Effektive Ladungstrennung in einem intermolekularen Komplex aus Elektronendonor und doppelarmiger Triade: ein Modellsystem für die Kontrolle des Elektronentransfers durch Umgebungseffekte
“…The second approach is in principle more close to nature since in the natural system the components are not directly linked but rather held together by a supramolecular structure involving the protein matrix. , Nevertheless this topic has been investigated to a limited extent. − The covalently linked systems 1 studied by various researchers are in principle linear systems of the type 1a . − Nature's system however consists of two branches, so the system 1b we have published as a model structure comes more close to the natural system (Scheme ). , 1 Schematic Drawing of Covalently Linked Model Compounds for the Photochemical Reaction Center: Unidirectional, 1a , and Our Bidirectional System, 1b …”
Mimicking the fundamental processes of the photosynthetic reaction center is a large field of research over
the past decade. We present as biomimetic model systems for electron transfer the mono- and heteroleptic
ruthenium complexes 2−9 containing differently substituted bipyridazine−glycol ligands. Depending on the
number of glycol chains of the complexes 2−9, they are divided into three classes: A (2 branches, 2−4); B
(3 branches, 5−6) and C (6 branches, 7−9). UV, fluorescence, single-photon counting, and laser flash
photolysis were employed as techniques for photophysical characterization. Redox properties were determined
using cyclic voltammetry. Detailed steady-state quenching studies of 2−9 with MV2+, OV2+, and MPVS
have shown different supramolecular interactions between sensitizer and acceptor in the case of MV2+. These
effects may be explained by π−π donor−acceptor attractions as well as hydrophobic interactions. Supporting
molecular modeling studies have been done. The suitability as biomimetic model systems was shown by
testing the ruthenium complexes 2−9 in artificial photosynthesis systems. Two typical reactions were
selected: the sacrificial reduction of water and the reduction of CO2 to CH4. The use of 2−9 leads to
satisfactory hydrogen production from the reduction of water. In the CH4/CO2 system, complexes 7−9 worked
efficiently.
“…The second approach is in principle more close to nature since in the natural system the components are not directly linked but rather held together by a supramolecular structure involving the protein matrix. , Nevertheless this topic has been investigated to a limited extent. − The covalently linked systems 1 studied by various researchers are in principle linear systems of the type 1a . − Nature's system however consists of two branches, so the system 1b we have published as a model structure comes more close to the natural system (Scheme ). , 1 Schematic Drawing of Covalently Linked Model Compounds for the Photochemical Reaction Center: Unidirectional, 1a , and Our Bidirectional System, 1b …”
Mimicking the fundamental processes of the photosynthetic reaction center is a large field of research over
the past decade. We present as biomimetic model systems for electron transfer the mono- and heteroleptic
ruthenium complexes 2−9 containing differently substituted bipyridazine−glycol ligands. Depending on the
number of glycol chains of the complexes 2−9, they are divided into three classes: A (2 branches, 2−4); B
(3 branches, 5−6) and C (6 branches, 7−9). UV, fluorescence, single-photon counting, and laser flash
photolysis were employed as techniques for photophysical characterization. Redox properties were determined
using cyclic voltammetry. Detailed steady-state quenching studies of 2−9 with MV2+, OV2+, and MPVS
have shown different supramolecular interactions between sensitizer and acceptor in the case of MV2+. These
effects may be explained by π−π donor−acceptor attractions as well as hydrophobic interactions. Supporting
molecular modeling studies have been done. The suitability as biomimetic model systems was shown by
testing the ruthenium complexes 2−9 in artificial photosynthesis systems. Two typical reactions were
selected: the sacrificial reduction of water and the reduction of CO2 to CH4. The use of 2−9 leads to
satisfactory hydrogen production from the reduction of water. In the CH4/CO2 system, complexes 7−9 worked
efficiently.
“…A particularly interesting and well-developed field for the application of modular approaches is the synthesis of photoredox-active assemblies to convert solar into chemical energy. Polypyridylruthenium compounds are well suited for these purposes and have been extensively used for studies in this context. − Meyer et al have reported a series of donor−acceptor complexes with a tris(2,2‘-bipyridine)ruthenium chromophore covalently attached to a lysine side chain. − Incorporation of this ruthenium unit into small peptides has been described also …”
Section: Introductionmentioning
confidence: 99%
“…Polypyridylruthenium compounds are well suited for these purposes and have been extensively used for studies in this context. [7][8][9][10][11][12][13][14][15][16][17] Meyer et al have reported a series of donoracceptor complexes with a tris(2,2′-bipyridine)ruthenium chro-mophore covalently attached to a lysine side chain. [18][19][20] Incorporation of this ruthenium unit into small peptides has been described also.…”
Synthetic amino acids suitable for the assembly of small,
redox-active metallopeptides are described.
N
α-((1,1-Dimethylethoxy)carbonyl)-N
ε-(2-pyridylmethyl)-l-lysine
(1),
N
α-acetyl-S-(2-pyridylmethyl)-l-cysteine
(2), and N
α-acetyl-S-(2-(2-pyridyl)ethyl)-l-cysteine
(3) have been synthesized by alkylation of the
N
α-protected amino acids.
Their [Ru(bipy)2]2+ complexes
[(bipy)2Ru(BocLysCH2py)]2+
(4),
[(bipy)2Ru(AcCysCH2py)]2+
(5), and [(bipy)2Ru(AcCys(CH2)2py)]2+
(6) have been prepared by reactions of the ligands with
[Ru(bipy)2Cl2]. On the basis
of
1H-NMR spectroscopy, 4−6 can be
described best as trans-tetrapyridine complexes with the
lysine amino N
atom and the cysteine S atom occupying one of the apical positions.
It was shown by luminescence spectroscopy
that 4 can serve as a possible photoredox-active module for
the construction of photochemically active peptides.
The redox properties of the complexes are described with the aid
of the Lever parameters. It was demonstrated
that the amino acid ligands in 5 and 6 can be
viewed as methionine units. Particularly interesting is the
unique
redox chemistry of 4. Upon metal oxidation, a
two-electron ligand oxidation occurred, followed by fast
hydrolytic
cleavage of the lysine−methylpyridine N−C bond. The physical
and chemical properties of the compounds are
discussed in terms of future applications in biomimetic chemistry such
as the activation of small molecules.
“…2 During the last three decades, extensive research efforts have been directed to adapt the principles of charge separation in the photosynthetic apparatus to artificial systems. Ingenious photosensitizer–electron acceptor chains in covalently linked molecular structures,3–6 supramolecular structures,7–9 or organized microenvironments10–12 have been reported as means to stimulate photoinduced vectorial electron transfer and to accomplish charge separation. The concept of vectorial electron transfer and enhanced charge separation was also adopted in semiconductor nanoparticle systems.…”
A change of direction: The intensity and direction of photocurrents in photosensitizer–electron acceptor dyads anchored to electrodes is controlled by the orientation and composition of the subunits. DNA templates attached to electrode surfaces act as scaffolds for the assembly of the dyads, which comprise either CdS nanoparticles or ruthenium(II) polypyridyl complexes in conjunction with viologen units that act as relays (see picture).
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