Abstract
Small, inorganic hydrides are likely hiding in plain sight, waiting to be detected toward various astronomical objects. AlH2OH can form in the gas phase via a downhill pathway, and the present, high-level quantum chemical study shows that this molecule exhibits bright infrared features for anharmonic fundamentals in regions above and below that associated with polycyclic aromatic hydrocarbons. AlH2OH along with HMgOH, HMgNH2, and AlH2NH2are also polar with AlH2OH having a 1.22 D dipole moment. AlH2OH and likely HMgOH have nearly unhindered motion of the hydroxyl group but are still strongly bonded. This could assist in gas phase synthesis, where aluminum oxide and magnesium oxide minerals likely begin their formation stages with AlH2OH and HMgOH. This work provides the spectral data necessary to classify these molecules such that observations as to the buildup of nanoclusters from small molecules can possibly be confirmed.
Highlights
Al–O bonds are known in evolved stars and one exoplanet atmosphere in the form of AlOH and AlO (Tenenbaum and Ziurys, 2009; Tenenbaum and Ziurys, 2010; Takigawa et al, 2017; Chubb et al, 2020)
Their spectral features will be computed via quartic force fields (QFFs) which are fourth-order Taylor series expansions of the internuclear Hamiltonian. Their utilization defined with accurate electronic structure methods have previously produced anharmonic fundamental vibrational frequencies to within 0.70% error as well as B and C rotational constants to within 0.12% error of gas phase experiment (Huang et al, 2011; Fortenberry et al, 2012a, Fortenberry et al, 2012b; Zhao et al, 2014; Morgan and Fortenberry, 2015; Theis and Fortenberry, 2016; Bizzocchi et al, 2017; Kitchens and Fortenberry, 2016; Fortenberry and Francisco, 2017; Fuente et al, 2017; Wagner et al, 2018; Fortenberry and Lee, 2019; Gardner et al, 2021). The accuracy of such methods has led to the first interstellar observation of HOCO+ in the ]5 1 state (Bizzocchi et al, 2017) as well as the first laboratory observation of ArOH+ (Wagner et al, 2018), both based on previously existing quantum chemical data produced in our group (Fortenberry et al, 2012b; Theis and Fortenberry, 2016)
Both are based on coupled cluster theory at the singles, doubles, and perturbative triples [CCSD(T)] level of theory (Raghavachari et al, 1989; Shavitt and Bartlett, 2009; Crawford and Schaefer III, 2000), but one utilizes the explicitly correlated F12b formalism (CCSD(T)-F12b) (Adler et al, 2007)
Summary
Al–O bonds are known in evolved stars and one exoplanet atmosphere in the form of AlOH and AlO (Tenenbaum and Ziurys, 2009; Tenenbaum and Ziurys, 2010; Takigawa et al, 2017; Chubb et al, 2020). The present work utilizes similar quantum chemical computations as employed previously for OAlOH and AlOH (Fortenberry et al, 2020) to produce molecular structures, energies, and spectroscopic data for the four molecules at the nexus of strongly bound and containing highly abundant atoms as determined in earlier work (Doerksen and Fortenberry, 2020): AlH2OH, HMgOH, AlH2NH2, and HMgNH2 These structures are known to challenge conventional thinking in that AlH2OH is planar, HMgOH is linear, and the two N-containing species are C2v structures (Alabugin et al, 2014; Fugel et al, 2018; Sheridan and Ziurys, 2000; Xin et al, 2000; Grotjahn et al, 2001; Burton et al, 2019). The accuracy of such methods has led to the first interstellar observation of HOCO+ in the ]5 1 state (Bizzocchi et al, 2017) as well as the first laboratory observation of ArOH+ (Wagner et al, 2018), both based on previously existing quantum chemical data produced in our group (Fortenberry et al, 2012b; Theis and Fortenberry, 2016)
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