Syntheses, structures, photoluminescence and theoretical studies of xanthone in crystalline resorcinarene-based inclusion complexes.

Two new crystalline resorcinarene-based xanthone inclusion complexes, CECRxanthoneMeOH (1), and HECR2 xanthone6 MeOH (2) (CECR = C-ethylcalix[4]resorcinarene, HECR = hexaethylresorcin[6]arene) have been prepared to study the relation between photophysical properties and solid-state structure. Compared with the neat crystals, the xanthone phosphorescence is severely quenched in both solids, but the lifetime is an order of magnitude larger in 2, in which xanthone occurs as a dimer, than in 1, in which it occurs as a monomer. The electronic transitions involved in the photoluminescent process, and the relation between the energy levels of host and guest and emission quenching of the guest in the supramolecular solid have been investigated by means of time-dependent density functional theory (TDDFT) calculations.