A ground triplet dinuclear copper(II) spiro-complex involving tetraiminoneopentane

Tetrakis(2-pyridylmethyleneimino)neopentane (L) was designed to form a spiro-structure after complex formation, where L plays a role of a double tetradentate bridging ligand. The X-ray diffraction study of [Cu2L(CF3SO3)4] clarified that the molecular structure was topologically spiro but the two coordination basal planes were not orthogonal with the dihedral angle of 49.8(1)°. The χmT value of [Cu2L(CF3SO3)4] showed a small increase on cooling below 10 K, indicating the presence of ferromagnetic coupling. Fitting to a singlet–triplet model gave 2J/kB = +0.293(7) K. The density-functional-theory calculation of the [Cu2L]4+ core reproduced the ferromagnetic coupling. Furthermore, from another calculation after removal of the neopentyl skeleton, through-bond interaction is clarified to be major in the exchange mechanism. The intervening sp3-hybridized carbon atoms may be spin-polarized.