Complexation of unsaturated carbon-carbon bonds in pi-conjugated polymers with transition metals.

The present paper explores the possibility of preparing pi-conjugated organometallic polymer hybrid systems based on a poly(p-phenylene ethynylene) (PPE) derivative, in which the ethynylene moieties of the polymer are coordinated to platinum(II) centers. The use of the "bifunctional" [Pt-(mu-Cl)Cl(PhCH=CH(2))](2) (2) allows, under appropriate conditions, the formation of three-dimensionally cross-linked, conjugated PPE-platinum(II) networks. The synthesis of [Pt-(mu-Cl)Cl(PhC(triple bond)CPh)](2), as a model compound, and a series of model reactions of 2 with diphenylacetylene (3) have enabled an NMR study which has revealed a number of equilibria, and suggests a mixed Pt-styrene-acetylene complex as a key structure. As expected, the coordination of Pt markedly influences the photophysical characteristics of the PPE. The photoluminescence is efficiently quenched, and the absorption maximum in the visible regime experiences a hypsochromic shift upon complexation with 2.