X-Ray and Theoretical Study of Cyclophane-tetracyanoethylene Charge Transfer Complexes

Abstract The crystal structures of a series of 1/1 complexes of tetracyanoethylene (TCNE) with cyclophanes containing two, three and four phenyl rings are compared. In all cases parallel and identical columns of alternately stacked donors and acceptors are found, as in complexes of planar molecules with TCNE. Complexes of several two phenyl ring cyclophanes are isostructural. When three phenyl rings are present in the donor molecule only two of them overlap with TCNE in the complex. A disorder of the TCNE molecule on two orientations is observed in several structures. Empirical intermolecular potential and extended Mickel calculations are used to explain these observations. It is found that interstack interactions determine the different orientations of TCNE with respect to the cyclophane while the intrastack ones determine the relative population of these orientational alternatives.