The geometrical isotope effect of C–H⋯O type hydrogen bonds revealed by multi-component molecular orbital calculation

2015

J. Comput. Chem.

Three different H/D isotope effect in nine H3 XH(D)···YH3 (X = C, Si, or Ge, and Y = B, Al, or Ga) hydrogen-bonded (HB) systems are classified using MP2 level of multicomponent molecular orbital method, which can take account of the nuclear quantum nature of proton and deuteron. First, in the case of H3 CH(D)···YH3 (Y = B, Al, or Ge) HB systems, the deuterium (D) substitution induces the usual H/D geometrical isotope effect such as the contraction of covalent R(C-H(D)) bonds and the elongation of intermolecular R(H(D)···Y) and R(C···Y) distances. Second, in the case of H3 XH(D)···YH3 (X = Si or Ge, and Y = Al or Ge) HB systems, where H atom is negatively charged called as charge-inverted hydrogen-bonded (CIHB) systems, the D substitution leads to the contraction of intermolecular R(H(D)···Y) and R(X···distances. Finally, in the case of H3 XH(D)···BH3 (X = Si or Ge) HB systems, these intermolecular R(H(D)···Y) and R(X···Y) distances also contract with the D substitution, in which the origin of the contraction is not the same as that in CIHB systems. The H/D isotope effect on interaction energies and spatial distribution of nuclear wavefunctions are also analyzed.

Section: Nuclear Quantum Effect and H/d Isotope Effectsupporting

confidence: 66%

Section: Nuclear Quantum Effect and H/d Isotope Effectmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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H/D isotope effect on charge-inverted hydrogen-bonded systems: Systematic classification of three different types in H₃XH^…YH₃(X = C, Si, or Ge, and Y = B, Al, or Ga) with multicomponent calculation

2015

J. Comput. Chem.

“…17,18 More complicated and high-precision nuclear basis functions can be easily constructed by our FV-OPT program which can variationally determine optimum exponent value of each basis function. Although the nuclear wave function should be expanded by a suitable number of nuclear basis sets, we have already demonstrated that single s-type GTF is usable to clearly discuss the H / D isotope effect.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, many-body effect plays a very important role for the equilibrium geometry of porphine molecule, as well as porphycene molecule. 17,18 Our MCគMO method has been already extended to Møller-Plesset perturbation 19 and configuration interaction 20 methods beyond the mean field approximation. Many theoretical methods are developed for the quantum effect of hydrogen nucleus.…”

Section: Introductionmentioning

confidence: 99%

H ∕ D isotope effect on porphine and porphycene molecules with multicomponent hybrid density functional theory

The Journal of Chemical Physics

2006

To analyze the H/D isotope effect on porphine and porphycene molecules including the protonic/deuteronic quantum nature and electron correlation efficiently, the authors have developed the new scheme of the multicomponent hybrid density functional theory [MC_(HF+DFT)]. The optimized geometries of porphine, porphycene, and these deuterated isotopomers by our MC_(HF+DFT) method are in good agreement with the experimental "high-symmetric" structures, contrary to the "low-symmetric" geometries optimized by pure multicomponent Hartree-Fock method. The optimized geometries for HD-porphine and HD-porphycene molecules, in which an inner hydrogen is replaced to a deuterium, are found to be low symmetric. Such drastic geometrical change induces the electronic polarization, and gives rise to the slight dipole moment values in these HD species. Their results clearly indicate that the difference of the nuclear quantum nature between inner proton and inner deuteron directly influences the molecular geometry and electronic structure.

Why is N···Be distance of NH₃H⁺···DBeH shorter than that of NH₃D⁺···HBeH? paradoxical geometrical isotope effects for partially isotope‐substituted dihydrogen‐bonded isotopomers

2013

J Comput Chem

The partial isotope substitution for the change of geometrical parameters, interaction energies, and nuclear magnetic shielding tensors (σ) of dihydrogen-bonded NH3X(+)···YBeH (X, Y = H, D, and T) systems is analyzed. Based on the theoretical calculation, the distance between heavy atoms RN···Be of NH3H(+) ···DBeH is clearly found to be shorter than that in NH3D(+)···HBeH. Such apparently paradoxical geometrical isotope effect (GIE) on RN···Be is revealed by the cooperative effect of two kinds of (1) primary covalent-bonded GIE and (2) secondary dihydrogen-bonded one. We have demonstrated that (1) the covalent bond lengths become shorter by heavier isotope-substitution and (2) the dihydrogen-bonded distance RX···Y becomes shorter by heavier Y and lighter X isotope-substitution due to the difference of electronic structure reflected by the nuclear distribution. We have also found that interaction energy of NH3H(+)···DBeH is stronger than that of NH3D(+)···HBeH and isotopic deshielding effect of magnetic shielding becomes large in lighter isotope.