Terpyridine ligands with ter- and quater-phenyl substituents at the 4â² position provide bis(ligand)Co(II) complexes showing very different magnetic properties to those of their analogues with long-chain aliphatic substituents, with no evidence of âre-entrantâ behavior involving multiple high- and low-spin species. Structure determinations of [Co(tptpy)2](BF4)2·CH3OH and [Co(qptpy)2](BPh4)2·3.5dmf·2H2O (dmf = N,N-dimethylformamide) show the metal ion centres in both to be relatively distant and that the âterpyridine embraceâ observed to be partially retained in their analogues is completely lost. Consideration of available structural and magnetic data for these and other Co(II) complexes of functionalised terpyridines and terpyridine itself provides evidence that spin crossover behaviour may be regulated by face-to-face contacts of the pyridyl units of the head groups.
在 4-位具有三苯基和四苯基取代基的三联
吡啶配体提供的双(
配体)Co(II) 配合物显示出与其具有长链脂肪族取代基的类似物非常不同的磁性,并且没有证据表明涉及多个高自旋和低自旋物种的重入行为。 [Co(tptpy)2](
BF4)2·CH3OH 和 [Co(qptpy)2](BPh4)2·3.5dmf·2H2O (dmf =
N,N-二甲基甲酰胺) 的结构测定显示了两者中的
金属离子中心相对较远,并且观察到在其类似物中部分保留的“三联
吡啶拥抱”完全丢失了。考虑到这些和其他官能化三联
吡啶的 Co(II) 配合物和三联
吡啶本身的可用结构和磁性数据,提供了自旋交叉行为可能通过头基
吡啶基单元的面对面接触来调节的证据。