Center for Magnetic Resonance

A.N. Shestakov, A.S. Pankova, P. Golubev, A.F. Khlebnikov, M.A. Kuznetsov

“Brønsted acid mediated cyclizations of ortho-aryl(ethynyl)pyrimidines”

Tetrahedron, 2017, 73 (27-28), 3939–3948
DOI: 10.1016/j.tet.2017.05.070

A high-yielding procedure for the synthesis of 5-aryl-4-(arylethynyl)pyrimidines from easily available 2-aryl-3-hydroxyacrylates is reported. These pyrimidines readily undergo cyclization in strong Brønsted acids and, depending on the substitution in alkynylpyrimidines and the water content of the reaction mixture, yield either benzo[f]quinazolines or derivatives of spiro[cyclohexa-2,5-diene-1,5′-cyclopenta[d]pyrimidin]-4-one. In most cases the cyclization proceeds nearly quantitatively. DFT calculations support the proposed mechanisms induced by the protonation of the triple bond in 5-aryl-4-(arylethynyl)pyrimidines. Fluorescent properties of the obtained heterocycles are also described.

A.I. Solomatina, I.O. Aleksandrova, A.J. Karttunen, S.P. Tunik, I.O. Koshevoy

“Dibenzothiophene-platinated complexes: probing the effect of ancillary ligands on the photophysical performance”

Dalton Transactions, 2017, 46, 3895-3905
DOI: 10.1039/C7DT00349H

Cyclometalation of dibenzothienyl-pyridine (HPyDBT) afforded a series of platinum(II) complexes Pt(PyDBT)(L)Cl (L = DMSO, 1; P(p-C6H4-X)3 (X = H, 2; CF3, 3; OMe, 4; NPh2, 5); 1,3,5-triaza-7-phosphaadamantane, 6; 2,6-dimethylphenyl isocyanide, 7). Chelating bidentate LL ligands formed cationic compounds [Pt(PyDBT)(LL)]+ (LL = 1,2-bis(diphenylphosphino)benzene, 8; 2,2′-bipyridine, 9; 1,10-phenanthroline, 10). Oxidation of a thienyl sulfur atom allowed for the isolation of the sulfone derivative Pt(PyDBT)(PPh3)Cl (11). The title complexes were characterized crystallographically (except 7). Investigation of their photophysical behavior revealed solid state phosphorescence with quantum yields up to 0.45 for neat powders. The ancillary ligands L show a minor influence on the emission energies of the neutral compounds, but affect dramatically the intensity of luminescence. In contrast, the cationic species with diimine ligands demonstrate a significant contribution of the LL fragments into the emissive T1 states that leads to a certain mixing of 3IL and 3LL′CT transitions and causes a substantial bathochromic shift of emission.

E. G. Vlakh, E. V. Grachova, D. D. Zhukovsky, A. V. Hubina, A. S. Mikhailova, J. R. Shakirova, V. V. Sharoyko, S. P. Tunik, T. B. Tennikova

“Self-assemble nanoparticles based on polypeptides containing C-terminal luminescent Pt-cysteine complex”

Scientific Reports, 2017, 7, Article number 41991
DOI: 10.1038/srep41991

The growing attention to the luminescent nanocarriers is strongly stimulated by their potential application as drug delivery systems and by the necessity to monitor their distribution in cells and tissues. In this communication we report on the synthesis of amphiphilic polypeptides bearing C-terminal phosphorescent label together with preparation of nanoparticles using the polypeptides obtained. The approach suggested is based on a unique and highly technological process where the new phosphorescent Pt-cysteine complex serves as initiator of the ring-opening polymerization of α-amino acid N-carboxyanhydrides to obtain the polypeptides bearing intact the platinum chromophore covalently bound to the polymer chain. It was established that the luminescent label retains unchanged its emission characteristics not only in the polypeptides but also in more complicated nanoaggregates such as the polymer derived amphiphilic block-copolymers and self-assembled nanoparticles. The phosphorescent nanoparticles display no cytotoxicity and hemolytic activity in the tested range of concentrations and easily internalize into living cells that makes possible in vivo cell visualization, including prospective application in time resolved imaging and drug delivery monitoring.