DFT B3LYP Research Articles

Spectroscopic and electronic structure characterization of hydrogen bonding in 2-Bromohydroquinone

2-Bromohydroquinone species form both intra- and inter-molecular H-bonds. The evidences for the H-bonds have been observed in the solid-phase Mid IR (4000−400 cm−1) and Near IR (8000−5000 cm−1) absorption spectra with two intensely broad bands near 3263 and 3222 cm−1 and a broad absorption in 7000−5200 cm−1 with a band maximum at 6335 cm−1. Dimer and trimer models with DFT's B3LYP and BP86 functionals using 6-31G(d) and 6-311++G(d,p) basis sets have been proposed for the OH⋯O bonding in 2-Bromohydroquinone. Out of the four predicted conformers, one trans and one cis conformers with nearly 1:1 Boltzmann populations, are separated by very small energy difference of 0.03 kcal/mol and this is confirmed by two chemical shifts at 9.0 and 9.3 ppm from an 1H NMR spectrum. On the basis of Quantum Theory of Atoms in Molecules (AIM) and reduced density gradient plots of electron densities and its isosurfaces by non-covalent interactions (NCI) method, the influence of the OH⋯Br, weak van der Waals and OH⋯O bond interactions on the stability of dimer and trimer structures have been analysed. From the natural bond orbital (NBO) analysis, it is explained that the formation of H-bonding may be attributed to charge transfer from the lone pair orbital n(O) of the base Oxygen into the vacant antibonding orbital σ*(OH) of the acid OH in the OH⋯O bonding. The Near IR concentration-dependent spectra demonstrate that the sample of 2-Bromohydroquinone is composed of OH⋯O bonded species and dissociate into non-bonded species as the mole fraction of the solvent (acetonitrile/1,4-dioxane) is increased. The band observed at 7095 cm−1 at 0.09 M is identified as the first overtone of the OH stretching mode of the weak complex of 2-Bromohydroquinone and acetonitrile. The solvent effects on all the observed solution-phase NIR spectra are not ruled out.

Perfluorinated porphyrazines. 3. Synthesis, spectral-luminescence and electrochemical properties of perfluorinated octaphenylporphyrazinatozinc(II)

Octakis(pentafluorophenyl)porphyrazinatozinc(II), [ZnPAF40], has been prepared by template cyclotetramerization of perfluorinated α,β-dicyanostylbene in the presence of ZnCl2 in a melt. Influence of perfluorination of phenyl rings on spectral, electrochemical and acid-base properties of porphyrazine macrocycle is revealed by comparison with octaphenylporphyrazinatozinc(II), [ZnPA], which was prepared similarly from trans-α,β-dicyanostylbene. B3LYP DFT calculations show that perfluorination of phenyl rings stabilizes the frontier molecular orbitals of the porphyrazine macrocycle and slightly increases the HOMO-LUMO gap. As a result the reduction of the macrocycle is strongly facilitated and observed for [ZnPAF40] at 0.26 V vs Ag/AgCl, by 0.56 V in the less negative region as compared to [ZnPA]. Perfluorination leads to hypsochromic shift of the Q-band (lowest ππ* transition) in the electronic absorption spectra from 633 nm for [ZnPA] to 623 nm for [ZnPAF40] and increases the fluorescence quantum yield ФF from 0.12 to 0.19, respectively (values in THF). [ZnPAF40] has higher efficiency in generation of singlet oxygen (ФΔ = 0.60) than [ZnPA] (ФΔ = 0.37) (in THF). Introduction of 40 fluorine atoms decreases the basicity of the porphyrazine macrocycle almost by 3 orders of magnitude according to spectrophotometric titration study in CH2Cl2-CF3COOH medium.

Laser-induced linear and non-linear optical features in novel benzoxazole-based on donor-acceptor chromophores

The photophysical properties of donor-acceptor based benzoxazoles were investigated by means of steady-state and time-resolved fluorescence techniques. Additionally, laser stimulated second-order optical effects (preliminary second harmonic generation (SHG) were studied. The studies show that the nitro-benzoxazole derivatives decorated with different alkylo/arylo amino groups dissolved in medium polar aprotic solvents: tetrahydrofuran and butyl chloride, exhibit dual fluorescence from the locally excited state (1LE) and a highly polar charge transfer (CT) state. Ambient-temperature time-resolved fluorescence investigations prove the bimodal kinetics of the excited-state electron transfer reaction 1LE→1CT. The lack of any CT emissions in cyclohexane and highly polar acetonitrile is presumably due to an efficient inter-system crossing process or fast deactivation of a low-lying CT state. In addition, strong CT properties inspired us to check a possibility to vary the absorption of the first UV–Vis maxima under influence of the external bicolour coherent laser light and the related optical second harmonic generation (SHG). The two coherent beams of the infrared Er:glass laser at 1540 nm/770 nm formed gratings in the photopolymer solidified chromophore. The performed experiments are compared with the theoretically calculated electronic parameters within the B3LYP DFT approach. The presented data open novel type of materials, allowing to operate its transparency using external IR laser light in the near IR spectral range.

The growth of PAHs and soot in the post-flame region

The PAHs-C2H2 pathway (PAHs + C2H2 → intermediate → product + H2) has been shown, in theory, to be the important contributor to the growth of polycyclic aromatic hydrocarbons (PAHs) and soot in the post-flame region where H atoms are rare. Calculations of the potential energy surface (PES) using the DFT B3LYP 6-311 + G(d,p) method, and the reaction rate coefficients using the RRKM theory, reveal that armchair and bridge surface sites share similar kinetic characteristics, and are more likely to be the targets of C2H2 molecules in flames compared to zig-zag and 5-membered ring surface sites. Results show that the energy barrier of a 2-H elimination reaction (14–23.8 kcal/mol) is much lower than that of a 1-H elimination (typically 30–40 kcal/mol) for some molecules. The formation of pyrene from phenanthrene via HACA (PAHs + H → PAHs radical (+ C2H2) → intermediate → product + H) and PAHs-C2H2 pathways is investigated using a closed homogeneous zero-dimensional reactor with combustion parameters abstracted from the premixed stagnation C2H4/O2/Ar sooting flame. Results show that the HACA pathway is the dominant pathway for the formation of PAHs and soot surface growth in the main-flame region where H atoms are abundant, but that the PAHs-C2H2 pathway is the preferred pathway in the post-flame region. Our study also suggests that the soot nucleation involving a chemical coalescence of moderate-sized PAHs into a crosslinked three-dimensional structure via the addition reactions of PAHs and PAH radicals in the main-flame region should be considered for inclusion in any soot modeling.

The binding of calcium ion with different groups of superplasticizers studied by three DFT methods, B3LYP, M06-2X and M06

Three different DFT methods, B3LYP, M06-2X and M06, with PCM (polarized continuum model) solvent environment were performed to study the binding of Ca2+ with different groups of superplasticizers. Small monomers contained one or two groups, respectively, called as phosphonate, phosphate, carboxylate, sulfonate, sulfate and alkoxide were selected as theoretical models. The stable binding conformations of Ca2+ with monomers containing a single group optimized by the three DFT methods are similar and the binding strength follows the order, phosphonate ≈ phosphate > carboxylate > sulfonate ≈ sulfate > alkoxide ≈ water. The chemical reactivity and the electrophilic attack, not the natural atomic charges, of those monomers contribute significantly to the binding strength with Ca2+. The stable conformations of monomers containing two groups binding with Ca2+ are complex and the structures of the complexes by the three DFT methods are different for the phosphonate and phosphate. However, the order of the binding energies of those monomers with calcium ions calculated by the three DFT method are consistent and also agree with that of the monomers containing a single group. The values of the binding energies are two times more than the binding energies of the monomers containing single group.

A thermochemical study on the primary oxidation of sulfur

ABSTRACTSeveral chemical reactions related to the oxidation and combustion of sulfur are investigated using a number of computational chemistry methods with the objective of determining appropriate methods for use in developing an elementary reaction mechanism for oxidation of sulfur. Calculations are focused on thermochemical properties and reaction energetics for reactive species and transition state structures for reactions in the oxidation/combustion of sulfur. Reactions involving several intermediates resulting from the reactions of S2 with oxygen were investigated with the density functional theory B3LYP (with several basis sets) and BB1K/GTLarge. The composite ab-initio methods G2, G3, G3MP2, G3B3, G3MP2B3 and CBS-QB3 were also used. Enthalpies of a series of sulfur compounds and transition state structures are calculated using the ab-initio and DFT calculations. The calculations were combined with isodesmic reaction analysis, whenever possible, in order to cancel error and improve the accuracy of the calculations. Results show that all B3LYP DFT calculations including the 6–311++G(3df,2p) basis set show poor outcome in estimating the enthalpy of reactions involving S2. The six composite methods have all shown consistency with each other and their calculated reaction energies/bond energies are in good agreement with the available literature. Kinetic parameters for calculation of the kinetic parameters on SO3 dissociation to SO2 and O using the canonical transition state theory are reported.

New assignment of 14N NQR spectral lines for tetrazoles derivatives

In recent years, considerable interest has been shown in the study of tetrazole derivatives, which attract attention as highly nitrogenous compounds for use as an isosteric substitutes for various functional groups that leads to creation of novel biologically active substances. NQR techniques, being sensitive to the local environment of 14N nuclei, provide great opportunities to study these new substances. To make investigation of complex compounds containing tetrazoles derivatives easier and more reliable a correctly assigned 14N NQR spectra of tetrazoles are required. Here we report on the results of our DFT B3LYP calculations of 14N NQR spectral parameters (quadrupole coupling constant Qcc and the asymmetry parameter of the electric field gradient η) for tetrazole, 5-aminotetrazole and 5-aminotetrazole monohydrate. It has been found that the commonly accepted assignment of the 14N NQR spectral lines for these molecules is incorrect. A new assignment for these molecules is proposed.

FTIR study of acetylacetone, D2-acetylacetone and hexafluoroacetylacetone–water complexes in argon and nitrogen matrices

Association of acetylacetone molecules with water was studied by means of infrared absorption spectroscopy aided by matrix isolation technique. The spectra of acetylacetone–water mixtures isolated in low temperature argon and nitrogen matrices revealed additional spectral bands, not observed in the spectra of pure substances, thus confirming the formation of hydrogen bonded complexes. The precise assignment of the spectral bands was performed by varying the sample concentration, performing annealing experiments and DFT B3LYP 6-311++G(3df, 3pd) calculations. Positions of the associated water bands indicate a medium strength hydrogen bond comparable to the one observed in the water trimers. The effect of hydrogen bond formation is rather minimal for the acetylacetone molecule and our experiments confirm no significant influence on an internal hydrogen bond structure or dynamics in the acetylacetone molecule. Similar conclusions are valid in the case of the D2O D2-acetylacetone complex. Different situation is observed when CH3 groups in acetylacetone are replaced with CF3 groups. The calculated energy of the complex is twice as small. This is also confirmed by a very small bounded OH stretch shift. This observation confirms that the electronic structure of the molecular groups even relatively far away from the hydrogen bond accepting atom has a large influence on its possibility to form a hydrogen bond.

Molecular simulation and experimental study on thermal decomposition of N,N′-dinitrosopentamethylenetetramine

N,N′-dinitrosopentamethylenetetramine (DNPT), which is a widely used as blowing agent in the rubber industry, tends to be unstable when affected by high temperature and specific impurities. The runaway of DNPT has caused several accidents and led to enormous economic losses in the world. We determined its thermal hazard properties and decomposition paths for process safety. Characteristic parameters of pure and impure (added with water and nitric acid) DNPT were obtained under different heating rates by differential scanning calorimetry experiments. Those parameters were used to calculate the apparent activation energy with the Kissinger method. Thermogravimetry was used to obtain exothermic onset temperature and peak temperature under different heating rates. The apparent activation energy of DNPT decomposition reaction was achieved by model-free kinetics approach. Quantum mechanics model was used to explore the thermal decomposition reaction pathways of DNPT. DFT B3LYP density functional method, and the 6-311++G (D) basis set was selected for molecular simulation by Gaussian 09 software. The single point energy, zero-point energy, thermal energy, thermal enthalpy, and thermal free energy were acquired. The bond dissociation energy (BDE) at different excited states was calculated. By comparing BDE of different excited states, the thermal decomposition reaction pathways can be predicted. The results of experiments and simulations can be applied as safety guidance to deal with DNPT’s loss prevention during transportation, handling, and storage, even emergency response.

Kinetics of Decomposition Reactions of Acetic Acid Using DFT Approach

Object:Excessive amount of oxygen content in unprocessed bio-oil deteriorates the quality of bio-oil which cannot be used in transportation vehicles without upgrading. Acetic acid (CH3COOH) is a vital component of ‘acids’ catalogue of unprocessed bio-oil produced from thermochemical conversions of most of biomass feedstocks such as switchgrass, alfalfa, etc. In this study, the decomposition reactions of acetic acid are carried out by two reaction pathways,i.e., decarboxylation and dehydration reactions. In addition, the reaction rates of decomposition are analysed in a wide range of temperatures,i.e., 298-900 K and at atmospheric pressure.Method:All quantum chemical calculations are performed in the gas phase using two DFT functionals, B3LYP and M06-2X, with 6-31g(d) basis set. The dehydration reaction of acetic acid proceeds directly from ground state structure of acetic acid, whereas, decarboxylation reaction forms an unstable intermediate of acetic acid to initiate the proton migration. Barrier height and kinetics study for both reactions and theories are different and illustrated in the reaction pathway and rate profiles, respectively. Furthermore, both levels of theories offer similar structural configurations but they differ slightly in energetics.Conclusion:The reaction kinetics of both reactions is linearly fitted and the Arrhenius equations corresponding to each decomposition mechanism are generated by fitting the data from line equation.

Design of Exceptionally Strong Organic Superbases Based on Aromatic Pnictogen Oxides: Computational DFT Analysis of the Oxygen Basicity in the Gas Phase and Acetonitrile Solution.

DFT B3LYP calculations convincingly showed that aromatic pnictogen oxides offer scaffolds suitable for tailoring powerful organic superbases exhibiting exceptional oxygen basicity in both the gas phase and polar aprotic acetonitrile solution. With their protonation enthalpies and pKa values, they surpass the basicity of classical proton sponges and related nitrogen bases. The most potent system is provided with two arsenic oxide moieties on the phenanthrene framework assisted by the two phosphazeno groups in the para-position to both basic centers. With its proton affinity PA = 300.5 kcal mol-1, the latter system breaks the gas-phase hyperbasicity threshold of 300 kcal mol-1, while its pKa = 54.8 promotes it as an unprecedented superbase in acetonitrile. The origin of such a dramatic basicity enhancement is traced to a fine interplay between (a) steric repulsions of the two negatively charged oxygens destabilizing a neutral base, (b) favorable intramolecular [O-H···O]- hydrogen bonding in conjugate acids, and (c) efficient cationic resonance upon protonation supported by the electron-donating substituents. Given the growing interest in highly basic compounds together with related basic catalysts and metal complexing agents, we hope that the results presented here will open a new avenue of research in these fields and direct attention toward utilizing aromatic pnictogen oxides in designing improved organic materials.

Unraveling the Critical Role Played by Ado762'OH in the Post-Transfer Editing by Archaeal Threonyl-tRNA Synthetase.

Archaeal threonyl-tRNA synthetase (ThrRS) possesses an editing active site wherein tRNAThr that has been misaminoacylated with serine (i.e., Ser-tRNAThr) is hydrolytically cleaved to serine and tRNAThr. It has been suggested that the free ribose sugar hydroxyl of Ado76 of the tRNAThr (Ado762'OH) is the mechanistic base, promoting hydrolysis by orienting a nucleophilic water near the scissile Ser-tRNAThr ester bond. We have performed a computational study, involving molecular dynamics (MD) and hybrid ONIOM quantum mechanics/molecular mechanics (QM/MM) methods, considering all possible editing mechanisms to gain an understanding of the role played by Ado762'OH group. More specifically, a range of concerted or stepwise mechanisms involving four-, six-, or eight-membered transition structures (total of seven mechanisms) were considered. In addition, these seven mechanisms were fully optimized using three different DFT functionals, namely, B3LYP, M06-2X, and M06-HF. The M06-HF functional gave the most feasible energy barriers followed by the M06-2X functional. The most favorable mechanism proceeds stepwise through two six-membered ring transition states in which the Ado762'OH group participates, overall, as a shuttle for the proton transfer from the nucleophilic H2O to the bridging oxygen (Ado763'O) of the substrate. More specifically, in the first step, which has a barrier of 25.9 kcal/mol, the Ado762'-OH group accepts a proton from the attacking nucleophilic water while concomitantly transferring its proton onto the substrates C-Ocarb center. Then, in the second step, which also proceeds with a barrier of 25.9 kcal/mol, the Ado762'-OH group transfers its proton on the adjacent Ado763'-oxygen, cleaving the scissile Ccarb-O3'Ado76 bond, while concomitantly accepting a proton from the previously formed C-OcarbH group.

Carbazole-Based Mono and Bis-styryl NLOphores: Structure Property Correlations

A detailed study of linear and nonlinear optical (NLO) properties obtained by spectroscopy and DFT computations of carbazole-based D-π-A (mono) and A-π-D-π-A (bis) extended styryl dyes is presented. Four different DFT functionals, B3LYP, MO6, BHandHLYP, and CAM-B3LYP are used for computations. The structure–property relationship is examined by correlating bond length alternation/bond order alternation with NLO properties of the dyes. The bis-carbazole styryl dyes possess a higher second-order hyperpolarizability (β) than the mono-carbazole styryl dyes. An increase in the polarity of the environment causes an increase in the first-order hyperpolarizability (β CT or β 0) and second-order hyperpolarizability (γ) of the mono- and bis-carbazole styryl compounds. The NLO properties calculated by the CAM-B3LYP and BHandHLYP functionals show good agreement with the spectroscopic results.

Quantum chemical study of binuclear adducts of cobalt azomethine complexes with pyrene-4,5,9,10-tetraimine

A computer simulation of 2 : 1 adducts of cobalt azomethine complexes with pyrene-4,5,9,10-tetraimine was carried out within the framework of the density functional theory (DFT B3LYP*/6-311++G(d,p)). It was shown that the variation of the substituents at the nitrogen atoms of cobalt bischelates, as well as the annulation of the five-membered ring to the azomethine fragment, considerably affects the relative energies of the isomers with different spin states. Compounds, which can manifest one- and two-step redox-isomeric rearrangements, accompanied by the migration of paramagnetic centers, were revealed.

Estimation of hydrophilicity of coals by using the quantum chemistry calculation

The hydrophilicity is an important parameter in characterizing the floatability of coals in floatation. To quantify the hydrophilicity, the quantum chemistry calculation was used to calculate the hydrogen bonding energies in the wetting process by DFT B3LYP 6-31G. It is known that the floatability of lignite is much lower than that of the high-volatile bituminous coal from the natural floatability test. Besides, the hydrophilic sites were mainly oxygen functional groups. From XPS results, it is indicated that there were four kinds of oxygen functional groups, including OH, CO, CO and COOH in lignite, while there were three kinds of oxygen functional groups, containing OH, CO and CO in the high-volatile bituminous coal. On the other hand, the simulation results showed that the hydrogen bonding energy of these hydrophilic sites are in the following order−COOH>−OH>C−O>C=O. The released hydrogen-bonding energies were calculated to be 2.36kcal/mol for lignite and 1.31kcal/mol for high-volatile bituminous coal, respectively. In addition, the calorimetric experiments also showed that the wetting heats were 105.37J/g (lignite) and 47.00J/g (high-volatile bituminous coal). The hydrogen bond energy distribution of each hydrophilic sites showed that all the four kind hydrophilic sites impacted the lignite hydrophilicity remarkably whereas only OH and CO affected the hydrophilicity of high-volatile bituminous coal. It was revealed that the difficulty in lignite flotation was dominated by the complex contribution to hydrophilicity of the oxygen functional groups.

Insights on spin delocalization and spin polarization mechanisms in crystals of azido copper(II) dinuclear complexes through the electron spin density Source Function.

The Source Function (SF) tool was applied to the analysis of the theoretical spin density in azido CuII dinuclear complexes, where the azido group, acting as a coupler between the CuII cations, is linked to the metal centres either in an end-on or in an end-end fashion. Results for only the former structural arrangement are reported in the present paper. The SF highlights to which extent the magnetic centres contribute to determine the local spin delocalization and polarization at any point in the dimetallic complex and whether an atom or group of atoms of the ligands act in favour or against a given local spin delocalization/polarization. Ball-and-stick atomic SF percentage representations allow for a visualization of the magnetic pathways and of the specific role played by each atom along these paths, at given reference points. Decomposition of SF contributions in terms of a magnetic and of a relaxation component provides further insight. Reconstruction of partial spin densities by means of the Source Function has for the first time been introduced. At variance with the standard SF percentage representations, such reconstructions offer a simultaneous view of the sources originating from specific subsets of contributing atoms, in a selected molecular plane or in the whole space, and are therefore particularly informative. The SF tool is also used to evaluate the accuracy of the analysed spin densities. It is found that those obtained at the unrestricted B3LYP DFT level, relative to those computed at the CASSCF(6,6) level, greatly overestimate spin delocalization to the ligands, but comparatively underestimate magnetic connection (spin transmission) among atoms, along the magnetic pathways. As a consequence of its excessive spin delocalization, the UB3LYP method also overestimates spin polarization mechanisms between the paramagnetic centres and the ligands. Spin delocalization measures derived from the refinement of Polarized Neutron Diffraction data seem in general superior to those obtained through the DFT UB3LYP approach and closer to the far more accurate CASSCF results. It is also shown that a visual agreement on the spin-resolved electron densities ρα and ρβ derived from different approaches does not warrant a corresponding agreement between their associated spin densities.

Valence-tautomeric adducts of Co(II) diketonates based on annelated di-o-quinones: Computer simulation

The computer simulation (DFT B3LYP*/6-311++G(d,p)) is performed for the adducts of divalent cobalt diketonates with di-o-quinones in which the quinone rings are separated by the cycloalkane spacers. The isomers containing dianion–diradical forms of the redox-active ligand, the character of exchange between unpaired electrons of which depends on the spacer structure, correspond to the ground states of the considered compounds. Strong antiferromagnetic interactions (J > 400 cm–1) are predicted for the most stable electromers of the adducts of Co(II) bis(chelates) with 9,10-dimethyl-9,10-ethanoanthracene-2,3,6,7(9H,10H)-tetraone, whereas a weak exchange favoring paramagnetism in a wide temperature range is expected for the ground states of the binuclear complexes with the isomeric 5,10-dimethyl-4b,5,9b,10-tetrahydroindeno[2,1-a]indene-2,3,7,8-tetraone spacer. The electromers of the complex with the hexafluoroacetylacetone ligands are characterized by close values of the total energies, due to which the complex becomes a promising object for the development of spin qubits.

Influence of the nature of solvent and substituents on the oxidation potential of 2,2,6,6-tetramethylpiperidine 1-oxyl derivatives

The influence of solvent (DMF, MeCN, and water) and R1, R2 substituent nature on the formal oxidation potential (E°´) of 4-R1,R2-2,2,6,6-tetramethylpiperidine 1-oxyls (1a—f) on a glass carbon electrode was studied by cyclic voltammetry. It was shown that for all the solvents the observed dependence had the form E°´ = ρ″σ″ + b, where σ″ is the substituent constant. The b values decreased with an increase of the solvent solvating ability, while the values ρ″ are similar for all the solvents, surpassing the corresponding values for nitroxyls of the imidazoline series with substituents at position 3, which can be interpreted as an abnormally strong influence of the substituent remote from the reaction center in 1a—f. The experimental values E°´ were linearly correlated with the reaction free energy values (ΔG) calculated by DFT B3LYP and MP2 for the gas phase contribution and by HF/PCM for the contribution of solvation effects. When applying the B3LYP and the HF/PCM approaches in combination, the dependence of E°´ on ΔG for all the considered solvents was described by a linear correlation equation with a slope close to unity and a constant term which was close to the theoretical value of the absolute potential of the reference electrode used.

Self-trapped exciton configurations in Beryllium Oxide

The modern radiation technology, nuclear engineering, non-linear optics are associated with radiation-resistant optical material study. Evolution of electronic excitations in these materials is a complex multichannel process which currently has no integrated model. A special role belongs to the low-symmetry single crystals, such as beryllium oxide (BeO). We present theoretical results that advance our understanding of exciton-based channel of electronic excitations relaxation. The four possible self-trapped exciton (STE) configurations in beryllia single crystal have been investigated by using a quantum mechanical approach (Hartree-Fock and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL09 code). B3LYP DFT functional with 30% of exact exchange was used (B3LYP30). All calculations were performed using periodic boundary conditions and full SC geometry relaxation. The lattice distortion and charge density distribution for considered defect configurations were obtained. STE-A1 luminescence energy was found to be 6.0 eV for HF and 6.5 eV for B3LYP30; STE-A2 luminescence energy was found to be 9.2 eV for HF and 7.8 eV for B3LYP30. STE-B1 luminescence energy was found to be 5.5 eV for HF, 6.2 eV for B3LYP30; STE-B2 luminescence energy was found to be 4.7 eV for HF.

Study of the mechanism of formation of heterocyclic disulfonium dications from 1,3-benzothiazole-2-thiol and 1-iodopropan-2-one

The potential energy surface for the formation of heterocyclic disulfonium dications from 1,3-benzothiazole-2-thiol and 1-iodopropan-2-one has been analyzed at the DFT B3LYP level of theory. The reaction involves oxidation of 1,3-benzothiazole-2-thiol to the corresponding disulfide, followed by alkylation of the exocyclic sulfur atoms. Stabilization of the salt with iodide anion is initiated by thermodynamically controlled reaction with molecular iodine, leading to the formation of stable structure with triiodide anion.