Antenna-sensitizer complexes

Amadelli R, Argazzi R, Bignozzi CA, Scandola F. Design of antenna-sensitizer polynuclear complexes. Sensitization of titanium dioxide with [Ru(bpy)2(CN)2] Ru(bpy(COO)2)2L /Am Chem Soc 1990 112 7099-103. 

From the whole of the electrochemical, spectroscopic and photophysical infonnation. achieved from these and previous studies, it has been possible to designed an antenna sensitizer trinuclear complex NC-Ru (bpy)j-CN-Ru°(bpy(COO)j)j-NC-Ru (bpy)2.ChP, which has been shown to perform as an efficient molecular device for the sensitization of semiconductor electrodes in the visible region [16-19]. 

Taking the imaginative, though somewhat futuristic approach out-lined in Section 1.4, some of the polynuclear complexes discussed in this article can be viewed as very simple photochemical molecular devices. Examples are the Ru(II)-Cr(III) chromophore-luminophore systems of Section 4, which perform the function of spectral sensitization (Fig 7a). The coupling of the systems for photoinduced electron transfer and charge shift described in Section 3 could lead to triads for photoinduced charge separation (Fig 7b). The trichromophoric systems described in section 5.2 can be viewed as very simple examples of the antenna effect (Fig. 7a), while the longer chain-like systems of Section 5.2 could be considered as "molecular optical fibers" suitable for remote photosensitization (Fig. 7a) and other related functions. The system described in Section 5.3, on the other hand, couples antenna effect and photoinduced electron transfer into an antenna-sensitizer function. 

Although the development of antenna-sensitizer devices for the spectral sensitization of semiconductors might have some practical impact, it would clearly be unrealistic to consider most of the work described in this article of direct relevance to photocatalysis. It seems likely, however, that the need for increasing efficiency and selectivity will lead towards the development of complex photocatalytic systems of supramolecular nature. Thus, further fundamental studies on ways to control and direct photoinduced energy and electron transfer processes in supramolecular systems seem to be worthwhile. 

It is therefore important to bear in mind the dependency of the carotenoid spectrum upon properties of the environment for in vivo analysis, which is based on the application of optical spectroscopies. This approach is often the only way to study the composition, structure, and biological functions of carotenoids. Spectral sensitivity of xanthophylls to the medium could be a property to use for gaining vital information on their binding sites and dynamics. The next sections will provide a brief introduction to the structure of the environment with which photosynthetic xanthophylls interact—light harvesting antenna complexes (LHC). 

One must take enough psilocybin to allow the sound to be audible. This sound we understand to be the Electron Spin Resonance (ESR) of the psilocybin alkaloids within the mushroom. The presence of rapidly metabolizing high-energy tryptamines within the ayahuasca acts as an antenna that sensitizes the neural matrix to the spin resonance energy of the Stropharia psilocybin. It is this principle that allows the signal to be made audible. It must then be amplified via the tryptamine admixture antenna to what is felt to be its fullest amplitude. Then, via vocal sound, this energy is placed into the harmine complex within the body and within the mushroom which has been, in some small part,... 

As it is well known, sensitization of Ln-centered luminescence can be achieved via an intramolecular energy transfer upon excitation of organic ligands, instead of using direct excitation of the weak Lnm absorption bands. This phenomenon now called antenna effect or luminescence sensitization has first been observed in 1942 by Weissman for europium(III) complexes formed with salicylaldehyde and with /3-diketonates, more particularly benzoyl-acetonate (ba, 48a), dibenzoylmethanate (dbm, 48b) and wieta-nitrobenzoylacctonatc (47a, fig. 41) (Weissman, 1942). 

Ru(bpy)3+ complex placed into the inner cavity of the vesicle was used as such antenna . The lifetime of the triplet-excited state of this complex ( 0.6 ps) is sufficiently long, so that before its deactivation it can experience numerous collisions with the inner surface of the vesicle membrane and thus with the porphyrin molecules embedded into the membrane. Indeed, it was found that the introduction of Ru(bpy)2 + into the inner volume of the vesicle leads to the sixfold increase of the rate of the transmembrane PET [58, 61]. This effect results, first, from the spectral sensitization due to the light absorption by the ruthenium complex in the spectral region where porphyrin does not absorb, and, second, from the two-three fold increase of transfer from 3Ru(bpy)i+ to ZnTPPin. 

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