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In this computational work we study complexes with two equivalent intermolecular hydrogen bonds formed between trimethyl phosphine oxide and two identical proton donors ("twin" hydrogen bonds) for a set of 70 proton donor molecules. The changes in the phosphorus chemical shift and stretching frequency of the PO group upon complexation correlate quite well with the total strength of two hydrogen bonds. A set of explicit numerical dependences is proposed for assessing interatomic distances and hydrogen bond strengths from spectral data. Comparison with the results obtained for analogous previously studied 1 : 1 complexes allowed us to analyze in detail anticooperativity effects on the geometry, energy and spectral parameters. Two hydrogen bonds compete for the PO acceptor group and their mutual weakening increases nonlinearly with the strengthening of the complex, reaching approximately 25% in energy (which corresponds to 0.1 Å lengthening for short strong H-bonds), which is clearly seen in NMR and IR spectra and correlates well with the changes in the spectral parameters.

In this work IR spectral characteristics of PO groups are used to evaluate the strength of OHO hydrogen bonds. Three phosphine oxides: triphenylphosphine oxide, tributylphosphine oxide and hexamethylphosphoramide are investigated as proton acceptors. The results of the experimental IR study and DFT calculation of 30 complexes formed by phosphine oxides with various substituted phenols or CF 3 CH 2 OH in CCl 4 solution at room temperature are reported. We show that the PO vibrational frequency changes non-linearly upon hydrogen bond formation and strengthening and that the shift of the PO band could be used for the estimation of hydrogen bond strength in complexes with phosphine oxides. The accuracy of these estimations and the influence of solvation effects on the main characteristics of complexes are discussed.

In this computational work applicability of IR spectral parameters for evaluations of OH···N hydrogen bond length is discussed. For a set of 124 complexes with OH···N hydrogen bond formed by combinations of methanol/acetic acid and pyridine (and their fluorine substituted versions) geometries, energies and IR parameters were calculated at MP2/def2-TZVP level of theory. For a number of IR parameters (the shift of proton donor group stretching vibration Δν s , increase of its intensity I, the low-frequency hydrogen bond stretching vibration ν σ , bending in-plane δ and out-of-plane γ vibrations) equations linking them with interatomic distances are proposed, the robustness and accuracy of such equations are discussed. The enthalpy of OH···N hydrogen bond formation ΔH was also linked with electron density parameters in (3; -1) critical point., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In this work we evaluate the possibility of using the NMR and IR spectral properties of the PO group to estimate the geometry and strength of hydrogen bonds which it forms with OH-, NH- and CH-acids. The results of the DFT study of 70 hydrogen-bonded 1 : 1 complexes of a model trimethylphosphine oxide, Me 3 PO, with various proton donors in the gas phase and in aprotic medium (modelled as a polarizable continuum) are presented. Four types of hydrogen bonds with the general formula Me 3 PO⋯H-A were considered, where the A atom is O, C, and N (neutral or cationic acids). Within the selected set of complexes the hydrogen bond energy varies over a wide range ( ca. 0-85 kJ mol -1 ). We show that it is possible to use simple correlations to estimate the energy and geometry of OHO, NHO and CHO hydrogen bonds from the changes of isotropic 31 P NMR chemical shifts and harmonic PO stretching vibration frequencies upon complexation. Such correlations also could be used to estimate the proton-donating ability (and Brønsted acidity; p K a ) of OH acids.

In this work, the nuclear magnetic resonance (NMR) and IR spectroscopic markers of the complexation between 5-fluorouracil (5-FU) and β-cyclodextrin (β-CD) in solid state and in aqueous solution are investigated. In the attenuated total reflectance(ATR) spectra of 5-FU/β-CD products obtained by physical mixing, kneading and co-precipitation, we have identified the two most promising marker bands that could be used to detect complex formations: the C=O and C-F stretching bands of 5-FU that experience a blue shift by ca. 8 and 2 cm -1 upon complexation. The aqueous solutions were studied by NMR spectroscopy. As routine NMR spectra did not show any signs of complexation, we have analyzed the diffusion attenuation of spin-echo signals and the dependence of the population factor of slowly diffusing components on the diffusion time (diffusion NMR of pulsed-field gradient (PFG) NMR). The analysis has revealed that, at each moment, ~60% of 5-FU molecules form a complex with β-CD and its lifetime is ca. 13.5 ms. It is likely to be an inclusion complex, judging from the independence of the diffusion coefficient of β-CD on complexation. The obtained results could be important for future attempts of finding better methods of targeted anticancer drug delivery.

The hydrogen-bonded self-associates of dimethylphosphinic (1), diphenylphosphoric (2), phenylphosphinic (3), and bis(2,4,4-trimethylpentyl)phosphinic (4) acids have been studied by using liquid-state NMR down to 100 K in a low-freezing polar solvent, CDF 3 /CDClF 2 . The H/D isotope effects on 1 H NMR chemical shifts caused by partial deuteration of hydroxyl groups unambiguously reveal the stoichiometry of the self-associates and the cooperativity of their hydrogen bonds. In all cases, cyclic trimers are the dominant form, while cyclic dimers are present as a minor form for 1 and 2. Due to the asymmetry of substituents, cyclic trimers of 3 exist in two isomeric forms, depending on the orientation of the phenyl groups with respect to the plane of the hydrogen bonds. The racemic mixture of 4 leads to the coexistence of up to 64 isomers of cyclic trimers, many of which are chemically equivalent or effectively isochronous. The mole fractions of such isomers deviate from the statistically expected values. This feature could provide information about the relative stabilization energies of hydrogen-bonded chiral self-associates. The complexation of 4 with SbCl 5 (complex 5) suppresses the self-association and 5 exists exclusively in the monomeric form with chemically non-equivalent 31 P nuclei in RS, SR and RR/SS forms.

A partial-wave analysis of the mesons from the reaction pi(-)p --> pi(+)pi(-)pi(-)pi(0)pi(0)p has been performed. The data show b(1)pi decay of the spin-exotic states pi(1)(1600) and pi(1)(2000). Three isovector 2(-+) states were seen in the omegarho(-) decay channel. In addition to the well known pi(2)(1670), signals were also observed for pi(2)(1880) and pi(2)(1970).

The MARS code is under continuous development and has recently undergone substantial improvements that further increase its reliability and predictive power in numerous shielding, accelerator, detector and space applications. The major developments and new features of the MARS15 (2004) version described in this paper concern an extended list of elementary particles and arbitrary heavy ions and their interaction cross sections, inclusive and exclusive nuclear event generators, module for modelling particle electromagnetic interactions, enhanced geometry and histogramming options, improved MAD-MARS Beam Line Builder, enhanced graphical user interface and an MPI-based parallelisation of the code.

The MARS15 Monte Carlo code capabilities to deal with time-consuming deep penetration shielding problems and other computationally tough tasks in accelerator, detector and shielding applications, have been enhanced by a parallel processing option. It has been developed, implemented and tested on the Fermilab Accelerator Division Linux cluster and network of Sun workstations. The code uses a message passing interface MPI. It is scalable and demonstrates good performance. The general architecture of the code, specific uses of message passing and effects of a scheduling on the performance and fault tolerance are described.

The factors that need to be taken into account to achieve spectroscopic accuracy for triatomic molecules are considered focusing on H3+ and water as examples. The magnitude of the adiabatic and non-adiabatic corrections to the Born-Oppenheimer approximation is illustrated for both molecules, and methods of including them ab initio are discussed. Electronic relativistic effects are not important for H3+, but are for water for which the magnitude of the various effects is discussed. For H3+ inclusion of rotational non-adiabatic effects means that levels can be generated to an accuracy approaching 0.01 cm(-1); for water the error is still dominated by the error in the correlation energy in the electronic structure calculation. Prospects for improving this aspect of the calculation are discussed.

An amplitude analysis of an exclusive sample of 5765 events from the reaction pi- p-->eta'pi- p at 18 GeV/c is described. The eta'pi- production is dominated by natural parity exchange and by three partial waves: those with J(PC) = 1(-+), 2(++), and 4(++). A mass-dependent analysis of the partial-wave amplitudes indicates the production of the a2(1320) meson as well as the a4(2040) meson, observed for the first time decaying to eta'pi-. The dominant, exotic (non- qq) 1(-+) partial wave is shown to be resonant with a mass of 1.597+/-0.010(+0.045)(-0.010) GeV/c2 and a width of 0.340+/-0.040+/-0.050 GeV/c2. This exotic state, the pi1(1600), is produced with a t dependence which is different from that of the a2(1320) meson, indicating differences between the production mechanisms for the two states.