Heterocyclic boronates as colorimetric and chemical sensors for dialkyltin derivatives

Abstract

The relevance of recognition for diorganotin (IV) species has been increased due to biological and environmental issues. The development of molecules able to carry out the recognition process of diorganotin (IV) compounds by simple analytical techniques is an interesting research topic. This paper describes the synthesis of three heterocyclic boronates obtained by the reaction of one equivalent of 5-formyl-2-furanboronic acid with two equivalents of 2-aminophenol (1), 4‑hydroxy-3-aminobenzoic acid (2) or 4-nitro-2-aminophenol (3). Reactions resulted in a π-conjugated systems by the formation of two new six membered fused heterocycles since the furan ring opening, as corroborated by single X-ray diffraction analysis for compound 1. Compounds 1–3 are green-colored solids with melting points higher than 300 °C. A solvatochromic effect was observed having the absorption band maxima values between 525 and 600 nm. The presence of donor atoms (N, O) in the boronates allow the use as chemical sensors for dialkyltin derivatives (Me2SnO, Bu2SnO, Me2SnCl2, Bu2SnCl2) by UV–Vis and fluorescence techniques. The recognition process for dialkyltin derivates was detected by color changes in solution and even because the presence of a new absorption band in UV–Vis spectra which is shifted to 600 and 621 nm for compounds 1 and 2, respectively. Boronate 2 showed lower Limit Of Detection values (LOD) of 237 nM for Me2SnCl2 and 234 nM for Bu2SnCl2. Less affinity was noticed for trialkyl derivates ((CH3)3SnCl and (CH3)3SnOH).