Structures and solvatochromic phosphorescence of dicationic terpyridyl-platinum(II) complexes with foldable oligo(ortho-phenyleneethynylene) bridging ligands

Abstract

A series of binuclear organoplatinum(II) complexes, [(tBu 3tpy)Pt-(C≡C-1,2-C 6H 4) n-C≡C-Pt(tBu 3tpy)]-[ClO 4] 2 (1-7, n = 1, 2, 3, 4, 5, 6, 8; tBu 3tpy = 4,4′,4″-tri- tert-butyl-2,2′:6′,2″-terpyridine) with foldable oligo(orthophenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 3·2.5 CH 3OH, 5·CH 3CN, and 6·4CH 3CN, each of the bridging orthophenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40%, the emission of complexes 3-7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho-phenyleneethynylene linkers in acetonitrile/water mixtures is postulated. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.