Encapsulated chromophores

Ultimately, the encapsulated chromophore must be interfaced with hole- and electron-transporting elements to afford an actual OLED device. In this context, a dendrimer is ideally suited since it not only provides steric protection (site... 

Figure 7.17 Luminescent hybrid materials with encapsulated chromophores...

Several behaviors have been explored for encapsulated units that extend beyond those discussed here. These are mentioned briefly to indicate the wide variety of roles that dendritic encapsulation can play. Fluorescence quenching of an encapsulated chromophore can be attenuated by reducing the relative accessibility of dioxygen (a small molecule)1-7 or larger units such as other chromophore-encapsulated... 

Furuta, R, J. Brooks, M.E. Thompson, and J.M.J. Frkhet. 2003. Simultaneous light emission from a mixture of dendrimer encapsulated chromophores A model for single-layer multichromophoric organic light-emitting diodes. J Am Chem Soc 125 13165-13172. 

Jen a al. have developed dendronized polymeric NEO materials that have shown significantly improved poling efficiency by encapsulating chromophore with dendritic substituents that can electronically shield the core, ii-electrons, and form spherical molecular shapes." "" " Figure 6 illustrates different molecular architectures of dendronized side-chain NLO polymers with crosslinkers. The diverse selections of molecular architectures provide additional flexibility in the molecular engineering of high-performance polymeric NLO materials. Moreover, the unique nanoscale environment created by the shape and size, dielectric properties, and distribution of chromophores in crosslinkable polymers with dendrons and dendrimers can all play critical roles in maximizing the macroscopic EO properties of polymeric NEO materials. 

Stability of the chromophore was observed usiag uv-vis spectroscopy, the authors conclude that this sol—gel method of chromophore encapsulation does not provide any real thermal or oxidative protection in either the covalendy or noncovalently bonded state. 

The encapsulating hexadentate ligand (148) forms [Ni(148)]2+ with a distorted octahedral geometry. This can be oxidized to a Ni111 species in which a substitution reaction by sulfate in the NiN6 chromophore is observed.514... 

Related to these dimetallic systems, though not involving transition metals, are the boratastilbene complexes such as a " [ H 5 C 5 B-CH =CH-CH 4 -C H =C H P h ]" (isoelectronic with distyrylbenzene chromophores) that show aggregation-dependent photophysics. In nonpolar solvents, they form tightly bound ion pairs that are poorly luminescent, but in polar solvents, or when the counter ions are encapsulated in crown ethers, strong emission is observed as a result of intramolecular charge transfer.130... 

Chromophoric change. UV/vis- or fluorescent-active and water-soluble chromophores such as pyranine and carboxyfluorescein are encapsulated in... 

Related complexes where two ligands encapsulate the lanthanide center have been reported (38,39). Coordination of a second antenna ligand may increase the luminescence by excluding deactivating solvent molecules to date, however, photophysical studies for these complexes have not been published. A recent paper details ternary complexes with an additional chromophore, antipyrene (antipy)... 

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 ... 

Examination of the cyclic voltammetry (CV) of the Zn-porphyrin dendrimers in THF and CH2C12 with Bu4N+PF6 (0.1 m) electrolyte revealed first oxidation potentials up to 300 mV (THF) less positive than the corresponding values obtained for the unshielded tetraester, Zn-porphyrin core. These preliminary electrochemical experiments suggested dendritic encapsulation of redox-active chromophores can effectively influence the electrophone environment controlled and well-conceived cascade architecture can lead to new avenues of selective redox catalyst design. 

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