One-electron reduction of [Pt(bpy)(2)](2+) (bpy = 2,2’-bipyridyl) in aqueous solution results in the formation of black-green lustrous needles on solid electrodes. The crystalline needles grow perpendicularly from the substrate surface and reach lengths of 1-2 cm. Elemental analysis, X-ray photoelectron spectroscopy, and electrochemical measurements indicate that the new compound is a genuine Pt-I complex with a d(9) electronic configuration and with the composition [Pt(bpy)(2)]NO3 . 2H(2)O. X-ray crystallographic analysis shows that the crystalline needles consist of Linear chains of discrete [Pt-I(bpy)(2)] units with a Pt--Pt distance of 3.563(1) Angstrom and with each bipyridyl ligand overlapping face-to-face (eclipsed) with its nearest neighbor. At the monomeric level, the structure of [Pt-I(bpy)al units exhibits a distorted square-planar configuration with structural parameters very similar to those of the parent Pt-II complex, [Pt(bpy)(2)](NO3)(2) . H2O. The new linear-chain compound was prepared by chemical and electrochemical methods. The resulting crystals are relatively stable in air but oxidize slowly over a period of weeks. Scanning electron microscopy reveals that the crystals are tubular with a hollow near-hexagonal morphology. Cooperative effects influence the optical and electrical properties of the crystals. Because of extensive solid-state interactions between stacked monomeric [Pt-I(bpy)(2)] units, the crystals absorb strongly over the whole visible region and far into the near infrared. Their room temperature electrical conductivity is relatively high, 10 Ohm(-1) cm(-1).