Orientational Order-Disorder Effects in Molecular Crystals as Evidenced by Low-Frequency Raman Spectra

The studies of reorientational motions of molecules in crystals of organic compounds by low-frequency Raman spectroscopy are briefly reported. Some examples illustrate the efficiency of the investigation of order-disorder phenomena in organic crystals by the temperature dependence of low-frequency vibrational spectra combined with simultaneous calculations of the molecular dynamics by the atom-atom potentials (AAP) method. The conditions have been determined which are necessary in order to affect the low-frequency Raman spectra by anisotropy of molecular reorientations in crystals

Взаимодействие аниона [2-В10Н9О(СН2)4О]− с вторичными аминами

Objectives. One of the most promising methods of treating malignant tumors is 10B-neutron capture therapy. While compounds based on cluster boron anions [BnHn]2− (n = 10, 12) are often used as boron-containing agents due to the very high specific concentration of boron atoms per particle, the use of such compounds is associated with the need to develop new methods for the functionalization of boron clusters associated with the production of boron-containing derivatives containing biologically active functional groups. One of the most convenient methods of modification of [BnHn]2− (n = 10, 12) anions is the interaction of their derivatives containing cyclic oxonium-type substituents with negatively charged or neutral nucleophilic reagents. The disclosure of substituents of this type leads to the formation of closo-borates with functional groups separated from the cluster by an alkoxyl spacer chain. The purpose of this study is to develop methods for the synthesis of derivatives of the closo-decaborate anion [B10H10]2− with pendant nitrogen-containing groups.Methods. The general control of the reactions of the disclosure of cyclic substituents was carried out on the basis of 11B nuclear magnetic resonance (NMR) spectroscopy data. The structure of the obtained derivatives, including the nature of the attached functional groups, was determined using 1H, 13C attached proton test (APT) NMR and infrared (IR) spectroscopy data. The molecular weight of the synthesized compounds was confirmed by electrospray ionization mass-spectrometry (ESI–MS).Results. The interaction of the anion [2-B10H9O(CH2)4O]− with secondary amines (dimethylamine, dipropylamine, diallylamine, dibutylamine, diisobutylamine, morpholine, di-sec-butylamine) in an ethanol environment is investigated. As a result of the reactions, a cyclic substituent is shown to expand with the addition of a nucleophilic reagent. Seven new derivatives of the closodecaborate anion with pendant nitrogen-containing groups have been synthesized.Conclusions. A developed method for obtaining closo-decaborates with ammonium groups separated from the boron cluster by an alkoxyl spacer group is presented. It is shown that the use of amines of various structures does not fundamentally affect the course of the reactions, allowing the composition and structure of the target derivatives to be effectively regulated. The resulting compounds can be involved in further modification reactions due to a reactive pendant group, as well as being suitable for use as effective polydentate ligands. Closo-decaborates with pendant nitrogen-containing groups and their derivatives are of considerable interest in the synthesis of compounds for use in 10B-neutron capture therapy of malignant tumors.Цели. 10B-нейтронозахватная терапия является одним из наиболее перспективных методов лечения злокачественных опухолей. В качестве борсодержащих агентов нередко применяются соединения на основе кластерных анионов бора [BnHn]2− (n = 10, 12), как имеющие очень высокую удельную концентрацию атомов бора в расчете на одну частицу. Однако использование таких соединений связано с необходимостью разработки новых методов функционализации борных кластеров, связанных с получением борсодержащих производных с биологически активными функциональными группами. Одним из наиболее удобных методов модификации анионов [BnHn]2− (n = 10, 12) является взаимодействие их производных, содержащих циклические заместители оксониевого типа, с отрицательно заряженными или нейтральными нуклеофильными реагентами. Раскрытие заместителей данного типа приводит к образованию клозо-боратов с функциональными группами, отделенными от кластера алкоксильной спейсерной цепочкой. Целью настоящего исследования является разработка методов синтеза производных клозо-декаборатного аниона [B10H10]2− с пендантными азотсодержащими группами.Методы. Общий контроль протекания реакций раскрытия циклических заместителей осуществлялся на основании данных 11B спектроскопии ядерного магнитного резонанса (ЯМР). Строение полученных производных, в том числе природу присоединенных функциональных групп определяли на основании данных 1H, 13C ЯМР с тестом на присоединенные протоны (APT) и инфракрасной спектроскопии (ИК). Молекулярную массу синтезированных соединений подтверждали методом масс-спектрометрии с ионизацией электрораспылением (ИЭР-МС).Результаты. Исследовано взаимодействие аниона [2-B10H9O(CH2)4O]− с вторичными аминами (диметиламин, дипропиламин, диаллиламин, дибутиламин, диизобутиламин, морфолин, ди-втор-бутиламин) в среде этанола. Показано, что в результате реакций происходит раскрытие циклического заместителя с присоединением нуклеофильного реагента. Синтезированы семь новых производных клозо-декаборатного аниона с пендантными азотсодержащими группами.Выводы. Разработан новый метод получения клозо-декаборатов с аммониевыми группами, отделенными от борного кластера алкоксильной спейсерной группой. Показано, что применение аминов различного строения принципиально не влияет на ход протекающих реакций и позволяет эффективно регулировать состав и строение целевых производных. Полученные соединения могут быть вовлечены в дальнейшие реакции модификации за счет реакционноспособной пендантной группы, а также могут быть использованы в роли эффективных полидентатных лигандов. Клозо-декабораты с пендантными азотсодержащими группами и их производные представляют значительный интерес в синтезе соединений, перспективных для применения в 10B-нейтронозахватной терапии злокачественных опухолей

Specific features of the electronic, spin, and atomic structures of a topological insulator Bi2Te2.4Se0.6

The specific features of the electronic and spin structures of a triple topological insulator Bi2Te2.4Se0.6, which is characterized by high-efficiency thermoelectric properties, have been studied with the use of angular- and spin-resolved photoelectron spectroscopy and compared with theoretical calculations in the framework of the density functional theory. It has been shown that the Fermi level for Bi2Te2.4Se0.6 falls outside the band gap and traverses the topological surface state (the Dirac cone). Theoretical calculations of the electronic structure of the surface have demonstrated that the character of distribution of Se atoms on the Te–Se sublattice practically does not influence the dispersion of the surface topological electronic state. The spin structure of this state is characterized by helical spin polarization. Analysis of the Bi2Te2.4Se0.6 surface by scanning tunnel microscopy has revealed atomic smoothness of the surface of a sample cleaved in an ultrahigh vacuum, with a lattice constant of ~4.23 Å. Stability of the Dirac cone of the Bi2Te2.4Se0.6 compound to deposition of a Pt monolayer on the surface is shown.This study was supported by the Ministry of Education and Science of the Russian Federation, the St. Petersburg State University (project nos. 11.38.271.2014 and 15.61.202.2015), and the Russian Foundation for Basic Research (project nos. 12-02-00226, 13-02-91327, 14-08-31110, and 13-02-12110). The research was also performed at the Resource Center “Physical Methods of Surface Investigation” at St. Petersburg State University. We are also grateful to collaborators of the Helmholtz-Zentrum (Berlin) for financial and technical support.Peer reviewe

Search for decays of the 125 GeV Higgs boson into a Z boson and a ρ or ϕ meson

Decays of the 125 GeV Higgs boson into a Z boson and a ρ^0(770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at √s = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb⁻¹. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740–940 and 730–950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels

Search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at s \sqrt{\mathrm{s}} = 13 TeV

Results are reported from a search for the lepton flavor violating decay τ → 3μ in proton-proton collisions at $\sqrt{\mathrm{s}}$ = 13 TeV. The data sample corresponds to an integrated luminosity of 33.2 fb$^{-1}$ recorded by the CMS experiment at the LHC in 2016. The search exploits τ leptons produced in both W boson and heavy-flavor hadron decays. No significant excess above the expected background is observed. An upper limit on the branching fraction B(τ → 3μ) of 8.0 x 10$^{-8}$ at 90% confidence level is obtained, with an expected upper limit of 6.9 x 10$^{-8}$

Observation of the B⁰_s → X(3872)ϕ Decay

Using a data sample of proton-proton collisions at √s = 13  TeV, corresponding to an integrated luminosity of 140  fb⁻¹ collected by the CMS experiment in 2016–2018, the B⁰_s → X(3872)ϕ decay is observed. Decays into J/ψπ⁺π⁻ and K⁺K⁻ are used to reconstruct, respectively, the X(3872) and ϕ. The ratio of the product of branching fractions B[B⁰_s → X(3872)ϕ]B[X(3872) → J/ψπ⁺π−] to the product B[B⁰_s → ψ(2S)ϕ]B[ψ(2S) → J/ψπ⁺π−] is measured to be [2.21±0.29(stat)±0.17(syst)]%. The ratio B[B⁰_s → X(3872)ϕ]/B[B⁰ → X(3872)K⁰] is found to be consistent with one, while the ratio B[B⁰_s → X(3872)ϕ]/B[B⁺ → X(3872)K⁺] is two times smaller. This suggests a difference in the production dynamics of the X(3872) in B⁰ and B⁰_s meson decays compared to B⁺. The reported observation may shed new light on the nature of the X(3872) particle

Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at sNN\sqrt{sNN} =5.02 TeV

The first measurement of the dependence of γγ→μ$^{+}$ μ$^{-}$ production on the multiplicity of neutrons emitted very close to the beam direction in ultraperipheral heavy ion collisions is reported. Data for lead-lead interactions at $\sqrt{^{s}NN}$=5.02 TeV, with an integrated luminosity of approximately 1.5nb$^{-1}$, are collected using the CMS detector at the LHC. The azimuthal correlations between the two muons in the invariant mass region 88.3. The back-to-back correlation structure from leading-order photon-photon scattering is found to be significantly broader for events with a larger number of emitted neutrons from each nucleus, corresponding to interactions with a smaller impact parameter. This observation provides a data-driven demonstration that the average transverse momentum of photons emitted from relativistic heavy ions has an impact parameter dependence. These results provide new constraints on models of photon-induced interactions in ultraperipheral collisions. They also provide a baseline to search for possible final-state effects on lepton pairs caused by traversing a quark-gluon plasma produced in hadronic heavy ion collisions

Inclusive search for highly boosted Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at <mml:msqrt>s</mml:msqrt>=13 TeV

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