A luminescent copper(I) sulfide cluster [Cu-4(mu-dtpm)(4)(mu(4)-S)](PF6)(2) (3) {dtpm = bis[bis(4-methylphenyl)-phosphino]methane} has been synthesized and characterized by X-ray crystallography. Its photophysical and electrochemical properties have also been studied. The long-lived photoluminescence of 3 is assigned to originate from an excited state with a parentage of large ligand-to-metal charge-transfer LMCT [(S2-) --> Cu-4] character, with mixing of metal-centered MC [(ds/dp) Cu(I)(4)] state, The phosphorescent state of 3, as well as those of its analogues [Cu-4(mu-dppm)(4)(mu(4)-S)](PF6)(2) (1) and [Cu-4(mu-dppm)(4)(mu(4)-Se)](PF6)(2) (2), have been found to undergo facile electron-transfer reactions with different pyridinium accepters, which have been investigated with nanosecond transient absorption spectroscopy. Crystal data for 3 : a = 37.38(1) Angstrom, b = 15.905(7) Angstrom, c = 27.761(5) Angstrom, beta = 128.69(1)degrees, V = 12881(6) Angstrom(3), Z = 4.