Rotational spectra and molecular structures of organometallic and organic molecules

Understanding the nature of chemical bonds constitutes a major theme of this thesis. This thesis investigates the gas phase rotational spectra, electronic charge distributions and molecular structures of organometallic and organic molecules, using high-resolution pulsed beam Fourier transform microwave spectroscopy (PBFTMS) and computational methods. High-resolution rotational spectra and structural parameters were obtained for the following organometallic molecules in the singlet electronic state, including three symmetric and five asymmetric top complexes: C₅H₅Nb(CO)₄, CH₃Mn(CO)₅, MnRe(CO)₁₀, C₅H₅Mo(CO)₃H, C₅H₅W(CO)₃H, C₅H₅NiC₃H₅, C5H₄(CH₃)FeC₅H₅ and (C₅H₄(CH₃))₂Fe. High-resolution rotational spectra and structural parameters were obtained for three organic molecules in the singlet electronic state: ortho-benzyne (C₆H₄) and the keto-enol tautomers, 2-hydroxypyridine and 2-pyridone (C₅H₅NO). In addition to the tautomeric forms, pure rotational spectra of the H-bonded dimer, 2-hydroxypyridine:2-pyridinone, were also obtained. These detailed spectral investigations yielded novel and useful information about the molecular properties of these molecules. Primarily, these results provided information regarding chemical bonding, vibrational ground state structures, structural isomers, conformational behavior, metal-hydrogen bonding and electronic charge distributions. Density functional theory (DFT) and ab-initio calculations were carried out in conjunction with the experiments, providing additional insights into further understanding the equilibrium structures, structural isomers and the electric field gradient distributions for these molecules