：
Y. Umebayashi;K. Matsumoto;Yutaka Mune;Yue Zhang;S. Ishiguro
N，N-二甲基丙酰胺（DMPA）的丙酰基CH_3CH_2CO-中的甲基和氧先前已显示为平面顺式。本测量的拉曼光谱在不同的温度下表明存在另一种异构体的平衡与平面顺式。根据从头算计算结果，它是一个非平面的交错构象，C-C-C-O二面角约为100 °。90°，即丙酰基的甲基位于酰胺O-C-N平面上方。随着温度的升高，平衡向非平面交错构象移动。从平面顺式到非平面交错构象的ΔH°值为5.0 kJ mol−1，与理论值（6.6 kJ mol−1）非常一致。的锰（II）离子是五溶剂化的DMPA，它阐明，非平面交错构象是优选的平面顺式构象DMPA分子绑定到锰（II）离子。这归因于与金属离子结合的溶剂分子之间的溶剂化空间效应。结合DMPA从平面顺式构象到非平面交错构象的构象变化的ΔH°值为−11 kJ mol−1。
The methyl group and oxygen in the propionyl group CH3CH2CO– of N,N-dimethylpropionamide (DMPA) have been previously shown to be planar cis. The present measurements of Raman spectra at varying temperature indicate the presence of another isomer in equilibrium with the planar cis one. It is suggested that, according to our ab initio MO calculation, it is a non-planar staggered conformer with a C–C–C–O dihedral angle of ca. 90°, i.e. the methyl group of the propionyl group is located above the amide O–C–N plane. The equilibrium shifts to the non-planar staggered conformer with increasing temperature. The ΔH° value for the conformational change from the planar cis to non-planar staggered conformer in the bulk is 5.0 kJ mol−1, which is in good agreement with the theoretical ones (6.6 kJ mol−1). The manganese(II) ion is five-solvated in DMPA, and it is elucidated that the non-planar staggered conformer is preferred to the planar cis conformer for DMPA molecules bound to the manganese(II) ion. This is ascribed to the solvation steric effect among solvent molecules bound to the metal ion. The ΔH° value for the conformational change of the bound DMPA from the planar cis to non-planar staggered conformation is −11 kJ mol−1.