Molekulare Programmierung von Helicität

Rowan, Alan E.; Nolte, Roeland J. M.

doi:10.1002/(sici)1521-3757(19980116)110:1/2<65::aid-ange65>3.0.co;2-k

Cited by 126 publications

(6 citation statements)

References 63 publications

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“…The formation of chiral aggregate structures was reported before for other systems. However, they were either grown on chiral templates such as DNA [72], or chirality was induced by external stimulus [73] or due to chirality of the molecules [74]. It is known, for example, that PIC molecules in solution are chiral due to a twist of the two quinoline-rings against each other which is either right-or left-handed [75].…”

Section: Chiralitymentioning

confidence: 99%

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

Kirstein¹,

Daehne

2006

International Journal of Photoenergy

132

225

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The simultaneous chemical linkage of cyanine dye chromophores with both hydrophobic and hydrophilic substituents leads to a new type of amphiphilic molecules with the ability of spontaneous self-organization into highly ordered aggregates of various structures and morphologies. These aggregates carry the outstanding optical properties of J-aggregates, namely, efficient exciton coupling and fast exciton energy migration, which are essential for the build up of artificial light harvesting systems. The morphology of the aggregates depends sensitively on the molecular structure of the chemical substituents of the dye chromophore. Accordingly, lamellar ribbon-like structures, vesicles , tubes, and bundles of tubes are found depending on the dyes and the structure can further be altered by addition of surfactants, alcohols, or other additives. Altogether the tubular structure is the most noticeable structural motif of these types of J-aggregates. The optical spectra are characterized in general by a complex exciton spectrum which is composed of several electronic transitions. The spectrum is red-shifted as a total with respect to the monomer absorption and exhibits resonance fluorescence from the lowest energy transition. For the tubular structures, the optical spectra can be related to a structural model. Although the molecules itself are strictly achiral, a pronounced circular dichroism (CD) is observed for the tubular aggregates and explained by unequal distribution of left- and right-handed helicity of the tubes. Photo-induced electron transfer (PET) reactions from the dye aggregates to electron acceptor molecules lead to superquenching which proves the delocalization of the excitation. This property is used to synthesize metal nanoparticles on the aggregate surface by photo-induced reduction of metal ions.

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Section: Chiralitymentioning

confidence: 99%

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

Kirstein¹,

Daehne

2006

International Journal of Photoenergy

132

225

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“…In artificial supramolecular architectures, helicity can be introduced by conformational restrictions of macromolecules, inter- or intramolecular hydrogen bonds, or coordination to metal ions. , …”

Section: Introductionmentioning

confidence: 99%

“Let's Twist Again”Double-Stranded, Triple-Stranded, and Circular Helicates

2001

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“…The formation of supramolecular architectures by self-assembly to obtain a well-defined microscopic organization and macroscopic characteristics is one main objective of supramolecular chemistry. − Controlling helicity, ,, in particular, has attracted strong interest because of the great opportunities for applications in material science, chemical sensing, and enantioselective catalysis. The spontaneous self-assembly of molecules into complex structures is the result of a multitude of effective noncovalent interaction processes such as hydrogen bonding, electrostatic, dipole−dipole, van der Waals, and solvophobic interactions.…”

Section: Introductionmentioning

confidence: 99%

“…The spontaneous self-assembly of molecules into complex structures is the result of a multitude of effective noncovalent interaction processes such as hydrogen bonding, electrostatic, dipole−dipole, van der Waals, and solvophobic interactions. A variety of artificial self-assembled chiral structures comprising helical fibers and twisted ribbons of sugars, phospholipids and gemini surfactants, helicenes, helical metal complexes, block copolymers, or the coiled aggregates of (crown ether phthalocyaninato) polysiloxanes have been created from chiral or racemic mixtures employing the spectrum of noncovalent interactions in their design. Despite the efforts and the success in design and synthesis, the detailed mechanism of chirality transfer from the chiral molecular building block to the chiral superstructure is often unknown.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Helicity of Tubular J-Aggregates by Chiral Alcohols

2003

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The achiral 3,3‘-bis(3-carboxypropyl)-5,5‘,6,6‘-tetrachloro-1,1‘-dioctylbenzimidacarbocyanine dye (C8O3) self-aggregates in aqueous solution to form optically active helical J-aggregates. A three-phasic circular dichroism (CD) spectrum with positive Cotton effect at 568 nm, negative Cotton effect at 582 nm, and positive Cotton effect at 605 nm (+,−,+) is usually found and ascribed to molecular excitons. The predominance of the (+,−,+) signature means that the generation of chirality is enantioselective. The CD signal increases by a factor of about 100 when the chiral (R)-2-octanol is added to an aggregated solution, and the CD signal is further amplified by a factor of about 5 when the alcohol is present in the solvent prior to aggregation. The signature of the CD signal reverses if the enantiomeric (S)-2-octanol is used instead, and for a molar alcohol/dye ratio R of about 20, the spectra become mirror images in good approximation; i.e., the chirality of the alcohol and the CD spectra of aggregates are correlated. The net effect of chiral alcohols is an increased excess of aggregates with a particular handedness due to induced circular dichroism. Samples containing (S)-2-octanol showed that their “reversed” CD spectra ((−,+,−) signature) are not fully stable when stored for longer times at ambient temperature. The spectral changes indicate a gradually increasing contribution from aggregates with the opposite sense of handedness ((+,−,+) signature). Electron micrographs reveal left helix handedness for the majority of aggregates in the presence of (R)-2-octanol ((+,−,+) signature), while right helix handedness predominates for the aggregates in the presence of (S)-2-octanol ((−,+,−) signature).

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Molekulare Programmierung von Helicität

Cited by 126 publications

References 63 publications

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

“Let's Twist Again”Double-Stranded, Triple-Stranded, and Circular Helicates

Controlling the Helicity of Tubular J-Aggregates by Chiral Alcohols

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