Energy Transfer in Solution

The rdadve steady-state quantum yield of die dentw is given by 

These repressions are valid for immobile donors and acceptors for which the orientatiem fKtor is randonuzed 1 rotational diffusion (1 = ). For randomly distributed acc tors, where rotation is much ower than the donor decay, = 0476. Still more complex expressions are necessaiy if the donor and acc Xor diffuse tfairing the lifrtime of the excited st (Chapters 14 and 15). The complex decay of dtmor fiunesceiMx Ejects the time-depmdent populatitMi of D A pairs. Those donors with neaiby aoc tors decay more rapidly, and demors more distant from acc tors decay more slowly. 

The tenn Ao is called the critical concentration and rqnesents the acceptor concentration that results in 76% energy transfer This concentration, in mdes per liter (Af) can be calculated from Eq. [13.30] or from a simplified tpressiem,  

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Lamola, A. A. (1969). Electronic energy transfer in solutions theory and application. In Leermakers, P. A., and Weissberger, A. (eds.), Energy Transfer and Organic Photochemistry, Technique of Organic Chemistry 14 17-132. Interscience Publishers, New York. 

A. A. Lamola, Electronic Energy Transfer in Solution Theory and Applications, in Techniques of Organic Chemistry, XIV, P. A. Leermakers and A. Weissberger, eds., Interscience, New York (1969), pp. 17-132. 

E. Gaviola and P. Pringsheim Demonstration of resonance energy transfer in solutions... 

Energy transfer in solution occurs through a dipole-dipole interaction of the emission dipole of an excited molecule (donor) and the absorptive moment of a unexcited molecule (acceptor). Forster<40) treated the interaction quantum mechanically and derived and expression for the rate of transfer between isolated stationary, homogeneously broadened donors and acceptors. Dexter(41) formulated the transfer rate using the Fermi golden rule and extended it to include quadrupole and higher transition moments in either the donor or the acceptor. Following the scheme of Dexter, the transfer rate for a specific transition is... 

The final form of the expression for the rate constant A Et, for energy transfer in solution, expressed in the units of litre mol-1 s-1 is... 

The fact that the rate of exothermic triplet energy transfer in solution approaches the diffusion-controlled limit does not establish that every collision of donor and acceptor is 100% efficient in transferring energy. Rebbert and Ausloos have measured the efficiencies with which several compounds quench acetone phosphorescence in the vapor phase.160,161 They find that with compounds such as oxygen,... 

Beckerle JD, Cavanagh RR, Casassa MP, Heilweil EJ, Stephenson JC. Subpicosecond study of intramolecular vibrational energy transfer in solution-phase Rh(CO)2acac. Chem Phys 1992 160 487-496. 

Lamola A. Energy transfer in solution theory and applications. Energy Trans. Organ. Chem. 1969 14 17-132. 

Time-resolved fluorescence spectroscopy and fluorescence anisotropy measurements have been applied to study (i) excimer formation and energy transfer in solutions of poly(acenaphthalene) (PACE) and poly(2-naphthyl methacrylate) (P2NMA) and (ii) the conformational dynamics of poly(methacrylic acid) (PMA) and poly (acrylic acid) as a function of solution pH. For PACE and P2NMA, analysis of projections in which the spectral, temporal and intensity information are simultaneously displayed have been used to re-examine kinetic models proposed to account for the complex fluorescence decay behaviour that is observed. Time-resolved fluorescence anisotropy measuranents of fluorescent probes incorporated in PMA have led to the proposal of a "connected cluster" model for the hypercoiled conformation of this polymer existing at low pH. 

Lamola, Electronic energy transfer in solution Theory and applications, in Energy Transfer and Organic Photochemistry, A.A. Lamola and N.J. Turro, Eds. pp. 17 132, Interscience, New York (1969) A. Reiser, Photoreactive Polymers The Science and Technology of Resists, p. 72, John Wiley Sons, Hoboken, NJ (1989). 

Scherer, P. O. J. Seilmeier, A. Kaiser, W., Ultrafast intra- and intermolecular energy transfer in solutions after selective infrared excitation. J. Chem. Phys. 1985, 83, 3948-3957. 

Due to the low mole ratio of dye units present, the above copolymers, with perylene dyes in the main chain or as end groups, show energy transfer only in the solid state. If the dyes are attached on the side chain, then copolymers containing much higher mole ratios of chromophore are accessible. The copolymer 123 (Scheme 57) in which 33% of the fluorene units have dyes attached (m n = 2 1) showed energy transfer in solution as well as in a thin film [224]. The emission colour differed slightly between the two states, with the emission maximum appearing at A,max = 561 nm in solution with a shoulder at 599 nm, and at Xmax = 599 nm in the solid state. This is probably due to interaction of the chromophores in the solid phase. 

Figure 6.15 Energy transfer in. solution. Deactivation of electronically excited molecules. Symbols D is excited electron-donor (singlet or triplet) A is electron-acceptor S is singlet state T is triplet state.

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