The Synthesis and Anion Recognition Property of Symmetrical Chemosensors Involving Thiourea Groups: Theory and Experiments

Acridinedione as selective flouride ion chemosensor: a detailed spectroscopic and quantum mechanical investigation

The use of small molecules as chemosensors for ion detection is rapidly gaining popularity by virtue of the advantages it offers over traditional ion sensing methods. Herein we have synthesized a series of acridine(1,8)diones (7a-7l) and explored them for their potential to act as chemosensors for the detection of various anions such as fluoride (F-), acetate (OAc-), bromide (Br-), iodide (I-), bisulfate (HSO4 -), chlorate (ClO3 -), perchlorate (ClO4 -), cyanide (CN-), and thiocyanate (SCN-). Acridinediones were found to be highly selective chemosensors for fluoride ions only. To investigate in detail the mechanism of selective fluoride ion sensing, detailed spectroscopic studies were carried out using UV-visible, fluorescence and 1H NMR spectroscopy. Fluoride mediated (NH) proton abstraction of acridinedione was found to be responsible for the observed selective fluoride ion sensing. Quantum mechanical computational studies, using time dependent density functional theory (TDDFT) were also carried out, whereupon comparison of acridinedione interaction with fluoride and acetate ions explained the acridinedione selectivity for the detection of fluoride anions. Our results provide ample evidence and rationale for further modulation and exploration of acridinediones as non-invasive chemosensors for fluoride ion detection in a variety of sample types.

A comparative study of the metal binding behavior of alanine based bis-thiourea isomers

Two new symmetrical bis-thiourea, 2,2′-[{(terephthaloylbis(azanediyl)bis(carbonothioyl) bis(azanediyl)}dipropanoic acid] (1A) and 3,3′-[{(terephthaloylbis(azanediyl)bis (carbonothioyl)bis(azanediyl)} dipropanoic acid] (1B) were synthesized by the reaction of terephthaloyl chloride with α- and β-alanine in good yields. Their binding properties were investigated with various metal cations using UV–Vis titration experiments. Both isomers exhibited effective binding with Ag⁺, Cu²⁺, Hg²⁺, Pb²⁺, Fe²⁺ and Fe³⁺ cations. However, in the presence of other cations, such as Na⁺, Ni²⁺, Co²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Ca²⁺, Sn²⁺, Al³⁺, and anions tetrabutylammonium Cl⁻ and H₂PO₄⁻, no interaction occurred. Both isomers displayed similar trends towards binding with metal cations.

Novel quinoxaline based chemosensors with selective dual mode of action: nucleophilic addition and host–guest type complex formation

New quinoxalinium salts1–5have been exploited as chemosensorsvianaked eye, UV-Vis absorption, fluorescence quenching and¹H NMR experiments.