The crystal structures of free radical salts and complexes. VII. [1,2-Di(N-ethyl-4-pyridinium)ethylene]2+(7,7,8,8-tetracyanoquinodimethane)42−

[1,2-Di(N-ethyl-4-pyridinium)ethylene] z + (7,7,8,8-tetracyanoquinodimethane)42-, (DEPE) 2 + (TCNQ)42-, crystallizes in two forms" a metallic form (DEPE)2+(TCNQ) l I with a high electrical conductivity of 150-2200 f~-i cm-X and a semiconducting form (DEPE)2+(TCNQ)42II with an intermediate conductivity of 10 -3 f~-i cm-l, both measured at 300 K along the TCNQ stacking direction. Evidence of structural differences between forms I and II has been obtained from X-ray powder photographs. (DEPE)Z+(TCNQ) 2II is triclinic, space group P ] with a=7.964, b=15.549, c=16.200/~, e= 123.46, ,8= 125.55, y= 76.00 °, Z= 1. The structure was solved by the Patterson method and refined to R=0.073 for 3017 reflexions. The mean dimensions of chemically similar bonds of the two crystallographically independent TCNQ moieties indicate a delocalization of charge.