Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L) 3 ] 2+ complex cations with dimethylderivatives of 2,2′-bipyridine and TCNQ

Abstract

From the aqueous-methanolic systems Ni(NO3)2 -LiTCNQ -5,5'-dmbpy and Ni(NO3)2 -LiTCNQ-4,4'-dmbpy three novel complexes [Ni(5,5'-dmbpy)3](TCNQ)2 (1), [Ni(4,4'dmbpy)3](TCNQ)2 (2) and [Ni(4,4'-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2•0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5'-dmbpy)] 2+ (1) or [Ni(4,4'-dmbpy)] 2+ (2 and 3). The anionic parts of the respective crystal structures 1-3 are formed by TCNQ ⋅anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ) 2with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2-300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ ⋅anionradicals with S = 1/2 while the (TCNQ-TCNQ) 2dianion is magnetically silent. The magnetic behaviour was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ ⋅anion-radicals.

An Old Crystallization Technique as a Fast, Facile, and Adaptable Method for Obtaining Single Crystals of Unstable “Li2TCNQF4” and New Compounds of TCNQ or TCNQF4: Syntheses, Crystal Structures, and Magnetic Properties

“…Within our broader interest in the crystal structures and magnetic properties of heterospin Ni­(II) complexes with the TCNQ AR, , we have prepared a novel heterospin complex [Ni­(2 ampy ) 2 (TCNQ) 2 ] ( 1 ; 2 ampy = 2-aminomethyl-pyridine) with two TCNQ ARs coordinated to the Ni­(II) central atom. This compound has been prepared in two different ways, as microcrystals from a methanol solution of NiCl 2 ·6H 2 O and 2 ampy with LiTCNQ and as single crystals of sufficient quality for X-ray structure determination from the reaction in methanol of crystals of an insoluble 2 ampy coordination compound, [Ni­(2 ampy ) 2 (NO 3 ) 2 ], with soluble LiTCNQ, in a fast, facile procedure designed to avoid decomposition.…”