Vanillin based colorimetric and fluorometric chemosensor for detection of Cu(II) ion: DFT calculation, DNA / BSA interaction and molecular docking studies

Abstract

• Vanillin based chemosensor ligand VNP has been designed and synthesized. • The ligand VNP can recognize Cu 2+ ion by colorimetric and fluorometric method. • The ligand VNP and VNP-Cu complex molecular structures are optimized by using DFT calculation. • The binding studies of ligand VNP with biomolecules like DNA, BSA and HSA are performed. • The interaction between the ligand VNP and biomolecules are confirmed by molecular docking studies. Vanillin based Schiff base ligand VNP was designed and synthesized which was used to study the calorimetric detection of Cu 2+ by a colour change from colourless into pink in the presence of other metal ions like Co 2+ , Ni 2+ , Zn 2+ , Pb 2+ , Hg 2+ , Sr 2+ , Cd 2+ , Ca 2+ , Na + , K + , Al 3+ and Cr 3+ in CH 3 CN/H 2 O (9/1, v/v) mixture. Similarly, the ligand VNP also exhibited fluorometric detection of Cu 2+ by “turn-off” process when compared with other metal ions which do not show any notable spectral changes. The ligand VNP is coordinated with Cu 2+ which results the formation of the VNP-Cu complex has the binding stoichiometric ratio at 1:1 as determined by ESI-MS, as well as job’s plot analysis and it was further explained by the CHEQ mechanism. The optimized geometry of the VNP and VNP-Cu complex was analysed by DFT methods, which results confirms the formation of the VNP-Cu complex. The detection range for the Cu 2+ is 2.34 μM. Furthermore, the effective interaction of VNP with the various biomolecules (BSA, HSA and DNA) has been analyzed by absorption and emission spectroscopic techniques. The obtained results were clearly indicates that the interaction between the VNP and biomolecules have better binding ability and which is confirmed by molecular docking studies.