http://www.cnr.it/ontology/cnr/individuo/prodotto/ID51138
Iridium terpyridine complexes as functional assembling units in arrays for the conversion of light energy (Articolo in rivista)
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- Label
- Iridium terpyridine complexes as functional assembling units in arrays for the conversion of light energy (Articolo in rivista) (literal)
- Anno
- 2008-01-01T00:00:00+01:00 (literal)
- Alternative label
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Lucia Flamigni, Jean-Paul Collin, Jean-Pierre Sauvage (literal)
- Pagina inizio
- Pagina fine
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
- Rivista
- Note
- ISI Web of Science (WOS) (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- Istituto ISOF-CNR, Via P. Gobetti 101, 40129 Bologna, Italy; Laboratoire de Chimie Organo-MineĀ“rale, UMR 7177 CNRS, UniversiteĀ“ Louis Pasteur, Institut Le Bel, 4 rue Blaise Pascal, 67070 Strasbourg, France (literal)
- Titolo
- Iridium terpyridine complexes as functional assembling units in arrays for the conversion of light energy (literal)
- Abstract
- In photosynthesis, sunlight energy is converted into a chemical
potential by an electron transfer sequence that is started by an
excited state and ultimately yields a long-lived charge-separated
state. This process can be reproduced by carefully designed multicomponent
artificial arrays of three or more components, and the
stored energy can be used to oxidize or reduce molecules in solution,
to inject electrons or holes, or to create an electron flow.
Therefore, the process is important both for artificial-photosynthesis
research and for photovoltaic and optoelectronic applications.
Molecular arrays for photoinduced charge separation often
use chromophores that resemble the natural ones. However, new
synthetic components, including transition metal complexes, have
had some success.
This Account discusses the use of bis-terpyridine (tpy) metal complexes
as assembling and functional units of such multicomponent
arrays. M(tpy)2
n+ complexes have the advantage of yielding linear
arrays with unambiguous geometry. Originally, Ru(tpy)2
2+ and
Os(tpy)2
2+ were used as photosensitizers in triads containing typical
organic donors and acceptors. However, it soon became evident
that the relatively low excited state of these complexes could act as
an energy drain of the excited state of the photosensitizer and, thus,
seriously compete with charge separation.
A new metal complex that preserved the favorable tpy geometry and yet had a higher energy level was needed. We
identified Ir(tpy)2
3+, which displayed a higher energy level, a more facile reduction that favored charge separation, a longer
excited-state lifetime, and strong spectroscopic features that were useful for the identification of intermediates. Ir(tpy)2
3+
was used in arrays with electron-donating gold porphyrin and electron-accepting free-base porphyrins. A judicious change
of the free-base porphyrin photosensitizer with zinc porphyrin allowed us to shape the photoreactivity and led to charge
separation with unity yield and a lifetime on the order of a microsecond.
In a subsequent approach, an Ir(tpy)2
3+ derivative was connected to an amine electron donor and a bisimide electron
acceptor in an array 5 nm long. In this case, the complex acted as photosensitizer, and long-lived charge separation over
the extremities (>100 ?s, nearly independent of the presence of oxygen) was achieved. The efficiency of the charge separation
was modest, but it was improved later, after a modification aiming at decoupling the donor and photosensitizer components.
This study represents an example of how the performances of an artificial photofunctional array can be modeled
by a judicious design assisted by a detailed knowledge of the systems. (literal)
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