A new family of ESIPT and AIE-active triphenylamine-appended unsymmetrical azine derivatives is reported.

The stabilisation energies of five ionic and neutral organic crystal structures containing various halogen bonds (I···I, Br···Br, I···Br, I···S and Br···S) were calculated using the DFT-D3 method (B97D/def2-QZVP). Besides them, the ionic I3(-)···I2 and neutral I2···I2, complexes (in the crystal geometries) were also studied. The nature of the bonds was deduced from the electrostatic potential evaluated for all subsystems. In almost all the cases, the σ-hole was positive; it was negative only for the ionic I3(-) system (although more positive than the respective belt value). The strongest halogen bonds were those that involved iodine as a halogen-bond donor and acceptor. Among ionic X···I3(-) and neutral X···I2 and X···Y dimers, the neutral X···I2 complexes were, surprisingly enough, the most stable; the highest stabilisation energy of 13.8 kcal mol(-1) was found for the I2···1,3-dithiole-2-thione-4-carboxylic acid complex. The stabilisation energies of the ionic I3(-)···I2 and neutral I2···1,3-dithiole-2-thione-4-carboxylic acid (20.2 and 20.42 kcal mol(-1), respectively) complexes are very high, which is explained by the favourable geometrical arrangement, allowing the formation of a strong halogen bond. An I···I halogen bond also exists in the neutral I2···I2 complex, having only moderate stabilisation energy (3.9 kcal mol(-1)). This stabilisation energy was, however, shown to be close to that in the optimal gas-phase L-shaped I2···I2 complex. In all the cases, the dispersion energy is important and comparable to electrostatic energy. Only in strong halogen bonds (e.g. I3(-)···I2), the electrostatic energy becomes dominant.

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A new mixed nickel–sodium complex has been synthesized from Ni(ClO4)2 and tris(8‐methyl 2‐oxo‐quinolidine amino ethylamine) with a 1:1 molar ratio in methanol and has been characterized by various analytical, spectroscopy and X‐ray diffraction studies which confirmed an octahedral geometry around the nickel ion. Further, structural optimization of the complex was performed using DFT calculations. The ligand and complex were evaluated for their binding affinity with CT‐DNA and an intercalative type of binding interaction was proposed from the absorption and fluorescence titration experiments. Albumin binding interaction of the ligand and complex was determined by absorption, fluorescence and synchronous spectral techniques at room temperature, suggesting the static quenching mechanism of BSA with the compounds. Antioxidant studies revealed the radical scavenging potential of Ni(II) complex. The anticancer activity of the ligand and complex was probed via in vitro cytotoxicity against human breast (MCF7) and lung (A549) cancer cell lines by MTT assay. Further, cytological changes observed in acridine orange/ethidium bromide and DAPI staining methods validated the cytotoxic potential of the complex.

Hydrogen bonds and their strength were analysed based on their X-H proton-donor bond properties and the parameters of the H-Y distance (Y proton acceptor). Strong, moderate and weak interactions in hydrogen-bond types were verified through the proton affinities of bases (PA), deprotanation enthalpies of acids (DPE) and the chemical shift (σ ). The aromaticity and anti-aromaticity were analysed by means of the NICS (0) (nucleus-independent chemical shift), NICS (1) and NICS (0), NICS (1) of hydrogen-bonded molecules. The strength of a hydrogen bond depends on the capacity of hydrogen atom engrossing into the electronegative acceptor atom. The correlation between the above parameters and their relations were discussed through curve fitting. Bader's theory of atoms in molecules has been applied to estimate the occurrence of hydrogen bonds through eight criteria reported by Popelier et al. The lengths and potential energy shifts have been found to have a strong negative linear correlation, whereas the lengths and Laplacian shifts have a strong positive linear correlation. This study illustrates the common factors responsible for strong, moderate and weak interactions in hydrogen-bond types.