Bis-o-Semiquinonate Zinc Complexes with the Bidentate N-Donor Ligands: Synthesis and Magnetic Properties

Abstract

Biradical mononuclear SQ₂\({\text{ZnL}}_{2}^{4}\) and SQ₂ZnL⁵ complexes, binuclear SQ₂Zn(L³)ZnSQ₂ complex, and coordination polymers (SQ₂ZnL¹⁽²⁾)_n are synthesized by the reactions of bis(3,6-di-tert-butyl-o-benzosemiquinonato)zinc (SQ₂Zn) with the bidentate N-donor ligands (L^1–5) (pyrazine (L¹), 4,4'-dipyridyl (L²), phenazine (L³), 4-cyanopyridine (L⁴), and pyrimidine (L⁵)). The structures of the synthesized compounds are determined by X-ray diffraction analysis (СIF files CCDC nos. 1846558–1846563). The binuclear SQ₂Zn(L³)ZnSQ₂ and mononuclear SQ₂ZnL⁵ complexes contain pentacoordinated metal atoms, whereas zinc in the compounds based on the L^1,2,4 ligands exists in the octahedral environment with the trans-arranged o-semiquinonate ligands. The coordination polymers (SQ₂ZnL¹⁽²⁾)_n are capable of depolymerizing on dissolution in organic solvents. According to the data of measuring the temperature dependence of the magnetic susceptibility, the antiferromagnetic exchange between unpaired electrons of the organic radical anions is observed in crystals of the synthesized compounds.