Exploring the dark: detecting long-lived Nile Red (ILCT)-I-3 states in Ru(ii) polypyridyl photosensitisers

Two novel Ru(ii) photosensitisers sporting ethynyl-Nile Red chromophores are shown to absorb strongly in the visible region, and to have two distinct but weakly emissive states ((ILCT)-I-1* and (MLCT)-M-3*). In addition a long-lived, lower energy 'dark' (non-emissive) triplet excited state is identified ((ILCT)-I-3*) and successfully exploited for singlet oxygen generation.