Amine-Hydrogen Halide Complexes: Experimental Electric Dipole Moments and a Theoretical Decomposition of Dipole Moments and Binding Energies

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• 作者：Carolyn S. Brauer ; Matthew B. Craddock ; Jacob Kilian ; Erik M. Grumstrup ; M. Christopher Orilall ; Yirong Mo ; Jiali Gao ; Kenneth R. Leopold
• 刊名：Journal of Physical Chemistry A
• 出版年：2006
• 出版时间：August 24, 2006
• 年：2006
• 卷：110
• 期：33
• 页码：10025 - 10034
• 全文大小：134K
• 年卷期：v.110,no.33(August 24, 2006)
• ISSN：1520-5215

文摘

The Stark effect has been observed in the rotational spectra of several gas-phase amine-hydrogen halidecomplexes and the following electric dipole moments have been determined: H₃¹⁵N-H³⁵Cl (4.05865 ± 0.00095D), (CH₃)₃¹⁵N-H³⁵Cl (7.128 ± 0.012 D), H₃¹⁵N-H⁷⁹Br (4.2577 ± 0.0022 D), and (CH₃)₃¹⁵N-H⁷⁹Br (8.397± 0.014 D). Calculations of the binding energies and electric dipole moments for the full set of complexesR_n(CH₃)_3-nN-HX (n = 0-3; X = F, Cl, Br) at the MP2/aug-cc-pVDZ level are also reported. The blocklocalized wave function (BLW) energy decomposition method has been used to partition the binding energiesinto contributions from electrostatic, exchange, distortion, polarization, and charge-transfer terms. Similarly,the calculated dipole moments have been decomposed into distortion, polarization, and charge-transfercomponents. The complexes studied range from hydrogen-bonded systems to proton-transferred ion pairs,and the total interaction energies vary from 7 to 17 kcal/mol across the series. The individual energy componentsshow a much wider variation than this, but cancellation of terms accounts for the relatively narrow range ofnet binding energies. For both the hydrogen-bonded complexes and the proton-transferred ion pairs, theelectrostatic and exchange terms have magnitudes that increase with the degree of proton transfer but are ofopposite sign, leaving most of the net stabilization to arise from polarization and charge transfer. In all of thesystems studied, the polarization terms contribute the most to the induced dipole moment, followed by smallerbut still significant contributions from charge transfer. A significant contribution to the induced moment ofthe ion pairs also arises from distortion of the HX monomer.