Important Routes for Methanediol Formation by Formaldehyde Hydrolysis Catalyzed by Iodic Acid and for the Contribution to an Iodic Acid Sink by the Reaction of Formaldehyde with Iodic Acid Catalyzed by Atmospheric Water

Methanediol formed by the hydrolysis of formaldehyde is an important intermediate in the formation of formic acid in the atmosphere. However, the formation of methanediol by the direct reaction of formaldehyde (HCHO) with water (H2O) is not feasible in the gas phase in the atmosphere due to the very high enthalpy of activation at 0 K for the HCHO + H2O reaction. Here, by using quantum chemical methods and reaction rate theory, we report a new mechanistic route for the iodic acid-catalyzed gas-phase hydrolysis of formaldehyde. The present findings show that iodic acid serves as an excellent catalyst in this reaction, decreasing the enthalpy of activation at 0 K from 36.01 kcal/mol for the HCHO + H2O reaction to −13.28 kcal/mol for the HCHO + H2O + HIO3 reaction with respect to the separate reactants. Additionally, the calculation results also show that water can catalyze the HCHO + HIO3 reaction, decreasing the enthalpy of activation at 0 K for the HCHO + HIO3 reaction from 2.96 to −10.00 kcal/mol. The calculated kinetics results reveal that the gas-phase hydrolysis of formaldehyde catalyzed by iodic acid can make a substantial contribution to the sink of formaldehyde and the formation of methanediol below 260 K. The reaction of formaldehyde with iodic acid catalyzed by water dominates over the HIO3 + OH reaction under full atmospheric conditions. The present findings are expected have broad implications for understanding the formation of methanediol and the sink of formaldehyde and iodic acid in the atmosphere

Structural and Electronic Properties of Single-Atom Transition Metal-Doped Boron Clusters MB₂₄ (M = Sc, V, and Mn)

A theoretical study of geometrical structures, electronic properties, and spectral properties of single-atom transition metal-doped boron clusters MB24 (M = Sc, V, and Mn) is performed using the CALYPSO approach for the global minimum search, followed by density functional theory calculations. The global minima obtained for the VB24 and MnB24 clusters correspond to cage structures. Interestingly, the global minima obtained for the ScB24 cluster tend to a three-ring tubular structure. Population analyses and valence electron density analyses reveal that partial electrons on transition-metal atoms transfer to boron atoms. The localized orbital locator of MB24 (M = Sc, V, and Mn) indicates that the electron delocalization of ScB24 is stronger than that of VB24 and MnB24, and there is no obvious covalent bond between doped metals and B atoms. The spin density and spin population analyses reveal that MB24 (M = Sc, V, and Mn) have different spin characteristics which are expected to lead to interesting magnetic properties and potential applications in molecular devices. The calculated spectra indicate that MB24 (M = Sc, V, and Mn) has meaningful characteristic peaks that can be compared with future experimental values and provide a theoretical basis for the identification and confirmation of these single-atom transition metal-doped boron clusters. Our work enriches the database of geometrical structures of doped boron clusters and can provide an insight into new doped boron clusters

Geometric Structure, Electronic, and Spectral Properties of Metal-free Phthalocyanine under the External Electric Fields

Here, the ground-state structures, electronic structures, polarizability, and spectral properties of metal-free phthalocyanine (H2Pc) under different external electric fields (EEFs) are investigated. The results show that EEF has an ultrastrong regulation effect on various aspects of H2Pc; the geometric structures, electronic properties, polarizability, and spectral properties are strongly sensitive to the EEF. In particular, an EEF of 0.025 a.u. is an important control point: an EEF of 0.025 a.u. will bend the benzene ring subunits to the positive and negative x directions of the planar molecule. Flipping the EEF from positive (0.025 a.u.) to negative (−0.025 a.u.) flips also the bending direction of benzene ring subunits. The H2Pc shows different dipole moments projecting an opposite direction along the x direction (−84 and 84 Debye for EEFs of −0.025 and 0.025 a.u., respectively) under negative and positive EEF, revealing a significant dipole moment transformation. Furthermore, when the EEF is removed, the molecule can be restored to the planar structure. The transformation of the H2Pc structure can be induced by the EEF, which has potential applications in the molecular devices such as molecular switches or molecular forceps. EEF lowers total energy and reduces highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap; especially, an EEF of 0.025 a.u. can reduce the HOMO–LUMO gap from 2.1 eV (in the absence of EEF) to 0.37 eV, and thus, it can enhance the molecular conductivity. The first hyperpolarizability of H2Pc is 0 in the absence of EEF; remarkably, an EEF of 0.025 a.u. can enhance the first hyperpolarizability up to 15,578 a.u. Therefore, H2Pc under the EEF could be introduced as a promising innovative nonlinear optical (NLO) nanomaterial such as NLO switches. The strong EEF (0.025 a.u.) causes a large number of new absorption peaks in IR and Raman spectra and causes the redshift of electronic absorption spectra. The changes of EEF can be used to regulate the structure transformation and properties of H2Pc, which can promote the application of H2Pc in nanometer fields such as molecular devices

Theoretical Studies on Gas-Phase Reactions of Sulfuric Acid Catalyzed Hydrolysis of Formaldehyde and Formaldehyde with Sulfuric Acid and H₂SO₄···H₂O Complex

The gas-phase reactions of sulfuric acid catalyzed hydrolysis of formaldehyde and formaldehyde with sulfuric acid and H₂SO₄···H₂O complex are investigated employing the high-level quantum chemical calculations with M06-2X and CCSD­(T) theoretical methods and the conventional transition state theory (CTST) with Eckart tunneling correction. The calculated results show that the energy barrier of hydrolysis of formaldehyde in gas phase is lowered to 6.09 kcal/mol from 38.04 kcal/mol, when the sulfuric acid is acted as a catalyst at the CCSD­(T)/aug-cc-pv­(T+d)­z//M06-2X/6-311++G­(3df,3pd) level of theory. Furthermore, the rate constant of the sulfuric acid catalyzed hydrolysis of formaldehyde combined with the concentrations of the species in the atmosphere demonstrates that the gas-phase hydrolysis of formaldehyde of sulfuric acid catalyst is feasible and could be of great importance for the sink of formaldehyde, which is in previously forbidden hydrolysis reaction. However, it is shown that the gas-phase reactions of formaldehyde with sulfuric acid and H₂SO₄···H₂O complex lead to the formation of H₂C­(OH)­OSO₃H, which is of minor importance in the atmosphere