[Mn(CO)(5)Br] reacts with cysteamine and 4-aminothiophenyl with a ratio of 2:3 in refluxing tetrahydrofuran to the complexes of the type [{(OC)(3)Mn}(2)(mu-SCH2CH2NH3)(3)]Br-2 ( 1, CORM-EDE1) and [{(OC)(3)Mn}(2)(mu-SC6H4-4-NH3)(3)]Br-2 (2, CORM-EDE2). Compound 2 precipitates during refluxing of the tetrahydrofuran solution as a yellow solid whereas 1 forms a red oil that slowly solidifies. Recrystallization of 2 from water yields the HBr-free complex [{(OC)(3)Mn}(2)(mu-S-C6H4-4-NH2)(2)(mu-SC6H4-4NH(3))] (3). The n-propylthiolate ligand (which is isoelectronic to the bridging thiolate of 1) leads to the formation of the di- and tetranuclear complexes (OC)(4)Mn(mu-S-nPr)(2)](2) and (OC)(3)Mn(mu-S-nPr)](4). CORM-EDE1 possesses ideal properties to administer carbon monoxide to biological and medicinal tissues upon irradiation (photoCORM). Isolated crystalline CORM-EDE1 can be handled at ambient and aerobic conditions. This complex is nontoxic, highly soluble in water, and indefinitely stable therein in the absence of air and phosphate buffer. CORM-EDE1 is stable as frozen stock in aqueous solution without any limitations, and these stock solutions maintain their CO release properties. The reducing dithionite does not interact with CORM-EDE1, and therefore, the myoglobin assay represents a valuable tool to study the release kinetics of this photo CORM. After CO liberation, the formation of MnHPO4 in aqueous buffer solution can be verified.