Gallium(III) complexes with 1,3-pdta-type of ligands: The influence of an alkyl substituent in 1,3-propanediamine chain and the metal counter cation on the structural properties of the complex

The hexadentate 1,3-propanediamine-N,N,N’,N’-tetraacetate (1,3-pdta4−) and (±)-1,3-pentanediamine-N,N,N’,N’-tetraacetate (1,3-pndta4−) ligands were used for the synthesis of two new gallium(III) complexes, Na[Ga(1,3-pdta)]·3H2O (1) and Ba[Ga(1,3-pndta)]2·3H2O (2). Complexes 1 and 2 were characterized by IR and NMR (1H and 13C) spectroscopy and single crystal X-ray diffraction analysis. The obtained results have shown that both hexadentate 1,3-pdta4− and 1,3-pndta4− ligands are coordinated to gallium(III) ion through the two nitrogen and four carboxylate oxygen atoms. Both complexes show significant octahedral distortion since the mean angular deviation is nearly four degrees per angle. However, the octahedral distortion of complex 2 is lower than of 1, as indicated by the ΣΔ(Oh) values (48° and 49° versus 53°, respectively). The binding interactions of the complexes 1 and 2 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) were studied by fluorescence emission spectroscopy. Both complexes can bind to the serum albumin reversibly, while their affinity to ct-DNA is rather low.