Temperature-dependent photoluminescence (PL) and structural studies of (TPA) AuBr, 2,(TPA) AuI, 3, and [(TPAH) AuI][Aul2], 4, are reported. Unlike (TPA) AuCl, 1, compound 2 has twoemission bands with relative intensities which depend upon the excitation wavelength used. Upon excitation at 320 nm, a strong orange emission centering at 647 nm is observed. Changing the excitation wavelength to 340 nm results in the observance of only a bright white, structured emission centering ca. 450 nm. Each of the two emission bands shows a distinct excitation spectrum, suggesting poor coupling between the excited states responsible for the emissions. Compared to that of 2, the LE band of 3 is blue-shifted to 617 nm, whereas the structured HE band is unshifted at ca. 450 nm. The relative intensity of the LE band to the HE band decreases (with no shift in energy) whenthe excitation wavelength is changed from 320 to 350 nm. Similar to those of 2, the emission bands of 3 also are sensitive to the excitation energy. The HE bands of both 2 and 3 are short lived (< 10 ns) whereas the LE bands have lifetimes of 0.8 and 2.7/¿ s, respectively. On the basis of these observations, the complexes appear to show multiple emitting states in their solid state structures. The systematic changes occurringwith variation of the halide X and the lifetime data suggest that the LE band originates from a triplet metal-centered transition (3MC). The HE emission band appears to originate from a halide to metal charge transfer ('XMCT) excited state. Protonation of the ligand TPA significantly alters the PL properties of the complexes in accord with changes in the Au··-Au separation. The metal-centered LE band of the protonated complex (TPAHBr) AuBr, 2P, is observed at the blue-shifted position of 587 nm when compared to that of 2. Protonation of 3 with 0.1 Nhc1 produces 4. Compound 4 luminesces strongly with emission maxima at 655 nm at 78 K. A simple model that correlates the LE emission with the Au··-Au separation has been developed. The Au··-Au separations in these species are predicted from the position of the emission energy using the equation (E+ P)/r= constant, where E is the emission energy, P is the singlet—triplet separation, and r corresponds to the Au··* Au distance. The result is supported by extended Hückel MO calculations where, upon shortening of the Au··-Au separation, the HOMO (rtu) orbital destabilizes and causes a decrease in the HOMO—LUMO gap. Crystal data:[(TPAH) AuI][Aul2], 4, orthorhombic, Pnma (No. 62) with a= 15.453 (3) Á, b= 11.050 (2) Á, c= 9.113 (2) Á, V= 1556.1 (5) Á3, Z= 4, R= 0.0419, Rw= 0.0548.