Reduced Radial Electric Quadrupole Moment Function for Diatomic Molecules.

The prospect of constructing global electric quadrupole moment functions (EQMFs) of diatomic molecules by morphing their theoretical approximants within the framework of the reduced radial curve (RRC) approach is explored by performing model calculations for the ground electronic states of H and HF. The reduced quadrupole moment curves probed, constructed for a set of differently accurate theoretical EQMFs, coincide with their best many-parameter analytic counterparts so closely that they can be used as their accurate few-parameter representations. No other such functional representation is available in the literature.

Three-Parameter Electric Dipole Moment Function for the CO Molecule.

A global electric dipole moment function of the ground electronic state of carbon monoxide is constructed by morphing its best theoretical approximants from the literature to the best available experimental data within the framework of the reduced radial curve approach. The resulting functions coincide with their best many-parameter empirical counterparts so closely that they can be used as highly accurate three-parameter representations. Apparently, given the mathematical nature of the problem addressed, this approach can be applied equally well to all radial molecular functions that have similarly cumbersome shapes as the function probed.

Reduced Radial Curves of Diatomic Molecules.

The prospect of using the concept of a universal reduced potential energy curve (RPC) for a broader class of radial molecular functions is explored by performing appropriate model calculations for the electric dipole moment functions of the hydrogen halides HF, HCl, and HBr. The reduced radial functions of the model systems, constructed from their best available theoretical approximants, coincide so closely that they can be used as few-parameter universal representations of functions available in the literature. Given the mathematical nature of the problem addressed here, the results are not limited to the functions studied but can be applied equally well to all radial molecular functions that have similar shapes, such as electric quadrupole moment and dipole polarizability functions.

Hydrogen Bonding with Hydridic Hydrogen-Experimental Low-Temperature IR and Computational Study: Is a Revised Definition of Hydrogen Bonding Appropriate?

Spectroscopic characteristics of MeSi-H···Y complexes (Y = ICF, BrCN, and HCN) containing a hydridic hydrogen were determined experimentally by low-temperature IR experiments based on the direct spectral measurement of supersonically expanded intermediates on a cold substrate or by the technique of argon-matrix isolation as well as computationally at harmonic and one-dimensional anharmonic levels. The computations were based on DFT-D, MP2, MP2-F12, and CCSD(T)-F12 levels using various extended AO basis sets. The formation of all complexes related to the redshift of the Si-H stretching frequency upon complex formation was accompanied by an increase in its intensity.

The stability of covalent dative bond significantly increases with increasing solvent polarity.

It is generally expected that a solvent has only marginal effect on the stability of a covalent bond. In this work, we present a combined computational and experimental study showing a surprising stabilization of the covalent/dative bond in MeNBH complex with increasing solvent polarity. The results show that for a given complex, its stability correlates with the strength of the bond.