Electronic supplementary information (ESI) available: a table of intermolecular contacts for compounds 2, 5, 6, 8, 15, 3·TCNQ, 4·TCNQ, 1·18, 1·19·2C4H8O2, 5
+˙I3
−·I2
and 16
+˙I3
−, and a figure of the crystal structure of complex 1·18. See http://www.rsc.org/suppdata/jm/b1/b101866n/