Three homoleptic copper(II) complexes have been prepared which feature 6-halogen-substituted 2-pyridonate ligands [Cu2(xhp)4}n](n= 1, xhp = 6-chloro- or 6-bromo-2-pyridonate; n= 2, xhp = 6-fluoro-2-pyridonate). X-ray structural analysis of the complexes showed that for the chlorine- and bromine-substituted derivatives a dinuclear complex forms where the xhp ligands are arranged to give a dimeric unit with idealised D2d symmetry. For the fluorine-substituted ligand smaller steric requirements allow rearrangement to occur to give dinuclear units with approximate C4v symmetry, which can then dimerise giving tetrametallic molecules. The Cu ⋯ Cu contacts within these species are around 2.5 Å, and to investigate the nature of the Cu ⋯ Cu interaction variable-temperature EPR and magnetic studies were carried out. These revealed strong antiferromagnetic exchange between the S=½ centres; EPR also revealed a weak interdimer exchange which was not evident from susceptibility measurements.
我们制备了三种同色
铜(II)配合物,它们具有 6-卤素取代的
2-吡啶甲酸配体 [Cu2(xhp)4}n](n= 1,xhp = 6-
氯或 6-
溴-
2-吡啶甲酸;n= 2,xhp = 6-
氟-
2-吡啶甲酸)。对这些配合物的 X 射线结构分析表明,
氯和
溴取代的衍
生物形成了双核配合物,其中 xhp
配体的排列形成了具有理想 D2d 对称性的二聚单元。对于
氟取代的
配体,较小的立体要求允许发生重排,产生近似 C4v 对称性的双核单元,然后二聚产生四
金属分子。为了研究 Cu ⋯ Cu 相互作用的性质,我们进行了变温 EPR 和磁性研究。这些研究揭示了 S=½ 中心之间强烈的反
铁磁性交换;EPR 还揭示了微弱的嵌体间交换,而这种交换在电感测量中并不明显。