Spectroscopy and quantum-chemical calculations of nitro-bis-bipyridyl complexes of ruthenium(II) with 4-substituted pyridine ligands


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Abstract

The luminescence, absorption, and luminescence excitation spectra of complexes cis-[Ru(bpy)2(L)(NO2)]+ [bpy = 2,2′-bipyridyl, L = pyridine, 4-aminopyridine, 4-dimethylaminopyridine, 4-picoline, isonicotinamide, or 4,4′-bipyridyl] in alcoholic (4 : 1 EtOH–MeOH) solutions are studied at 77 K. A linear correlation is established between the energy of the lowest electronically excited metal-toligand charge transfer state dπ(Ru) → π*(bpy) of the complexes and the pKa parameter of the free 4-substituted pyridines used as ligands L. The B3LYP/[6-31G(d)+LanL2DZ(Ru)] hybrid density functional method is used to optimize the geometry of complexes and calculate their electronic structure and the charge distribution on the atoms of the nearest environment of ruthenium(II) ions. It is shown that there exists a mutually unambiguous correspondence between the charge on the nitrogen atom of ligands L coordinated in the complex and the pKa parameter of ligands. The calculated energies of the electronically excited metal-to-ligand charge transfer states of complexes linearly (correlation coefficient 0.99) depend on the charge on the nitrogen atom of ligands L, which completely agrees with the experimental data.

About the authors

K. I. Reshetova

Laboratory Photoactive Nanocomposite Materials

Email: chris_resh@mail.ru
Russian Federation, Peterhof, St. Petersburg, 198904

I. V. Krauklis

Faculty of Physics

Email: chris_resh@mail.ru
Russian Federation, Peterhof, St. Petersburg, 198904

S. V. Litke

Faculty of Physics

Email: chris_resh@mail.ru
Russian Federation, Peterhof, St. Petersburg, 198904

A. Yu. Ershov

Institute of Chemistry

Email: chris_resh@mail.ru
Russian Federation, Peterhof, St. Petersburg, 198904

Yu. V. Chizhov

Faculty of Physics

Author for correspondence.
Email: chris_resh@mail.ru
Russian Federation, Peterhof, St. Petersburg, 198904

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