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Molecular structures of various molecules were examined. First, a systematic investigation of the As2Fn / As2Fn¯ systems was carried out using Density Functional Theory. From the first four studied species (As2Fn, n = 1-4), all neutral molecules and their anions are shown to be stable with respect to As-As bond breaking. The global minima of the neutral As2Fn species, n = 5-8, are weakly bound complexes, held together by dipole-dipole interactions. All such structures have the AsFm-AsFn form, where (m,n) is (2,3) for As2F5, (3,3) for As2F6, (4,3) for As2F7 and (5,3) for As2F8. The anions As2Fn¯ , n = 5-8, are shown to be stable with respect to the As-As bond breaking, and we predict that all of them have fluorine-bridged or fluorine-linked structures. Next, in support of mass-selected infrared photodissociation (IRPD) spectroscopy +experiments, coupled cluster methods have been used to study the V(H2O) and +5555ArV(H2O) complexes. Four lowest-lying quintet states (A1, A2, B1 and B2), all of -1which appear within a 6 kcal mol energy range, were examined. Our computations show an opening of 2°-3º in the equilibrium bond angle of H2O due to its interaction with the metal ion. Zero-point vibrational averaging increases the effective bond angle further by 2.0°-2.5º, mostly due to off-axis motion of the heavy vanadium atom rather than changes in the water bending potential. The total theoretical shift in the bond angle of about +4° is significantly less than the widening near 9º deduced from IRPD experiments. Last, the equilibrium molecular structures of the two lowest-energy conformers of glycine, Gly-Ip and Gly-IIn, have been characterized by high-level ab initio electronic structure computations. Based on experimentally measured vibrationally averaged effective rotational constant sets of several isotopologues and our ab initio data for structural constraints and zero-point vibrational shifts, least-squares structural refinements were performed to determine improved Born Oppenheimer equilibrium structures of Gly-Ip and Gly-IIn. The barrier to planarity separating Gly-IIp and Gly--1IIn has been determined to be 20.5 cm. The equilibrium torsional angle 2(NCCO) of Gly-IIn, characterizing the deviation of its heavy-atom framework from planarity, is 11º.