Structural distortions of the spin-crossover material [Co(pyterpy)2](TCNQ)2 mediated by supramolecular interactions

The incorporation of TCNQ(center dot-) (7,7,8,8-tetracyanoquinodimethane) radicals as counterions for the spin-crossover material [Co(pyterpy)(2)](TCNQ)(2)center dot solvent (pyterpy = 4'-(4 '''-pyridyl)-2,2':6',2 ''-terpyridine) leads to structural distortions of the [Co(pyterpy)(2)](2+) spin-crossover cation as compared to [Co(pyterpy)(2)](PF6)(2). Variable temperature structural and magnetic studies indicate that the supramolecular p-stacking interactions between the terminal pyridyl groups and TCNQ radicals play a crucial role in the spin-crossover properties.