Anharmonic Vibrational Frequencies of Water Borane and Associated Molecules

Abstract

Water borane (BH3OH2) and borinic acid (BH2OH) have been proposed as intermediates along the pathway of hydrogen generation from simple reactants: water and borane. However, the vibrational spectra for neither water borane nor borinic acid has been investigaged experimentally due to the difficulty of isolating them in the gas phase, making accurate quantum chemical predictions for such properties the most viable means of their determination. This work presents theoretical predictions of the full rotational and fundamental vibrational spectra of these two potentially application-rich molecules using quartic force fields at the CCSD(T)-F12b/cc-pCVTZ-F12 level with additional corrections included for the effects of scalar relativity. This computational scheme is further benchmarked against the available gas-phase experimental data for the related borane and HBO molecules. The differences are found to be within 3 cm−1 for the fundamental vibrational frequencies and as close as 15 MHz in the B0 and C0 principal rotational constants. Both BH2OH and BH3OH2 have multiple vibrational modes with intensities greater than 100 km mol−1, namely ν2 and ν4 in BH2OH, and ν1, ν3, ν4, ν9, and ν13 in BH3OH2. Finally, BH3OH2 has a large dipole moment of 4.24 D, which should enable it to be observable by rotational spectroscopy, as well.

Fluoro Hydrogen Peroxide: A Plausible Molecular Form of Naturally-Occurring Fluorine

“…Regardless, the differences between the two QFF methods are meant to improve the rovibrational data collected from the F12-TZ QFF method. In fact, previous studies 54,68 utilizing F12-TZ-cCR QFF report that the rotational constants generated contain, on average, less error when compared to those of previous gasphase experiments than those of either F12-TZ or CcCR QFFs. Therefore, the rotational constants introduced in this work via the F12-TZ-cCR QFF methodology will provide the necessary data for benchmarking, laboratory analysis, and potential atmospheric or astrophysical detection via rotational spectroscopy.…”

“…Furthermore, fundamental vibrational frequencies generated from the F12-TZ methodology in previous studies 46,47,51,69,70 suggest exceedingly high accuracy for comparison to previous experiments. However, much like the rotational constants, previous theoretical work 54,68 utilizing the new F12-TZ-cCR QFF methods show almost as, if not more, accurate fundamentals than F12-TZ when compared to previous gas-phase experimental studies. The high accuracy exhibited by both QFF methods in previous studies further suggests their validity for application in generating highly accurate vibrational frequencies for a molecule such as HOOF.…”

“…53 The F12-TZ-cCR QFF method has been shown to find a sweet-spot between the significantly reduced computational cost of F12-TZ and the accuracy of CcCR. 53,54 Regardless of QFF method, the molecular geometry of HOOF is first optimized with exceptionally tight convergence criteria via the MOLPRO 2020.1 quantum chemical package. 55 The F12-TZ QFF optimizes its geometry at the CCSD(T)-F12b/cc-pVTZ-F12 level of theory, while F12-TZ-cCR optimizes the geometry at the CCSD(T)-F12b/cc-pCVTZ-F12 level.…”

“…With these corrections applied to the F12-TZ QFF method, this second QFF methodology will henceforth be abbreviated F12-TZ-cCR . The F12-TZ-cCR QFF method has been shown to find a sweet-spot between the significantly reduced computational cost of F12-TZ and the accuracy of CcCR. , …”

Spectroscopy and Photochemistry of OAlNO and Implications for New Metal Chemistry in the Atmosphere

“…This QFF method utilized herein uses the CCSD­(T)-F12b level with the inclusion of explicit core–electron correlation in the cc-pCVTZ-F12 basis set and scalar relativistic corrections also present in the previous composite methodology. This new composite method will henceforth be abbreviated “F12-TZ-cCR.” The F12-TZ-cCR methodology has been previously used to produce more accurate rovibrational spectroscopic data than that of both F12-TZ and other canonical CCSD­(T)-based composite methods with the added benefit of a decrease in computational cost compared to the composite method. − Consequently, the F12-TZ-cCR QFF is employed herein to provide accurate predictions for the rovibrational character of the aluminum-containing species investigated in this work.…”