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The lack of observational data for the AlO molecule in the mesosphere/lower thermosphere may be due to ablated aluminum reacting quickly to form other species. Previously proposed reaction pathways show that aluminum could be ablated in the atmosphere from meteoritic activity, but there currently exist very limited spectroscopic data on the intermediates in these reactions, limiting the possible detection of said molecules. As such, rovibrational spectroscopic data are computed herein using quartic force field methodology at four different levels of theory for the neutral intermediates AlCO3, OAlO2, and HOAlO2. Each molecule exhibits multiple vibrational modes with large vibrational transition intensities. For instance, the C–O stretch (ν1) in AlCO3 has a harmonic intensity of 536 km mol−1, the Al–O stretch (ν2) in OAlO2 has an intensity of 678 km mol−1, and the out-of-plane torsion (ν9) in HOAlO2 has an intensity of 158 km mol−1. All three molecules have exceptionally large dipole moments of 6.27, 4.21, and 5.04 D, respectively. These properties indicate that all three molecules are good candidates for potential atmospheric observation utilizing vibrational and/or rotational spectroscopic techniques. [ABSTRACT FROM AUTHOR]

The difficulty of quantum chemically computing vibrational, rotational, and rovibrational reference data via quartic force fields (QFFs) for molecules containing aluminum appears to be alleviated herein using a hybrid approach based upon CCSD(T)‐F12b/cc‐pCVTZ further corrected for conventional CCSD(T) scalar relativity within the harmonic terms and simple CCSD(T)‐F12b/cc‐pVTZ for the cubic and quartic terms: the F12‐TcCR+TZ QFF. Aluminum containing molecules are theorized to participate in significant chemical processes in both the Earth's upper atmosphere as well as within circumstellar and interstellar media. However, experimental data for the identification of these molecules are limited, showcasing the potential for quantum chemistry to contribute significant amounts of spectral reference data. Unfortunately, current methods for the computation of rovibrational spectral data have been shown previously to exhibit large errors for aluminum‐containing molecules. In this work, ten different methods are benchmarked to determine a method to produce experimentally‐accurate rovibrational data for theorized aluminum species. Of the benchmarked methods, the explicitly correlated, hybrid F12‐TcCR+TZ QFF consistently produces the most accurate results compared to both gas‐phase and Ar‐matrix experimental data. This method combines the accuracy of the composite F12‐TcCR energies along with the numerical stability of non‐composite anharmonic terms where the non‐rigid nature of aluminum bonding can be sufficiently treated. [ABSTRACT FROM AUTHOR]

A series of five Re(pyNHC‐aryl)(CO)3X complexes varying the "X" ligand where pyNHC is a pyridyl N‐heterocyclic carbene have been synthesized and characterized through NMR, UV/Vis absorption spectroscopy, IR, mass spectrometry, time‐correlated single photon counting, computational analysis, and cyclic voltammetry. The photocatalytic reduction of CO2 to CO in the presence of a sacrificial electron donor with these complexes is evaluated using a simulated solar spectrum (AM 1.5G). Comparison of Br and CH3CN as the "X" ligand shows the same photocatalytic activity (both 32 TON). The use of Cl, NCS and P(OEt)3 "X" ligands all led to diminished reactivity with as little as 2 TON for the P(OEt)3 complex. These results were rationalized through computational analysis of "X" dissociation and excited‐state lifetime measurements. These results highlight the importance of the "X" ligand selection on catalysis with Re‐pyNHC complexes. [ABSTRACT FROM AUTHOR]

B The Cover Feature b shows the impact of an "X" ligand on the performance of photocatalysts reducing CO SB 2 sb to CO via a series of pyridyl N-heterocyclic carbene rhenium tricarbonyl complexes. These catalysts show impressive rate and durability in this reaction upon judicious "X" ligand selection. These catalysts show impressive rate and durability in this reaction upon judicious "X" ligand selection. [Extracted from the article]

The lack of observational data for the AlO molecule in the mesosphere/lower thermosphere may be due to ablated aluminum reacting quickly to form other species. Previously proposed reaction pathways show that aluminum could be ablated in the atmosphere from meteoritic activity, but there currently exist very limited spectroscopic data on the intermediates in these reactions, limiting the possible detection of said molecules. As such, rovibrational spectroscopic data are computed herein using quartic force field methodology at four different levels of theory for the neutral intermediates AlCO3, OAlO2, and HOAlO2. Each molecule exhibits multiple vibrational modes with large vibrational transition intensities. For instance, the C-O stretch (ν1) in AlCO3 has a harmonic intensity of 536 km mol-1, the Al-O stretch (ν2) in OAlO2 has an intensity of 678 km mol-1, and the out-of-plane torsion (ν9) in HOAlO2 has an intensity of 158 km mol-1. All three molecules have exceptionally large dipole moments of 6.27, 4.21, and 5.04 D, respectively. These properties indicate that all three molecules are good candidates for potential atmospheric observation utilizing vibrational and/or rotational spectroscopic techniques., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)