Light conversion molecular devices

The next category of f)-diketones are 4-acyl-l-phenyl-3-methyl-5-pyrazolones (see Eigure 2.5) and their analogs of 3-phenyl-4-acyl-5-isoxazolones (see Eigure 2.6). The latter type of P-diketones have stronger acidities (lower pA a values) than the former, and have recently been smdied as promising light conversion molecular devices [46-51]. 

Figure 2.20 Asymmetric unit of complexes Tb(L )3(H20)2, thermal ellipsoids drawn with 30% probability and hydrogen atoms omitted for clarity [51a], (Reproduced from S. Iju, M.L.P. Reddy, A.H. Cowley and K.V. Vasudevan, 3-Phenyl-4-acyl-5-isoxazolonate complex of Tb + doped into poly-P-hydroxybutyrate matrix as a promising light-conversion molecular device, Journal of Materials Chemistry, 19, 5179-5187, 2009, by permission of the Royal Society of Chemistry.)...

Raj, D.B.A., Biju, S., and Reddy, M.L.P. (2009) 4,4,5,5,5-Pentafluoro-l-(9H-fluoren-2-yl)-l,3-pentanedione complex of Eu with 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene oxide as a promising light-conversion molecular device. Dalton Transactions, 7519-7528. 

The photophysics of lanthanide complexes has drawn considerable attention in recent years, in part because of the potential applications of lanthanides (sensors, electroluminescent displays, etc.) and several recent reviews highlighting applications of luminescent lanthanide complexes have appeared. A discussion of infrared f-f luminescence of Yb, Nd, and Er in complexes having macrocyclic ligands such as porphyrins, cyclen derivatives, and calixarenes was published by Korovin and Rusakova. " In addition, DaSilva and co-workers describe the development of highly luminescent lanthanide complexes and their application as light-conversion molecular devices. ... 

Sabbatini et al. 1993). An efficient antenna is expected to lead to metal luminescence much more intense than that obtained upon metal excitation since lanthanide ions are characterized by very low molar absorption coefficients. These complexes can be considered light-conversion molecular devices because they are able to transform light absorbed by the ligand into light emitted by the ions via an intramolecular energy transfer (Balzani and Scandola 1991). 

The photosynthetic process thus provides us with an example of a complex, light-powered photochemical molecular device which uses light as an energy supply in order to facilitate energy conversion. In green plants, this molecular device is located within a specially-adapted photosynthetic membrane. 

Fig. 18. Light-conversion photochemical molecular device, consisting of two components, a light collector (or antenna, lightabsorbing groups A) and a light emitter E, and performing a three-step process absorption (A), energy transfer (ET), and emission (E).

The unique luminescent properties of rare earth metal clathrochelates have been used in the development of luminescent materials (luminophores and laser materials). The luminescence of these clathrochelates in solution makes their application as biological probes and concentrators of the luminescence (i.e., the antenna effect ) promising. These complexes can also serve as efficient molecular devices to convert UV light absorbed by the ligand to lanthanide ion luminescence in the visible region. Even in very dilute (10-5 mol l-i) solutions, the conversion of irradiated photons to luminescent ones has been observed to occur at a rate of approximately 1%. For rare earth metal aqua ions at the same concentration, the efficiency of conversion is equal to 4 x IQ- % [212, 390-392]. 

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