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Titolo:
COUNTERION EFFECTS IN THE SPECTRA AND STRUCTURE OF SOLVATOCHROMIC COPPER(II) CHELATES CONTAINING 1,2-DIAMINES AND BETA-KETOENOLS
Autore:
TSIAMIS C; TZAVELLAS LC;
Indirizzi:
UNIV THESSALONIKI,DEPT CHEM GR-54006 SALONIKA GREECE
Titolo Testata:
Inorganica Chimica Acta
fascicolo: 2, volume: 207, anno: 1993,
pagine: 179 - 190
SICI:
0020-1693(1993)207:2<179:CEITSA>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
METAL-COMPLEXES; SOLVENTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
60
Recensione:
Indirizzi per estratti:
Citazione:
C. Tsiamis e L.C. Tzavellas, "COUNTERION EFFECTS IN THE SPECTRA AND STRUCTURE OF SOLVATOCHROMIC COPPER(II) CHELATES CONTAINING 1,2-DIAMINES AND BETA-KETOENOLS", Inorganica Chimica Acta, 207(2), 1993, pp. 179-190

Abstract

The contemporaneous reaction of copper(II) 'salts' with certain beta-diones and N-substituted 1,2-diaminoethanes (enR) is reported. The influence of gamma-position derivatives of 2,4-pentanedione, X-acacH (X=H, CN, NO2), is described and the contribution of anions to the stability, the stereochemistry and the electronic structure of the resulting mixed-ligand chelates is discussed. Spectroscopic observations disclose that the bidentate ligands form chelate rings with copper(II) as common vertex. Whenever the [Cu(beta-dionato)enR]+ entity pertains, the IR and the electronic excitation spectra, in conjunction with other physicochemical measurements, suggest that the CuN2O2 chromophore attainsa virtually square-planar structure. Copper(II) in the [Cu(beta-dionato)enR]+ entity lacks coordination saturation and, in addition to electrostatic interactions that prevail when bulky polyatomic anions counterbalance the positive charge, it is capable of forming covalent bondswith neutral molecules and charged species such as the halides and pseudohalides. The basal CuN202 plane is distorted upon coordination of unidentate ligands residing on the apex of the resulting square-pyramidal structure. Further increase in the coordination number of copper(II) by bidentate anions or neutral molecules leads to tetragonally distorted octahedral structures. This change in the symmetry of the field induced on copper(II) is revealed by spectral shifts that also disclose covalent interactions in the encounters of the CuN202 chromophore with polar or polarisable molecules. These interactions are enhanced with increasing ability of the attacking species to act as an electron pair donor. Linear dependence of the ligand field excitation maxima on the donicity of the attacking species is established. Rearrangement involving rapture of the Cu-0 bond and formation of the CuN4 chromophore accompanies the addition of NN-dimethylethylenediamine, Me2en, to Cu(CN-acac)2. The charge in the resulting [Cu(Me2en)2]2+ entity is neutralised by the anion of the 3-cyano-2,4-pentanedione, CN-acac-, that binds to copper(II) through the nitrogen atom coordinating as nitrile. Thecoordination of a beta-ketoenol as unidentate ligand through an atom other than oxygen or carbon has no precedence.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 03/12/20 alle ore 16:09:21