Concerted supramolecular motifs: inverted sextuple aryl embraces in crystalline tris(9-anthracenyl)phosphine

Crystalline tris(9-anthracenyl)phosphine 1 contains an unusual supramolecular motif, an inverted sextuple aryl embrace (ISAE) of a pair of phosphines. This embrace, which is maintained by six intermolecular edge-to-face interactions between anthracenyl groups, differs from the normal sextuple phenyl embraces (SPE) of Ph3P in that the phosphines are inverted relative to each other. The P-C vectors are directed away from the interaction zone in the ISAE, rather than into the interaction zone as in the SPE, The ISAE has (3) over bar symmetry. The net attractive energy of this concerted supramolecular motif is calculated to be 165 kJ mol(-1) for the ISAE pair. Each molecule of 1 is also involved in three quadruple anthracenyl embraces with three other neighbouring molecules, in geometry comparable with the parallel quadruple phenyl embraces of Ph3P and Ph(4)p(+). (C) 1997 Elsevier Science Ltd.