Two-way vapochromism of a luminescent platinum(II) complex with phosphonic-acidfunctionalized bipyridine ligand

A luminescent Pt(II) complex [Pt(CN)(2)(H(4)dpbpy)] (1P; H(4)dpbpy = 2,2'-bipyridine-4,4'-diphosphonic acid) bearing a phosphonic-acid-functionalized bipyridine ligand was successfully synthesized and its unique two-way vapochromic behaviour investigated. X-ray structure analyses of both the anhydrous 1P and penta-hydrated 1P.5H(2)O phases clearly reveal the activation of intermolecular Pt. Pt interactions through the adsorption of water vapour. Emission spectroscopy reveals that the penta-hydrated 1P.5H(2)O complex exhibits an orange emission at 585 nm that shifts in two directions, to a blue-green emission at 469 nm by drying at 100 degrees C or to a red emission at 701 nm by drying under vacuum at room temperature. Thermogravimetric analyses and powder X-ray diffraction studies clearly reveal that anhydrous 1P, with negligible intermolecular Pt. Pt interactions, is formed by drying at 100 degrees C whereas the monohydrate 1P.H2O phase, with effective Pt. Pt interactions, is formed by drying under vacuum.