Excitation dependent emissive multi stimuli responsive ESIPT organic luminogen for monitoring sea food freshness.

Excited state intramolecular proton transfer (ESIPT) organic luminophores with excitation wavelength-dependent color tunability have drawn significant attention due to their exceptional photoluminescent properties in solution and solid state. A novel salicylaldehyde-based Schiff's base molecule, (E)-N'-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (BHN) exhibited stimuli (excitation wavelength and pH) induced changes in fluorescence properties which was utilised for applications like trace level water sensing in organic solvents (THF, acetone and DMF), detection and quantification of biogenic amines and anticounterfeiting. In the solution state, BHN rendered a ratiometric detection and quantification of ammonia, diethylamine and trimethylamine, which is further supported by DFT studies. The photoluminescent response of BHN towards various biogenic amines was later utilised to monitor shrimp freshness. The investigation carried out highlights the potential versatility of ESIPT hydrazones, which renders multi stimuli responsive behaviour that can be utilised for water sensing, anticounterfeiting and the detection and quantification of biogenic amines.

Spectroscopic, crystal structure and DFT-assisted studies of some nickel(II) chelates of a heterocyclic-based NNO donor aroylhydrazone: in vitro DNA binding and docking studies.

Five new nickel(II) complexes have been synthesised with an NNO donor tridentate aroylhydrazone (HFPB) employing the chloride, nitrate, acetate and perchlorate salts, and all the complexes are physiochemically characterized. Elemental analyses suggested stoichiometries as Ni(FPB)(NO3)]·2H2O (1), [Ni(HFPB)(FPB)]Cl (2), [Ni(FPB)(OAc)(DMF)] (3), [Ni(FPB)(ClO4)]·DMF (4), [Ni(FPB)2] (5). Aroylhydrazone is found coordinating in deprotonated iminolate form in four of the complexes (1, 3, 4, 5) however in one case (complex 2), two aroylhydrazone moieties are binding to the metal centre in the neutral and anionic forms. The structure of the bisligated complex 5, found using single crystal X ray diffraction studies confirmed that the metal has a distorted octahedral N4O2 coordination environment, with each of the two deprotonated ligands coordinating through the pyridine nitrogen, imino-hydrazone nitrogen and the enolate oxygen of the hydrazone moiety. To compare and study, the electronic interactions and stabilities of the metal complexes, various quantum chemical parameters were calculated. Moreover, Hirshfeld surface analysis was carried out for complex 5 to determine the intermolecular interactions. The biophysical attributes of the ligand and complex 5 have been investigated with CT-DNA and experimental outcomes show that the Ni(II) complex exhibited higher binding propensity towards DNA as compared to ligand. Furthermore, to specifically understand the type of interactions of the metal complexes with DNA, molecular docking studies were effectuated. In addition, the electronic and related reactivity behaviors of the ligand and five Ni(II) complexes were studied using B3LYP/6-31 + + G**/LANL2DZ level. As expected, the obtained results from Natural Bond Orbital (NBO) computations displayed that the resonance interactions (n → π* and π → π*) play a determinant role in evaluating the chemical attributes of the reported compounds.

Amine functionalized carbon quantum dots from paper precursors for selective binding and fluorescent labelling applications.

We report a novel synthesis route for preparing carbon quantum dots (CQDs) of customized surface functionality from readily available precursors. The synthetic strategy is based on the chemical modification of paper precursors prior to preparing CQDs from them. The pre-synthesis modification of paper precursors with (3-Aminopropyl) triethoxy silane (APTES) enabled us to synthesize CQDs with amine functional groups on the surface. The silane coupling via condensation between the ethoxy group of APTES and the cellulose hydroxyl group on the paper resulted in the tethering of amine groups on the paper substrates, which are retained as surface-bound species during the synthesis of CQDs from the modified paper. Amine functionalization on the surface of CQDs helped us use them in applications such as DNA binding. We analyzed the interaction of CQDs with calf thymus DNA (CT-DNA), and the results imply their propensity as an efficient biological probe. The synthetic strategy presented here can also be extended to other functional groups.

N'-[(E)-(3-Fluoro-pyridin-2-yl)methyl-idene]pyridine-3-carbohydrazide dihydrate.

The organic molecule in the title dihydrate, C12H9FN4O·2H2O, exists in the E conformation with respect to the azo-methane C=N double bond. The mol-ecule is approximately planar, with a maximum deviation of 0.117 (1) Šfor the carbonyl O atom from the mean plane of the mol-ecule. Both pyridine rings are essentially coplanar with the central C(=O)N2C unit [dihedral angles = 1.99 (7) and 5.71 (8)°], exhibiting a significant difference in dihedral angles from its benzohydrazide analogue. The crystal packing features N-H⋯O, O-H⋯N and O-H⋯O hydrogen-bond inter-actions, which lead to the formation of a chain along the c-axis direction through one of the water mol-ecules present, and these chains are stacked one over the other by means of π-π inter-actions [with centroid-centroid distances of 3.7099 (10) and 3.6322 (10) Å] between the aromatic rings in neighbouring anti-parallel mol-ecules, building a three-dimensional supra-molecular network.

N'-[(E)-(3-Fluoro-pyridin-2-yl)methyl-idene]benzohydrazide monohydrate.

The title compound, C(13)H(10)FN(3)O·H(2)O, exists in the E conformation with respect to the azomethane C=N double bond. The mol-ecule is close to planar with a maximum deviation of 0.286 (2) Å. The pyridine ring is essentially coplanar with the central C(= O)N(2)C unit [dihedral angle = 2.02 (3)°] and the phenyl ring exhibits a dihedral angle of 14.41 (10)° with respect to the central unit. The crystal structure features O-H⋯N, N-H⋯O and O-H⋯O hydrogen-bond inter-actions between the solvent water and the benzohydrazide mol-ecules, as well as C-H⋯O hydrogen bonds and C-F⋯π [3.0833 (18) Å] inter-actions.