Rational enhancement of the coordination capability of Ru(III)(salen)-nitronyl nitroxide building block: A step towards 2p–3d–4d magnetic edifices

Abstract

The reaction of [Ru(salen)(PPh 3)Cl] and the 5-imidazol-substituted nitronyl nitroxide radical (NIT-(5)ImH) yields the [Ru(salen)(PPh 3)(NIT-(5)ImH)](ClO 4) ( 1) complex which has been characterized by single crystal X-ray diffraction. This analysis reveals that the Ru(III) ion is coordinated to a tetradentate salen 2− ligand in equatorial positions while one PPh 3 ligand and one NIT-(5)ImH radical are coordinated in axial positions. This led to Ru III ions in tetragonally elongated octahedral geometry. From the magnetic point of view ferromagnetic intramolecular interaction ( J 1 = +2.47 cm −1) have been found between the Ru(III) ion and the coordinated NIT-(5)ImH while no significant intermolecular antiferromagnetic interactions are observed at low temperature leading to a ground spin state S = 1. The absence of intermolecular magnetic interaction is explained by considering the crystal packing of ( 1) where the [Ru(salen)(PPh 3)(NIT-(5)ImH)] + moieties are relatively well isolated. This has to be compared with the situation observed in the previously reported [Ru(salen)(PPh 3)-(NIT)] + compound ( 2) where ferromagnetic Ru III–NIT interaction were identified and the crystal packing generate intermolecular antiferromagnetic interactions that complicated the study. The analysis of this compound confirms the rather isotropic g values that were found of ( 2) and of [Ru(salen)(PPh 3)(N 3)], ( 3) a radical-free analogue. Moreover it is also a step towards extended structures based on Ru III–NIT moieties since this compound possesses a free bischelating site likely to coordinate additional metallic ions.