Some new heterocyclic chromophores have been synthesized by greenway method. These chromophores have been evaluated by analysing their solvatochromic properties and molecular optical nonlinearities. Their hyperpolarizability (beta) has been calculated theoretically. The non-zero tensor components of the imidazole derivatives reveal that they possess potent non-linear optical (NLO) behaviour. Measurements of absorption solvatochromism have been interpreted with Marcus and Reichardt-Dimroth solvent functions to estimate the transition dipoles. Good correlation exists between absorption as well as fluorescence wavenumbers obtained by the multi-component linear regression employing the Taft and Catalan solvent parameters with the experimental values. (C) 2011 Elsevier B.V. All rights reserved.
Physicochemical studies of chemosensor imidazole derivatives: DFT based ESIPT process
A series of substituted imidazoles have been synthesized in very good yield under a solvent free condition using molecular iodine as the catalyst. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. DFT calculations on energy, dipole moment, charge distribution of the rotamers in the ground and excited states of the imidazole derivatives have been performed and discussed. DFT analysis about HOMO, HOMO-1, LUMO and LUMO+1 has been carried out and discussed. The energy barrier for the interconversion of two rotamers is too high in the excited state than the ground state that is shown by PES calculation. The molecular electrostatic potential surface (MEP) has also been employed to show the higher electron density at N(3) nitrogen. Fluorescence enhancement has been found in the presence of transition metal ions and this may result from the suppression of radiationless transitions from the n-pi* state in the chemosensors. (C) 2012 Elsevier B.V. All rights reserved.
Microwave-Assisted Nickel-Catalyzed One-Pot Synthesis of 2,4,5-Trisubstituted Imidazoles
novel, highly efficient, and one-pot microwave-assisted synthesis of 2,4,5-trisubstitutedimidazoles using a newly developed Schiff’s base complex nickel catalyst (Ni-C) is described. The approach involves the reaction of various aldehydes with benzil and ammonium acetate in the presence of the Ni-C catalyst to furnish cyclized products in excellent yields. The Ni-C catalyst exhibited remarkable catalytic