Design and Photophysical Properties of Zinc(II) Porphyrin‐Containing Dendrons Linked to a Central Artificial Special Pair

Brégier, Frédérique; Aly, Shawkat M.; Gros, Claude P.; Barbe, Jean‐Michel; Rousselin, Yoann; Harvey, Pierre D.

doi:10.1002/chem.201101832

Cited by 29 publications

(30 citation statements)

References 91 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…14 for the dendrimer-containing species 3(Cu)-G x (G x = G 1 , G 2 , or G 3 ) in solution where the two waves are clearly marked by red bars. 18 The gap between the two is function of the distance between the two interacting Cu(II). Using a calibration relationship, the Cu … Cu separation is estimated be somewhere between 4.2 and 4.9 Å.…”

Section: Determination Of the Structure Of The Artificial Special Pairmentioning

confidence: 99%

“…G x = G 1 , G 2 , or G 3 (see structures above). Image modified from Brégier et al 18 . The spectral region where the component g Ќ usually appears is not shown.…”

Section: Fig 12mentioning

confidence: 99%

“…25). 18 On the basis of the positions of the 0−0 phosphorescence peaks, the role of the triplet donor and acceptor is assigned to the bis(copper(II)porphyrin) unit (DPX is the spacer and X-ray and EPR spectroscopy establish short interplanar distance and Cu···Cu separation) and zinc(II)porphyrin antenna, respectively (Fig. 26).…”

Section: Applications Of the Photophysical Concepts Related To Artifimentioning

confidence: 99%

“…Brégier et al 18 The mesityl substituents are used to avoid porphyrin stacking. Reproduced with permission from Wiley.…”

Section: Fig 25 Structures Of the Dendrimers 3(m)-g X Investigated Inmentioning

confidence: 99%

“…The thermal ellipsoids are shown at 50% probability. Image modified from Brégier et al18 Modified and reproduced with permission from Wiley.…”

mentioning

confidence: 99%

See 4 more Smart Citations

What can we learn from artificial special pairs?

HarveyPierre

2014

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

Plants and photosynthetic bacteria obtain their energy from sunlight or surrounding radiation. Their photosynthetic membranes are composed of a much elaborated series of antenna molecules based on chlorophylls or bacteriochlorophylls, carotenoids playing multiple roles, various electron transport accessories, and central special pairs. The latter components are the most difficult to mimic with exactitude because the structure−property relationship depends on many factors including interplanar distance, slip angle, substituents, metal, and axial ligand. To this list of factors to control with quasi-perfection, one should also add the thermal activation (i.e., temperature). Over the past 15 years or so (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013), an intensive collaboration with Professor Roger Guilard (Université de Bourgogne, Dijon) dealt with elucidating the role of each parameter to provide the best design of artificial special pairs capable of responding or behaving like the natural special pairs, namely with regards with the antenna effect. The latest feature is one of the defence mechanisms slowing down the rate for the primary electron transfer from the special pair to the electron transport accessories. This review highlights the advances in this challenging area of mimicry of the photophysical events in biological systems, namely the artificial special pairs designed in our laboratory for the antenna processes.Résumé : Les végétaux et les bactéries photosynthétiques puisent leur énergie dans la lumière du soleil ou les rayonnements environnants. Leurs membranes photosynthétiques sont composées d'une série complexe d'antennes, systèmes molécules formés de chlorophylles ou bactériochlorophylles, de caroténoïdes aux rôles multiples, de divers dispositifs de transport électronique et de paries centrales spéciales. Ces derniers composants sont les plus difficiles à reproduire avec précision car la relation entre structure et propriété dépend de nombreux facteurs parmi lesquels la distance interplanaire, l'angle de glissement, les substituants, le métal et le ligand axial. À cette liste de facteurs à contrôler avec quasi-perfection, il faut ajouter l'activation thermique (c.-à -d. la température). Au cours des 12 dernières années (plus exactement entre 2001 et 2013), une collaboration active avec le professeur Roger Guilard (de l'Université de Bourgogne, à Dijon) a eu pour objectif d'élucider le rôle de chacun des paramètres afin de concevoir, de façon optimale, des paires spéciales artificielles capables de réagir ou de se comporter comme les paires spéciales naturelles, notamment en ce qui concerne l'effet produit par les antennes. La dernière caractéristique est l'un des mécanismes de défense qui diminue le taux du transfert électronique primaire de la paire spéciale vers les dispositifs de transport électronique. La présente étude les avancées réalisées dans le domaine de la reproduction des phénomènes photophysiques présents dans les systèmes biologiques, en particulier la...

show abstract

Section: Determination Of the Structure Of The Artificial Special Pairmentioning

confidence: 99%

“…G x = G 1 , G 2 , or G 3 (see structures above). Image modified from Brégier et al 18 . The spectral region where the component g Ќ usually appears is not shown.…”

Section: Fig 12mentioning

confidence: 99%

Section: Applications Of the Photophysical Concepts Related To Artifimentioning

confidence: 99%

“…Brégier et al 18 The mesityl substituents are used to avoid porphyrin stacking. Reproduced with permission from Wiley.…”

Section: Fig 25 Structures Of the Dendrimers 3(m)-g X Investigated Inmentioning

confidence: 99%

“…The thermal ellipsoids are shown at 50% probability. Image modified from Brégier et al18 Modified and reproduced with permission from Wiley.…”

mentioning

confidence: 99%

See 3 more Smart Citations

What can we learn from artificial special pairs?

HarveyPierre

2014

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

Dendron to Central Core S₁–S₁ and S₂–S_n (n>1) Energy Transfers in Artificial Special Pairs Containing Dendrimers with Limited Numbers of Conformations

Harvey

Brégier

Aly

et al. 2013

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

Two dendrimers consisting of a cofacial free-base bisporphyrin held by a biphenylene spacer and functionalized with 4-benzeneoxomethane (5-(4-benzene)tri-10,15,20-(4-n-octylbenzene)zinc(II)porphyrin) using either five or six of the six available meso-positions, have been synthesized and characterized as models for the antenna effect in Photosystems I and II. The presence of the short linkers, -CH2O-, and long C8H17 soluble side chains substantially reduces the number of conformers (foldamers) compared with classic dendrimers built with longer flexible chains. This simplification assists in their spectroscopic and photophysical analysis, notably with respect to fluorescence resonance energy transfer (FRET). Both steady-state and time-resolved spectroscopic measurements indicate that the cofacial free bases and the flanking zinc(II)-porphyrin antennas act as energy acceptor and donor, respectively, following excitation in either the Q or Soret bands of the dendrimers. The rate constants for singlet electronic energy transfer (k(EET)) extracted from the S1 and S2 fluorescence lifetimes of the donor in the presence and absence of the acceptor are ≤ (0.1-0.3)×10(9) and ∼2×10(9) s(-1) for S1→S1 (range from a bi-exponential decay model) and about 1.5×10(12) s(-1) for S2→S(n) (n>1). Comparisons of these experimental data with those calculated from Förster theory using orientation factors and donor-acceptor distances extracted from computer modeling suggest that a highly restricted number of the many foldamers facilitate energy transfer. These foldamers have the lowest energy by molecular modeling and consist of one or at most two of the flanking zinc porphyrin antennas folded so they lie near the central artificial special pair core with the remaining antennas located almost parallel to and far from it.

show abstract

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

Nikkonen

Oliva

Kahnt

et al. 2014

Chemistry A European J

View full text Add to dashboard Cite

In the present study, a biomimetic reaction center model, that is, a molecular triad consisting of a chlorin dimer and an azafulleroid, is synthesized and its photophysical properties are studied in comparison with the corresponding molecular dyad, which consists only of a chlorin monomer and an azafulleroid. As evidenced by (1) H NMR, UV/Vis, and fluorescence spectroscopy, the chlorin dimer-azafulleroid folds in nonpolar media into a C2 -symmetric geometry through hydrogen bonding, resulting in appreciable electronic interactions between the chlorins, whereas in polar media the two chlorins diverge from contact. Femtosecond transient absorption spectroscopy studies reveal longer charge-separated states for the chlorin dimer-azafulleroid; ≈1.6 ns in toluene, compared with the lifetime of ≈0.9 ns for the corresponding chlorin monomer-azafulleroid in toluene. In polar media, for example, benzonitrile, similar charge-separated states are observed, but the lifetimes are inevitably shorter: 65 and 73 ps for the dimeric and monomeric chlorin-azafulleroids, respectively. Nanosecond transient absorption and singlet oxygen phosphorescence studies corroborate that in toluene, the charge-separated state decays indirectly via the triplet excited state to the ground state, whereas in benzonitrile, direct recombination to the ground state is observed. Complementary DFT studies suggest two energy-minima conformations, that is, a folded chlorin dimer-azafulleroid, which is present in nonpolar media, and another conformation in polar media, in which the two hydrophobic chlorins wrap the azafulleroid. Inspection of the frontier molecular orbitals shows that in the folded conformation, the HOMO on each chlorin is equivalent and is shared owing to partial π-π overlap, resulting in delocalization of the conjugated π electrons, whereas the wrapped conformation lacks this stabilization. As such, the longer charge-separated lifetime for the dimer is rationalized by both the electron donor-acceptor separation distance and the stabilization of the radical cation through delocalization. The chlorin folding seems to change the photophysical properties in a manner similar to that observed in the chlorophyll dimer in natural photosynthetic reaction centers.

show abstract

Design and Photophysical Properties of Zinc(II) Porphyrin‐Containing Dendrons Linked to a Central Artificial Special Pair

Cited by 29 publications

References 91 publications

What can we learn from artificial special pairs?

What can we learn from artificial special pairs?

Dendron to Central Core S₁–S₁ and S₂–S_n (n>1) Energy Transfers in Artificial Special Pairs Containing Dendrimers with Limited Numbers of Conformations

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

Contact Info

Product

Resources

About

Design and Photophysical Properties of Zinc(II) Porphyrin‐Containing Dendrons Linked to a Central Artificial Special Pair

Cited by 29 publications

References 91 publications

What can we learn from artificial special pairs?

What can we learn from artificial special pairs?

Dendron to Central Core S1–S1 and S2–Sn (n>1) Energy Transfers in Artificial Special Pairs Containing Dendrimers with Limited Numbers of Conformations

Photoinduced Charge Transfer in a Conformational Switching Chlorin Dimer–Azafulleroid in Polar and Nonpolar Media

Contact Info

Product

Resources

About

Dendron to Central Core S₁–S₁ and S₂–S_n (n>1) Energy Transfers in Artificial Special Pairs Containing Dendrimers with Limited Numbers of Conformations