Experimental and computational study of complexes between quats and naphthalenophanes

A number of neutral cyclophanes incorporating either a 2,6- or a 2,7-dioxynaphthalene unit have been synthesised and their binding properties toward tetramethylammonium and N-methylpyridinium picrates assessed by means of a H-1 NMR spectroscopic technique. A parallel computational study based on molecular mechanics and molecular dynamics calculations has been carried out. There is at least a rough agreement between complexation phenomena based on cation -pi interactions in solution and molecular mechanics calculations in the gas phase, in that the stability trend seen across the series of naphthalenophane/tetramethylammonium complexes is satisfactorily reproduced. Furthermore, there is a clear corre-spondence between the magnitude of the observed upfield shifts upon complexation and the calculated structures of host-guest complexes.