A series of donor-acceptor complexes containing sulfur trioxide have been studied in the gas and condensed phases using density functional theory. The condensed phase is represented using the polarizable continuum model. The systems investigated include complexes of nitrogen-containing donor molecules, (CH(3))(n)H(3-n)N (n = 0-3), with SO(3) and complexes of oxygen-containing donor molecules, (CH(3))(m)H(2-m)O (m = 0-2), with SO(3). Significant differences are observed between the gas- and condensed-phase properties of the complexes as a result of the ability of the condensed-phase medium to support higher charge separation between the donor and acceptor. The gas/condensed-phase behavior of two nitrogen-containing complexes, (CH(3))H(2)N-SO(3) and (CH(3))(2)HN-SO(3), has been investigated for the first time. These complexes exhibit properties intermediate to the previously observed H(3)N-SO(3) and (CH(3))(3)N-SO(3) complexes. Systematic trends in the gas- and condensed-phase structure and properties have been observed as methyl groups are added to the donor molecule. In addition, two oxygen-containing complexes, CH(3)OH-SO(3) and (CH(3))(2)O-SO(3), have been characterized for the first time. The differences between the gas- and condensed-phase properties of the oxygen-containing complexes are, in many cases, larger than those of the nitrogen-containing complexes, and therefore they represent an intriguing new class of complexes for potential experimental observation. Finally, a strong correlation between the charge transfer and binding energy has been obtained for both the nitrogen- and oxygen-containing complexes of sulfur trioxide.
Ab initio calculations have been performed to determine the structure and energies of the ground and first two excited electronic states of CHF2. The 6-31+G*, 6-311++G**, aug-ccpVDZ, and aug-cc-pVTZ basis sets were utilized at the MP2 and CCSD(T) levels of theory for the structures and energies of minima and transition states on the ground electronic surface. The 6-31+G*, 6-311++G** basis sets were utilized at the CIS, CASSCF, and MRCI levels of theory for characterization of the excited electronic states. The ground state was found to be pyramidal, the first excited state is possibly dissociative and the second excited state planar. Vertical transition energies for transitions from the ground to the first and second excited states were found to range from 61 355 to 71 372 cm-1 at the CIS level of theory. Shallow local minima on the à state potential energy surface with long C−H bonds of about 2.0 Å were located by using two-dimensional potential surface scans. Upon excitation to the B̃ state, the C−H bond stays constant near 1.08 Å, the C−F bond lengthens from 1.33 to 1.45 Å, the H−C−F bond angle increases from 114° to 133°, and the F−C−F angle decreases from 110° to 93°.
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