Diorganotin(IV) complexes of
N-acetyl-L-cysteine (H(2)NAC; (R)-2-acetamido-3-sulfanylpropanoic
acid) have been synthesized and their solid and
solution-phase structural configurations investigated by FTIR, Mössbauer, (1)H, (13)C and (119)Sn NMR spectroscopy. FTIR results suggested that in R(2)Sn(IV)NAC (R = Me, Bu, Ph) complexes NAC(2-) behaves as dianionic tridentate
ligand coordinating the
tin(IV) atom, through
ester-type carboxylate,
acetate carbonyl
oxygen atom and the deprotonated thiolate group. From (119)Sn Mössbauer spectroscopy it could be inferred that the
tin atom is pentacoordinated, with equatorial R(2)Sn(IV) trigonal bipyramidal configuration. In DMSO-d(6)
solution, NMR spectroscopic data showed the coordination of one
solvent molecule to
tin atom, while the coordination mode of the
ligand through the
ester-type carboxylate and the deprotonated thiolate group was retained in
solution. DFT (Density Functional Theory) study confirmed the proposed structures in
solution phase as well as the determination of the most probable stable ring conformation.
Biological investigations showed that Bu(2)
SnCl(2) and NAC2 induce loss of viability in HCC cells and only moderate effects in non-
tumor Chang liver cells. NAC2 showed lower cytotoxic activity than Bu(2)
SnCl(2), suggesting that the binding with NAC(2-) modulates the marked cytotoxic activity exerted by Bu(2)
SnCl(2). Therefore, these novel butyl derivatives could represent a new class of anticancer drugs.