STABILIZATION OF TCNQ ANION-RADICAL WITH DIAMINE AND TRIAMINE COMPLEXES OF NICKEL AND COPPER

The reactivity of the organic acceptor 7,7,8,8-tetracyanoquinodimethan e (TCNQ) in its neutral or anionic radical forms with saturated di- an d triamino derivatives of nickel and copper such as the cationic compl exes with ethylenediamine, [M(en)(3)](2+), trimethylenediamine, [M(tn) (2)(H2O)(2)](2+), and diethylenetriamine, [M(dien)(2)](2+), is discuss ed on the basis of the metal environment stability. The products obtai ned show either substitution of some labile ligands from the metal coo rdination sphere and a-coordination of the anionic TCNQ or alternative ly displacement of the counter-ion by anionic TCNQ with maintenance of the coordination around the metal. The complexes studied show the TCN Q groups forming dimeric, or trimeric, anionic associations with stron g antiferromagnetic intradimer coupling between the radical units. The complex [Ni(dien)(2)](TCNQ)(2) shows a weaker TCNQ-TCNQ coupling with a singlet-triplet equilibrium observable at temperatures above 60 K f rom its contribution to the total magnetic susceptibility of the compl ex.