Tetracyanoquinodimethanido derivatives of (terpyridine)- and (phenanthroline)metal complexes -: Structural and magnetic studies of radical-ion salts

Several derivatives of formulae [M(terpy)(2)](TCNQ)(2) or [M(terpy)(2)](TCNQ)(3) (M = Ni, Cu, Zn; terpy = 2,2':6',2"-terpyridine; TCNQ= 7,7,8,8-tetracyanoquinodimethane) and [M(phen)(3)](TCNQ)(2) or [M(phen)(3)](TCNQ)(4) (M = Fe, Ni; phen = 1,10-phenanthroline) have been obtained. The crystal structures of [M(terpy)(2)](TCNQ)(2) (M = Ni, Cu) show that the metal is surrounded by the terpyridine nitrogen atoms in a closed octahedral environment and the TCNQ anions are dimerised by pi overlap. The cationic [M(terpy)(2)](2+) and the anionic [TCNQ](2)(2-) groups alternate in the crystal. For the derivatives with three TCNQ groups, the existence of a stack of trimeric [TCNQ](3)(2-) ions having electronic delocalisation is proposed. The compound [Fe(phen)(3)](TCNQ)(2), which shows a strong interaction between TCNQ anions, led to the formation of a sigma bond in the diamagnetic species [TCNQ-TCNQ], while the nickel analogue is expected to have a localised structure formed by alternation of cationic metal complexes and dimeric [TCNQ](2)(2-) anions similar to those observed in the analogous terpy derivatives. The derivatives having four TCNQ groups also show electronic delocalisation and a 1D stack based on the magnetic data is proposed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).