Highly selective acridinium based cyanine dyes for the detection of DNA base pairs (adenine, cytosine, guanine and thymine)

In the current study, the DFT calculations are performed to investigate the binding properties of nonsymmetric cyanine dyes (1a, 1b, 1c and 1d) for DNA base pairs. The effect of change in methine chain between two heterocycles on reactivity is explored through chemical reactivity descriptors (Global) including ionization potential (IP), electron affinity (EA), hardness (eta), softness (S), electronegativity (chi) and MEP (molecular electrostatic potential). The results of reactivity descriptors reflect the increase in the sensitivity of cyanine by increasing methine chain. Interaction behavior of cyanine dyes 1a to 1d with DNA nitrogenous bases is rationalized by comparing the electronic and geometric parameters. The interaction energies calculated at M05-2X/6-31 + + G(d,p) level of theory, suggest stronger interaction of cyanine dyes with DNA nitrogenous bases. The choice of density functional for UV-Vis is obtained through a benchmark study against available experimental data. Red shift in UV-Vis spectrum is obtained upon interaction with nucleic bases.