In vitro binding studies of organotin(IV) complexes of 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol with CT-DNA and nucleotides (5′-GMP and 5′-TMP): Effect of the ancillary ligand on the binding propensity |
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Authors: | Farukh Arjmand Fatima Sayeed Shazia Parveen |
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Institution: | Department of Chemistry, Aligarh Muslim University, Aligarh, UP 202002, India |
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Abstract: | The chiral benzimidazole ligand, 1,2-Bis(1H-benzimidazol-2-yl)ethane-1,2-diol, L, exhibiting coordination mode with an oxygen atom of alcohol group directed towards the metal ion and another -OH group with different molecular axis directed away from the metal center was utilized as a building block for organotin complexes C18H19N4O2SnCl], C28H23N4O2SnCl] and C52H42N4O2Sn2] (1-3). Complexes 1 and 3 exhibit a pentacoordinate geometry while the complex 2 reveals hexacoordinated environment around the Sn(IV) metal ions as evidenced by 119Sn NMR studies. The DNA binding ability of benzimidazole ligand and their organotin(IV) complexes 1-3 were examined by employing different biophysical methods. The absorption titration of the complexes with CT-DNA reveal significant hyperchromic effect together with strong bathochromic shift of 4-5 nm which infer substantial binding of the complexes with CT-DNA. The intrinsic binding constant Kb values of the complexes 1-3 were found to be 2.16 ± 0.04 × 104, 3.47 ± 0.04 × 104 and 4.60 ± 0.04 × 103 M−1, respectively, suggesting pronounced binding of complex 2 with DNA double helix. The mechanism of binding of the complexes was further ascertained by the interaction studies of these complexes with nucleotides (5′-GMP and 5′-TMP) using absorption spectroscopy suggesting a clear preference for 5′-GMP binding which was further authenticated by NMR (1H and 31P NMR) studies. |
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Keywords: | Organotin(IV) complexes DNA binding 5&prime -GMP & 5&prime -TMP Circular dichroism |
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