Biphenyl-type sensing system in proton-rich environment by fluorescence and quantum-chemical calculations

Abstract

[EN] Biphenyl derivative N-allyl-N'-(4'-nitro[1,1'-biphenyl]-4-yl)thiourea (BP1) was synthesized as a functional fluorescent sensor for protons and their photophysical properties were studied. The influence of environment protonation on photophysical properties of the biphenyls in solutions was investigated using UV absorption, steady-state and time-resolved fluorescence spectroscopy. Semiempirical and DFT calculations and optimization of the molecular structure of the biphenyl derivatives in vacuum, in polar solvents and in a proton-rich environment were conducted using the HyperChem, Amsol and Gaussian3 software package. Fluorescence quenching with addition of acidic acid was observed and the Stern-Volmer quenching rate constant was about 3.0 x 10(9) M-1 s(-1). Intermolecular hydrogen bonds formations by the protons with the sulphur being substituted to the biphenyls generate charge movement and strong increase (x 5) of the dipole moment of the fluorophore. (C) 2010 Elsevier B.V. All rights reserved.