Defect Formation, T-Atom Substitution and Adsorption of Guest Molecules in MSE-Type Zeolite Framework—DFT Modeling

We used computational modeling, based on Density Functional Theory, to help understand the preference for the formation of silanol nests and the substitution of Si by Ti or Al in different crystallographic positions of the MSE-type framework. All these processes were found to be energetically favorable by more than 100 kJ/mol. We suggested an approach for experimental identification of the T atom position in Ti-MCM-68 zeolite via simulation of infrared spectra of pyridine and acetonitrile adsorption at Ti. The modeling of adsorption of hydrogen peroxide at Ti center in the framework has shown that the molecular adsorption was preferred over the dissociative adsorption by 20 to 40 kJ/mol in the presence or absence of neighboring T-atom vacancy, respectively.

Computational Insights in DNA Methylation: Catalytic and Mechanistic Elucidations

Methylation at C5 position of cytosine (5mC) is the most abundantly occurring methylation process at CpG island, which has been well-known as an epigenetic modification linked to many human’s diseases. Recently, another methylation approach has been discovered to show that DNA methyltransferases (DNMTs) promote the addition of methyl group at position 3 to yield 3mC. The existence of 3mC can cause severe damages to the DNA strand, such as blocking its replication, repair, and transcription, affecting its stability, and initiating a double-strand DNA break. To gain a deeper insight into the formation of 3mC, we have performed density functional theory (DFT) modeling studies at different levels of theory to clearly map out the mechanistic details for this new methylation approach. Our computed results are in harmony with pertinent experimental observations and shed light on a crucial off-target activity of DNMTs.

Case Study in a Conceptual DFT Investigation of New Corrosion Inhibitor

Inhibition efficiency of thiosemicarbazide derivative, namely 4-ethyl-1-(4-oxo-4-phenylbutanoyl)thiosemicarbazide (EOPT) on corrosion of mild steel, was investigated utilizing the density functional theory (DFT) modeling techniques in the aqueous phase. Chemical parameters at the quantum level, such as energies of highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), dipole moment (µ), absolute electronegativity (χ), global hardness (η), softness (σ), and the fraction of electrons transferred (∆N) have been determined at the B3LYP level of theory with 6-31G (d, p) basis set.

CH Activation by a Heavy Metal Cation: Production of H2 from the Reaction of Acetylene with C4H4-Os(+) in Gas phase

While first-row transition metal cations, notably Fe(+), catalyze the gas-phase conversion of acetylene to benzene, a distinct path is chosen in systems with Os, Ir, and Rh cations. Rather than losing the metal cation M(+) from the benzene–M(+) complex, as is observed for the Fe(+) system, the heavy metal ions activate CH bonds. The landmark system C4H4-Os(+) reacts with acetylene to produce C6H4-Os(+) and dihydrogen. Following our work on isomers of the form C2nH2n-Fe(+), we show by DFT modeling that the CH bonds of the metalla-7-cycle structure, C6H6-Os(+), are activated and define the gas-phase reaction path by which H2 is produced. The landmark structures on the network of reaction paths can be used as a basis for the discussion of reactions in which a single Os atom on an inert surface can assist reactions of hydrocarbons.