The structure of the 1:2 complex 4-ethylmorpholinium 7,7,8,8-tetra­cyanoquinodimethanide, HEM(TCNQ)2, at 294 K

C6HI4NO + . 2C ~2H4N; ~/2, HEM(TCNQ) 2, is triclinic, space group P1, with a = 14.177 (2), b = 7.558 (1), c=13.427(2)A, a =92.29(2), fl=80.81(1), y= 105.68(1) °, U=1367A 3, Z=2; dc=1.275, din= 1.267 Mg m -3. Final Rw(F)= 0.071 for 5291 independent reflections. The structure consists of sheets of TCNQ molecules parallel to (100), separated by HEM groups. Within the sheet TCNQ molecules, united in tetramers, form columns along c. Each tetramer is builtup of two dimers related by an inversion centre. The distance between TCNQ molecules within a dimer is 3.23 (l)A; the intradimer overlap is of the ringexternal-bond type. Within a tetramer the separation between the dimers is 3.31 (1)A, and between successive tetramers 3.42 (1)/k, with overlaps of the shifted ring-ring and ring-external-bond type, respectively. At the HEM positions two randomly disordered molecules are found which differ in orientation. Their main conformational difference is the location of the ethylCH 3 group with respect to the ring. Owing to Coulomb interaction with the HEM molecules there is a localization of charge on the two symmetrically relatedinner TCNQ molecules of the tetramers