Structures, electronic and thermodynamic properties of NiB2n (n=7-11) and their anions: A theoretical study

Based on the Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) searching method and density functional theory (DFT), theoretical studies about structures, electronic and thermodynamic properties have been investigated systematically at the TPSSh/6-311+G(d) level for NiB2n0/- (n=7-11) clusters. Results found that the lowest energy structures possess a Ni atom-centered double ring tubular boron structures, NiB180/- except. Relative stabilities were analyzed via computing their vertical ionization potentials (VIP), vertical electronic affinity (VEA), adiabatic electronic affinity (AEA), HOMO-LUMO gaps and hardness. The infrared spectra, Raman spectra and photoelectron spectra were computationally simulated to facilitate their experimental characterizations. At last, aromatic properties (Nucleus independent chemical shift) and thermodynamic properties (enthalpy and entropy) with temperature were discussed in detailed for studied systems.

Crystallographic structure, activity prediction, and hydrogen bonding analysis of some CSD-based 3,3'-bis-indole derivatives: A review

Herein we report crystallographic comparison of some geometrical and structural features for a series of biologically relevant bis-indole derivatives. Selected bond distances and bond angles of interest in a series of bis-indole derivatives have been discussed in detail. The biological activity of the substances has been correlated with based the structure-activity relationships (SAR) base which provides the different possibility of activity (Pa) and possibility of inactivity (Pi). For a better understanding of the packing interactions existing among these derivatives, an overview of crystal structure analysis with emphasis on the intramolecular hydrogen bonding in some bis-indole derivatives is presented. The role of hydrogen bonding in the crystal structure assembly of bis-indole derivatives has been found to be predominant and this observation reveals significant impact of hydrogen bonding in high value of drug-likeness of these bio-molecules.

Insulative Phase Formation and Polarization Resistance of PrBaCo2−xCuxO5+δ under Thermal Stress

The degradation behavior of PrBaCo2−xCuxO5+δ (x = 0, 0.2, 0.5) under thermal stress was investigated in terms of phase formation and polarization resistance. The tetragonal phase was indexed in all compositions of PBCCux, and the secondary phase, BaO, was identified after thermal degradation in the crystal structure analysis. BaO formation is induced by the nature of perovskite to terminate the surface with AO layer. For pristine specimens, the oxygen vacancy peak ratio was increased from 57% to 60% according to the decrease in the average oxidation number of the B-site ion with Cu doping. After thermal deterioration, the oxidation number of B-site ions was increased, and the M = O bonding peak increased due to the decrease in oxygen vacancies and BaO formation according to the thermal stress. In all compositions, the electrical conductivity decreased from 1000 S/cm to 17 S/cm, and the polarization resistance increased approximately 200 times. These results are considered to be related to the increase in the oxidation number of B-site ions along with the formation of secondary phases.

Synthesis of Unexpected Dimethyl 2-(4-Chlorophenyl)-2,3-dihydropyrrolo[2,1-a]isoquinoline-1,3-dicarboxylate via Hydrolysis/Cycloaddition/Elimination Cascades: Single Crystal X-ray and Chemical Structure Insights

Hydrolysis/[3 + 2] cycloaddition/elimination cascades employed for the synthesis of unexpected tricyclic compound derived from isoquinoline. Reaction of ethylene derivative 1 with the isoquinoline ester iminium ion 2 in alkaline medium (MeOH/NEt3) under reflux for 1 h resulted in the formation of the fused pyrrolo[2,1-a]isoquinoline derivative 3. Its structure was elucidated by X-ray single crystal and other spectrophotometric tools. Hirshfeld calculations for 3 and its crystal structure analysis revealed the importance of the short O…H (19.1%) contacts and the relatively long H…C (17.1%), Cl…H (10.6%) and C…C (6.1%) interactions in the molecular packing. DFT calculations were used to compute the electronic and spectroscopic properties of the studied system. The studied compound has polar nature (3.5953 Debye). TD-DFT calculations assigned the shortest wavelength band (220 nm) to the HOMO−1→LUMO+2 (57%), HOMO−1→LUMO+4 (14%) mixed excitations. The calculated NMR chemical shifts correlated very well with the experimental data (R2 = 0.93–0.94).