This paper investigates the reactivity and optical properties of transition metal-incorporated organoantimony(V) clusters prepared by a solvothermal route. The detailed structural characterization of novel heterometallic M(2)Sb(4) oxo clusters is reported herein. Single crystal X-ray diffraction revealed the formation of hexanuclear organoantimony(V) based oxo clusters [(p-ClC(6)H(4)Sb)(4)V(2)(O)(2)(μ(3)-O)(2)(μ(2)-O)(2)(t-BuPO(3))(4)(μ(2)-OCH(3))(4)] (1), [M(2)(p-iPr-C(6)H(4)Sb)(4)(μ(3)-O)(2)(μ(2)-O)(2)(μ(2)-OCH(3))(4)(t-BuPO(3))(4)(py)(2)]·xCH(3)OH, where M = Mn, x = 2 (2), Co, x = 1 (3), Ni, x = 2 (4) and Cu, x = 2 (5). The magnetic behaviour of the clusters was probed by magnetic susceptibility measurements. Optical absorption studies showed that bandgap reduction can be achieved by incorporating an appropriate transition metal into the homometallic Sb(6) oxo cluster.