Quantum Chemical Investigation Of Some Typical OLED And Multifunctional Materials

Quantum mechanical calculations were carried out to study the molecular geometry, the electronic structure and some other electronic properties of tris(o-phenylenedioxy) cyclotriphosphazene (TPP), tris(8-hydroxyquinolinato)gallium (Gaq3) and its "CH'VN substituted derivatives, dinuclear and mononuclear Copper(I) complexes of 3,5-bis (trifluoro methyl)pyrazole and related bis(pyrazolyl) borate.Using ab initio HF and DFT (B3LYP) methods, the basis set and method dependence of the optimal geometry of tris(o-phenylenedioxy)cyclotriphosphazene proved that polarized functions are necessary for an appropriate description of geometry characteristics and electronic structure of this compound. B3LYP/6-31G(d) optimized geometry was found to agree well with crystal data. The study of the electronic structure of the neutral molecule has shown that the frontier orbitals are strongly localized on the three spirocyclic side groups, while injection effect of charge on the structure of the molecule has small structural changes on it, implying a certain stability of the molecular structure.In a partially similar study made on Gaq3 molecular geometry and optical properties, it was found that the flexible basis set with diffuse and polarized orbitals (6-31+G*), in combination with electron correlation (DFT-B3LYP) is required for an accurate description of the molecular geometry for ground state. The best agreement between simulated and experimental spectra, both in terms of maximum absorption and emission wavelengths (respectively 426 & 531 nmvs 393 & 526 nm of experimental average) was achieved with TD-B3LYP/3-21G* and that for the Stokes Shift (122 nm vs 133 nm) achieved using TD-B3LYP/6-31+G*. For the same OLED material, our study has shown that Ga/Al substitution effects (comparatively to Alq3) on the optical properties should be more ascribed to the induced geometrical parameters changes involving the metal atom rather than the d orbitals of this.Equilibrium geometry configurations of the "CH'VN Alq3 and Gaq3 derivatives were calculated by DFT (B3LYP/6-31G*) method. The FMO and gap energy calculation for all compounds has been performed at HF/6-31G* level of theory. It was shown that comparatively to the molecule parents, the HOMO and LUMO are stabilized, the net effect being however an increasing/decreasing of the gap (Eg) depending on the position of substituted group. Based on the equilibrium geometries, the effect of the substitution on the absorption and emission spectra was evaluated using TDB3LYP/3-21G*. An important blueshift was predicted for 5-substituted 8-hydroxyquinoline derivatives, an important red one being observed for 4-substituted ones. Interestingly, relatively significant blue and red shifts were also predicted for the 7- and 2-substituted derivatives. In this work, the correlation between the spectrum shifts and the Metal-ligand bonding is also discussed.The ground state and low-lying excited electronic states in mononuclear and dinuclear {H₂B[3,5-(CF3)₂Pz]₂M(2,4,6-Cn)}, M₁, and {[3,5-(CF3)₂Pz]M(2,4,6-Cn)}₂, M₂ were studied using density functional theory. The electronic properties of the molecule are calculated using the B3LYP functional while excited singlet and triplet states are examined using TD-B3LYP. The calculated energies of the lowest singlet (and triplet) states are 3.57 (3.36), 3.72 (3.53), 4.86 (4.44) and 4.54 (3.96) eV respectively for Cu₁ Cu₂, Ag₁ and Ag₂. All of the low-lying transitions calculated in this study are categorized as MLCT transitions because the metal d character of two highest occupied molecular orbitals within 68 - 72.8% for Cu₁ and Cu₂ and 43.5 - 48.5% for Ag₁ and Ag₂. From the analysis of the predicted emission spectra of these complexes, the calculated low-lying triplets were the only one found to be localized in the visible region with the predicted emission wavelengths of 418.55 nm for Cu₁, 420.50 nm for Cu₂ and 423.15 nm for Ag2 in good agreement with available experimental data. Furthermore the emitting states were assigned as ³MLCT (Cu-3d→Cn-Ï€*) mainly...