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11.
Fausto Puntoriero Scolastica Serroni Maurilio Galletta Alberto Juris Antonino Licciardello Claudio Chiorboli Sebastiano Campagna Franco Scandola 《Chemphyschem》2005,6(1):129-138
The new heptanuclear ruthenium(II) dendron, [Cl(2)Ru{(micro-2,3dpp)Ru[(micro-2,3-dpp)Ru(bpy)2]2}2](PF6)12 (1; 2,3-dpp=2,3-bis(2'-pyridyl)pyrazine; bpy = 2,2'-bipyridine), was prepared by means of the "complexes as ligands/complexes as metals" synthetic strategy, and its absorption spectrum, redox behavior, and luminescence properties were investigated. Compound 1 is a multicomponent species, which contains three different types of chromophores (namely, the {Cl(2)Ru(micro-2,3-dpp)2} core, the {Ru(micro-2,3dpp)3}2+ intermediate, and the {(bpy)2Ru(micro-2,3-dpp)}2+ peripheral subunits) and several redox-active sites. The new species exhibits very intense absorption bands in the UV region (epsilon value in the 10(5)-10(6) M(-1) cm(-1) range) as a result of spin-allowed ligand-centered (LC) transitions, and intense bands in the visible region (epsilon value in the 10(4)-10(5) M(-1) cm(-1) range) as a result of the various spin-allowed metal-to-ligand charge-transfer (MLCT) transitions. The redox investigation (accomplished by cyclic and differential pulse voltammetry) indicates that 1 undergoes a series of reversible metal-centered oxidation and ligand-centered reduction processes within the potential window investigated (+1.90 / -1.40 V vs. the standard calomel electrode, SCE). The assignment of each absorption bond and redox process to specific subunits of 1 was achieved by comparison with the properties of smaller multinuclear species of the same family, namely [Cl(2)Ru{(micro-2,3-dpp)Ru(bpy)2}2]4+ (2), [(bpy)2Ru(u-2,3-dpp)Ru(bpy)2]4+ (4), and [Ru{(micro-2,3-dpp)Ru(bpy)2}3]4+ (5). The title compound exhibits luminescence both at room temperature in acetonitrile fluid solution and at 77 K in butyronitrile rigid matrix. The emission is attributed to the triplet MLCT (3MLCT) state involving the core {Cl(2)Ru(micro-2,3-dpp)2} subunit. Interestingly, the 3MLCT levels involving the peripheral {(bpy)2Ru(micro-2,3-dpp)}2+ subunits are deactivated by energy transfer to the emitting level, in spite of the presence of interposed high-energy (Ru(micro-2,3-dpp)3}2+ components, which, in other dendrimers, acted as "isolating" subunits toward energy-transfer processes. Ultrafast experiments on 1 and on the parent species 2 and 5 allowed us to rationalize this behavior and highlight that a sequential two-step electron-transfer process can be held responsible for the efficient overall energy transfer, which offers a way to overcome a limitation in antenna metal dendrimers. 相似文献
12.
Galletta M Campagna S Quesada M Ulrich G Ziessel R 《Chemical communications (Cambridge, England)》2005,(33):4222-4224
The triplet emitting state of an indacene at 774 nm (of 50 ms life-time) was observed for the first time in new ruthenium(II) complexes based on bipartite ligands carrying one or two indacene subunits linked via phenylethynyl connectors to terpyridine fragments. 相似文献
13.
Ileana Ielo Giulia Rando Fausta Giacobello Silvia Sfameni Angela Castellano Maurilio Galletta Dario Drommi Giuseppe Rosace Maria Rosaria Plutino 《Molecules (Basel, Switzerland)》2021,26(19)
Relevant properties of gold nanoparticles, such as stability and biocompatibility, together with their peculiar optical and electronic behavior, make them excellent candidates for medical and biological applications. This review describes the different approaches to the synthesis, surface modification, and characterization of gold nanoparticles (AuNPs) related to increasing their stability and available features useful for employment as drug delivery systems or in hyperthermia and photothermal therapy. The synthetic methods reported span from the well-known Turkevich synthesis, reduction with NaBH4 with or without citrate, seeding growth, ascorbic acid-based, green synthesis, and Brust–Schiffrin methods. Furthermore, the nanosized functionalization of the AuNP surface brought about the formation of self-assembled monolayers through the employment of polymer coatings as capping agents covalently bonded to the nanoparticles. The most common chemical–physical characterization techniques to determine the size, shape and surface coverage of AuNPs are described underlining the structure–activity correlation in the frame of their applications in the biomedical and biotechnology sectors. 相似文献