A Highly Selective and Sensitive Sequential Recognition Probe Zn2+ and H2PO4− Based on Chiral Thiourea Schiff Base

Abstract

A series of novel chiral thiourea fluorescent probes HL1–HL6 were designed and synthesized from (1R,2R)-1,2-diphenylethylenediamine, phenyl isothiocyanate, and different substituted salicylic aldehydes. All of the compounds were confirmed by 1H NMR, 13C NMR, and HRMS. They exhibit high selectivity and sensitivity to Zn2+ in the presence of nitrate ions with the detection limit of 2.3 × 10−8 M (HL5). Meanwhile, their zinc (II) complexes (L-ZnNO3) showed continuous response to H2PO4− in acetonitrile solution. The identification processes could further be verified by supramolecular chemistry data analysis, X-ray single-crystal diffraction analysis, and theoretical study. The research provides reliable evidence for an explanation of the mechanism of action of thiourea involved in coordination, which is important for the application of thiourea fluorescent probes. In short, the sensors HL1–HL6 based on chiral thiourea Schiff base will be promising detection devices for Zn2+ and H2PO4−.

A Simple Schiff Base Probe for Quintuplicate-Metal Analytes with Four Emission-Wavelength Responses

“…At the same time, the fluorescent emission for ABJ-MS at 530 nm was simultaneously decreased alongside the appearance of a new strong emission band at 434 nm along with the increasing HCl amount. The optical responses for ABJ-MS to the addition of HCl can be rationalized as follows: ABJ-MS may coexist as a mixture of enol-imine and keto-enamine isomers, although favors the keto-enamine isomer under a neutral environment, which is approved by the proton band at 13.52 ppm and is associated with an intramolecular hydrogen band (O…H-N) in the 1 H NMR for ABJ-MS [4,30]. Upon the addition of HCl, the H + firstly coordinates with the oxygen atom in the C=O unit from the keto-enamine isomer, which inhibits the intramolecular H-bonding interaction, promotes…”

“…The optical responses for ABJ-MS to the addition of HCl can be rationalized as follows: ABJ-MS may coexist as a mixture of enol-imine and keto-enamine isomers, although favors the keto-enamine isomer under a neutral environment, which is approved by the proton band at 13.52 ppm and is associated with an intramolecular hydrogen band (O. . .H-N) in the 1 H NMR for ABJ-MS [4,30]. Upon the addition of HCl, the H + firstly coordinates with the oxygen atom in the C=O unit from the keto-enamine isomer, which inhibits the intramolecular H-bonding interaction, promotes the conversion from the keto-enamine isomer to the enol-imine isomer, and results in a bathochromic shift in the maximum absorption from ABJ-MS [48,49].…”

“…For example, Zn 2+ as an essential element has taken part in some physiological activities. Yet, the insufficiency/surfeit of zinc ions could cause Friedreich's ataxia, Alzheimer's and Parkinson's diseases [3,4]. Similarly, excessive/deficient Cu 2+ could bring about certain neurological sickness and gastrointestinal disturbances, Fe 3+ may induce liver and kidney diseases as well as metabolism maladjustment, while Al 3+ can cause some damage to human s central nervous and immune systems [5][6][7][8].…”

Recent Advances in Chiral Schiff Base Compounds in 2023

“…Significant progress has been made in the spectroscopic analysis of new optical activities that go beyond UV-visible circular dichroism. In wet analysis, a highly selective and sensitive ion recognition probe based on a "chiral" thiourea Schiff base has been reported [16]; the study of optical activity is still important.…”