Acoplamiento electronico en compuestos de valencia mixta del grupo VIII, puenteados por cianuro [recurso electronico] = Electronic coupling in mixed valence cyanide bridged group VIII compounds / Melina Brenda Rossi ; director: Luis M. Baraldo Victorica.

Format:

Book

Thesis/Dissertation

Author/Creator:

Rossi, Melina Brenda.

Contributor:

Baraldo Victorica, Luis M, dir.

Language:

Spanish

Subjects (All):

Quimica inorganica.

Chemistry, Inorganic.

Local Subjects:

Quimica inorganica.

Chemistry, Inorganic.

Other Title:

Electronic coupling in mixed valence cyanide bridged group VIII compounds

Place of Publication:

Buenos Aires, Argentina : Universidad de Buenos Aires, 2011.

Summary:

En este trabajo se desarrolla la sintesis, la caracterizacion estructural y el estudio de las propiedades espectroscopicas y electroquimicas de una familia de compuestos dinucleares y trinucleares del grupo VIII, puenteados por el ligando cianuro. El objetivo principal es estudiar el acoplamiento electronico entre los centros metalicos y maximizar dicha interaccion, ajustando las variables mas determinantes. La reaccion directa entre monomeros de Ru(II), conteniendo piridinas de basicidad variable, y un hexacianometalato (III) (Fe(III) o Co(III), da lugar a dimeros de formula trans-[(L)RuII(py)4(?-NC)FeIII(CN)5]- y [RuII(DMAP)5(?-NC)MIII(CN)5]-, segun la identidad del fragmento central. La interpretacion de las propiedades espectroscopicas, haciendo uso del modelo de dos estados de Mulliken - Hush, revela que estos sistemas aumentan la interaccion metal - metal, a medida que ambos fragmentos se acercan en energia. Aun asi, se observa que todos ellos pertenecen a la Clase II, segun la clasificacion de Robin - Day, siendo dominante la configuracion [RuII-FeIII]. Sin embargo, el comportamiento espectroscopico observado para el dimero [RuII(DMAP)5(?-NC)FeIII(CN)5]- y el trimero de valencia mixta [(CN)5FeII(?-CN)RuII(DMAP)5(?-NC)FeIII(CN)5]5-, en metanol, evidenciando un incremento en la comunicacion electronica entre los centros metalicos, propicio la preparacion de compuestos conteniendo osmio, bajo el supuesto de que la mayor extension radial de los orbitales d del osmio incrementaria la mezcla metal - metal. De esta forma, se prepararon y estudiaron los sistemas trinucleares, de formula [(CN)5OsIII(?-CN)RuII(DMAP)5(?-NC)MIII(CN)5]4- (M: Co(III), Os(III), Fe(III)). La estructura cristalina de estos compuestos evidencia la presencia de arreglos lineales. Las distancias de enlace en el sistema simetrico sugieren una interaccion extendida a lo largo del eje internuclear. Las propiedades espectroscopicas de los sistemas asimetricos revelan que la interaccion rutenio - osmio es la que domina. El sistema simetrico, en metanol, presenta un comportamiento proximo a la delocalizacion electronica (Clase III). Sin embargo, la especie de valencia mixta no exhibe un incremento en el acoplamiento donor - aceptor, debido a la fuerte interaccion entre el fragmento {OsII(CN)5} y el solvente, desacoplando la interaccion extendida a lo largo del eje internuclear. Estos resultados establecen un limite de maxima interaccion para estos sistemas.

This work explores the synthesis, structural caharactarization and the electrochemical and spectroscopic behavior of a family of mixed valence cyanide - bridged dinuclear and trinuclear compounds, containing transition metals of group VIII. The aim of this work is to study the electronic coupling between the metal centres and try to enhance the interaction among them. The reaction of trans-[(L)RuII(py)4Cl]+ or [RuII(DMAP)5(OH)]+complexes with an hexacyanometallate (III) of Fe(III) or Co(III) results in the formation of a family of dinuclear compounds, with molecular formula trans-[(L)RuII(py)4(?-NC)FeIII(CN)5]- or [RuII(DMAP)5(?-NC)MIII(CN)5]-, according to the identity of the ruthenium moiety. The electronic spectroscopy of these compounds show MMCT bands, which are treated according with the Mulliken - Hush two states model approach. Even though results show that the metal - metal interaction is enhanced, as the metal centres come closer, all of these compounds belong to Class II, according to Robin - Day classification, indicating a ground state with [RuII-FeIII] character. However, the spectroscopic behavior of the dinuclear compound [RuII(DMAP)5(?-NC)MIII(CN)5]- as well as the mixed valence trinuclear compound [(CN)5FeII(?-CN)RuII(DMAP)5(?-NC)FeIII(CN)5]5-, in methanol, showing an even higher electronic communication among the metal centres, encouraged the synthesis of a family of trinuclear osmium compounds, with molecular formula [(CN)5OsIII(?-CN)RuII(DMAP)5(?-NC)MIII(CN)5]4- (M: Co(III), Os(III), Fe(III)), given the fact that the more extended osmium d orbitals would give rise to an enhanced mixing between the metal moieties. The crystalline structure of these compounds reveals a linear configuration among the metallic centres. The remarkable bond lengths observed for the symmetric osmium compound suggest an extended metal - metal interaction. The spectroscopic properties of the non - symmetric compounds reveal a higher mixing between the ruthenium - osmium metal moieties. As for the symmetric compound, it ?s behavior in a methanolic solution shows some degree of electronic delocalization. Nevertheless, the mixed valence species does not show an enhanced mixing, due to the stronger interaction among the {OsII(CN)5} moiety and the solvent molecules, precluding the extended electronic communication. These results may settle a higher limit of interaction between these metal moieties.

Notes:

Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales.

OCLC:

811372031