Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium

The (2,2′-bipyrazine)ruthenium(II)- and (2,2′-bipyridine)osmium(II)-tetracyanide complexes were prepared as sodium and potassium salts, respectively. Assignments of the MLCT (dπ(M) →- p(L-L)) and IL (π(L-L) → π(L-L)) bands were performed analyzing spectra in aqueous solution and in organic solvents....

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Autores principales: Posse, M.E.G., Katz, N.E., Baraldo, L.M., Polonuer, D.D., Colombano, C.G., Olabe, J.A.
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Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00201669_v34_n7_p1830_Posse
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00201669_v34_n7_p1830_Posse2023-10-03T14:16:42Z Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium Posse, M.E.G. Katz, N.E. Baraldo, L.M. Polonuer, D.D. Colombano, C.G. Olabe, J.A. The (2,2′-bipyrazine)ruthenium(II)- and (2,2′-bipyridine)osmium(II)-tetracyanide complexes were prepared as sodium and potassium salts, respectively. Assignments of the MLCT (dπ(M) →- p(L-L)) and IL (π(L-L) → π(L-L)) bands were performed analyzing spectra in aqueous solution and in organic solvents. Upon changing the solvent, we detected strong solvatochromic shifts, the energies of the MLCT bands going to lower values when the Lewis acidity of the solvent (measured by the Gutmann’s acceptor number) was decreased. Redox potential values for the Ru(III,II) and Os(III,II) couples were also solvent-dependent, decreasing with the decrease in acceptor number. The basicities of coordinated cyanides toward the proton were measured through spectrophotometric titrations; the pKa values so obtained, together with the IR measurements in the C-N stretching region (in solid samples and in organic solvents), and the potentials for ligand (L-L) reduction (in dimethylformamide solutions) were used as additional indicators of the s-p bonding interactions. Bipyrazine behaves as a stronger p-acceptor than bipyridine for a given metal center. On the other hand, for the same ligand environment, the Os(II) metal center behaves as a stronger p-donor compared to ruthenium and iron. The p-acceptor ability of the chelating ligand is enhanced in weakly acceptor solvents, associated with the changes in specific cyanide-solvent interactions. The complexes emit poorly in aqueous solutions at room temperature, with low quantum yields, as predicted by the potentials of the M(III,II) couples. The excited states are very strong reductants, as well as very weak oxidants. © 1995, American Chemical Society. All rights reserved. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00201669_v34_n7_p1830_Posse
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description The (2,2′-bipyrazine)ruthenium(II)- and (2,2′-bipyridine)osmium(II)-tetracyanide complexes were prepared as sodium and potassium salts, respectively. Assignments of the MLCT (dπ(M) →- p(L-L)) and IL (π(L-L) → π(L-L)) bands were performed analyzing spectra in aqueous solution and in organic solvents. Upon changing the solvent, we detected strong solvatochromic shifts, the energies of the MLCT bands going to lower values when the Lewis acidity of the solvent (measured by the Gutmann’s acceptor number) was decreased. Redox potential values for the Ru(III,II) and Os(III,II) couples were also solvent-dependent, decreasing with the decrease in acceptor number. The basicities of coordinated cyanides toward the proton were measured through spectrophotometric titrations; the pKa values so obtained, together with the IR measurements in the C-N stretching region (in solid samples and in organic solvents), and the potentials for ligand (L-L) reduction (in dimethylformamide solutions) were used as additional indicators of the s-p bonding interactions. Bipyrazine behaves as a stronger p-acceptor than bipyridine for a given metal center. On the other hand, for the same ligand environment, the Os(II) metal center behaves as a stronger p-donor compared to ruthenium and iron. The p-acceptor ability of the chelating ligand is enhanced in weakly acceptor solvents, associated with the changes in specific cyanide-solvent interactions. The complexes emit poorly in aqueous solutions at room temperature, with low quantum yields, as predicted by the potentials of the M(III,II) couples. The excited states are very strong reductants, as well as very weak oxidants. © 1995, American Chemical Society. All rights reserved.
format JOUR
author Posse, M.E.G.
Katz, N.E.
Baraldo, L.M.
Polonuer, D.D.
Colombano, C.G.
Olabe, J.A.
spellingShingle Posse, M.E.G.
Katz, N.E.
Baraldo, L.M.
Polonuer, D.D.
Colombano, C.G.
Olabe, J.A.
Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
author_facet Posse, M.E.G.
Katz, N.E.
Baraldo, L.M.
Polonuer, D.D.
Colombano, C.G.
Olabe, J.A.
author_sort Posse, M.E.G.
title Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
title_short Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
title_full Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
title_fullStr Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
title_full_unstemmed Comparative Bonding and Photophysical Properties of 2,2′-Bipyridine and 2,2′-Bipyrazine in Tetracyano Complexes Containing Ruthenium and Osmium
title_sort comparative bonding and photophysical properties of 2,2′-bipyridine and 2,2′-bipyrazine in tetracyano complexes containing ruthenium and osmium
url http://hdl.handle.net/20.500.12110/paper_00201669_v34_n7_p1830_Posse
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