Theoretical studies of molecular vibrational spectra, OLED materials and carbon nanotube confined chemistry

The performance of electronic structure methods in calculated vibrational frequencies and spectral intensities was investigated. Comparisons were made between Hartree-Fock and MP2, and a variety of local, gradient-corrected and hybrid DFT methods. For infrared intensities, the inclusion of electron correlation was found to be essential in obtaining quantitative results. For Raman intensities, the basis set used in the calculations was found to be the dominant factor. The Sadlej pVTZ electric property basis set was found to provide excellent vibrational intensities at reduced computational cost. Harmonic frequency scaling factors for Hartree-Fock, SVWN, BLYP, B3LYP, B3PW91 and MP2 using the Sadlej pVTZ basis set were determined by regressions analysis.; Infrared assignments were made for the material N,N′-diphenyl-N,N ′-bis(1-naphthyl)-1,1′-biphenyl-4,4 ″-diamine (NPB) using the B3LYP/6-31G(d) level of theory. Using the assignments, the changes in thin solid films upon thermal annealing was investigated. Upon annealing, the average orientation of the NPB naphthyl groups become predominately flat with respect to the surface.; The lowest energy S₁ excited state of tris-(8-hydroxyquinoline)-aluminum(III) (Alq3) was characterized using singles configuration interaction and time-dependent density functional theory. The lowest singlet electronic transition is primarily localized on one of the quinolate ligands. The emission wavelength and Stokes shift, calculated using TD-B3LYP, are in very good agreement with experimental values. The vibronic structure observed in low temperature emission spectra is assigned.; The surface enhanced Raman spectrum of phthalimide was simulated using a computationally simple model for the surface species, achieving useful results.; The interaction potential curve for the a3Σ +_u state if Li₂ was calculated using the QCISD(T)/cc-pV5Z level of theory. Equilibrium constants and vibrational levels for 7Li₂ are in excellent with experiment.; The effect of confinement inside carbon nanotubes on chemical reaction enthalpies and activation energies was investigated for the Menshutkin reaction. Inside carbon nanotubes, the reaction barrier and the overall reaction endothermicity are found to be significantly reduced, compared to gas phase. Confinement inside carbon nanotubes closely resembles the effect of solvation and chemical reactions in which there is a separation of charge along the reaction coordinate will be enhanced inside fullerene based materials due to their large intrinsic polarizabilities.