Synthesis of Some New Bis- 2, 3-Dihydroquinazolin-4(1H)-one Derivatives from Dapsone Drug and Investigating their Liquid Crystalline Properties and Antibacterial Activities

During this paper, new Schiff's base derivatives [F1-F5] were prepared through the reaction of dapsone drug with different substituted benzaldehyde compounds. Schiff's bases were then converted into 2,3-dihyroquinazolin-4(1H)-one derivatives [F6-F10] through the reaction with 2-amino benzoic acid in ethanol. The synthesized compounds were identified by their physical properties using UV-Vis, FT-IR and 1H-NMR analyses. The liquid crystalline properties of some prepared compounds revealed smectic and nematic phases. Using two separate bacterial species, Pseudomonas aeruginosa (Gram -ve) and Staphylococcus aureus (Gram +ve), the antimicrobial activities of certain synthesized compounds [F1,F2,F7,F8] were investigated using the agar diffusion process. The findings revealed that some of the assayed compounds had antimicrobial activities against the bacteria tested.

Zn2+ -Schiff’s base Complex as an “On-Off-On” Molecular Switch and a Fluorescence Probe for the Cu2+ and Ag+ ions

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of the Schiff’s base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H2L) and its metal complexes with Zn2+, Cu2+ and Ag+ ions. The study aims to investigate the behavior of H2L and the binuclear Zn2+ complex (1), as fluorescent probes for the detection of metal ions (Zn2+, Cu2+ and Ag+) using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT). The six conformers of the H2L ligand were optimized using B3LYP/6-311++G** level of theory, while the L-2-metal complexes were optimized by applying B3LYP functional with LANL2DZ/6-311++G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6-311++G** basis set for C, O, N and H atoms and LANL2DZ basis set for the metal ions (Zn2+, Cu2+ and Ag+). The computational results of B3LYP functional were in excellent agreement with the experimental ones. Hence, it has been adopted for performing the emission calculations. The results indicated that, the metal complex (1) can act as a fluorescent chemosensor, for the detection of Ag+ and Cu2+ ions through the mechanism of the Intermolecular Charge Transfer (ICT) and as a molecular switch “On-Off-On” via the replacement of Cu2+ by Ag+ ions, as proved experimentally.

STRUCTURAL FEATURES, COMPUTATIONAL STUDIES AND BIOLOGICAL ANALYSIS: SCHIFF’S BASE LIGAND AND ITS COORDINATION COMPOUNDS

Structure and biological application based analysis has been carried out for Schiff’s base ligand containing nitrogen and sulphur donor atoms and also for a series of its coordination compounds. Ligand benzil-bis(5-amino-1,3,4-thiadiazole-2-thiol) (L) has been prepared and structural features of ligand investigated by elemental analyses, IR, 1 H-NMR, mass spectra and molecular modeling studies. The chemical reaction of the prepared ligand with metal ions afforded mononuclear coordination compounds of Mn(II) and Co(II) metal ions. The characterization of the coordination compounds is being based on the techniques i.e. elemental analysis, infra-red, UV-visible as well as melting point, molar conductivity and magnetic moment measurement. A computational study has been done to understand the miscellaneous coordination modes of ligand to metal ions. Characterization result shows that coordination compounds exhibit a six coordinated geometrical arrangement i.e. octahedral geometry. The biological inhibition zone (antifungal and antibacterial activities) of synthesized compounds, i.e. ligand and its coordination compounds, has been monitored using well diffusion technique

Synthesis of Schiff’s Bases from 2-Amino-4H-1, 3-Oxazine / Thiazine and Substituted Aldehydes and their Transition Metal Complexes

Objective: Many methods can be found in literature for the synthesis a Oxazines and Thiazines. Few are reported for one-pot multi component cyclo-condensation of an alkayane urea / Thiourea and Aldehyde to 2- amino-4H-1, 3-Oxazines or Thiazines. Different catalysts are reported like Trifluoro-acetic acid, glacial acetic acid under reflux condition Mandal and Co-workers have utilized perchloric acid (HClO4) supported on silica gel as catalyst under solvent free condition ytterbium trifluorate [Yb(OTF)3] plays role of Lewis acid. It is also used in several Diel’s-Alder cyclo-addition reactions. Inspired these observations, development of simple effective synthetic strategy for the synthesis of 2-amino-4H-1, 3-Oxazium & Thiazines was attempted. Material and Methods: One pot multi-component synthesis of Schiff’s base as new ligand an their complexes with Ni, Fe, Co and Cu and developed using 2-amino-4H-1,3 Oxazines /Thiazines and substituted Aldehydes, different catalyst are used to synthesize of 2-amino 4H-1,3 Oxazines. Its characterization is confirmed by taking IR, NMR spectra. The Schiff’s base act as ligand is bidentate, when it is treated to metal complexes in 1:1 ratio (metal: ligand) complexes are formed. Result: By using the bioactive molecules like 2-amino-4H-1, 3 Oxazine / Thiazines, Schiff’s Bases can be synthesized by using different aldehydes. These Schiff’s Bases has antitumor, antipyretic, anti-inflammatory property. And these Schiff’s bases treated with bioactive metals like Co, Fe, Cu, Zn which enhances their bio-activity. Conclusion: All these synthesized Schiff’ Bases and their metal complexes having bioactive properties.