Development of piperazine conjoined 1,2,3-triazolyl-γ-propyltriethoxysilanes: Fluorometric detection of Cr3+ ions and computational study

Abstract

Chromium is essential for some biochemical processes, and excess is a big concern that shows adverse effects on human health and the environment. Therefore, it is urgent to design new sensors to detect chromium ions rapidly. The present study discusses the synthesis of piperazine conjoined 1,2,3-triazolyl-γ-propyltriethoxysilanes (4a-4b) and development of 4a as fluorescence turn-on sensor for the detection of Cr3+ ions. The mechanistic insights reveal to the restricted CN rotation and inhibited intramolecular charge transfer (ICT) process. In addition, Job's plot and Benesi-Hildebrand plot justify the 1:1 binding affinity with a binding constant of 9.96 × 105 M−1 for [ligand 4a + Cr3+] complex and the limit of detection for Cr3+ ions is observed as 6.06 × 10-8 M. The fluorescence spectral changes, 1H NMR spectra and DFT studies provide evidences for ligand 4a and Cr3+ ions interactions. Further, the reversibility of the ligand 4a from [ligand 4a + Cr3+] complex on the addition of EDTA can be used in the construction of molecular logic gate where Cr3+ and EDTA are considered as inputs and the fluorescence intensity at 398 nm as output. Further, compounds 4a-4b were then evaluated for their antibacterial activity against bacterial strains (Escherichia coliand Staphylococcus aureus), revealing a modest activity. The binding mode of ligand 4a to Staphylococcus aureus (PDB ID − 3U2K) and Escherichia coli (PDB ID − 5Z4O) was investigated using an in-silico molecular docking technique, which revealed that the triazole ring and silanyl group are involved in hydrogen bonding with proteins and may be the cause of the ligand's antibacterial activity. The ligand 4a demonstrated a high affinity for binding within the active sites of proteins with binding energies of −7.97 kcal/mol (3U2K) and −8.68 kcal/mol (5Z4O).