Electroactive chromophores

Dandliker, P. J. Diederich, F. Gross, M. Knobler, C. B. Louati, A., Sanford, E., (1994) Dendritic porphyrins Modulating redox potentials of electroactive chromophores with pendant multifunctionality ... 

Diederich et al.11921 reported the divergent synthesis of dendrimers possessing porphyrin cores with the aim of modeling redox potentials of electroactive chromophores via environmental polarity modification. The dendrimers thus can be considered as electron-transfer protein mimics for such proteins as cytochrome c oxidation potentials for cytochrome c in aqueous solution are known to be 300-400 mV more positive than those reported for similarly ligated heme mimics lacking hydrophobic peptide encapsulation J193a ... 

A recording technique of holograms and the non-destructive readout in a photorefractive polymer, utilizes two-photon absorption. The holograms are formed through the photorefractive effect. The technique uses the excitation of the electroactive chromophore with femtosecond pulses, followed by charge injection into a PVK matrix. The holograms can be fully erased with a pulsed laser beam. However, they are insensitive to continuous wave laser beams with the same wavelength. 

Dandliker PJ, Diederich F, Gross M, Knobler CB, Louati A, Sanford EM (1994) Dendritic porphyrins modulating redox potentials of electroactive chromophores with pendant multifunctionality. Angew Chem Int Ed 33(17) 1739-1742... 

Dendritic molecules with electroactive units at either the focal point or core have been reported [92, 97]. There are, however, only a few examples of such moieties specifically pinned within cascade infrastructure. Our recent efforts in this direction [104-106] involve the incorporation of chromophoric 1,4-di-aminoanthraquinone (35) within the cascade infrastructure. Dendrimers based on a four-directional pentaerythritol core were synthesized using the extended 1 — 3 building block 36. A high dilution technique was applied to synthesize 36... 

The determination of endogenous compounds and drugs in biological matrices has always presented a formidable challenge as one has to consider various factors before attempting to develop a suitable HPLC assay. These include the physicochemical properties of the compound such as the pKa value, solubility, volatility, particular functional groups (e.g., possessing chromophores, fluorophores, or electroactive characteristics), potential metabolites, and the required sensitivity and specificity. All these aspects will determine the type of extraction processes, analytical column selection, and suitable detector systems to be used as part of the HPLC apparatus. 

The attention devoted to supramolecular sensitizers containing multifold chromophoric and electroactive centers arises from the construction of molecular devices based on nanometric and well-defined molecular architectures [4]. The use of these species for sensitization of titanium dioxide has provided fundamental insights into interfacial electron-transfer processes. 

An island dff-pff bond structure may explain why most polyphosphazenes are colorless rather than colored materials, and are insulators rather than electronic conductors. Exceptions do exist, but the exceptions are for polymers that have chromophores in the side groups or which bear electroactive side units. 

It is widely known that electrochemical detection can be used as an alternative for the analysis of drug substances that have no chromophores, but do have electroactive sites such as quaternary ammonium groups. Rocuronium bromide is an N-substituted piperazine, which has an electroactive center and therefore enables the use of electrochemical detection [26, 28]. Moroever, this detection method leads to the observation acceptable sensitivity and selectivity in compound analysis, and can be used without prior derivatization [14],... 

When such photo switching chromophores are immobilized on an electrode, vectorial electron flow from the electrode to electroactive species in solution can be controlled by photoirradiation.[37,38] Using an n-octadecanethiol-modified gold electrode incorporated with diarylethene 28a, it was possible to switch vectorial electron transport from the electrode to hexacyanoferrate(m) in solution by photoirradiation. 

In this chapter, we intend to revise the most recent contributions to the aforementioned aspects of Pc research. We will describe how the versatile chemistry of Pcs makes possible the preparation of monofunctionalized macrocycles, mainly aimed at preparing multicomponent systems through reaction with other electroactive moieties. The controlled organization of Pcs in solution and the incorporation of these chromophores into macromolecular structures, as well as the preparation of mono-, bi-, and three-dimensional nanostructures, will be the object of study. Finally, some examples of Pc-based devices (solar cells, sensors, transistors, etc.) will also be given as an example of the real applicability of these molecules. 

The detection of carbohydrates in chromatographic effluent has traditionally been a difficult problem due to the lack of a suitable chromophore or electroactive functionality. As a result, detection has typically been based on derivatization to form a chromophore, refractive index or UV detection at low wavelengths. Each of these approaches has inherent drawbacks which renders them less than satisfactory where sensitivity is of concern. If one considers the thermodynamics of carbohydrate oxidation, one would predict they are relatively easy to oxidize. In fact, the direct heterogeneous oxidation at conventional electrode materials (i.e. carbon, platinum or gold) does not occur due to kinetic constraints. 

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