A novel series of thiolato bridged manganese(I) based flexible/semiflexible ester functionalized dinuclear metallacycles have been obtained under one-pot reaction conditions. Three precursor self-assembly of Mn₂(CO)₁₀, diphenyl disulfide, and flexible/semiflexible ester functionalized ditopic pyridyl ligands (L) [L = 1,3-bis(4-pyridyl)propane (bpp), o-phenylene diisonicotinate (pdi), ethanediyl di-4 pyridine carboxylate (edp), 1,4-butanediyl di-4-pyridine carboxylate (bdp), 1,6-hexanediyl di-4-pyridine carboxylate (hdp), 4-pyridine carboxylic acid diethylene glycol diester (pcadgd), and 4-pyridine carboxylic acid triethylene glycol diester (pcatgd)] afforded the formation of dinuclear metallacycles with the general formula [{(CO)₃Mn(μ-SC₆H₅)₂Mn(CO)₃}(μ-L)] (1–7). The metallacycles 1–7 were characterized by IR, NMR, UV/Vis, and ESI-mass spectroscopic techniques and elemental analysis. The single-crystal X-ray structures of the metallacycles 1, 2, and 6 revealed the existence of a dinuclear metallacyclic framework. Cytotoxic activities of 1–7 have been evaluated towards various cancer cell lines, together with CO releasing (COR) studies for 1 and 3.