A copper complex receptor for nanomolar sulfide sensing and applications in DNA/BSA binding

Abstract

Traditionally toxic sulfide species (S^2–, HS^–, and H₂S) play indispensable roles in various biological, environmental, and industrial processes. However, excessive exposure to these species can result in numerous chronic diseases. Considering the importance of sulfide recognition, we have synthesized and characterized a simple 1:1 Cu(II) complex of L (CuCl₂L receptor) based on a substituted 2,6-dipyrazinylpyridine (dppy) moiety (L = 4-(2,6-di(pyrazin-2-yl)pyridin-4-yl)-N,N-dimethylaniline). The complex was analyzed both experimentally and computationally using DFT and TD-DFT calculations. The in-situ prepared CuCl₂L receptor is employed to selectively recognize sulfide species (detection limit: 82.50 nM) in the presence of other anions in higher concentration (ten equivalents of F^–, Cl^–, Br^–, I^–, CH₃CO₂^–, HCO₃^–, H₂PO₄^–, NO₃^–, SO₃^2–, SO₄^2–, S₂O₃^2–, CO₃^2–, and HPO₄^2– (10 mM)) in aqueous acetonitrile (2:1 v/v, 10 mM HEPES buffer, pH 7.4) through absorption spectral studies. Furthermore, the receptor is successfully utilized for various real-time detection applications and demonstrated significant intercalative binding interaction with Calf–Thymus DNA (CT-DNA) and good binding interactions with bovine serum albumin (BSA), supported by viscometry and molecular docking studies.