Pentacoordinated bis-o-benzosemiquinonato zinc complexes with different N-ligands: Structure and magnetic properties

Pentacoordinated bis-o-semiquinonato zinc complexes with different neutral ligands were synthesized. The measurements of magnetic susceptibilities show that all distorted square pyramidal complexes are characterized by the intramolecular antiferromagnetic exchange between radical centers. The magnitude of the magnetic exchange interactions between spins of o-semiquinonate ligands was found to be influenced by the radical separation distance. [Display omitted] •The synthesis of new pentacoordinated bis-o-semiquinonato zinc complexes.•The intramolecular antiferromagnetic exchange between o-semiquinonate radicals.•The correlation between the magnetic exchange and distance between radicals. New pentacoordinated paramagnetic bis-o-semiquinonato zinc complexes with different neutral ligands (3,6-SQ)2Zn·L 1–5 (where 3,6-SQ – 3,6-di-tert-butyl-o-semiquinonate anion, L=2,6-dimethyl-N-(thiophen-2-ylmethylene)aniline (L1) (1), 2,6-diisopropyl-N-(pyridin-4-ylmethylene)aniline (L2) (2), N-(pyridin-4-ylmethylene)aniline (L3) (3), 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (L4) (4) and 4,4′-dipyridyl (L5) (5)) were synthesized. The crystal structures of compounds 1–3, 5 were investigated using X-ray diffraction. The coordination polyhedron of all complexes was found to be a distorted (τ=0–0.3) square pyramid. The measurements of magnetic susceptibilities show that all complexes are characterized by the intramolecular antiferromagnetic exchange between o-semiquinonate radical centers (J=−155.76(28), −53.56(18), −52.57(25), −80.67(27) and −85.77(91)K for 1–5 respectively). The magnitude of the magnetic exchange interactions between spins of semiquinonate ligands was found to be influenced by the radical separation distance. A smaller distance between radical centers leads to the increasing magnetic exchange interaction magnitude.