N-Dansyl-carbazoloquinone; a chemical and electrochemical fluorescent switch

Fluorescence Sensors Based on Hydroxycarbazole for the Determination of Neurodegeneration-Related Halide Anions

The environmental presence of anions of natural origin or anthropogenic origin is gradually increasing. As a tool to tackle this problem, carbazole derivatives are an attractive gateway to the development of luminescent chemosensors. Considering the different mechanisms proposed for anion recognition, the fluorescence properties and anion-binding response of several newly synthesised carbazole derivatives were studied. Potential anion sensors were designed so that they combined the native fluorescence of carbazole with the presence of hydrogen bonding donor groups in critical positions for anion recognition. These compounds were synthesised by a feasible and non-expensive procedure using palladium-promoted cyclodehydrogenation of suitable diarylamine under microwave irradiation. In comparison to the other carbazole derivatives studied, 1-hydroxycarbazole proved to be useful as a fluorescent sensor for anions, as it was able to sensitively recognise fluoride and chloride anions by establishing hydrogen bond interactions through the hydrogen atoms on the pyrrolic nitrogen and the hydroxy group. Solvent effects and excited-state proton transfer (ESPT) of the carbazole derivatives are described to discard the role of the anions as Brönsted bases on the observed fluorescence behaviour of the sensors. The anion-sensor interaction was confirmed by 1H-NMR. Molecular modelling was employed to propose a mode of recognition of the sensor in terms of complex stability and interatomic distances. 1-hydroxycarbazole was employed for the quantitation of fluoride and chloride anions in commercially available medicinal spring water and mouthwash samples.

Structures and intriguing conformational behavior of 1- and 2-naphthalenesulfonamides as determined by gas-phase electron diffraction and computational methods

The saturated vapors of 1- and 2-naphthalenesulfonamides (1-NaphSA and 2-NaphSA) were studied by the gas-phase electron diffraction/mass-spectrometric method at 413(9) and 431(9) K. According to quantum chemical calculations (DFT/B3LYP and MP2 with cc-pVDZ, aug-cc-pVDZ, cc-pVTZ, and aug-cc-pVTZ basis set) 1-NaphSA possesses four conformers with different orientations of the SO2NH2 fragment relative to the naphthalene frame and eclipsed or staggered orientation of the N-H and S═O bonds, whereas 2-NaphSA possesses only two conformers with different orientations of the N-H and S═O bonds. It was experimentally established that vapors over 1-NaphSA and 2-NaphSA exist predominantly (up to 75 mol %) of low-energy conformers of C1 symmetry in which the C-S-N planes deviate from perpendicular orientation relative to the naphthalene skeleton with near eclipsed orientation of the N-H and S═O bonds of the SO2NH2 fragment. The following geometrical parameters (Å and degrees) of the dominant conformers were derived: r(h1)(C-H) = 1.089(4), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.761(10), r(h1)(S-O)av = 1.425(3), r(h1)(S-N) = 1.666(10), ∠C-C1-C = 119.8(2), ∠C1-S-N = 104.5(22), C9-C1-S-N = 69.5(30) for 1-NaphSA; r(h1)(C-H) = 1.083(5), r(h1)(C-C)av = 1.411(3), r(h1)(C-S) = 1.780(7), r(h1)(S-O)av = 1.427(4), r(h1)(S-N) = 1.668(6), ∠C-C2-C = 123.0(3), ∠C2-S-N = 103.6(19), C1-C2-S-N = 110(10) for 2-NaphSA. The connection between nonequivalence of the C-C bonds in the naphthalene frame and spatial orientation of the substituents SO2NH2 is discussed. Transition states between conformers and enantiomers were determined.

Synthesis, molecular docking and antibacterial evaluation of new 1,4-naphthoquinone derivatives contains carbazole-6,11-dione moiety

A new series of new 1,4-naphthoquinone derivatives containing carbazole-6,11-dione moiety, which has not been reported yet, has been synthesized from 1,4-naphthoquinone and 4-aminophenylsulfone involving a Michael addition, benzoylation, and Pd-catalyzed coupling. This set of compounds has been evaluated for in vitro antibacterial studies against different Gram-positive and Gram-negative bacteria, and most of the synthesized compounds exhibited good antibacterial activity and the minimum inhibitory concentrations (MICs) are compared with the standard drugs used. Compound 7 exhibited good antibacterial activity among all the molecules studied with the best MIC of 2.1 μg/mL against Bacillus subtilis. To understand the molecular interactions with targeted proteins, the molecular docking of all the synthesized compounds were carried out; between 14 molecules docked, compound 7 was the one with the best glide and E model score of -7.73 and -95.37, respectively. In all docked molecules, compound 5 exhibited least glide and E model score of -4.55 and -101.56, respectively. Figureᅟ

Redox-controlled fluorescence modulation (electrofluorochromism) in triphenylamine derivatives

The study of the chemical and electrochemical fluorescence switching properties of a family of substituted triphenylamine derivatives is reported.