Reliability of interacting quantum atoms (IQA) data computed from post-HF densities : impact of the approximation used

The performance of BBC1, BBC2 and Müller approximations, in terms of reliability of IQA data, was investigated at the CCSD, CCSD(T) and MP2 levels using glycol, as a case study, in interpreting the relative stability of its conformers, one with H-bond type intramolecular interaction and the other with a steric clash between two O-atoms. The CCSD/BBC1 level appeared to be perfectly suited as a reference needed to evaluate all possible levels of theory/approximation combinations (LoT/LoA). We found the reliability trend LoT/BBC1 > LoT/BBC2 > LoT/Müller (as well as its origin) and concluded that the Müller approximation should not be used when the accuracy of IQA-defined energy terms is considered. Moreover, we have established that the requirement of reproducing, by IQA calculations, electronic energy is desirable but not a necessary requirement when a comparative approach is used, such as in FAMSEC-based analysis (FAMSEC = fragment attributed molecular system energy change). A new criterion is proposed to assess the quality of IQA data for comparative analyses, ΔE(IQA) ≈ ΔE, where ΔE(IQA) and ΔE are the IQA and electronic energy differences, respectively, between the fin-state and ref-state of a molecular system. The closer ΔE(IQA) approaches ΔE, the closer the FAMSEC data approach values obtained at the exceptionally well performing CCSD/BBC1 level, regardless of the LoT/LoA combination used. Importantly, the MP2/BBC1 level performed nearly as well as the CCSD/BBC1 level in comparative studies. The origin of the MP2/BBC1 approximation's exceptional and the MP2/Müller approximations's acceptable performance in explaining the relative stability of glycol conformers has been uncovered and discussed in detail.Tthe National Research Foundation of South Africa (Grant Number 105855).http://www.rsc.org/journals-books-databases/about-journals/PCCP2018-05-30hj2018Chemistr

Hydrogen-bonding interactions in monomeric dimethylcuprates. A theoretical study

The hydrogen-bonding interactions between dimethylcuprate anions of monomeric lithium dimethylcuprate solvates and C–H bonds of molecules which solvate lithium cation were studied. The NBO analysis and analysis of internuclear distances are used to reveal these interactions in B3LYP and MP2 calculated monomeric lithium dimethylcuprates (LDMCs), and in the published X-ray structures of monomeric dimethylcuprates. The relevance of QTAIM analysis for the description of hydrogen-bonding interactions in LDMCs is evaluated. Different types of hydrogen bonds (HBs), e.g. C–H···Cu and C–H···C HBs as well as C–H···H dihydrogen bonds are revealed by the calculations of monomeric lithium dimethylcuprates with the cation surrounded by solvent molecules. All of these HB types were found to exist in the solid state between dimethylcuprate anion and C–H bonds of the solvent or ligand molecules. Multiple HBs of different types and strengths are simultaneously formed with dimethylcuprate anions in the monomeric cuprates studied. It is demonstrated that multiple hydrogen-bondings, accompanied by an unsymmetrical interaction of the dimethylcuprate anion with C–H bonds, can lead to impressive geometrical changes, including e.g. different C–Cu bond lengths in some “solvent-separated ion pairs”. In some monomeric cuprates the C–Cu–C unit of dimethylcuprate anion was found to bend even in the absence of Cu···Cu interactions

Structure of (Me2Cu)Li • 3DME and its oligomers [(Me2Cu)Li • 3DME]n (n = 2-5): a theoretical study

The structures of monomeric lithium dimethylcuprate solvated by three 1,2-dimethoxyethane (DME) molecules (Me2Cu)Li · 3DME and its oligomers [(Me2Cu)Li · 3DME] n (n = 2–5) in the gas phase were studied using the density functional theory. The structures of these systems are compared with that of (Me2Cu)Li · 3DME in the crystal. It is shown that numerous C-H…Cu and C-H…C hydrogen bonds, as well as C-H…H dihydrogen bonds between DME molecules, which solvate lithium cations, and corresponding dimethylcuprate anions significantly affect the formation and structure of these compounds in the gas and solid phases

BODIPY-Pyrene and Perylene Dyads as Heavy-Atom-Free Singlet Oxygen Sensitizer

https://doi.org/10.1002/cptc.201800020Dyads combining BODIPY as an electron acceptor and pyrene or perylene as electron donor subunits were prepared and their photophysical properties were studied by steady?state and transient spectroscopy. Depending on the structure of the subunits and the polarity of the media, the dyads show either bright fluorescence or photo?induced electron transfer (PeT) in solution. Charge?transfer (CT) states formed as a result of PeT and were found to yield triplet excited states of the BODIPY. In the presence of molecular oxygen, the dyads sensitize singlet oxygen (1O2) with quantum yields of up to 0.75

Estudo cefalométrico comparativo dos espaços naso e bucofaríngeo nas más oclusões Classe I e Classe II, Divisão 1, sem tratamento ortodôntico, com diferentes padrões de crescimento A Comparative cephalometric study of the naso and oropharyngeal space in malocclusions Class I and Class II Division 1, without orthodontic treatment with different growth patterns

A finalidade deste estudo foi comparar os espaços aéreos naso e bucofaríngeo em indivíduos com má oclusão Classe I e Classe II, divisão 1, segundo Angle, do gênero masculino e feminino, com idade média de 11 anos e 6 meses, com padrão de crescimento normal e vertical, não tratados ortodonticamente. A amostra desse estudo foi dividida em dois grupos: 40 pacientes apresentando Classe I e 40 pacientes com Classe II, divisão 1, cada grupo subdividido de acordo com o padrão de crescimento facial: normal e vertical. Os espaços aéreos naso e bucofaríngeo foram avaliados segundo a análise de McNamara Jr., pelas medidas NFa-NFp e BFa-BFp. A análise dos resultados obtidos revelou que, a medida do espaço bucofaríngeo para Classe I com padrão de crescimento vertical e para o espaço nasofaríngeo para Classe II com padrão normal de crescimento apresentaram-se semelhantes à medida padrão da amostra de McNamara Jr.. As outras medidas apresentaram-se estatisticamente menores. Na comparação entre os grupos, o espaço nasofaríngeo no grupo Classe I com padrão de crescimento vertical, apresentou-se menor do que nos grupos Classe I e grupo Classe II divisão 1, ambos com padrão de crescimento normal. O espaço bucofaríngeo não sofreu alteração significante de um grupo para outro. Em relação à hipertrofia da tonsila faringeana, apenas o grupo Classe I com padrão de crescimento vertical apresentou obstrução; para hipertrofia das tonsilas palatinas, apenas o grupo Classe I com padrão de crescimento vertical e Classe II com padrão de crescimento normal apresentou hipertrofia das tonsilas palatinas.<br>The aim of this study is to compare the naso and oropharyngeal air space in people with malocclusion class I and class II division 1, according to Angle, with mean age from 8 to 15 years old with normal and vertical growth pattern not treated orthodontically. This study was divided into two groups: 40 patients with class I, and 40 with class II, division 1 subdivided according to facial growth: normal and vertical. The naso and oropharyngeal airway space was assessed according to McNamara's analysis by using the Nfa-NFp and Nba-NBp measurements. The analysis of the results obtained revealed that, the oropharyngeal measurements for class I with pattern vertical growth and nasopharyngeal class II with pattern normal growth were similar to the reference measures in McNamara's sample. The other measurements were statistically smaller. In the comparison between groups, the oropharyngeal spaces did not show a difference between one group and another. The nasopharyngeal space in the class I group with vertical growth, showed a narrower space than in the class I group and in the class II group with pattern normal growth. In relation to adenoids hypertrophy, only class I with pattern vertical growth showed obstruction; for tonsils hypertrophy, only class I with pattern vertical growth and class II with pattern normal growth showed tonsils hypertrophy