Reaction of [(3-bdppmapy)(AuCl)2] with NaHmba (3-bdppmapy = N,N'-bis-(diphenylphosphanylmethyl-3-aminopytidine, H2mba = 2-mercaptobenzoic acid) resulted in a new tetranuclear Au/P/S complex [(3-bdppmapy)2(AuHmba)3(AuCl)] (1). Upon excitation at 370 nm, 1 exhibited solid state, room temperature, green fluorescent emission (QY = 4.7%, τ = 2.58 ns) which was significantly enanced at lower temperatures due to strengthening of the Au-Au interaction. Different ratios of 1 with phosphor N630 in PMMA were used to make thermochromic photoluminescent films and fibres that could be fabricated into an optical thermometer sensitive over temperature ranges 80-300 K and 300-370 K.