Center for Magnetic Resonance

V.V. Mulloyarova, I.S. Giba, M.A. Kostin, G.S. Denisov, I.G. Shenderovich, P.M. Tolstoy

“Cyclic Trimers of Phosphinic Acids in Polar Aprotic Solvent: Symmetry, Chirality and H/D Isotope Effects on NMR Chemical Shifts”

Phys. Chem. Chem. Phys., 2018, 20, 4901-4910
DOI: 10.1039/C7CP08130H

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, CDF₃/CDClF₂. The H/D isotope effects on ¹H 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 SbCl₅ (complex 5) suppresses the self-association and 5 exists exclusively in the monomeric form with chemically non-equivalent ³¹P nuclei in RS, SR and RR/SS forms

V.A. Rozentsvet, O.A. Stotskaya, V.P. Ivanova, M.G. Kuznetsova, P.M. Tolstoy, S.V. Kostjuk

“Structural characterization of polybutadiene synthesized via cationic mechanism”

J. Polym. Sci. A, 2018, 56, 387-398
DOI: 10.1002/pola.28905

The microstructure of polybutadiene synthesized via cationic polymerization using TiCl4‐based initiating systems has been investigated using 1D (1Н, 2Н, and 13С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans‐1,4‐unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2‐structures was also detected, while cis‐1,4‐units were totally absent. The signals of carbon atoms of three types of head groups (trans‐1,4‐, 1,2‐, and tert‐butyl) and two types of end groups (trans‐1,4‐Cl and 1,2‐Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert‐butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2‐units distributed randomly along the polybutadiene chain as separate units between trans‐1,4‐structures.

V.A. Rozentsvet, O.A. Stotskaya, V.P. Ivanova, M.G. Kuznetsova, P.M. Tolstoy, S.V. Kostjuk

“Structural characterization of polybutadiene synthesized via cationic mechanism”

J. Polym. Sci., Part A: Polym. Chem., 2018, 56, 387–398.
DOI: 10.1002/pola.28905

The microstructure of polybutadiene synthesized via cationic polymerization using TiCl4-based initiating systems has been investigated using 1D (1Н, 2Н, and 13С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans-1,4-unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2-structures was also detected, while cis-1,4-units were totally absent. The signals of carbon atoms of three types of head groups (trans-1,4-, 1,2-, and tert-butyl) and two types of end groups (trans-1,4-Cl and 1,2-Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert-butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2-units distributed randomly along the polybutadiene chain as separate units between trans-1,4-structures.

A.V. Artem’ev, I.Yu. Bagryanskaya, E.P. Doronina, P.M. Tolstoy, A.L. Gushchin, M.I. Rakhmanova, A.Yu. Ivanove, A.O. Suturina

“A new family of clusters containing a silver-centered tetracapped [Ag@Ag4(μ3-P)4] tetrahedron, inscribed within a N12 icosahedron”

Dalton Transactions, 2017, 46, 12425-12429.
DOI: 10.1039/C7DT02597A

An unprecedented silver-centered P-tetracapped [Ag@Ag4(μ3-P)4] tetrahedron inscribed within a N12 icosahedral cage has been discovered in the novel family of luminescent clusters. The latter are easily self-assembled by reacting AgI salts with tris(2-pyridyl)phosphine (Py3P).