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.

Theoretical Analysis of OLED Performances of Some Aromatic Nitrogen-Containing Ligands

It is well-known that tris(8‐hydroxyquinoline) aluminum (Alq3) complex and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine compound (TPD) are widely used as electron transfer material (ETL) and hole transfer material (HTL) in organic light emitting diode (OLED) structure, respectively. Considering the reference materials, in the present work, the OLED performances of some cyclic aromatic structures such as 4,4ꞌ-azopyridine [AZPY], 4,4ꞌ-bipyridine [BIPY], 1,2-bis[4ꞌ-(4-methylphenyl)2,2ꞌ:6ꞌ2ꞌꞌ-terpyridin-6-yl]ethyne (BISTERPY), 5,5ꞌ-diamino-2,2ꞌ-bipyridine (DABP), dipyrido[3,2-a:2ꞌ,3ꞌ-c]phenazine (DPP), 4,7-phenanthroline (PHEN) including nitrogen atom have been theoretically analyzed. It is important to note that B3LYP/6-31G(d) and B3LYP/TZP levels of the theory were taken into account for the calculations about monomeric and dimeric structures, respectively. For a detailed theoretical analysis, the reorganization energies (λe and λh), adiabatic and vertical ionization potentials and electron affinities, the effective transfer integrals (Ve and Vh), and the charge transfer rates (We and Wh) of all compounds were computed by means of computational chemistry tools. In the light of calculated parameters, it is determined that these mentioned aromatic cyclic structures will be used in which layers of OLED structure. The results obtained in this study will be helpful in the design and applications of new molecules as OLED materials in the future.

Prediction of vertical ionization potentials for organic compounds by integral characteristics of optical spectra and the number of protons in molecules

In this review, the authors summarize the results of the first vertical ionization potentials with the structural and spectral integral descriptors of organic compounds: the integral oscillator strength defined in the visible or UV regions of the spectrum and the total number of protons in organic molecules. The adequate non-linear regression models relating the potentials of ionization as functions of the integral oscillator strength in the range between 6.53 eV and 1.63 eV (from 190 to 760 nm) and the total number of protons in organic molecules. The regularities were allowing to estimate the first ionization potentials for organic oxygen – and nitrogen-containing compounds established. The established regularities are interpreted as the influence of exchange and electrostatic interactions on the energies of the highest occupied molecular orbitals. The ionization potentials were calibrated according to the method of Hartree-Fock (RHF) method using 6-31G(d,p) basis set from the Koopmans' theorem. The obtained models allow us to estimate first ionization potentials of organic oxygen-and nitrogen-containing molecular systems by the integral oscillator strength and by the number of protons with an accuracy of 0.4 to 9%. This accuracy is quite suitable for practical applications. The research results can be used in chemistry, photochemistry, molecular electronics, photonics, and physical chemistry to study electron transfer processes, the characteristics of the band structure of nanoparticles. The present paper examples confirmed by statistical data processing.

Analysis and reporting recommendations for theoretical and experimental ionization potentials based on the study of 53 medium sized molecules using the IP-EOMCCSD method.

<div> <div> <div>The precision and accuracy of theoretical vertical ionization potential calculations has improved to the point where more care is needed to make valid comparisons with experimental measurements then is currently the norm. Vertical ionization potentials (IPs) computed using the IP-EOMCCSD method are reported for 53 medium sized molecules (6 – 32 atoms) and compared with statistically evaluated experimental vertical IPs. Based on this comparison, theoretical IPs should be extrapolated to the complete basis set limit and corrected for vibrational zero-point energy, while for experimental data the intensity weighted mean band position should be reported as the vertical IP. Experimental data available for ethylene, E-2-butene, 2,5-dihydrofuran and pyrrole were re-analyzed and compared with zero-point energy corrected complete basis set theoretical estimates, yielding an average discrepancy of 0.05 eV between theory and experiment. In contrast the average of reported experimental vertical IPs (the comparison usually made) yielded an average discrepancy of 0.25 eV between theory and experiment for these molecules. Further analysis of the remaining molecules in the data set suggests that the majority of reported experimental vertical IPs are low because band asymmetries were not accounted for when assigning IP values. This leads to fortuitous good agreement between experiment and computations using the smaller aug-cc-pVDZ basis set without zero-point correction. In the case of 1,4-cyclohexadiene there is strong evidence for experimental uncertainty accounting for the discrepency between theory and experiment. The presented results provide a benchmark for evaluating both experimental and theoretical estimates of vertical ionization potentials for the 53 molecules studied. </div> </div> </div>

Analysis and reporting recommendations for theoretical and experimental ionization potentials based on the study of 53 medium sized molecules using the IP-EOMCCSD method.

<div> <div> <div>The precision and accuracy of theoretical vertical ionization potential calculations has improved to the point where more care is needed to make valid comparisons with experimental measurements then is currently the norm. Vertical ionization potentials (IPs) computed using the IP-EOMCCSD method are reported for 53 medium sized molecules (6 – 32 atoms) and compared with statistically evaluated experimental vertical IPs. Based on this comparison, theoretical IPs should be extrapolated to the complete basis set limit and corrected for vibrational zero-point energy, while for experimental data the intensity weighted mean band position should be reported as the vertical IP. Experimental data available for ethylene, E-2-butene, 2,5-dihydrofuran and pyrrole were re-analyzed and compared with zero-point energy corrected complete basis set theoretical estimates, yielding an average discrepancy of 0.05 eV between theory and experiment. In contrast the average of reported experimental vertical IPs (the comparison usually made) yielded an average discrepancy of 0.25 eV between theory and experiment for these molecules. Further analysis of the remaining molecules in the data set suggests that the majority of reported experimental vertical IPs are low because band asymmetries were not accounted for when assigning IP values. This leads to fortuitous good agreement between experiment and computations using the smaller aug-cc-pVDZ basis set without zero-point correction. In the case of 1,4-cyclohexadiene there is strong evidence for experimental uncertainty accounting for the discrepency between theory and experiment. The presented results provide a benchmark for evaluating both experimental and theoretical estimates of vertical ionization potentials for the 53 molecules studied. </div> </div> </div>

Effects of Solvent-Salt Charge-Transfer Complexes on Oxidative Stability of Li-Ion Battery Electrolytes

Electrochemical stability windows of electrolytes largely determine the limitations of operating regimes and energy density of Li-ion batteries but the controlling degradation mechanisms are difficult to characterize and remain poorly understood. We investigate the oxidative decomposition mechanisms governing high voltage stability of multi-component organic electrolytes using computational techniques of quantum chemistry. The intrinsic oxidation potential is modeled using vertical ionization potentials (IP) of ensembles of anion-solvent clusters generated using molecular dynamics. In some cases, the IP of the solvent-anion complex is significantly lower than that of each individual component. This effect is found to originate from the oxidation-driven charge transfer complex formation between the anion and the solvent. We propose a simple model to quantitatively understand this phenomenon and validate it for 16 combinations of common anions (4,5-dicyano-2-(trifluoromethyl)imidazolium, bis-(trifluoromethane solfonimmide), tetrafluroborate, hexafluorophosphate) and solvents (dimethyl sulfoxide, dimethoxyethane, propylene carbonate, acetonitrile). This new understanding of the microscopic details of oxidation allows us to interpret trends in published experimental and computational results and to formulate design rules for rapidly assessing stability of electrolyte compositions.

Effects of Solvent-Salt Charge-Transfer Complexes on Oxidative Stability of Li-Ion Battery Electrolytes

Electrochemical stability windows of electrolytes largely determine the limitations of operating regimes and energy density of Li-ion batteries but the controlling degradation mechanisms are difficult to characterize and remain poorly understood. We investigate the oxidative decomposition mechanisms governing high voltage stability of multi-component organic electrolytes using computational techniques of quantum chemistry. The intrinsic oxidation potential is modeled using vertical ionization potentials (IP) of ensembles of anion-solvent clusters generated using molecular dynamics. In some cases, the IP of the solvent-anion complex is significantly lower than that of each individual component. This effect is found to originate from the oxidation-driven charge transfer complex formation between the anion and the solvent. We propose a simple model to quantitatively understand this phenomenon and validate it for 16 combinations of common anions (4,5-dicyano-2-(trifluoromethyl)imidazolium, bis-(trifluoromethane solfonimmide), tetrafluroborate, hexafluorophosphate) and solvents (dimethyl sulfoxide, dimethoxyethane, propylene carbonate, acetonitrile). This new understanding of the microscopic details of oxidation allows us to interpret trends in published experimental and computational results and to formulate design rules for rapidly assessing stability of electrolyte compositions.

Molecular Complexes of p-Chloranil with Aniline, Phenol and their Derivatives

Classification of simple supramolecular structures (for example molecular complexes), which has been introduced and described by Mulliken [1], is based on types of molecular orbitals of the components. In the paper [2], disadvantages of such classification are shown, which motivate us to return to the re-examination properties of molecular complexes. By this reason, there is a need to research the molecular complexes of one electron acceptor with a wide range of electron donor molecules. This paper have continued work (Part I [3]) on the chloranil complexes by studying the spectral properties complexes of N- and O-unsubstituting anilines and phenols. The present work aimed at analyzing linear relation the energies of charge-transfer bands of molecular complexes are related to ionization potentials of the donor components. All complexes conform to linear relations like involving both adiabatic and vertical ionization potentials of donor components. Mulliken [1] has been proposed to apply the vertical ionization potentials of donor components only. The development of photoelectron spectroscopy has led to the measurement of adiabatic and vertical ionization energies for thousands of molecules, which allow theirs to the present analysis of spectral properties molecular complexes.