Synthetic control of intrinsic ground-state defects in a mixed valence quasi-one-dimensional Pt halide chain

The new linear chain compound [Pt(en)(2)Cl-2][Pt(en)(2)][Pt(CN)(4)](2) has been synthesized through two independent methods to yield a quasi-one-dimen sional chain with very strong hydrogen bonding interactions. The high charg e density wave (CDW) character will be discussed in terms of an unusual hyd rogen bonding network which bridges adjacent chains but does not bridge adj acent oxidized and reduced units within a chain. Such a network is unique a nd breaks from known CDW trends derived from the template effect. The resul ts of the structural analysis by X-ray crystallography have shown that the chains grown from two independent methods are isostructural with one anothe r. Spectroscopic results (resonance Raman and diffuse reflectance) clearly demonstrate the presence of ground-state polaronic defects in crystals grow n from solution of stoichiometric amounts of subunits while crystals grown from Pt(IV) rich solutions display a complete absence of ground-state polar onic signatures. These results will be discussed in terms of how one can ch emically control the presence and amount of ground-state reduced site defec ts in the general class of MX materials. (C) 1999 Elsevier Science S.A. All rights reserved.