Influence of the Fluid-to-Film Transition on Photophysical Properties of MLCT Excited States in a Polymerizable Dimethacrylate Fluid

Photophysical properties of the salts [Ru(bpy)3](p-Tos)2, [Ru(dmb)3](PF6)2, [Ru(vbpy)3](PF6)2, and [Ru(phen)3](p-Tos)2 (bpy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine, vbpy = 4-methyl-4′-vinyl-2,2′-bipyridine, phen = 1,10-phenanthroline, and p-Tos = p-toluene sulfonate) in fluid and film polyethylene glycol dimethacrylate containing nine ethylene glycol spacers (PEG-DMA550) are reported. MLCT absorption energies and bandshapes are similar in fluid and film PEG-DMA550 pointing to similar local dielectric environments, presumably dominated by the polar acrylate groups. Emission energies and excited-to-ground state 0−0 energy gaps (E0), determined by emission spectral fitting, are blue-shifted, and band-widths-at-half height (Δv0,1/2) decreased, due to an expected “rigid medium effect” in PEG-DMA550 film. The extent of loss of medium dipole reorientation in the rigid environment, and the increased emission energies in the film, resulted in enhanced emission quantum yields and excited state lifet...