Ab initio calculations, at the MP2, QCISD, CCSD, and CASSCF levels of theory, have been performed to investigate the structure, stability, and properties of a new class of thermodynamically stable cations containing helium. These species have general formula XBeHe+ (X: monovalent group) and arise from the ligation of a helium atom to singlet ground state BeX+. The presently investigated systems include prototype "inorganic" ions such as HBeHe+, FBeHe+, ClBeHe+, HOBeHe+, and H2NBeHe+, as well as "organic" species such as H3CBeHe+, F3CBeHe+, HCZBeHe(+), H3C2BeHe+, and C6H5BeHe+. Irrespective of the substituent X, at any computational level, including the highly accurate Gaussian-3 (G3), the dissociation energies at 298.15 K of XBeHe+ into singlet ground-state BeX+ and He are predicted to be remarkably large and range from ca. 6 kcal mol(-1) for C6H5BeHe+ to ca. 11 kcal mol(-1) for FBeHe+. Thus, the electronic structure of the substituent X has an appreciable effect on the structure and stability of the XBeHe+ cations. We have also briefly examined the implications of our theoretical calculations for future gas-phase experiments aimed at the experimental observation and characterization of members of this new class of thermodynamically stable species of the lightest noble gas.
Beryllium-helium cations: computational evidence for a large class of thermodynamically stable species
ANTONIOTTI, Paola;
2003-01-01
Abstract
Ab initio calculations, at the MP2, QCISD, CCSD, and CASSCF levels of theory, have been performed to investigate the structure, stability, and properties of a new class of thermodynamically stable cations containing helium. These species have general formula XBeHe+ (X: monovalent group) and arise from the ligation of a helium atom to singlet ground state BeX+. The presently investigated systems include prototype "inorganic" ions such as HBeHe+, FBeHe+, ClBeHe+, HOBeHe+, and H2NBeHe+, as well as "organic" species such as H3CBeHe+, F3CBeHe+, HCZBeHe(+), H3C2BeHe+, and C6H5BeHe+. Irrespective of the substituent X, at any computational level, including the highly accurate Gaussian-3 (G3), the dissociation energies at 298.15 K of XBeHe+ into singlet ground-state BeX+ and He are predicted to be remarkably large and range from ca. 6 kcal mol(-1) for C6H5BeHe+ to ca. 11 kcal mol(-1) for FBeHe+. Thus, the electronic structure of the substituent X has an appreciable effect on the structure and stability of the XBeHe+ cations. We have also briefly examined the implications of our theoretical calculations for future gas-phase experiments aimed at the experimental observation and characterization of members of this new class of thermodynamically stable species of the lightest noble gas.
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