In this work, a study of the photophysical properties in different solvents and at different pH values of a luminogenic compound with a donor–π–acceptor (D–π–A) structure was carried out. The compound (Z)-3-(4-(4,5-diphenyl-1H-imidazol-2-yl)phenyl)-2-phenylacrylonitrile (2) was synthesized and characterized by SCXRD, FT-IR, ¹H NMR, ¹³C NMR, EIMS, UV-Vis absorption and fluorescence. The SCXRD characterization reveals a monoclinic system, P2₁/c, with Z = 4 and an imidazole core having hydrogen bonding with respect to water molecules present in the asymmetric unit. It leads to a strong π–π-interaction in the solid state. The fluorescence λ_max emission of the powder and thin film was observed at 563 nm and 540 nm respectively. Several degrees of positive solvatochromic fluorescence were observed due to different molecular conformations in various solvents. When the pH of the compound was changed with HCl or NaOH, a shift in the wavelength of emission was observed in a reversible manner. At pH 2, the λ_max of emission was at 541 nm whereas at pH 14 there were two emissions at 561 nm and 671 nm. Due to their good emission in the solid state, compound 2 was tested as an emitting layer in OLEDs; the devices showed an acceptable performance with a luminance average of 450 cd m⁻². The band gap was analyzed by optical absorption, cyclic voltammetry measurement and DFT calculations.

A homologous series of 1-alkyl-(N,N-dimethylamino)pyridinium bromides, termed compounds 1–11, was synthesized and studied for antibacterial and antifungal activity. Of these, compound 8, containing a ten-carbon alkyl chain, showed maximum inhibition against all the tested bacterial strains. The highest antibacterial activity using a disc diffusion method was recorded against Mycobacterium smegmatis [zone of inhibition (ZOI): 45.75±0.25 mm], followed by Escherichia coli, Proteus mirabilis, Vibrio cholerae, Staphylococcus aureus and Salmonella typhi. In addition to antibacterial activity, compounds 3–11 displayed good inhibitory action against the human opportunistic yeast pathogens Cryptococcus neoformans and various Candida spp. The maximum ZOI was observed against Cryptococcus neoformans (51.5±0.5 mm) using compound 8, with ZOIs of 23.5±0.5, 32.0±0.0, 27.75±0.25 and 41.5±0.5 mm against Candida albicans, Candida glabrata, Candida tropicalis and Candida krusei, respectively. Furthermore, compound 8 caused inhibition of the candidal yeast–hyphae transition at a concentration of 0.29 µM and also inhibited the secretion of extracellular hydrolytic enzyme such as secreted aspartyl proteinase at subinhibitory concentrations. Compound 8 showed very little haemolytic activity at a concentration of 0.58 µM (1.315±0.75 %), with its highest haemolytic activity (47.806±2.32 %) observed at a concentration of 2.9 µM.

This paper examines the use of electrooxidation for treatment of wastewater obtained from a pharmaceutical industry. The wastewater primarily contained Gentamicin and Dexamethasone. With NaCl as supporting electrolyte, the effluent was treated in a cylindrical flow reactor in continuous (single pass) mode under various current densities (2–5 A/dm²) and flow rates (10–40 L/h). By cyclic voltammetric (CV) analysis, the optimum condition for maximum redox reaction was determined. The efficiency of chemical oxygen demand (COD) reduction and power consumption were studied for different operating conditions. From the results it was observed that maximum COD reduction of about 85.56% was obtained at a flow rate of 10 L/h with an applied current density of 4 A/dm². FT-IR spectra studies showed that during electrooxidation, the intensities of characteristic functional groups such as N-H, O-H were reduced and some new peaks also started to appear. Probable theory, reaction mechanism and modeling were proposed for the oxidation of pharmaceutical effluent. The experimental results demonstrated that electrooxidation treatment was very effective and capable of elevating the quality of treated wastewater to the reuse standard prescribed for pharmaceutical industries.

A series of functionalized malonic acid half-ester derivatives (parent compound MHE-1), with variations in functional groups at different positions on the aromatic ring, have been synthesized and crystal structures are determined at room temperature (296 K). The methyl (4-CH₃, MHE-2) and chloro (4-Cl, MHE-3) derivatives are isomorphous with each other. The overall crystal packing of MHE-1–3 is similar. However, there are few differences observed between stacking of layers in these structures. Compounds with nitro (3-NO₂, MHE-4) and ethyl ester (2-COOC₂H₅, MHE-5) substituents crystallize in different space groups and thus crystal packing is different when compared to MHE-1–3. In all the structures, intramolecular N–H⋯O and O–H⋯O hydrogen bonds generate a two fused S(6) ring motif. A detailed study is carried out to visualize intermolecular interactions observed in all five crystal structures (MHE-1–5) using Hirshfeld surface (HS) analysis with two dimensional fingerprint plots. The relative contribution of intermolecular H⋯H contacts in MHE-3 is substantially lower than that in MHE-1–2, though similar crystal packing arrangements of MHE-1–3 and MHE-2 and MHE-3 are isomorphous. From HS analysis it is clear that the observed H⋯H contact contribution (MHE-3) is a consequence of the presence of the chlorine substituent and growing contribution of Cl⋯H contacts. The relative contributions of other intermolecular contacts involving various atoms are comparable in MHE-1–3 structures. The intermolecular interaction energies are quantified using PIXEL for various molecular pairs extracted from respective crystal structures. Interestingly, there are some invariant and variable intermolecular contacts observed between different groups in all five structures.

A detailed experimental and theoretical investigation on the intermolecular interactions in (Z)-3-(4-halophenyl)-2-(pyridin-2/3/4-yl)acrylonitriles is reported. The intermolecular interactions are analyzed and quantified by PIXEL, DFT and quantum theory of atoms in molecules (QTAIM) calculations. The results showed that the absence of strong classical hydrogen bonds and the presence of several weak intermolecular C–H⋯N, C–H⋯halogen, halogen⋯halogen and π stacking interactions play important roles in the stabilization of crystal structures. Four different π stacking dimers (homo parallel, homo slipped parallel, hetero anti-parallel and hetero anti-parallel slipped) are observed and found to be the most stabilized dimeric motifs in all structures. The hetero anti-parallel (−10.6 kcal mol⁻¹) and slipped anti-parallel (−9.1 kcal mol⁻¹) π⋯π interactions have the highest stabilization energies among the other interactions observed in the present study. The substituted halogen atoms (X = F, Cl and Br) are involved in the variant and invariant C–H⋯X, C⋯X and halogen⋯halogen interactions in all three families. The relative contributions of various non-covalent interactions are calculated using Hirshfeld surface analysis and 2D fingerprint plots. Further, detailed UV-vis spectral studies are reported for the title compounds in solution and solid phases. These results are compared with the simulated spectra and good agreement is found between experimental and theoretical spectra.