Photoelectron spectra and electronic structure of boron diacetate formazanates

Electronic structure, cationic, and excited states of nitrogen-containing spiroborates

CONTEXT

This paper presents the results of the study of the electronic structure and cationic and excited states of three spiroborate complexes (2-acetylacetonato-1,3,2-benzodioxaborol, its NH- and NMe-derivatives) and three corresponding ligands (acetylacetone, 4-aminopent-3-en-2-one, and 4-methylaminopent-3-en-2-one). Materials based on spiroborates are used in medicine, for example, as a drug carrier. In industry, spiroborate anions are used in ionic liquids and as alternative high performance lubricants. Analysis of experimental and calculated data allowed determining the influence of functional groups on the parameters of the electronic structure and energy of electronic transitions. Compared to acetylacetone and its NH- and NMe-derivatives, the upper filled molecular orbitals of the corresponding spiroborates are stabilized at 0.4-1.7 eV, which is due to the positive charge of the ligand due to the acceptor properties of the dioxyphenylene fragment. Among the studied compounds, when replacing the oxygen atom in the α-position with the NH- or NMe-group, a bathochromic shift of intense bands in the absorption spectra is observed, since the energy intervals between the orbitals of the π₃ and π₄ ligand are reduced. In addition, in a number of spiroborates, the violation of C_2v symmetry when replacing an oxygen atom leads to the appearance of a low-intensity maximum in the long-wave part of the absorption spectrum, due to the π₂^X → π₄ transition.

METHOD

Complexes were studied by photoelectron spectroscopy, absorption spectroscopy, and high-level ab initio quantum chemical computations, including the algebraic diagrammatic construction method for the polarization propagator of the second order (ADC(2)), the outer-valence Green's function (OVGF), the density functional theory (DFT), the time-dependent density functional theory (TDDFT) and the domain-based local pair natural orbital (EOM-DLPNO) methods. X-ray photoelectronic spectra of two spiroborates in the condensed state were measured using a two-chamber high-vacuum system MXPS XP (Omicron, Germany). UV-visible absorption spectra were recorded using a spectrophotometer 2550 (Shimadzu-UV, Japan). The geometry of all studied compounds was optimized by the DFT/B3LYP/Def2-SVP method. The energy of electron levels in the S₀ state and the distribution of electron density at each MO were obtained by the DFT/CAMB3LYP/cc-pVDZ method. The energies of excited states were obtained by the TDDFT/CAMB3LYP/cc-pVDZ, ADC(2)/cc-pVDZ and EOM-DLPNO/cc-pVDZ methods. All DFT and TDDFT calculations were carried out in the GAMESS (US) software computing package. ADC(2) calculations of excited states were performed using the Orca 4.0.1 software package. EOM-DLPNO and OVGF calculations were carried out in the Gaussian 16 software package.

XPS and quantum chemical analysis of 4Me-BODIPY derivatives

The results of a X-ray photoelectron spectroscopy (XPS) and steady-state absorption spectroscopy study of the electronic structure, and cationic and excited states of a series of 1,3,5,7-tetramethyl-substituted BODIPYs (4Me,2R-BODIPYs) are presented. The experimental data were interpreted using high-level ab initio quantum chemical computations, including the algebraic diagrammatic construction method for the polarization propagator of the second order (ADC(2)), the outer-valence Green's function (OVGF) method, the density functional (DFT) approach, and the time-dependent DFT (TD-DFT) approach. Substitution effects on the XPS and absorption spectra were determined for 2,6-positions of 4Me,2R-BODIPY pyrrole nuclei (R = H, Br, Bu, benzyl). A very satisfactory performance of the DFT Koopmans theorem analogue was demonstrated with respect to the energy intervals between the electronic levels of 4Me,2R-BODIPY above 13 eV (BHHLYP functional) and the values of the HOMO-LUMO energy gap (ωB97X functional).

Molecular docking and dynamics studies of Nicotinamide Riboside as a potential multi-target nutraceutical against SARS-CoV-2 entry, replication, and transcription: A new insight

The highly contagious Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which is a newborn infectious member of the dangerous beta-coronaviruses (β-CoVs) following SARS and MERS‐CoVs, can be regarded as the most significant issue afflicting the whole world shortly after December 2019. Considering CoVs as RNA viruses with a single-stranded RNA genome (+ssRNA), the critical viral enzyme RNA dependent RNA polymerase (RdRp) is a promising therapeutic target for the potentially fatal infection COVID-19. Nicotinamide riboside (NR), which is a naturally occurring analogue of Niacin (vitamin B3), is expected to have therapeutic effects on COVID-19 due to its super close structural similarity to the proven RdRp inhibitors. Thus, at the first phase of the current molecular docking and dynamics simulation studies, we targeted SARS-CoV-2 RdRp. On the next phase, SARS-CoV RdRp, human Angiotensin-converting enzyme 2, Inosine-5’-monophosphate dehydrogenase, and the SARS-CoV-2 Structural Glycoproteins Spike, Nonstructural viral protein 3-Chymotrypsin-like protease, and Papain-like protease were targeted using the docking simulation to find other possible antiviral effects of NR serendipitously. In the current study, the resulted scores from molecular docking and dynamics simulations as the primary determinative factor as well as the observed reliable binding modes have demonstrated that Nicotinamide Riboside and its active metabolite NMN can target human ACE2 and IMPDH, along with the viral S^pro, M^pro, PL^pro, and on top of all, RdRp as a potential competitive inhibitor.