Vibrational frequencies for a selected set of transition metal carbonyl complexes are computed with various forms of density functional theory (B3LYP, BP86, M06, M06-L), employing several different basis sets. The computed frequencies for the carbonyl stretches are compared to the experimental values obtained from gas phase infrared spectra of isolated neutrals and ions. Recommended carbonyl-stretch scaling factors which are developed vary significantly for different functionals, but there is little variation with basis set. Scaled frequencies compared to experimental spectra for cobalt and tantalum carbonyl cations reveal additional variations in multiplet patterns and relative band intensities for different functionals.

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Background: Coronavirus disease 2019 [severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)] infection at varying time points during the pregnancy can influence antibody levels after delivery. We aimed to examine SARS-CoV-2 IgG, IgM and IgA receptor binding domain of the spike protein and nucleocapsid protein (N-protein) reactive antibody concentrations in maternal blood, infant blood and breastmilk at birth and 6 weeks after SARS-CoV-2 infection in early versus late gestation. Methods: Mothers with SARS-CoV-2 infection during pregnancy were enrolled between July 2020 and May 2021. Maternal blood, infant blood and breast milk samples were collected at delivery and 6 weeks postpartum. Samples were analyzed for SARS-CoV-2 spike and N-protein reactive IgG, IgM and IgA antibodies. Antibody concentrations were compared at the 2 time points and based on trimester of infection (“early” 1st/2nd vs. “late” 3rd). Results: Dyads from 20 early and 11 late trimester infections were analyzed. For the entire cohort, there were no significant differences in antibody levels at delivery versus 6 weeks with the exception of breast milk levels which declined over time. Early gestation infections were associated with higher levels of breastmilk IgA to spike protein (P = 0.04). Infant IgG levels to spike protein were higher at 6 weeks after late infections (P = 0.04). There were strong correlations between maternal and infant IgG levels at delivery (P < 0.01), and between breastmilk and infant IgG levels. Conclusions: SARS-CoV-2 infection in early versus late gestation leads to a persistent antibody response in maternal blood, infant blood and breast milk over the first 6 weeks after delivery.

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