HF Levels Research Articles

Analysis of Pyridine, Picoline and Lutidine’s Adsorption Behavior on The Al (111)-lattice

The reactivity and adsorption behavior of five organic inhibitors of pyridine and its derivatives of 2-picoline, 3-picoline, 4-picoline, and 2,4-lutidine at the Al(111) lattice in hydrochloric acid was studied by the principle of the HF and B3LYP level using the 6-31G and LANL2DZ basis sets from the program package gaussian 03. The compound was adsorbed on the metal lattice based on the calculated results, mainly in their protonated forms. In the Al (111)-lattice, the charge is transferred to the inhibitor, and the organic inhibitor is adsorbed at the Al (111)-lattice in an inclined state. The quantum chemical calculations of molecular reactivity show that the frontier orbitals of the four additives are distributed around the nitrogen atom of the pyridine ring, the aluminum atom of Al (111)-lattice, and active electrophilic centers are located on the nitrogen atoms of the pyridine ring. All five molecules were adsorbed with the chemical adsorption on the Al (111)-lattice, and the order of adsorption was 2-picoline>2, 4-lutidine> 4-picoline> 3-picoline> pyridine. The N atoms of four derivatives form N-Al bonds with the Al atoms of the Al (111)-lattice, which makes derivatives stably adsorb on the Al lattice.

Fragment-Based Local Coupled Cluster Embedding Approach for the Quantification and Analysis of Noncovalent Interactions: Exploring the Many-Body Expansion of the Local Coupled Cluster Energy.

Herein, we introduce a fragment-based local coupled cluster embedding approach for the accurate quantification and analysis of noncovalent interactions in molecular aggregates. Our scheme combines two different expansions of the domain-based local pair natural orbital coupled cluster (DLPNO-CCSD(T)) energy: the many-body expansion (MBE) and the local energy decomposition (LED). The low-order terms in the MBE are initially computed in the presence of an environment that is treated at a low level of theory. Then, LED is used to decompose the energy of each term in the embedded MBE into additive fragment and fragment-pairwise contributions. This information is used to quantify the total energy of the system while providing at the same time in-depth insights into the nature and cooperativity of noncovalent interactions. Two different approaches are introduced and tested, in which the environment is treated at different levels of theory: the local coupled cluster in the Hartree–Fock (LCC-in-HF) method, in which the environment is treated at the HF level; and the electrostatically embedded local coupled cluster method (LCC-in-EE), in which the environment is replaced by point charges. Both schemes are designed to preserve as much as possible the accuracy of the parent local coupled cluster method for total energies, while being embarrassingly parallel and less memory intensive. These schemes appear to be particularly promising for the study of large and complex molecular aggregates at the coupled cluster level, such as condensed phase systems and protein–ligand interactions.

Predictive capacity of the brain natriuretic peptide in the screening of heart failure in a high altitude population

BackgroundHeart failure (HF) is growing in importance as a significant cause of disease and mortality. When It is suspected, it can be ruled out if BNP values are below 100 pg/mL. Diagnostic certainty can be obtained if echocardiogram shows reduced ejection fraction, diastolic dysfunction or right-sided heart disease. Physiological changes at high altitude are known to affect BNP values. This study pretends to evaluate BNP values when used for HF diagnosis in Huancayo, Perú, a high altitude population located at 3,250 m above sea level. MethodsThis is a cross-sectional, diagnostic test type study. A total of 83 medical charts of patients with suspected HF, admitted to the Emergency Room and Internal Medicine Service of Ramiro Prialé Prialé National Hospital, were reviewed. Data processing was performed with SPSS program for Windows version 21.0. Pearson's Chi Square test was used for categorical variables analysis and ANOVA for continuos variables. P values under 0.05 were considered significant. Results and conclusionsMedium age was 74 years. Patient’s characteristics that were associated with confirmed HF and high BNP levels were the following: presence of fatigue, night cough, elevated heart rate, shortness of breath, history of lung fibrosis and decreased oxygen arterial saturation (p < 0.05) Pulmonary hypertension, mitral and tricuspid regurgitation, and cor pulmonale were also associated with higher BNP levels. Most subjects had BNP values >100 pg/mL, with low specificity for HF diagnosis (11.5 %). Individuals without heart failure had mean BNP values above 300 pg/mL; while individuals with cor pulmonale had a mean of 975 pg/mL. BNP values were high in patients with or without HF. A cut-off point of ≥130pg/mL is proposed to increase specificity. The predictive capacity of BNP for HF identification at this high altitude population is low because of a high number of false positive results.

Involvement of Resting Heart Rate Variability in Chronotropic Responses During Exercise

PURPOSE:Although resting heart rate variability (HRV) and chronotropic responses (CR) are common prognostic factor for cardiovascular disease, it is still unknown whether relationships between two variables are affected by exercise. The current study was aimed to identify correlations between resting cardiac autonomic regulation and graded exercise test-derived CR.METHODS:We recruited apparently healthy men college students aged between 20 and 29 years (n=46). They were assigned to Lowand High groups which have been determined for medians involved in resting heart rate (HR) or HRV indices such as rMSSD, HF, and LF/HF ratio, respectively. CR and post-exercise heart rate recovery (HRR) were calculated from HR fluctuations during and after symptom-limited graded exercise test using the Bruce protocol.RESULTS: In HRR, there were no significant differences between all Low and High groups separated by resting levels of HR or HRV indices. However, all Low groups assigned according to resting cardiac vagal-related HRV indices such as rMSSD and HF showed significantly lower CR levels than those of High groups, respectively. Moreover, CRs derived from stage 1-3 of Bruce protocol were positively correlated resting rMSSD and HF levels, respectively.CONCLUSIONS:The findings of the current study suggest that resting levels of cardiac vagal-related HRV indices may have an impact on CR derived from a graded exercise test, as well as there is a significant association between resting cardiac vagal activity and HR response during incremental exercise.

Intermolecular interactions of the extended recognition site of VIM-2 metallo-β-lactamase with 1,2,4-triazole-3-thione inhibitors. Validations of a polarizable molecular mechanics potential by ab initio QC.

Molecular dynamics on the complexes of inhibitors with Zn-metalloproteins are a privileged area of applications of polarizable molecular mechanics potentials. With which accuracy could these reproduce the QC intermolecular interaction energies in the two mono-zinc cores and in the dizinc core, toward full-fledged MD simulations on the entire protein complexes? We considered the complexes of the extended recognition site of a Zn-dependent metallo-β-lactamase, VIM-2, produced by bacteria responsible for nosocomial infections, with five newly synthesized inhibitors sharing an original dizinc binding group, 1,2,4-triazole-3-thione (TZT). We considered the energy-minimized structures of each of the five VIM-2 complexes obtained with the SIBFA potential. Energy decomposition analyses (EDA) at the HF level enabled to compare the QC and the SIBFA ΔE values and their contributions in the zinc cores, with and without TZT, totaling 30 complexes. With one exception, the ΔE(QC) values were reproduced with relative errors <1.5%. We next considered the complex of the entire inhibitors with an extended model of VIM-2 recognition site, totaling up to 280 atoms. ΔE(SIBFA) could closely reproduce ΔE(QC). EDA analyses were resumed on the complexes of each inhibitor arm with its interacting VIM-2 residues. As a last step, EDA results at correlated levels were analyzed for the mono- and dizinc sites enabling comparisons with dispersion-augmented ΔE(SIBFA) and correlated multipoles and polarizabilities. Closely reproducing ΔE(QC) and the contrasting trends of its individual contributions should enable for dependable free energy perturbation studies and comparisons to recent experimental ΔG values, limiting as much as possible the reliance on error compensations.

A Theoretical Approach to New Triplet and Quintet (nitrenoethynyl)alkylmethylenes, (nitrenoethynyl)alkylsilylenes, (nitrenoethynyl)alkylgermylenes

Experimentally unreachable reactive intermediates of triplet and quintet (nitrenoethynyl)-X-methylenes, (nitrenoethynyl)-X-silylenes, and (nitrenoethynyl)-X-germylenes were compared and contrasted at B3LYP, M06-2X, WB97XD, HF, MP2, MP4, CCSD, and QCISD(T) levels with 6-311++G(d,p) basis set (X–M–C≡C–N; M=C, Si, and Ge; X = H (1), Me (2), Et (3), Pr (4), i-Pr (5), and t-Bu (6)). The effect of small and bulky groups on these acetylene linked reactive intermediates were studied. All triplet (nitrenoethynyl)-X-methylene species were identified as ground states with one local open-shell singlet carbene (δ1π1) and other local triplet nitrene moiety (π1π1) with 47.75-55.70 kcal/mol quintet-triplet energy gap (ΔEq-t). Silylene and germylene substitutions caused the reduction of ΔEq-t. One local closed-shell singlet silylene or germylene moiety (δ2π0) and one local triplet nitrene moiety (π1π1) were connected to make triplet (nitrenoethynyl)silylenes, and (nitrenoethynyl)germylenes. The species of (nitrenoethynyl)silylenes, and nitrenoethynyl)germylenes could be applied as dipolar intermediates in mechanism identification of chemical reactions. Quintet states were found as ground states with one local triplet divalency moiety (π 1π1) and also other local triplet nitrene moiety (π1π1).

Usefulness of the plasma branched-chain amino acid/aromatic amino acid ratio for predicting future cardiac events in patients with heart failure

BackgroundHeart failure (HF) is a hypercatabolic state that promotes branched-chain amino acid (BCAA) catabolic activity in the heart and skeletal muscle and reduces protein synthesis in the liver. Consequently, plasma free aromatic amino acids (AAAs) are increased. We investigated the prognostic value of the BCAA/AAA ratio (Fischer’s ratio, FR) in patients with HF. MethodsWe enrolled 157 consecutive patients hospitalized for worsening HF (81 men, 76 women; mean ± SD age 75 ± 14 years). Plasma BCAA levels (i.e. total leucine, isoleucine, valine) and AAA levels (i.e. total tyrosine, phenylalanine) were measured at a time when the patients were stabilized (at discharge). FR was calculated as the combined plasma BCAA levels divided by the AAA level. Cardiac events were defined as a composite of cardiac death and hospitalization for worsening HF. ResultsThe patients were divided into two groups based on the median FR (high-FR group: FR ≥ 3.1, n = 78; low-FR group: FR < 3.1, n = 79). Compared with the high-FR group, low-FR patients were older, had more prior hospitalizations for HF, lower albumin and cholinesterase levels, and lower geriatric nutritional risk index (GNRI). Altogether, 46 cardiac events occurred during the follow-up period (221 ± 135 days), including 14 cardiac deaths and 32 hospitalizations for worsening HF. In a Kaplan–Meier survival analysis, the low-FR group had more cardiac events than the high-FR group (log-rank, p < 0.001). The best cut-off value of FR was determined as 2.9 in the receiver operating characteristic curve for cardiac events. A multivariate Cox proportional hazards regression analysis showed that being in the low-FR group was an independent determinant of cardiac events from parameters of liver function tests and GNRI. ConclusionsFR might be useful for predicting future cardiac events in patients with HF, reflecting nutritional status which cannot be assessed by liver function tests and GNRI.

Quantitative structure–property relationship models to predict thermodynamic properties of some mono and polycyclic aromatic hydrocarbons using genetic algorithm‐multiple linear regression

AbstractPolycyclic aromatic hydrocarbons (PAHs) are a class of diverse organic compounds. Quantitative structure–property relationship (QSPR) models are used for modeling and predicting the thermodynamic properties of 45 monocyclic aromatic hydrocarbons (MAHs) and PAHs. Thermodynamic properties of PAHs such as heat capacity (C v; J mol−1 K−1), thermal energy (Eth; kJ mol−1), and entropy (S; J mol−1 K−1) are calculated at the HF level of theory and 6‐311G *basis sets using the Gaussian 09 program. A set of molecular descriptors is calculated for selected compounds using the software Dragon. The genetic algorithm (GA) and backward stepwise multiple linear regression (MLR) techniques are used to obtain suitable QSPR models. The predictive ability of the models is checked using several criteria for internal and external model validation. The results show that three descriptors (Uindex, nAT, HTe) can be efficiently used for estimating S, one descriptor (HTe) for modeling Eth, and also one descriptor (Uindex) for predicting C v of the considered compounds. The results and discussion lead to the conclusion that the models established by GA‐MLR have good correlation of the thermodynamic properties, which means QSPR models can be efficiently used for predicting the above‐mentioned properties and designing new molecules of MAHs and PAHs.

Trace Elements in the Lung Tissue Affected by Sarcoidosis.

In the lungs of 76 patients with verified sarcoidosis, 28 chemical elements were identified with neutron activation analysis. High levels of Ca, Fe, Cr, Co, Cs, Eu, Lu, Th, Hf, Au, and U and low level of Na compared to the control samples were determined in sarcoidosis. There were no significant differences in the content of Zn, Rb, La, Sm, Sr, Nd, As, Br, Ag, Tb, Sc, Ta, Sb, Ba, and Yb. Spearman correlation analysis shows multiple positive associations, with the maximum being in pairs as follows: Fe-Cr, Eu-La, Ce-Lu, Hf-Cr, Sc-Zn, Fe-Hf, Ce-Co, and Sb-Cr. These studies support the hypothesis that sarcoidosis is a response of the organism in the form of granulomatous inflammation when exposed to heavy metals and rare earth elements in the environment. We assume that the role of calcium and iron is to separate granulomas from the tissues of the body.

Complex formation in a liquid-liquid extraction-chromogenic system for vanadium(IV)

AbstractThe azo dye 4-(2-thiazolylazo)orcinol (TAO) and the cationic ion-pair reagent 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) were examined as constituents of a water-chloroform extraction-chromogenic system for vanadium(IV). The effects of TAO concentration, TTC concentration, pH and extraction time were examined. Under the optimum conditions the extracted complex has a composition of 1:2:1 (V:TAO:TTC). The absorption maximum, molar absorptivity and constant of extraction were determined to be λmax=544 nm, ε544=1.75×104 dm3 mol–1 cm–1 and Log Kex=4.1. The ground state equilibrium geometries of the possible monoanionic VIV-TAO 1:2 species were optimized by the HF method using 3-21G* basis functions. Their theoretical time dependent electronic spectra were simulated and compared with the experimental spectrum. The best fit was obtained for the structure in which one of the TAO ligands is tridentate, but the other is monodentate (bound to VIV through the oxygen which is in the ortho-position to the azo group) and forms a hydrogen bond N–H...O=V through its protonated heterocyclic nitrogen. Based on this unusual structure, which can explain some peculiarities of the complex formation between VIV and commonly used azo dyes, the ground state equilibrium geometry of the whole ternary 1:2:1 complex was computed at the HF and BLYP levels.

Electronic and Thermodynamic Properties of a Derivative of Dithiophosphonates

In this work, thermodynamic properties (Heat capacity, Entropies, Enthalpy, Gibbs free and Thermal energy) and frontier (HOMO, LUMO) molecular orbitals of a derivative dithiophosphonates molecule which is [+HN(C2H5)3][CH3CHOC6H3(CF3)2)(CH3OC6H4)PS2-] in the ground state were calculated by using the quantum chemical calculation method such as density functional theory (DFT) employing B3LYP and HF levels with the 6-31G(d) basis set. In addition, the frontier molecular orbitals analysis of the molecule were researched using computational methods. Properties about the charge density distribution of the title compound and its chemical reactivity has been investigated with mapping molecular electrostatic potential surface.

Substituent effects at nitrogen/phosphorus atoms of dialkaline earth metal complexes: Excess electron and large second‐hyperpolarizability

AbstractA number of imido‐, amido‐, and phosphido‐bridged dialkaline earth metal (M = Be, Mg, and Ca) complexes and their alkali metal (Li and Na) derivatives have been considered to study the ground state structure and the second‐hyperpolarizability. The calculated ground state geometries contain four‐membered MN(P)MN(P) ring having either planar or butterfly‐like bent structure. The second‐hyperpolarizability has been calculated at the HF and CCSD(T) levels using Sadlej's pol and aug‐pc‐2 basis sets, respectively. The addition of second hydrogen/alkali metal atom on nitrogen/phosphorus (N/P) atom substantially reduces the charge transfer from the alkaline earth metal atoms as the high negative charge on N/P exerts stronger push effect on the outermost electron pair in the “ns” sub‐shell of M. The excess electron density on the alkaline earth metal atoms plays a crucial role in the enhancement of second‐hyperpolarizability. The sum‐over‐state method calculated two‐photon contribution of second‐hyperpolarizability has been found to be significant. The variation of second‐hyperpolarizability has been explained satisfactorily in terms of the TD‐CAMB3LYP calculated spectroscopic properties in the light of two‐state model. The calculated mean second‐hyperpolarizabilities of alkali substituted amido‐ and phosphido‐bridged complexes are in the order of 107 au.

Aromaticity of Fullerenes, the Way to their Functionalization (Review)

Aromaticity is used to describe the durability and reactivity of structures containing delocalized  electrons.In this review article, the aromaticity of fullerenes patched with flowers of 6-and 8-membered ringsis discussed, optimized at the HF and DFT levels of theory, in terms of HOMA and NICS criteria. The aromatic character of these nanostructures allows for functionalization and finally for increasing their solubility in polar solvents. The overall conclusion is that several of the yet hypothetical molecular nanostructures herein described are serious candidates for new medicinal products, as a proposal for personalized medicine.

Effect of Electron Correlation on Intermolecular Interactions: A Pair Natural Orbitals Coupled Cluster Based Local Energy Decomposition Study.

The development of post-Hartree-Fock (post-HF) energy decomposition schemes that are able to decompose the HF and correlation components of the interaction energy into chemically meaningful contributions is a very active field of research. One of the challenges is to provide a clear-cut quantification to the elusive London dispersion component of the intermolecular interaction. London dispersion is well-known to be a pure correlation effect, and as such it is not properly described by mean field theories. In this context, we have recently developed the local energy decomposition (LED) analysis, which provides a chemically meaningful decomposition of the interaction energy between two or more fragments computed at the domain-based local pair natural orbitals coupled cluster (DLPNO-CCSD(T)) level of theory. In this work, this scheme is used in conjunction with other interpretation tools to study a series of molecular adducts held together by intermolecular interactions of different natures. The HF and correlation components of the interaction energy are thus decomposed into a series of chemically meaningful contributions. Emphasis is placed on discussing the physical effects associated with the inclusion of electron correlation. It is found that four distinct physical effects can contribute to the magnitude of the correlation part of intermolecular binding energies (Δ EintC): (i) London dispersion, (ii) the correlation correction to the reference induction energy, (iii) the correlation correction to the electron sharing process, and (iv) the correlation correction to the permanent electrostatics. As expected, the largest contribution to the correlation binding energy of neutral, apolar molecules is London dispersion, as in the argon dimer case. In contrast, the correction for the HF induction energy dominates Δ EintC in systems in which an apolar molecule interacts with charged or strongly polar species, as in Ar-Li+. This effect has its origin in the systematic underestimation of polarizabilities at the HF level of theory. For similar reasons, electron sharing largely contributes to the correlation binding energy of covalently bound molecules, as in the beryllium dimer case. Finally, the correction for HF permanent electrostatics significantly contributes to Δ EintC in molecules with strong dipoles, such as water and hydrogen fluoride dimers. This effect originates from the characteristic overestimation of dipole moments at the HF level of theory, leading in some cases to positive Δ EintC values. Our results are apparently in contrast to the widely accepted view that Δ EintC is typically dominated by London dispersion, at least, in the strongly interacting region. Clearly, post-HF energy decomposition schemes are very powerful tools to analyze, categorize, and understand the various contributions to the intermolecular interaction energy. Hopefully, this will eventually lead to insights that are helpful in designing systems with tailored properties. All analysis tools presented in this work will be available free of charge in the next release of the ORCA program package.

Fast quantum chemistry calculations for large molecules and condensed-phase systems: The developments and applications of generalized energy-based fragmentation approach

The GEBF approach could be applied to the ground-state energies (including the relative energies or binding energies) of a broad range of large systems including molecular clusters, supramolecular systems, proteins, nucleic acids, and etc. The computational levels include HF, DFT, second-order Moller-Plesset perturbation theory (MP2), coupled cluster singles and doubles (CCSD), CCSD with triples correction [CCSD(T)], and explicitly correlated MP2-F12 and CCSD(T)-F12 x ( x = a , b ) methods. With the GEBF energy derivatives (including energy gradients, Hessians, and so on), the approaches could be employed for optimizing the molecular geometries, performing ab initio molecular dynamics, computing the vibrational spectroscopies (including the IR and Raman spectroscopies) and nuclear magnetic resonance (NMR) chemical shifts of large systems at the HF, DFT, and MP2 levels. GEBF approach is also extended to the localized excited states by defining those subsystems including local excitation as the active subsystems, which are treated by the excited-state calculations at the time-dependent DFT or approximate equation-of-motion CCSD (CC2) levels. Then the GEBF-TDDFT or GEBF-CC2 could be used to compute electronic absorption spectra of solutions or large molecules with local excitations. The GEBF approach under the periodic boundary conditions (PBC) is also been implemented by constructing the subsystems in a super cell and employing the Ewald summation and compensation field methods to take the effect of the long-range electrostatic interaction of the crystal environment into account. The PBC-GEBF approach has been used to compute the lattice energies, crystal structures, IR and Raman spectra, and NMR chemical shifts of various condensed-phase systems, including molecular crystals, liquids, ionic liquid crystals, and solutions. Thus, the GEBF and PBC-GEBF approaches are expected to be widely applied to the energies, structures, and molecular properties of a broad range of large systems and condensed-phase systems.

Quantum chemical predictions of aqueous pKa values for OH groups of some α-hydroxycarboxylic acids based on ab initio and DFT calculations

Determination of pKa values, especially for OH groups of α-hydroxycarboxylic acids, is challenging and rarely reported. Here, successive pKa values for COOH, and more importantly for OH groups of the nine biologically important α-hydroxycarboxylic acids (glycolic, lactic, methyl lactic, α-hydroxybutyric, mandelic, atrolactic, benzilic, malic, and citramalic) were calculated computationally. We benchmarked the accuracy for predicting pKa values by HF, MP2, B3LYP, B97D, B2PLYP, M06-2X, G3 and CBS-QB3 levels of theory combined with CPCM and SMD solvation models applied to lactic acid whose experimental pKa values are reported in the literature. Also, we considered six thermodynamic cycles in combination with a number of DFT methods and some cavity sets, such as, UAKS, Pauling and Bondi to obtain the reasonable results. Finally, we employed two best methods to predict the pKa values of the remaining eight α-hydroxycarboxylic acids. Estimated pKa values of OH groups are reported for these α–hydroxycarboxylic acids that were not yet determined experimentally.

Ab Initio Studies on the Interaction Between Copper(I) and 5-Nitrotetrazolate Anion

&lt;p class="p1"&gt;Ab initio molecular orbital calculations on the interaction between Copper(I) and 5-nitrotetrazolate anion were done using different basis sets, at the HF, B3LYP and MP2 levels of theory. Three minima were found to 1A, 1B and IC structures of Cu(I)-5-NTz complex. At the B3LYP/LanL2DZ level, the energy difference between 1A and 1B was computed to be 8.18 kcal/mol, while that between 1A and 1C is 22.76 kcal/mol. The presence of both Cu-N and Cu-O interactions is revealed in 1A structure using both natural bond orbital and atoms-in-molecules analyses, which makes more stable than those of 1B and 1C complexes. The binding energy corrected for both ZPE and BSSE for 1A is found to be -150.59 kcal/mol at the B3LYP/LanL2DZ level. The barrier for the 1B &lt;span class="s1"&gt;→&lt;/span&gt; 1A and 1C &lt;span class="s1"&gt;→&lt;/span&gt; 1B conversion is calculated to be 7.80 kcal/mol and 9.40 kcal/mol, respectively.&lt;/p&gt;

Drug Design Outlook by Calculation of Second Virial Coefficient as a Nano Study

Intermolecular potential energy surface for an interaction of drug with Na has been examined using HF level of theory with 6-31G* basis set. The name of drug is meso-tetrakis (p-sulphonatophenyl) porphyrin (here after abbreviated to TSPP) . The numbers of Na+ have a significant effect on the calculated potential energy curve (including position, depth, and width of the potential well). Counterpoise (CP) correction has been used to show the extent of the basis set superposition error (BSSE) on the potential energy curves obtained for TSPPNa. The second virial coefficients are calculated by these data.

Quantum Chemical Computational Studies on a vic-Dioxime Ligand and Its Nickel Complex

In this study, the structural and bonding characteristic of 1-(2,6-Dimethylphenylamino)propane-1,2-dione dioxime ligand and its nickel(II) complex were examined by means of quantum chemical computations. Primarily, comprehensive calculations were performed on these compounds at the DFT, HF and semi-empirical levels of theory by using different basis sets. The structural accuracy of ligand and complex were investigated by comparing the calculated values to the bond lengths and angles measured in X-ray structures. Then, comparison of the methods was applied by considering quality factors calculated for different basis sets of each method. The theoretical structural studies on ligand and complex were carried out by UV-Vis, FT-IR and NMR spectral analysis. The calculated vibrational bands, electronic absorption spectrum and NMR chemical shifts were determined to be consistent with the experimental results. In additional, the characteristic of the metal-ligand interactions were demonstrated by natural bond orbital (NBO) analysis.

How Hot are Your Ions Really? A Threshold Collision-Induced Dissociation Study of Substituted Benzylpyridinium "Thermometer" Ions.

The first absolute experimental bond dissociation energies (BDEs) for the main heterolytic bond cleavages of four benzylpyridinium "thermometer" ions are measured using threshold collision-induced dissociation in a guided ion beam tandem mass spectrometer. In this experiment, substituted benzylpyridinium ions are introduced into the apparatus using an electrospray ionization source, thermalized, and collided with Xe at varied kinetic energies to determine absolute cross-sections for these reactions. Various effects are accounted for, including kinetic shifts, multiple collisions, and internal and kinetic energy distributions. These experimentally measured 0K BDEs are compared with computationally predicted values at the B3LYP-GD3BJ, M06-GD3, and MP2(full) levels of theory with a 6-311+G(2d,2p) basis set using vibrational frequencies and geometries determined at the B3LYP/6-311+G(d,p) level. Additional dissociation pathways are observed for nitrobenzylpyridinium experimentally and investigated using these same levels of theory. Experimental BDEs are also compared against values in the literature at the AM1, HF, B3LYP, B3P86, and CCSD(T) levels of theory. Of the calculated values obtained in this work, the MP2(full) level of theory with counterpoise corrections best reproduces the experimental results, as do the similar literature CCSD(T) values. Lastly, the survival yield method is used to determine the characteristic temperature (Tchar) of the electrospray source prior to the thermalization region and to confirm efficient thermalization. Graphical Abstract ᅟ.