Influence of steric confinement within zeolite Y on photoinduced energy transfer between [Ru(bpy)(3)](2+) and iron polypyridyl complexes

摘要

The spectroscopic and photophysical properties of zeolite-Y-entrapped [Ru(bpy)(3)](2+) co-doped with either [Fe(bpy)(3)](2+) or [Fe(tpy)(2)](2+) over a range of iron complex loadings are presented. In solution, [Ru(bpy)(3)](2+) undergoes efficient bimolecular energy transfer to [Fe(bpy)(3)](2+), whereas only radiative or trivial energy transfer occurs between [Ru(bpy)(3)](2+) and [Fe(tpy)(2)](2+). in sharp contrast, within zeolite Y, both [Fe(bpy)(3)](2+) and [Fe(tpy)(2)](2+) were found to effectively quench the donor emission. Fitting the Perrin model to the photophysical data yields an effective quenching radius of 32 and 27 angstrom, respectively, for [Fe(bpy)(3)](2+) and [Fe(tpy)(2)](2+). The long-range nature of the quenching suggests Forster energy transfer. Detailed spectroscopic investigations indicate that [Fe(tpy)(2)](2+) bound within zeolite Y undergoes significant distortion from octahedral geometry. This distortion results in increased oscillator strength and enhanced spectral overlap, between the [Ru(bpy)(3)](2+) (3)d pi-pi* donor emission and the co-incident acceptor (1)T2-Al-1 ligand field absorption compared with solution. This turns on an efficient energy transfer to [Fe(tpy)(2)](2+) within the confinement of the zeolite Y supercage. Overall, this is an interesting example of the ability of the zeolite environment to provoke new photophysical processes not possible in solution.