Kanagarathinam Saravanan

Synthesis and Photophysics of Some Novel Imidazole Derivatives Used as Sensitive Fluorescent Chemisensors

Some novel imidazole derivatives were developed for highly sensitive chemisensors for transition metal ions. Since these compounds are sensitive to different external stimulations such as UV irradiation, heat, increasing pressure and changing the environmental pH causing colour change and so they can be used as a ′multi-way′ optically switchable material. A prominent fluorescence enhancement was found in the presence of transition metal ions such as Hg2+, Pb2+ and Cu2+ and this was suggested to result from the suppression of radiationless transitions from the n-π* state in the chemisensors. The existence of C-H….O intramolecular hydrogen bonding in dmphnpi is confirmed by the Natural Bond Orbital analysis (NBO). The Mulliken, NBO charge analysis and the HOMO-LUMO energies were also calculated. The electric dipole moment (μ) and the first-hyperpolarisability (β) value of the investigated molecules have been studied both experimentally and theoretically which reveal that the synthesized molecules have microscopic non-linear optical (NLO) behaviour with non-zero values. Ground and excited state DFT calculation were carried out in order to find out dipole moment and energy.

Synthesis, Structure, Luminescent and Intramolecular Proton Transfer in Some Imidazole Derivatives

A group of novel 2-aryl imidazole derivatives were synthesized and characterized by NMR spectra, X-ray, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazoles (dmip and dmtip) have been studied using emission spectroscopy and it was detected that the two distinct ground state rotamers of I and II are responsible for the normal and the tautomer emission respectively. In hydrocarbon solvent, the tautomer emission predominates over the normal emission for both dmip and dmtip. This reveal that rotamer II is responsible for the tautomer emission and it is stabler than rotamer I which causes the normal emission. In alcoholic solvent like ethanol, a dramatic enhancement of normal emission is observed which was due to increased solvation, the more polar rotamer I become stabler than rotamer II. In dioxane—water mixtures it is observed that the addition of water inhibits the ESIPT process due to the formation of the intermolecular hydrogen bonding involving water. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the imidazole derivatives were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state.

Spectrofluorometric studies on the binding interaction of bioactive imidazole with bovine serum albumin: A DFT based ESIPT process

Bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. In hydrocarbon solvent, the tautomer emission predominates over the normal emission and in alcoholic solvent like ethanol; a dramatic enhancement of normal emission is observed which was due to increased solvation. DFT calculation on energy, charge distribution of the rotamers in the ground and excited states of the imidazole derivative were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than in the ground state. The interaction between bioactive imidazole derivative and bovine serum albumin (BSA) was investigated.

Displacement Reaction Using Ibuprofen in a Mixture of Bioactive Imidazole Derivative and Bovine Serum Albumin—a Fluorescence Quenching Study

The mutual interaction of imidazole derivative (PIPP) with bovine serum albumin (BSA) was investigated using photoluminescent studies. The fluorescence quenching mechanism of BSA by PIPP was analyzed and the binding constant was calculated. The binding distance between PIPP and BSA was obtained based on the theory of Forester’s non-radiation energy transfer. Displacement experiments were performed by using ibuprofen to identify PIPP binding site in BSA. The effect of some common ions on the binding constant between PIPP and BSA was also examined.

Antioxidant potential and antimicrobial screening of some novel imidazole derivatives: greenway efficient one pot synthesis

A series of substituted imidazoles have been synthesized under solvent-free condition by grinding 1,2-diketone, aromatic aldehyde, and ammonium acetate in the presence of molecular iodine as the catalyst. The short reaction time and easy workup make this protocol practically and economically attractive and are characterized by NMR spectra, X-ray, mass, and CHN analysis. Their antioxidant potential were evaluated using different in vitro antioxidant models namely, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical, superoxide anion, and hydroxyl radical scavenging activities. Their antibacterial screening against Staphylococcus aureus, Escherichia coli, and Klbesiella pneumoniae and antifungal activity against Aspergillus niger, Aspergillus flavus, and Candida-6 were also evaluated. Among all, dimethoxyphenyl substituent at N3 of the imidazole derivatives exhibited the highest hydroxy and superoxide anion radical scavenging activities, whereas dimethoxyphenyl substituent at N3 and fluorophenyl at C2 of the imidazole derivatives exhibited the highest DPPH radical scavenging activity.

4,5-Dimethyl-1,2-diphenyl-1H-imidazole monohydrate

In the title compound, C17H16N2·H2O, the imidazole ring is essentially planar [maximum deviation = 0.0037 (7) Å]. The imidazole ring makes dihedral angles of 80.74 (7) and 41.62 (7)° with the phenyl rings attached to the N and C atoms, respectively. The dihedral angle between the two phenyl rings is 75.83 (8)°. Intermolecular O—H⋯N and O—H⋯O hydrogen bonds are found in the crystal structure.

2-(4-Fluoro­phen­yl)-1-(4-meth­oxy­phen­yl)-4,5-dimethyl-1H-imidazole

In the title compound, C18H17FN2O, the imidazole ring makes dihedral angles of 76.46 (7) and 40.68 (7)° with the methoxyphenyl and fluorophenyl rings, respectively. The dihedral angle between the two benzene rings is 71.25 (6)°.

New iridium complexes with cyclometalated 2-arylimidazole ligands as highly efficient saturated green emitters.

Phosphorescence studies of a series of heteroleptic cyclometalated iridium(III) complexes have been carried out. From the photoluminescent properties, it was found that these complexes possess dominantly (3)MLCT and (3)π-π* excited states. The solvent shifts are interpreted in terms of Reichardt-Dimroth solvent E(T) parameters and Marcus theory. The results are consistent with prior assignments on the absorption band to a metal-to-ligand charge transfer excited state associated with chelating ligand. Emission kinetic studies reveal that k(r) increases with increasing λ(em) and linear correlation between ln(k(nr)) and energy gap. The effect of E(g) and ΔQ(e) on k(nr) is discussed in detail.

1-(3,5-Dimeth­oxy­phen­yl)-2-(4-fluoro­phen­yl)-4,5-dimethyl-1H-imidazole

In the title compound, C19H19FN2O2, the imidazole ring is essentially planar [maximum deviation = 0.0030 (8) Å] and makes dihedral angles of 66.45 (7) and 29.98 (7)° with the benzene rings attached to the ring N and C atoms, respectively. The dihedral angle between the two benzene rings is 64.79 (7)°. A C—H⋯π interaction is found in the crystal structure. The two methoxy groups were found to be disordered over two sets of sites with occupancy factors of 0.803 (4) and 0.197 (4). The F atom is disordered over two sites with occupancy factors of 0.929 (4) and 0.071 (4).