TD-DFT Calculation on UV-Vis Spectra of the Complex 8-((Trimethoxysilyl)methylthio)quinoline⋅ZnCl2

School of Materials and Chemical Engineering, West Anhui University, Lu’an, 237000 China; Laboratory of Bionic Sensors and Detection Technology, Lu’an, 237000 China; School of Life Sciences and Pharmaceutical Engineering, West Anhui University, Lu’an, 237000 China
Journal of Solution Chemistry (Impact Factor: 1.08). 01/2011; 40(1):147-153. DOI: 10.1007/s10953-010-9630-x

ABSTRACT The electronic structure and absorption spectra properties of the complex 8-((trimethoxysilyl)methylthio)quinoline⋅ZnCl2 in the gas phase and in acetonitrile (MeCN) have been investigated by means of DFT/TD-DFT calculations. Calculation results
indicate that the broad and weak experimentally observed absorption bands of the complex in MeCN at 335.6nm originates from
spin-forbidden singlet-triplet transitions, but the other experimentally observed absorption bands at 318.5nm, 310.6nm and
237.5nm arise from spin-allowed singlet-singlet transitions. Inclusion of MeCN as solvent leads to dramatic changes in the
electronic structures and energy levels of the frontier molecular orbitals of the complex, and hence transition mechanisms
of the absorption bands are also changed. For the complex, whether in the gas phase or in MeCN, the metal Zn does not participate
in the transitions involved, in the gas phase the calculated lowest-energy absorption band of the complex comes from π→π
∗ mixed with n→π
∗ transitions with LLCT (ligand-to-ligand charge transfer) character, while in MeCN, the calculated lowest-energy absorption
band is of LLCT/ILCT (intra-ligand charge transfer) character.

-TD-DFT-Solvent effect-Transition mechanism

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new series of quinolinolate osmium carbonyl complexes were synthesized and characterized by spectroscopic methods. Single-crystal X-ray diffraction studies indicate that these complexes consist of an octahedral ligand arrangement with one chelating quinolinolate, one tfa or halide ligand, and three mutually orthogonal terminal CO ligands. Variation of the substituents on quinolinolate ligands imposes obvious electronic or structural effects, while changing the tfa ligand to an electron-donating iodide slightly increases the charge density on the central osmium atom. These Os(II) complexes show salient dual emissions consisting of fluorescence and phosphorescence, the spectral properties and relaxation dynamics of which have been studied comprehensively. The results, in combination with the theoretical approaches, lead us to propose that the emission mainly originates from the quinolinolate pi pi* state. Both experimental and theoretical approaches generalize various types of intersystem crossing versus those of the tris(quinolinolate) iridium Ir(Q)3, and their relative efficiencies were accessed on the basis of the associated frontier orbital configurations. Our results suggest that [1d(pi)pi* absolute value(H(so))3 pi pi*] (or [3d(pi)pi* absolute value(H(so))1 pi pi*]) in combination with a smaller deltaE(S1-T1) gap (i.e., increasing the MLCT (d(pi)pi*) character) is the main driving force to induce the ultrafast S1 --> T1 intersystem crossing in the third-row transition metal complexes, giving the strong phosphorescent emission.
    Inorganic Chemistry 07/2005; 44(13):4594-603. · 4.79 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The conductor-like solvation model, as developed in the framework of the polarizable continuum model (PCM), has been reformulated and newly implemented in order to compute energies, geometric structures, harmonic frequencies, and electronic properties in solution for any chemical system that can be studied in vacuo. Particular attention is devoted to large systems requiring suitable iterative algorithms to compute the solvation charges: the fast multipole method (FMM) has been extensively used to ensure a linear scaling of the computational times with the size of the solute. A number of test applications are presented to evaluate the performances of the method.
    Journal of Computational Chemistry 05/2003; 24(6):669-81. · 3.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: As part of an effort to develop new lumaphors involving late transition metal ions, this report describes the synthesis and characterization of the first platinum(II) derivatives containing 2,2':6',2''-terpyridine (trpy) and cyanide as co-ligands. According to existing models, including cyanide in the coordination sphere should raise the energies and minimize the influence of short-lived d-d excited states that otherwise compromise the excited-state lifetime. Both [Pt(trpy)(CN)]+ and the 4'-cyano-2,2':6',2''-terpyridine analogue [Pt(CN-T)(CN)]+ are emissive in dichloromethane solution, but the signals are weak. Part of the problem is that the d-pi* charge-transfer excited states also rise in energy, so that the emission actually originates from a (3)pi-pi* state with a relatively low radiative rate constant. However, another member of the series, the 4'-dimethylamino-2,2':6',2''-terpyridine (dma-T) derivative [Pt(dma-T)(CN)]+, proves to be a very promising platform with an emission quantum yield of phi= 0.26 and an excited-state lifetime of tau = 22 micros in room-temperature, deoxygenated dichloromethane solution. In the dma-T complex the electron-rich dimethylamino substituent provides the basis for an emissive, but largely ligand-based, charge-transfer excited state. The orbital parentage is such that the photoluminescence persists in donating solvents like dimethylformamide, which ordinarily quenches d-pi* excited states in complexes of this type.
    Dalton Transactions 09/2005; · 4.10 Impact Factor