6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

J-aggregates are of significant interest for organic materials conceived by supramolecular approaches. Their discovery in the 1930s represents one of the most important milestones in dye chemistry as well as the germination of supramolecular chemistry. The intriguing optical properties of J-aggregates (in particular, very narrow red-shifted absorption bands with respect to those of the monomer and their ability to delocalize and migrate excitons) as well as their prospect for applications have motivated scientists to become involved in this field, and numerous contributions have been published. This Review provides an overview on the J-aggregates of a broad variety of dyes (including cyanines, porphyrins, phthalocyanines, and perylene bisimides) created by using supramolecular construction principles, and discusses their optical and photophysical properties as well as their potential applications. Thus, this Review is intended to be of interest to the supramolecular, photochemistry, and materials science communities.

J-aggregates: from serendipitous discovery to supramolecular engineering of functional dye materials.

Publisher Summary This chapter describes that the oligopeptides netropsin and distamycin A are bound to (dA.dT) rich regions of DNA through hydrogen bonding and van der Waals forces representing probably strong binding reactions. The abundance of (dG.dC) pairs gives rise to a weak type of binding as a result of lower hydrogen-bonding efficiency, and thus increased sensitivity to ionic environment appears. Tight binding occurs without intercalation. A suggestion for a possible hydrogen-bonding scheme of the netropsin DNA complex is presented in the chapter. Full understanding of the process of interaction between the oligopeptide antibiotics and DNA needs further intensive investigations. The chapter describes that the specificity and efficiency of the oligopeptide interaction seem to be strongly dependent on helical conformation. Tight binding fully explains the template inactivation of DNA in DNA-dependent DNA- and RNA-polymerase systems, but biological effects, such as antiviral activity or interference with multiplication of phage particles, are only partially explained by direct blocking of DNA. It also reviews that DNA and the exclusion of similar interactions with RNA, single stranded DNA and presumably with basic proteins imply usefulness in studies of nucleoproteins and in the elucidation of specific interactions in enzyme-DNA and repressor-operator systems. Finally, possible structural alterations may generate new applications. If it were possible to connect the netropsin-type structure with a suitable oligopeptide containing natural amino acids, one should expect novel modifications in binding properties.

Effects of the antibiotics netropsin and distamycin A on the structure and function of nucleic acids.

J-Aggregate sind von Interesse fur organische Materialen, die mithilfe supramolekularer Ansatze konzipiert werden. Ihre Entdeckung in den 1930er Jahren war ein Meilenstein der Farbstoffchemie und ein Startpunkt fur die supramolekulare Chemie. Die interessanten optischen Eigenschaften von J-Aggregaten (besonders ihre sehr schmalen, im Vergleich zu denen des Monomers rotverschobenen Absorptionsbanden und ihre Fahigkeit zur Delokalisierung und zum Transport von Excitonen) sowie das daraus resultierende Anwendungspotenzial motivierten Wissenschaftler, sich mit J-Aggregaten zu befassen, weshalb bereits zahlreiche Beitrage zu diesem Gebiet veroffentlicht wurden. Dieser Aufsatz gibt einen Uberblick uber nach supramolekularen Konstruktionsprinzipien hergestellte J-Aggregate verschiedener Farbstoffklassen (darunter Cyanine, Porphyrine, Phthalocyanine und Perylenbisimide) und diskutiert ihre optischen und photophysikalischen Eigenschaften sowie ihre Anwendungsperspektiven. Damit sollte dieser Ubersichtsartikel fur die supramolekulare und Photochemie wie auch die Materialwissenschaften von Interesse sein.

J‐Aggregate: von ihrer zufälligen Entdeckung bis zum gezielten supramolekularen Aufbau funktioneller Farbstoffmaterialien

Useful theories and models of the color and constitution of unsaturated organic compounds have been sought for more than a century. The promises of quantum chemistry have not yet been realized satisfactorily. The polymethine concept, a modern chemical theory of constitution, is an auspicious development.

https://science.sciencemag.org/content/sci/199/4334/1163.full.pdf

Color and Constitution: One Hundred Years of Research

In Farbstoffmolekulen, die zwei und mehr Polymethin-Strukturelemente, oder wenigstens ein Polymethin- und ein Polyen-Strukturelement enthalten, treten in der Regel Kopplungseffekte auf, die das spektroskopische Verhalten und andere physikalisch-chemische Eigenschaften bestimmen. Mit Hilfe der Kopplungskonzeption konnen u.a. die Chinonfarbstoffe, die Indigoide und die Indanthrene in ein allgemeines Farbsystem der Polymethine eingeordnet und neue Farbstoffstrukturen vorhergesagt werden.

D. Leupold

Papers

Kopplungsprinzipien organischer Farbstoffe