Now showing 1 - 3 of 3
  • Publication
    Excited state localization and internuclear interactions in asymmetric Ruthenium (II) and Osmium (II) bpy/tpy based dinuclear compounds
    The synthesis of two asymmetric dinuclear complexes with the formula [M(bpy)2(bpt)Ru(tpy)Cl]2+, where M = Ru (1a), Os(2a); bpy = 2,2’-bipyridyl; Hbpt = 3,5-bis(pyridin-2-yl)1,2,4-triazole and tpy = 2,2’,6’,2”-terpyridine, is reported. The compounds obtained are characterized by mass spectrometry, 1H-NMR, UV/vis/NIR absorption, luminescence and resonance Raman spectroscopy. Deuterium isotope labeling facilitates assignment of the 1H-NMR and resonance Raman spectra. The interaction between the two metal centers, mediated by the bridging 1,2,4-triazolato moiety in the mixed valent state, is assigned as type II based on the observation of metal to metal charge transfer absorption bands at 7090 and 5990 cm-1 for 1a and 2a, respectively. The extent of localization of the emissive excited state was determined by transient resonance Raman and emission spectroscopy. Both 1a and 2a show phosphorescence at the same wavelengths; however, whereas for compound 1a the emission is based on the Ru(tpy)Cl- center, for 2a the emissive state is localized on the Os(bpy)2- unit. This indicates that also in the excited state there is efficient interaction between the two metal centers.
      607Scopus© Citations 25
  • Publication
    Spectroelectrochemical properties of homo- and heteroleptic ruthenium and osmium binuclear complexes : intercomponent communication as a function of energy differences between HOMO levels of bridge and metal centres
    A series of binuclear ruthenium and osmium complexes [(bipy)2Ru(qpy)Ru(bipy)2]4+ (1), [(bipy)2-Os(qpy)Os(bipy)2]4+ (2)[(bipy)2Ru(pytr-bipy)Ru(bipy)2]3+ (3), [(bipy)2Ru(pytr-bipy)Os(bipy)2]3+ (4), [(bipy)2Os(pytr-bipy)Ru(bipy)2]3+(5) and [(bipy)2Os(bpbt)Os(bipy)2]2+ (6) {bipy = 2,2¹-bipyridyl; qpy = 2,2¹:5¹,5¹¹:2¹¹,2¹¹¹-quaterpyridyl; pytr-bipy = 3-(2,2¹-bipyrid-6-yl)-5-(pyrid-2-yl)-1,2,4-triazolato, and bpbt = 5,5¹-bis-(pyrid-2¹¹-yl)-3,3¹-bis-1,2,4-triazolato} are reported. Analysis of the electrochemical data focuses on structural factors and on determining the extent of electronic communication between the metal centres in the mixed valence oxidation state. Intervalence charge transfer (IT) bands could be identified in the spectra of the complexes 4 and 6 only. Analysis of their spectroelectrochemical data leads to the conclusion that the IT is superexchange mediated through the HOMO of the bridging ligand.
      471Scopus© Citations 16
  • Publication
    Electrochemical characterization of NiO electrodes deposited via a scalable powder microblasting technique
    In this contribution a novel powder coating processing technique (microblasting) for the fabrication of nickel oxide (NiOx) coatings is reported. ~1.2 μm thick NiOx coatings are deposited at 20 mm2 s−1 by the bombardment of the NiOx powder onto a Ni sheet using an air jet at a speed of more than 180 m s−1. Microblast deposited NiOx coatings can be prepared at a high processing rate, do not need further thermal treatment. Therefore, this scalable method is time and energy efficient. The mechano-chemical bonding between the powder particles and substrate results in the formation of strongly adherent NiOx coatings. Microstructural analyses were carried out using SEM, the chemical composition and coatings orientation were determined by XPS and XRD, respectively. The electroactivity of the microblast deposited NiOx coatings was compared with that of NiOx coatings obtained by sintering NiOx nanoparticles previously sprayed onto Ni sheets. In the absence of a redox mediator in the electrolyte, the reduction current of microblast deposited NiOx coatings, when analyzed in anhydrous environment, was two times larger than that produced by higher porosity NiOx nanoparticles coatings of the same thickness obtained through spray coating followed by sintering. Under analogous experimental conditions thin layers of NiOx obtained by using the sol–gel method, ultrasonic spray- and electro-deposition show generally lower current density with respect to microblast samples of the same thickness. The electrochemical reduction of NiOx coatings is controlled by the bulk characteristics of the oxide and the relatively ordered structure of microblast NiOx coatings with respect to sintered NiOx nanoparticles here considered, is expected to increase the electron mobility and ionic charge diffusion lengths in the microblast samples. Finally, the increased level of adhesion of the microblast film on the metallic substrate affords a good electrical contact at the metal/metal oxide interface, and constitutes another reason in support of the choice of microblast as low-cost and scalable deposition method for oxide layers to be employed in electrochemical applications.
      801Scopus© Citations 29