In this theoretical study, we investigate the electronic potential energy curves, spectroscopic parameters, vibrational energy levels and transition dipole moments for the diatomic dications BeRb2+, BeCs2+ and SrRb2+. We consider an ab initio approach based on the use of non-empirical pseudopotentials and parameterized l dependent polarization potentials. Results show that 1-22Σ+ for BeRb2+, 1-52Σ+ for BeCs2+ and 1-32Σ+ for SrRb2+ are repulsive. While the 32Σ+ for BeRb2+, 42Σ+ for BeCs2+ and 42Σ+ for SrRb2+ are metastable states. These states can accommodate some vibrational energy levels. Interesting avoided crossings between some 2+ states are localized and examined. Until now no experimental and theoretical studies have been made for each system. Consequently, we discuss our results by comparing with some data of similar systems. Besides, the transition dipole moments of the ground state to a few excited states are computed and presented. The information associated with the electronic structures, spectroscopic parameters as well as the transition properties that provide in this paper is anticipated to serve as guidelines for further experimental and theoretical researches for each diatomic dication considered in this work.
The atomic structure, spin states of the interface based on iron-porphyrin and armchair graphene nanoribbon (FeP/AGNR) and potential energy surface of FeP atop of AGNR migration is investigated via DFT theory. The multiplicity of Fe ion in iron porphyrin for all possible types of coordination is determined as a triplet. It is estimated that FeP would place atop AGNR at the position where two Fe-N bonds are located above the C-C bond, another two are located above C atoms. The barrier of migration of iron porphyrin complex atop of graphene armchair nanoribbon is found to be smaller the temperature factor, making the heterostructure to be in temperature equilibrium between different types of coordination of the iron porphyrin atop of graphene nanoribbon
Unique superhalogen properties of Pt(CN)n complexes (n = 1–6) containing cyanide (CN) pseudohalogen moieties bound with platinum (Pt) atom have been investigated under the quantum chemical formalism. The study involves theoretical calculations for both neutral and anionic forms of Pt(CN)n using density functional theory (DFT) with the hybrid functional B3LYP. In order to improve the accuracy of calculations, 6–311+G(d) basis set was implemented for CN moieties, whereas, SDD basis set supplemented with Stuttgart/Dresden relativistic effective core potential was used for Pt atom. HOMO–LUMO energy band gaps, vibrational frequencies and dissociation energies of Pt(CN)n complexes have been calculated to investigate their relative stability as well as reactivity. Additionally, superhalogen properties and salt forming capability of Pt(CN)n complexes have also been analyzed. Focus of analysis is on the delocalization of charges over attached CN ligands in successive members of the Pt(CN)n species. Reliable low–cost investigations on superacidity properties of associated protonated species have also been carried out keeping their industrial applications in mind.
We have recently developed a computational methodology to separate the effects of size, composition, symmetry and fluxionality in explaining the experimental photoelectron spectra of mixed-metal clusters. This methodology was successfully applied first in explaining the observed differences between the spectra of Al13- and Al12Ni- and more recently to explain the measured spectra of AlnMo-, n=3-5,7 clusters. The combination of our approach and new synthesis techniques can be used to prepare cluster based materials with tunable properties. In this work we use the methodology to predict the spectrum of Al6Mo-. This system was chosen because its neutral counterpart is a perfect octahedron and it is distorted to a D3d symmetry and was not observed in the recent experiments. This high symmetry cluster bridges the less symmetric Al5Mo- and Al7Mo-structures. The measured spectra of Al5Mo- has well defined peaks, while that of Al7Mo-does not. This can be explained by the fluxionality of Al7Mo-, as at least 6 different structures lie within the range that can be reached by thermal effects. We predict that Al6Mo- has well defined peaks, but some broadening is expected as there are two low-lying isomers, one of D3d and the second of D3h symmetry that are only 0.052 eV apart.
Etherification mechanism of 4,5-dihydroxy-1,3-bis (hydroxymethyl) imidazolidin-2-one (DMDHEU) with the primary alcohols and the –OH hydroxyl groups of cellulose chain (n=1-2) in acidic condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, intermediate complexes, carbocation intermediate, and transition states were optimized at B3LYP/6-311g(d,p) level and ONIOM (B3LYP/6-311g(d,p):PM3MM) level. Computational results indicate that the etherification adheres to unimolecular nucleophilic substitution (SN1) mechanism; the reactant and product can form the activated complexes with H+ ions in which H+ ions are occupied by the O-atom of C=O group in the reactant complex and the product complex. Potential energy surface (PES) of the reaction has the triple-well shape. Effect of substituent R in primary alcohol R-CH2OH (R = H, CH3, CH2CH3, CH2OCH3, CH2F) and cellulose chain on the reactivity is significant. The energy barrier of H+ ions releasing step is much higher than those of the activation steps. The calculational data is in the good agreement with the experimental data in the literature.
The polyphenyl chains with $n$ hexagons are the special graphs of unbranched polycyclic aromatic hydrocarbons. The objective of this study is to find the expected values of the multiplicative version of the atomic-bond connectivity index and geometric-arithmetic index of this class of special hydrocarbons. The average values of these two indices with respect to the set of all polyphenyl chains have been determined. Finally, the comparisons between the expected values of the aforementioned indices in the random polyphenyl and spiro chains, have been outlined.
In the current research chor, we are reporting the synthesis of 2-amino-6-methylpyrimidin-4-yl benzenesulfonate (AMPBS) and 2,6-diaminopyrimidin-4-yl benzenesulfonate (DAPBS) via O-benzenesulfonylation of 2-amino-6-methylpyrimidin-4-ol 1 and 2,6-diaminopyrimidin-4-ol 2 respectively. The structures of the synthesized compounds were characterized unambiguously by single crystal analysis (SC-XRD).Hirshfeld surface study showed that C-H…O, C-H…N and especially C-H…C hydrogen bond interactions are the key contributors to the intermolecular stabilisation in the crystal. The quantum chemical understanding about optimized geometry, natural bond orbitals (NBOs), frontier molecular orbitals (FMOs) and nonlinear optical (NLO) analysis for AMPBS and DAPBS were obtained by applying density functional theory (DFT) at B3LYP level and 6-311G(d,p) basis set. Time dependent density functional theory (TD-DFT)/ B3LYP/ 6-311G(d,p) level were employed to determine the photo physical properties of compounds. As a whole, the simulated results were found to have an excellent concurrence to the experimental results. The charge transfer phenomenon entitled compounds was determined by FMOs. Global reactivity parameters were obtained by using HOMO–LUMO energies of compounds. Overall, the computational results of AMPBS and DAPBS have outstanding agreement to experimental data. The computational study also showed that the title compounds have remarkable NLO properties.
L-lysine amino acid is cocrystallized with L-mandelic acid by the slow evaporation method. Single crystal X-ray analysis reveals that lysine-mandelic acid crystallized as a dihydrate form. In the crystalline state, the lysine molecule exists in the cationic form in which the backbone and side chain amino groups are protonated and the carboxylic acid is deprotonated. The carboxylic acid proton of the mandelic acid is transferred to the lysine side chain and thus carries a negatively charged ion. The lattice water molecules are located near the amino groups of the lysine. Intermolecular interactions formed between lysinium, mandelate and lattice water molecules are qualitatively analyzed using Hirshfeld surfaces and 2D-fingerprint plots. The energetics of different dimeric complexes is quantitatively analyzed using PIXEL energy analysis. Topological parameters derived from QTAIM framework are used to delineate the nature of different intermolecular interactions formed in the title complex.
This DFT study treats thermal metal-catalyzed alkene aziridination by azides, where the catalysts are copper(II) triflate, cobalt(II) porphin and ruthenium(II) porphin. Three azides RN3 (R = H, Me, Ac) react with alkene substrates in the presence of these catalysts leading to aziridine formation by a two-step catalysed mechanism. In Step I, the azide reacts with the catalyst to first form a metal nitrenoid via transition state TS1. The Ru(porph) catalyst is particularly effective for Step I. In Step II, the metal nitrenoid adds to the alkene via TS2 giving the aziridine product. Cu(trfl)2 is most effective as a catalyst for Step II. The facility order H > Me > Ac (with respect to the azide R group) holds for Step I, and the reverse order for Step II. Transition states TS1 and TS2 are described as “early” and “late”, respectively, in good accord with Hammond’s postulate.
A combined experimental work and molecular electron density theory (MEDT) analysis was performed to reveal the strict click of 1,2,3-triazole derivatives by Ag(I)-catalyzed azide-alkyne cycloaddition (AgAAC) reaction and its corresponding mechanistic pathway. Such straightforward protocol for the click formation of 1,4-disubstituted-1,2,3-triazoles makes use of AgCl as catalyst in water as solvent under ambient conditions., with excellent yields and simple experimental work-up. MEDT study was performed by using DFT calculations at the B3LYP/6-31G(d,p) (LANL2DZ for Ag) level in order to understand the observed regioselectivity in AgAAC reactions, and to delineate the number of silver(I) species and their roles in this clickable 1,2,3-triazole formation. The comparison of the mononuclear Ag(I)-acetylide and binuclear Ag(I)-acetylide in the AgAAC reaction paths concerning the AgAAC reactions, shows that the values of the energy barriers for the binuclear processes are smaller than that of the mononuclear one. The intramolecular nature of these AgAAC reactions accounts for the regioselective formation of the 1,4-regiosisomeric triazole derivatives. The ionic nature of the starting metallated species is revealed for the first time, ruling out any covalent interaction involving the silver(I) complexes throughout the reaction as supported by the ELF topological analysis of the electronic structure of the stationary points, reaffirming the zw-type mechanism of the AgAAC reactions.