A series of bisimine-bridged dicatechol ligands 2-H(4)-5-H(4) were synthesized and were used to prepare triple-stranded dinuclear helicate-type complexes with a length of up to more than 2 nm. X-ray structural analyses of Na(4)[(2)(3)V(2)], Na(4)[(3)(3)Ti(2)], Na(4)[(4)(3)Ti(2)], and Na(4)[(5)(3)Ti(2)], as well as temperature-dependent NMR investigations of Na(4)[(4)(3)Ti(2)] and Na(4)[(5)(3)Ti(2)]
合成了一系列的双
亚胺桥联的
邻苯二酚配体2-H(4)-5-H(4),并用于制备三链双核双螺旋结构型复合物,其长度最多可超过2 nm。Na(4)[(2)(3)V(2)],Na(4)[(3)(3)Ti(2)],Na(4)[(4)(3)的X射线结构分析)Ti(2)]和Na(4)[(5)(3)Ti(2)],以及Na(4)[(4)(3)Ti(2)]的温度依赖性NMR研究和Na(4)[(5)(3)Ti(2)]表明,在刚性线性
配体2和3以及理想化结构中具有C(2h)对称性的
配体5的情况下,非手性地形成同型手性螺旋。另一方面,
配体4具有理想的C(2v)对称性,导致杂手性介螺旋结构的形成具有出乎意料的高选择性。这归因于
配体4在内消旋化合物中比在螺旋络合物中采用更少限制的构象的能力。NMR研究表明,Na(4)[(4)(3)Ti(2)]的两个复杂单元都同时反转(LambdaDelta-> DeltaLambda)