Several six-coordinate Mo(III) complexes phosphoresce and undergo photooxidation in room-temperature solution. The phosphorescence of (Me-3[9]aneN(3))MoX3 (Me-3[9]aneN(3) = 1,4,7-trimethyl-1,4,7-triazacyclononane) in CH3-CN at room temperature occurs with the following maxima, lifetimes, and quantum yields : X = Cl, 1120 nm, 1.0 mu s, and 6.1 x 10(-5); X = Br, 1130 nm, 0.80 mu s, and 9.6 x 10(-5); and X = I, 1160 nm, 0.40 mu s, and 1.2 x 10(-4), respectively. The phosphorescences are assigned to the {E-2(g), T-2(1g)} --> (4)A(2g) transition. Solutions of HB(Me(2)pz)(3)(MoCl3-)-Cl-III Me(2)pzH = 3,5-dimethylpyrazole) in CH3CN, and solid MoCl3(py)(3) and (Me-3[9]aneN(3))-WCl3, also phosphoresce. (Me-3[9]aneN(3))MoX3 (X Cl, Br, I) complexes undergo reversible one-electron photooxidation upon irradiation in the presence of accepters such as TCNE and chloranil. (Me-3[9]aneN(3))MoX3 (X = Br, I only) are photooxidized irreversibly to [(Me-3[9]aneN(3))(MoX3)-X-IV](+) by C(NO2)(4) in CH3CN. In CH3CN-H2O (1:1 v/v), photoinitiated two-electron oxidation occurs : the primary photoproduct is Mo(IV), which disproportionates spontaneously to form [(Me-3[9]aneN(3))(MoOX2)-O-V](+).