Strongest Exchange Coupling in Gadolinium(III) and Nitroxide Coordination Compounds

The
largest antiferromagnetic coupling parameter was characterized to
be 2J/kB = −15.9(2)
K in [Gd­(hfac)3(6bpyNO)], where 6bpyNO stands for 2,2′-bipyridin-6-yl tert-butyl nitroxide. This molecule was designed according
to the empirical relation: more planar chelate favors stronger antiferromagnetic
coupling. The Gd–Orad bond is relatively short owing
to the tridentate character.

在配合物[Gd(hfac)₃(6bpyNO)]中，最大反铁磁耦合（antiferromagnetic coupling）参数经表征确定为2J/k_B = −15.9(2) K，其中6bpyNO指代2,2′-联吡啶-6-基叔丁基硝酰基。该分子依据经验规律设计而成：螯合配体的平面性越强，越有利于形成更强的反铁磁耦合作用。由于该配体具有三齿配位特性，Gd–Orad键的键长相对较短。