Vapochromic and mechanochromic films from square-planar platinum complexes in polymethacrylates

Square-planar platinum(II) complexes of the 4-dodecyloxy-2,6-bis(N-methylbenzimidazol-2'-yl) pyridine ligand have been blended into a series of methacrylate polymers. Each of the polymer films displayed vapochromic (yellow to red) and vapoluminescent behaviour as a result of the vapour induced change in the Pt-Pt interactions. The solid-state absorption and emission properties of the films were characterized, and the influence of the polymer matrix on the vapochromic response was investigated. Notably, the rate of recovery of the yellow colour after vapour-exposure was found to be dependent on the T-g of the matrices, and the response can be effectively erased and the materials restored to the original yellow colour within minutes by simply heating above their T-g. The polymer-complex blends also displayed interesting mechanochromic and mechanoluminescent properties upon deformation either by compression, scratching, or stretching. The accumulated data are consistent with a solvato- or mechano-induced structural rearrangement that results in a shortening of the Pt-Pt distances.