Ferromagnetic Coupling in the Heterospin Bis-Catecholato–Manganese(IV) Complex with Pyridine Substituted by Nitronyl-nitroxide

A new bis­(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py
ligands was synthesized and characterized [4-NIT-Py = pyridine substituted
at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated
an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination
core of the metal and in the chelate cycles that are representative
of the charge distribution between the metal and ligands displayed
a Mn­(IV)­(Cat2–)2 charge distribution.
Variable-temperature magnetic susceptibility measurements detected
intramolecular ferromagnetic coupling between the Mn­(IV) S = 3/2 spins and spins of nitronyl-nitroxyls
and intermolecular ferromagnetic interactions of spins of adjacent
nitronyl-nitroxide fragments in a chain of molecules at low temperatures.
The last phenomenon is revealed by short contacts between nitronyl-nitroxide
radicals of adjacent complex molecules.