Square-planar cations of the orange form of [Pt(Me(2)bzimpy)-Cl](PF6)center dot DMF [Me(2)bzimpy = 2,6-bis(N-methylbenzimidazol-2-yl)pyridine] stack along the b axis in a head-to-tail arrangement with short interplanar spacings (3.35 and 3.39 angstrom). Long intermolecular Pt center dot center dot center dot Pt contacts [4.336(2) and 4.565(2) angstrom] and comparatively short Me(2)bzimpy center dot center dot center dot Me(2)bzimpy distances are consistent with spectroscopic measurements for orange salts of Pt(Me(2)bzimpy)Cl+. The DMF solvent molecules line channels parallel to c, which may provide a conduit for vapor absorption. The crystals are vapochromic, changing from orange to violet upon exposure to acetonitrile vapor. The changes in spectroscopic properties accompanying vapor absorption are consistent with changes in intermolecular interactions between complexes.