Phenanthrimidazole as a fluorescent sensor with logic gate operations.

A novel sensor namely, 1-(1-(p-tolyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol was synthesised for the detection of anion as well as cation through intramolecular charge transfer mechanism. This compound was used for the selective detection of Zn(2+) ion as compared to other metal ions and the binding was evidenced from the new absorption band at 356 nm and switch on fluorescence at 453 nm. The switch on fluorescence can be explained on the basis of photoinduced electron transfer (PET) mechanism and it was demonstrated by logic gate functions.

Photoinduced electron transfer from phenanthrimidazole to magnetic nanoparticles.

The dynamics of photoinduced electron injection from (E)-1-(4-methoxyphenyl)-2-styryl-1H-phenanthro [9,10-d]imidazole (MPSPI) synthesised using nano TiO(2) as catalyst to Fe(2)O(3) nanocrystal has been studied by FT-IR, absorption, fluorescence and lifetime spectroscopic methods. The binding between nanoparticle and MPSPI is confirmed by binding constant and binding site. The distance between MPSPI and nanoparticle as well as the critical energy transfer distance has been obtained. The free energy change (ΔG(et)) for electron injection has also been deduced.

Multiple linear regression solvatochromic analysis of donar-acceptor imidazole derivatives.

Catalytic synthesis of some polysubstituted imidazoles under solvent-free condition is reported and their characterization has been carried out spectral techniques. Electronic spectral studies reveal that their solvatochromic behavior depends both the polarity of the medium and hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction in polar solvents modulated the order of the two close lying lowest singlet states. The solvent effect on absorption and emission spectral results has been analyzed by multiple parametric regression analysis. Solvatochromic effects on the emission spectral position indicate the charge transfer (CT) character of the emitting singlet states both in a polar and a non polar environment. The fluorescence decays for the imidazoles fit satisfactorily to a bi exponential kinetics. These observations are in consistent with quantum chemical calculations.

Study on conformational stability, molecular structure, vibrational spectra, NBO, TD-DFT, HOMO and LUMO analysis of 3,5-dinitrosalicylic acid by DFT techniques.

In this work we analyzed the vibrational spectra of 3,5-dinitrosalicylic acid (3,5DNSA) molecule. The total energy of eight possible conformers can be calculated by Density Functional Theory with 6-31G(d,p) as basis set to find the most stable conformer. Computational result identify the most stable conformer of 3,5DNSA is C6. The assignments of the vibrational spectra have been carried out by computing Total Energy Distribution (TED). The molecular geometry, second order perturbation energies and Electron Density (ED) transfer from filled lone pairs of Lewis base to unfilled Lewis acid sites for 3,5-DNSA molecular analyzed on the basis of Natural Bond Orbital (NBO) analysis. The formation of inter and intramolecular hydrogen bonding between OH and COOH group gave the evidence for the formation of dimer formation for 3,5-DNSA molecule. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra.

Binding interaction between 2-(naphthalen-1-yl)-1-p-tolyl-1H-phenanthro[9,10-d]imidazole and semiconductor nanomaterials.

The binding interaction of bioactive phenanthrimidazole with nanoparticulate WO3, Fe2O3, Fe3O4, CuO, ZrO2 and Al2O3 has been studied by electronic and life time spectral studies. The phenanthrimidazole adsorbs strongly on the surface of nanosemiconductor, the apparent binding constants have been determined from the fluorescence quenching. In the case of nanocrystalline insulator, fluorescence quenching through electron transfer from the excited state of the phenanthrimidazole to alumina is not possible, but it is due to energy transfer process.

Donor-acceptor binding interaction of 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole with semiconductor nanomaterials.

The dynamics of photoinduced electron injection from 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole (NTI) to pristine ZnO, Mn-doped TiO2 and BaTiO3 nanoparticles have been studied by absorption, fluorescence and lifetime spectroscopic methods. Both the absorption and fluorescence results suggest the association between the nanoparticles and NTI. The calculated free energy change (ΔGet) confirms the electron injection from NTI to nano semiconductors. The critical energy transfer distance between NTI and the nanoparticles have been deduced. The emission of NTI is enhanced by pristine ZnO and quenched by Mn-doped TiO2 and BaTiO3 nanoparticles which are likely due to change of LUMO and HOMO levels of NTI on its association with nano semiconductors. The strong adsorption of the NTI on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the NTI to the zinc ion on the surface of nanocrystals. Electron injection from photoexcited NTI to the CB(S(∗)→S(+)+eCB(-)) is likely to be the reason for the fluorescence enhancement.

Enhancing the photoluminescence of 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole anchored to superparamagnetic nanoparticles.

Synthesis and characterization of 1-(naphthalene-1-yl)-2,4,5-triphenyl-1H-imidazole has been carried out by spectral studies. The synthesized phosphated imidazole and phosphated imidazole bound magnetic nanoparticles were characterized using fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and powder X-ray diffraction (XRD). The photophysical characteristics of the synthesized phosphated imidazole and phosphated imidazole bound magnetic nanoparticles were investigated by steady-state absorption and emission spectra as well as time resolved fluorometry. The intensities of absorption and emission maxima increase in the following order, phosphated imidazole bound Fe2O3>phosphated imidazole>imidazole.

Turn-off of fluorescence of styryl phenanthrimidazole on doping ZnO nanoparticles with Ce(3+).

ZnO nanoparticles were doped with Ce(3+) by sol-gel synthesis and characterized by high-resolution scanning electron microscopy (HR-SEM), powder X-ray diffraction (XRD) and UV-visible diffuse reflectance (DRS) and photoluminescence (PL) spectroscopies. The dynamics of photoinduced electron injection from styryl phenanthrimidazole to Ce(3+)-doped ZnO nanoparticles has been studied by absorption, fluorescence and lifetime spectroscopic methods. Both the absorption and fluorescence quenching results suggest association between Ce(3+)-doped ZnO and the phenanthrimidazole. The free energy change (ΔGet) for electron injection has been calculated. The critical energy transfer distance between the phenanthrimidazole and Ce(3+)-doped ZnO nanoparticles has been deduced. In contrast to our earlier observation of enhancement of fluorescence of the phenanthrimidazole by ZnO nanoparticles, doping ZnO with Ce(3+) turns off its fluorescence. These findings provide a method to test the presence of Ce(3+) in ZnO nanocrystals.

Radiative and nonradioactive electron transfer in donor-acceptor phenanthrimidazoles.

Photoinduced electron transfer in a series of naphthyl substituted phenanthrimidazoles has been studied in solutions. The intramolecular charge transfer (CT) leads to a large Stokes shift and large dipole moment in the fluorescent state. Solvatochromic effects on the spectral position and profile of the stationary fluorescence spectra clearly indicate the CT character of the emitting singlet states of all the compounds studied. An analysis of the CT fluorescence lead to the quantities relevant for the electron transfer in the Marcus inverted region.

Spectroscopic studies on photoelectron transfer from 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole to ZnO, Cu-doped ZnO and Ag-doped ZnO.

The 2-(furan-2-yl)-1-phenyl-1H-phenanthro[9,10-d]imidazole [FPI] has been designed and synthesized as fluorescent sensor for nanoparticulate ZnO. The present work investigates the photoelectron transfer (PET) from FPI to ZnO, Cu-doped ZnO and Ag- doped ZnO nanoparticles using electronic and life time spectral measurements. Broad absorption along with red shift indicates the formation of charge-transfer complex [FPI-Nanoparticles]. The photophysical studies indicate lowering of HOMO and LUMO energy levels of FPI on adsorption on ZnO due to FPI- ZnO interaction. The obtained binding constant implies that the binding of FPI with nanoparticles was influenced by the surface modification of ZnO nanoparticles with Cu and Ag.

Photoinduced intramolecular electron transfer and electronic coupling interactions in π- expanded imidazole derivatives.

An intramolecular excited charge transfer (CT) analysis of imidazole derivatives has been made. The determined electronic transition dipole moments has been used to estimate the electronic coupling interactions between the excited charge transfer singlet state ((1)CT) and the ground state (S0) or the locally excited state ((1)LE). The properties of excited (1)CT state imidazole derivatives have been exploited by the significant contribution of the electronic coupling interactions. The excited state intramolecular proton transfer (ESIPT) analysis has also been discussed.

Kamlet-Taft and Catalán solvatochromism of some π-expanded phenanthrimidazole derivatives - DFT analysis.

Some π-expanded phenanthrimidazole derivatives have been synthesised and characterised by different spectral techniques. Kamlet-Taft and Catalán solvatochromism of synthesised phenanthrimidazole derivatives have been analysed. Non-linear optical (NLO) and natural bond orbital (NBO) analysis have been made by ab initio method to show intramolecular interactions. The energies of the HOMO and LUMO levels, the molecular electrostatic potential (MEP) energy surface, NBO studies have exploited the existence of intramolecular charge transfer (ICT) within the molecule.

Solid state synthesis and spectral investigations of nanostructure SnS2.

Nanometer sized SnS2 particles were synthesised by solid state reaction between tin chloride and thiourea in air at 150-350°C. The structural, morphological and optical properties were characterized by using X-ray diffraction (XRD), FT-IR, FT-Raman, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and UV-Vis spectra. The X-ray diffraction (XRD) pattern of the product was indexed to the hexagonal phase of SnS2. Crystallite size, microstrain and dislocation density were evaluated from the XRD data. EDS analysis indicated that the elemental ratio was similar to tin disulphide (SnS2). The blue shift in the absorption edge was observed from the UV-Vis spectrum. The photoluminescence spectra showed two emission peaks corresponding to blue and red emission.

Sensitive and selective PET-based π-expanded phenanthrimidazole luminophore for Zn2+ ion.

The novel photoinduced electron transfer (PET) chemosensor, 1-(1-(4-methoxyphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)naphthalen-2-ol [MPPN] and its zinc complex were synthesised and characterized by electronic spectral and Frontier molecular orbital energy analysis. MPPN becomes efficient fluorescent chemosensor upon binding with metal ions and shows a strong preference toward Zn(2+) ion. Density Functional theory (DFT) calculations reveal that luminescence of free MPPN originates from its orbital structure in which two π-orbitals (HOMO and HOMO-1) of the imidazole ring are situated between two π-orbitals (HOMO-2 and LUMO) of the naphthyl fragment. Therefore the absorption and emission processes occur between the two π- orbitals (HOMO-2 and LUMO). The two higher energy imidazole orbitals (HOMO and HOMO-1) serve as quenchers for the excited state of the molecule through nonradiative processes. Upon binding with Zn(2+) ion, MPPN becomes a highly luminescent with λemi - 421 nm. The significant enhancement of luminescence upon binding with Zn(2+) ion is attributed to the stabilization of HOMO-2 and HOMO-1 π-orbitals of imidazole ring upon their engagement in new bonds with Zn(2+) ion. The affinity of MPPN to zinc ion is found to be very high [K = 6 × 10(6) M(-1)] when compared with other metals ions. The nonlinear absorption coefficient γ for MPPN is 1.9 × 10(-12) m/W and 3.9 × 10(-11) m/W for MPPN-Zn complex.

Photophysical and excited-state intramolecular proton transfer of 2-(1-(3,5-dimethylphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenol: DFT analysis.

Fluorescent phenenthrimidazole derivatives have been synthesized and characterized by (1)H, (13)C NMR and mass spectral analyses. Synthesized compounds have been. The solvent effect on the absorption and fluorescence bands has been analyzed and supplement by computational studies. Phenenthrimidazole containing hydroxy group shows a single prominent absorption and emission in polar solvents and dual emission in non-polar solvents due to excited state intramolecular proton transfer (ESIPT). The ESIPT of 2-(1-(3,5-dimethylphenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenol was cross validated by the analysis of optimized geometry parameters, potential energy surface (PES), mulliken's charge distribution on the heavy atoms and molecular orbitals of its tautomers. Nonviability of ground state electron transfer was explained by HOMO-LUMO analysis. The intramolecular hydrogen bonding (IMHB) interaction has been explored by the calculation of electron density ρ(r) and the Laplacian Δ(2)ρ(r) at the bond critical point (BCP) using atoms-in-molecule (AIM) method and by calculation of hyper conjugative interaction between N17 lone pair and σ*(O53⋯H54) using natural bond orbital (NBO) analysis.

Spectral studies of 2-pyrazoline derivatives: structural elucidation through single crystal XRD and DFT calculations.

A series of biologically active N-thiocarbamoyl pyrazoline derivatives have been synthesized using anhydrous potassium carbonate as the catalyst. All the synthesized compounds were characterized by FT-IR, (1)H NMR, (13)C NMR spectral studies, LCMS, CHN Analysis and X-ray diffraction analysis (compound 7). In order to supplement the XRD parameters, molecular modelling was carried out by Gaussian 03W. From the optimized structure, the energy, dipolemoment and HOMO-LUMO energies of all the systems were calculated.

Dynamics of Solvent Controlled ESIPT of π-Expanded Imidazole Derivatives - pH Effect.

A set of π-expanded imidazole derivatives employing excited state intramolecular proton transfer (ESIPT) was designed and synthesized. The relationship between the structure and photophysical properties were thoroughly elucidated by comparing with the analogue blocked with ESIPT functionality. The compound possessing an acidic NH function as part of an intramolecular hydrogen bond system has much higher fluorescence quantum yield and Stokes shift and the π-expansion strongly influences the optical properties. The occurrence of ESIPT for imidazole tosylamide derivatives were less affected by the hydrogen-bonding ability of the solvents compared to the unprotected amine. The low pKa values for the monocation ⇌ neutral equilibrium indicate the presence of intramolecular hydrogen bonding between the amino proton and tertiary nitrogen atom.

Estimation of Excited State Dipolemoments from Solvatochromic Shifts-Effect of pH.

Multicomponent, highly efficient, catalytic synthesis of some polysubstituted imidazole under solvent-free condition is reported. Characterization of polysubstituted imidazole have been carried out by X-ray diffraction (XRD) and spectral techniques. Electronic spectral studies reveal that their solvatochromic behavior depends not only on the polarity of the medium but also on the hydrogen bonding properties of the solvents. Specific hydrogen bonding interaction in polar solvents modulated the order of the two close lying lowest singlet states. The solvent effect on both the absorption and emission spectral results have been analyzed by multiple parametric regression analysis. Solvatochromic effects on the emission spectral position indicate the charge transfer (CT) character of the emitting singlet states both in a polar and a non polar environment. The fluorescence decays for the imidazole fit satisfactorily to a single exponential kinetics. The prototropic studies of N,N-dimethyl-4-(1,4,5-triphenyl-1H-imidazol-2-yl)naphthalen-1-amine (DTINA) reveal that two monocations [imidazole nitrogen protanated (MC1) and dimethylamino nitrogen protanated (MC2)] and a dication [both imidazole nitrogen and dimethylamino nitrogen protanated (DC)] are formed by protonation in both ground and excited states. These observations are in consistent with quantum chemical calculations.

Tuning Photophysical and Electrochemical Properties of Phosphorescent Heteroleptic Iridium Complex Salts-as Chemosensors.

Photophysical and electrochemical studies of cyclometalated cationic heteroleptic iridium(III) complex salts have been carried out. For these complex salts the intense absorption bands appeared around 263 nm and are assigned to spin-allowed π-π* transitions of phenanthroline ligands. Moderately intense and weak absorption bands observed around 341 and 440 nm, respectively. These bands are assigned to spin-allowed metal to ligand charge transfer (1)MLCT and (3)MLCT transitions, respectively. The influence of anions and proton on the photophysical and electrochemical studies were also carried out. The emission wavelength was red shifted and emission color changed from yellow to red by the addition of CF3CO2H. The solution color changed from green to brown and the emission was quenched by the addition anions such as of F(-), CH3COO(-) and H2PO4(-).

Spectral and computational studies in substituted pyrrolyl styryl ketones--assessment of substituent effects.

A series of newly synthesized potent bioactive 2-pyrrolyl styryl ketone derivatives were characterized by spectral techniques. The effect of substituent on the absorption maximum, IR stretching frequencies and NMR chemical shifts were investigated. DFT calculations were made to calculate HOMO-LUMO energies and natural bond orbital analysis [NBO]. The electric dipole moment (µ) and the hyperpolarisability (ß) of the investigated molecules have also been studied and found that these synthesized molecules exhibits microscopic non-linear optical (NLO) behavior with non-zero tensor components.