Roy Snigdha, Das Sanju, Ray Ambarish, Parui Partha Pratim
Department of Chemistry, Jadavpur University Kolkata 700032 India
Department of Chemistry, Maulana Azad College Kolkata 700013 India.
RSC Adv. 2021 Sep 9;11(48):30093-30101. doi: 10.1039/d1ra05201b. eCollection 2021 Sep 6.
Detection of methanol (MeOH) in an ethanol (EtOH)/isopropanol ( PrOH) medium containing water is crucial to recognize MeOH poisoning in alcoholic beverages and hand sanitizers. Although chemical sensing methods are very sensitive and easy to perform, the chemical similarities between the alcohols make MeOH detection very challenging particularly in the presence of water. Herein, the fluorometric detection of a trace amount of MeOH in EtOH/ PrOH in the presence of water using alcohol coordinated Al(iii)-complexes of an aldehydic phenol ligand containing a dangling pyrazole unit is described. The presence of MeOH in the EtOH/ PrOH causes a change of the complex geometry from tetrahedral (Td) to octahedral (Oh) due to the replacement of the coordinated EtOH/ PrOH by MeOH molecules. The Td-complex exhibited fluorescence but the Oh-species did not, because of the intramolecular photo-induced electron transfer (PET). By interacting the Oh species with water, its one MeOH coordination is replaced by a water molecule followed by the proton transfer from the water to pyrazole-N which generates strong fluorescence by inhibiting the PET. In contrast, the water interaction dissociates the Td-complex to exhibit fluorescence quenching. The water induced reversal of the fluorescence response from the decrease to increase between the absence and presence of MeOH is utilized to detect MeOH in an EtOH/ PrOH medium containing water with a sensitivity of ∼0.03-0.06% (v/v). The presence of water effected the MeOH detection and allows the estimation of the MeOH contamination in alcoholic beverages and hand sanitizers containing large amounts of water.
在含有水的乙醇（EtOH）/异丙醇（PrOH）介质中检测甲醇（MeOH）对于识别酒精饮料和洗手液中的甲醇中毒至关重要。尽管化学传感方法非常灵敏且易于操作，但醇类之间的化学相似性使得甲醇检测极具挑战性，尤其是在有水存在的情况下。本文描述了使用含有悬挂吡唑单元的醛酚配体的醇配位铝（iii）配合物，在有水存在的情况下对EtOH/PrOH中痕量MeOH进行荧光检测。由于MeOH分子取代了配位的EtOH/PrOH，EtOH/PrOH中MeOH的存在导致配合物几何结构从四面体（Td）变为八面体（Oh）。由于分子内光诱导电子转移（PET），Td配合物表现出荧光，而Oh物种则没有。通过使Oh物种与水相互作用，其一个MeOH配位被一个水分子取代，随后质子从水转移到吡唑-N，通过抑制PET产生强荧光。相反，水相互作用使Td配合物解离，表现出荧光猝灭。利用水诱导的MeOH存在与否之间荧光响应从降低到增加的逆转，以约0.03 - 0.06%（v/v）的灵敏度检测含有水的EtOH/PrOH介质中的MeOH。水的存在影响了MeOH的检测，并允许估计含有大量水的酒精饮料和洗手液中MeOH的污染情况。
