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Three new N,N′,N′′-trisubstituted guanidine derivatives (L1, L2 and L3) were synthesized and characterized using NMR and mass spectral studies. The structures of these ligands have been confirmed using single-crystal XRD studies. The interactions between these ligands and calf-thymus DNA (CT-DNA) were investigated in vitro using different spectroscopic methods and molecular docking and simulation methods in a physiological buffer (pH 7.4). UV-Vis spectral titrations suggested the formation of an L2/CT-DNA complex. The addition of increasing amounts of CT-DNA enhanced the fluorescence of L2 with a binding constant on the order of 104 M−1, indicating fairly strong binding between them. Thermodynamic parameters ΔG0 < 0 and ‖ΔH0‖ < T‖ΔS0‖ suggested that the complexation is spontaneous and entropy-driven where hydrophobic interaction plays a dominant role in stabilizing the complex. Molecular docking and metadynamics simulation studies indicated partial intercalation of one of the phenyl rings between the base pairs of DNA, which is strongly supported by circular dichroism, viscosity measurements and KI quenching studies. [ABSTRACT FROM AUTHOR]

The title compound, C26H27BrN2O2S, has two fused pyrrolidine rings, each in a twist conformation. [ABSTRACT FROM AUTHOR]

The title compound (E)-N'-(4-chlorobenzylidene)-4-fluorobenzohydrazide monohydrate (CBFBH) is a novel hydrazone Schiff base compound, synthesized and characterized by FTIR, 1H and 13C NMR, UV-Vis and single crystal X-ray diffraction analyses. Quantum chemical computations were performed by Density Functional Theory (DFT) with B3LYP/6-311G (d,p) level to study the structural and spectral properties of the synthesized compound. Reliability of the crystal structure was visualized by Hirshfeld surface analysis. Third-order nonlinear optical polarization coefficient was calculated by Z-scan technique. [ABSTRACT FROM AUTHOR]

A new chemo-dosimeter AK4 containing quinoline fluorophore has rationally been designed, synthesised and characterized using 1H and 13C NMR and mass spectral techniques. The probe senses explicitly CN− ion through a dramatic enhancement in fluorescence over other commonly coexistent anions in H2O:DMSO (9:1 v/v) medium over a broad pH range (4–10). 1H NMR titration revealed the deprotonation followed by nucleophilic addition reaction of CN−, which was supported by 13C NMR and mass spectral examinations. The Job’s continuous variation method indicated the formation of a 1:1 adduct between AK4 and CN− with a binding constant of 1.62 × 104 M−1. A limit of detection (LOD) towards CN− of 0.69 µM has been determined, which is much lower than the World Health Organization (WHO) recommended limit of CN− in drinking water (1.9 µM). The changes in the optical properties of AK4 upon reaction with CN− were delineated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations. Moreover, fluorescence microscopic studies established that AK4 could be an effective probe for imaging intracellular CN− in HeLa cells. [ABSTRACT FROM AUTHOR]

Different spectroscopic techniques and Density Functional Theory (DFT)/Time-Dependent Density Functional Theory (TDDFT) calculations have been employed to investigate the dual channel CN− detection behaviour of the developed chemo-dosimeter (AK3). The CN− with AK3 reaction triggered a colour change from pale yellow to colourless and enhanced fluorescence. UV–Vis, fluorescence, 1H & 13C NMR and mass techniques coupled with theoretical calculations (Mulliken charges, dihedral angles) revealed that the CN− sensing process mechanism involves deprotonation of the N–H group followed by nucleophilic addition reaction. Detailed TD-DFT calculations showed that the relaxation of excited electrons from LUMO and to two different ground states is responsible for the weak/moderate fluorescence of AK3. Nucleophilic addition of CN− to the C-atom of the CH = CH bridge terminated the π-conjugation between donor and acceptor regions, reduced the coplanarity, decreased the ICT transition and consequently enhanced the fluorescence of the probe. The practical utility of the probe was demonstrated by detecting cyanide in food materials and determining CN− in environmental water samples. [ABSTRACT FROM AUTHOR]