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In this study, two chemosensors, N5R1 and N5R2, based on 5-(4-nitrophenyl)-2-furaldehyde, with varying electron-withdrawing groups, were synthesized and effectively employed for the colorimetric selective detection of arsenite anions in a DMSO/H 2 O solvent mixture (8 : 2, v/v). Chemosensors N5R1 and N5R2 exhibited a distinct color change upon binding with arsenite, accompanied by a spectral shift toward the near-infrared region (Δλ max exceeding 200 nm). These chemosensors established stability between a pH range 6-12. Among them, N5R2 displayed the lowest detection limit of 17.63 ppb with a high binding constant of 2.6163×10 5  M -1 for arsenite. The binding mechanism involved initial hydrogen bonding between the NH binding site and the arsenite anion, followed by deprotonation and an intramolecular charge transfer (ICT) mechanism. The mechanism was confirmed through UV and 1 H NMR titrations, cyclic voltammetric studies, and theoretical calculations. The interactions between the sensor and arsenite anions were further analyzed using global reactivity parameters (GRPs). Practical applications were demonstrated through the utilization of test strips and molecular logic gates. Real water samples, honey, and milk samples were successfully analyzed by both chemosensors for the sensing of arsenite., (© 2024 Wiley-VCH GmbH.)

Discriminating by color: A 2D colorimetric indicator array has been designed by a crystal engineering approach (NH-O hydrogen bonding and charge-transfer complexation) involving solid-state co-grinding for the visual discrimination of positional isomers of dihydroxynaphthalene. Factors governing the close packing of pi planes, and hence color of the complex, were determined by single-crystal X-ray analysis, allowing fine tuning by crystal engineering. A 2D colorimetric indicator array to discriminate isomers of dihydroxynaphthalene has been designed by using a crystal engineering concept combined with solid-state co-grinding and charge-transfer complexation. The NH-O supramolecular synthon between the pyridyl N atom of the probe and hydroxy group of the analyte has been observed in all reported single-crystal X-ray structures of resultant CT complexes. Solid-state co-grinding with aromatic solids easily provided the highly concentrated solvent-free conditions required to promote the formation of charge-transfer complexes with brighter color changes. Probe D (N,N'-bis-(4-pyridyl)pyromellitic diimide) showed an excellent ability to discriminate eight isomers of dihydroxynaphthalene with a wide variety of colors of the resultant CT complexes.

Organic salts based on dicyclohexylamine and substituted/unsubstituted cinnamic acid exhibit efficient gelation of organic fluids, including selective gelation of oil from an oil/water mixture. Among the cinnamate salts, dicyclohexylammonium 4-chlorocinnamate (1), 3-chlorocinnamate (2), 4-bromocinnamate (3), 3-bromocinnamate (4), 4-methylcinnamate (5) and the parent cinnamate (6) are gelators, whereas 2-chlorocinnamate (7), 2-bromocinnamate (8), 3-methylcinnamate (9), 2-methylcinnamate (10) and hydrocinnamate (11) are non-gelators. Non-gelation behaviour of 11 and various benzoate derivatives 12-18 indicate the significance of an unsaturated backbone in the gelation behaviour of the cinnamate salts. A structure-property correlation based on the single-crystal structures of most of the gelators (1, 3, 5 and 6) and non-gelators, such as 7, 8, 10-18, indicates that the prerequisite for the one-dimensional (1D) growth of the gel fibrils is mainly governed by the 1D hydrogen-bonded network involving the ion pair. All the non-gelators show either two- (2D) or zero-dimensional (0D) hydrogen-bonded assemblies involving the ion pair. The molecular packing of the fibres in the xerogels of 1, 3, 5 and 6 has also been established on the basis of their simulated powder diffraction patterns, XRPD of bulk solids and xerogels. Ab initio quantum chemical calculations suggests that pi-pi interactions is not a contributing factor in the gelation process.