Intermedi dinucleari nella reazione di ossidazione del cobalto(II) in presenza di acido picolinico

The oxidation reaction of cobalt(II) with sodium peroxide in aqueous solution in the presence of picolinic acid was investigated by visible spectroscopy. It was possibie to put into evidence two $\mu$ -peroxo bridged species, with complexation ration L/M = 2:2 and 4:2 respectively (T = - 5°C, ionic strenght 1,2M by $NaCl0_4$ and pH 2,40). The conditional concentrations quotients at equilibrium and molar absorptivities were determined using some graphical methods

Spectrophotometric study of the reaction between cobalt(II)-dipeptide complexes and molecular oxygen

The influence of pH and ligand structure on the reaction of cobalt(II) complexes with various dipeptides and molecular oxygen was examined. The minimum pH value required for the formation of dioxygen adducts was found to be about 6.5. This value should be related to amidic deprotonation of dipeptides, which seems to occur in the examined systems at particularly low values. The location and steric hindrance of the side chains of the dipeptides have a strong influence on the reaction rate. The presence of a substituent group on the N-terminal amino acid promotes oxygen coordination, while, when the substituent group ts on the C-terminal residual, a decrease of reaction rate is observed. A stabilizing effect of the aromatic ring on the dioxygen adducts is found only when the substituent is in the C-terminal position, and seems to be independent of the presence of additional coordinating groups. Some information regarding the mechanism of the irreversible decomposition of the cobalt(II) complexes has been obtained by studying the effect of pH and ligand structure on the reaction rate

Il Chiostro di Santa Maria dell Pace

Il volume è una raccolta di rilievi, con un testo critico introduttivo, che documentano l'organismo architettonico del Chiostro di Santa Maria della Pace in Roma. La pubblicazione consiste di un album di tavole grafiche collazionate in folio, sul modello editoriale dei Monumenti d'Italia di Gustavo Giovannoni. L'opera è il primo numero di una collana dal titolo: Conoscenza e rappresentazione dell'Architettura. Architetture del Cinquecento a Roma. Editata per iniziativa dell'Associazione per il rilievo, lo studio e il restauro del patrimonio architettonico. Fanno parte del Comitato scientifico della Collana: Arnaldo Bruschi, Oward Burns,Christoph Frommel, Jean Guillame, Paolo Marconi, Manfredo Tafuri, Claudio Tiberi, Giuseppe Zander; compongono il comitato redazionale Tancredi Carunchio, Vittorio Ceradini, Stanislao Cocchia, Alessandra Palminteri, Laura Petroni,Antonio Pugliano

Complessi del cobalto (III) con il legante polimerico poli (4-vinilpiridina)

The preparation of a cobalt(IIT) complex with $Coen_2$ (en = ethylenediamine) units bound with two pyridine nitrogen atoms of two different polymeric chains of poly-(4-vynilpyridine) in trans position was performed. The obtained compound is insoluble in water as well as in the most usual organic solvents, while it has partial solubility in some others, such as dimethylsulfoxide. By elemental analysis it was found that for 12-13 average pyridine nitrogen atoms, one cobalt(III) atom is available