Multicomponent arrays

Keywords Iridium complexes Cyclometalating ligands Phosphorescence Electrochemistry Multicomponent arrays OLEDs Photoinduced processes... 

In this work, we will review the optical, and to some extent, the electrochemical properties, of selected subfamilies of Ir(III) complexes. This will be done having in mind mainly (i) the actual interest in the manipulation and tuning of the photophysical properties of complexes playing as phosphorescence emitters, (ii) the possible use of Ir(III) centers as templating units for multicomponent arrays, particularly in view of charge separation (CS) schemes for the interconversion of light and chemical energy. 

We can now consider specific examples of micellar influence on the course of photoinduced electron transfer [25, 26]. The simplest photoinduced electron transfer involves photoionization, i.e., the transfer of an electron from the excited state of a solute to the solvent. The next level of complexity involves electron transfer from an excited donor to an acceptor or from an excited acceptor to a donor. Such reactions can occur either within a photoinert micelle, in a functionalized assembly, or through multicomponent arrays. 

We will review here work wherein several types of species incorporate the Ir-bis-terpy unit and derivatives. The search for multicomponent arrays, including metal-based photoactive centres in combination with electron donor and acceptor components, was started a couple of decades ago, and one of the first systems, compound 14+, was studied by Meyer et al. (Fig. 1) [5]. In this multicomponent system, the electron donor phenothiazine (PTZ) and the bridged 2,2/-bipyridinium (DQ) units are linked to the photoactive unit by flexible methylene connections. In this early example, excitation at the Ru-based chromophore ultimately yields a PTZ+-DQ" CS state which lives 165 ns and for which the transiently stored energy is 1.29 eV. 

A rich chemistry has flourished in the search for new luminescent systems see Luminescence and Luminescence Behavior Photochemistry of Organotransition Metal Compounds). A great variety of inorganic architectures have been obtained, including helicates and large multicomponent arrays. As an example, rack-type polynuclear ruthenium... 

Flamigni, L., F. Barigelletti, N. Armaroli, J.P. Collin, J.P. Sauvage, and J.A.G. Williams (1998). Photoinduced processes in highly coupled multicomponent arrays based on a ruthenium(II)bis(terpyridine) complex and porphyrins. Chem. Eur. J. 4, 1744-1754. 

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