Solvent-dependent electronic structures of selected donor (D)-acceptor (A) phenanthrimidazole derivatives containing styryl as an electron acceptor fragment in fluorescent charge transfer (CT) states have been investigated. Radiative charge recombination [CT / S 0 ] is discussed in terms of the Mulliken-Murrell model of the CT complexes and the Marcus theory of photoinduced electron transfer (ET). Solvatochromic effects on the fluorescence spectra indicate the CT character of the emitting singlet states and the analysis leads to the electron transfer in the Marcus inverted region. The fluorescence rate constants (k r ) and transition dipole moments (M) indicate that the electronic coupling between the emitting CT state and the ground state is a governing factor of the radiative transitions. Large values of M indicate a nonorthogonal geometry (confirmed by XRD) of the donor and acceptor subunits in the fluorescent states. Emission spectra of N,N-dimethyl-4-(2-styryl-1H-phenanthro[9,10-d]imidazol-1-yl)benzenamine is of interest because of the existence of dual emitting states where a locally excited state is responsible for fluorescence in nonpolar solvents. In polar solvents fluorescence is from a twisted intramolecular charge transfer (TICT) state. Density functional theory (DFT) calculations support the formation of the TICT state. The twist of the -N(CH 3 ) 2 group and the change in its hybridization in the excited state develops a high dipole moment and thereby stabilizes it to give the TICT fluorescence in polar solvents.

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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.

Photoelectron transfer to core/shell Mn–TiO2/ZnO and BaTiO3/ZnO nanospheres. Enhanced absorbance because of binding with nanosemiconductors. Enhanced emission due to charge injection from the excited ligand to CB of ZnO.

The synthesis of (E)-4-(2-(1-(4-chlorophenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)vinyl)-N,N-dimethylaniline (CPPIVI) has been carried out using TiO 2 (R) as catalyst under solvent free conditions and characterized by NMR spectral studies. The catalyst was characterized by scanning electron microscopy (SEM) and Xray diffractometry (XRD). The catalyst is reusable with satisfactory results. The synthesised phosphated styrylimidazole (PSI) and phosphated styrylimidazole bound magnetic nanoparticles (PSIMN) were characterized using SEM, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), XRD and Fourier-transform infrared spectroscopy (FT-IR). The intensities of the absorption and emission maxima are of the following order: PSIMN > PSI > CPPIVI. Conductance and VSM measurements were also carried out. The lifetime of the excited states of PSIMN, PSI and CPPIVI has been obtained. A prototropic study of CPPIVI has also been made at different concentrations.