EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ Scotland, UK.
Dalton Trans. 2018 Jun 19;47(24):8100-8109. doi: 10.1039/c8dt01963k.
A large family of chromium(iii) dimers has been synthesised and magneto-structurally characterised using a combination of carboxylate and diethanolamine type ligands. The compounds have the general formula [Cr2(R1-deaH)2(O2CR2)Cl2]Cl where R1 = Me and R2 = H (1), Me (2), CMe3 (3), Ph (4), 3,5-(Cl)2Ph (5), (Me)5Ph (6), R1 = Et and R2 = H (7), Ph (8). The compound [Cr2(Me-deaH)2Cl4] (9) was synthesised in order to study the effect of removing/adding the carboxylate bridge on the observed magnetic behaviour. Direct current (DC) magnetic susceptibility measurements showed ferromagnetic (FM) exchange interactions between the Cr(iii) centres in the carboxylate bridged family with coupling constants in the range +0.37 < J < +8.02 cm-1. Removal of the carboxylate to produce the dialkoxide-bridged compound 9 resulted in antiferromagnetic (AFM) exchange between the Cr(iii) ions. DFT calculations reveal the ferromagnetic exchange is the result of an orbital counter-complementarity effect occuring upon introduction of the bridging carboxylate.
一个庞大的铬(iii)二聚体家族已经被合成出来，并通过羧酸酯和二乙醇胺型配体的组合进行了磁结构表征。这些化合物具有通式[Cr2(R1-deaH)2(O2CR2)Cl2]Cl，其中 R1 = Me 和 R2 = H（1）、Me（2）、CMe3（3）、Ph（4）、3,5-(Cl)2Ph（5）、(Me)5Ph（6）、R1 = Et 和 R2 = H（7）、Ph（8）。为了研究去除/添加羧酸酯桥对观察到的磁行为的影响，合成了[Cr2(Me-deaH)2Cl4]（9）化合物。直流（DC）磁化率测量表明，羧酸酯桥联家族中的 Cr(iii)中心之间存在铁磁（FM）交换相互作用，耦合常数在+0.37 < J < +8.02 cm-1 范围内。去除羧酸酯生成二烷氧基桥联化合物 9 导致 Cr(iii)离子之间的反铁磁（AFM）交换。DFT 计算表明，引入桥接羧酸酯后发生轨道互补性效应，导致铁磁交换。
