Energy transfer-critical radii

The efficiency of resonance transfer is often given in terms of a critical radius R0. If R0 is the distance such that the rate of energy transfer is equal to the sum of all other donor deactivation rates... 

The sixth power dependence explains why resonance energy transfer is most sensitive to the donor-acceptor distance when this distance is comparable to the Forster critical radius. 

The tris-bipyridine complexes on the other hand are encapsulated by the oxalate network. Thus in the co-doped systems a [Cr(bpy)3]3+ complex happening to sit in the first acceptor shell of a given donor is much closer to this donor than a [Cr(bpy)3]3+ complex sitting in the second shell, n-n overlap between ligand orbitals of the donor and an acceptor in the first shell ensure efficient energy transfer on the sub-microsecond timescale mediated by exchange interaction. Additionally, the relative orientation of donor and acceptor plays an important role for the n-n overlap. For acceptors further away, for which there is no exchange pathway, dipole-dipole interaction takes over. With a critical radius of the order of 11 A, this is much less efficient and the overall quantum efficiency is thus less than unity. 

The important part for us is the fact that we can deduce the critical radius beyond which energy transfer does not occur. In a normal lattice, this distance is approximately ... 

CRITICAL RADIUS FOR ENERGY TRANSFER FROM SPHERICAL... 

The critical radius 117 of the resonant energy transfer from the triplet state of benzophenone to the singlet state of perylene at 77 in a mixture of chloroform and ether has been determined to be 68 A, a value similar to those obtained for related pairs of molecules.118... 

Ro critical radius for donor-acceptor energy transfer... 

In the example shown in Figure 5, four BODIPYs were covalently attached to the peiylene diimide core. In accordance with the increase in BODIPY number on the structure, extinction coefficient of the molecule at BODIPY s maximum absorbance wavelength (526 ran) increases dramatically to 250000M cm . Energy transfer efb-ciency was determined to be 99% with a critical Forster radius of 4.7 ran. In the second example shown in Figure 5, enhancement in emission of the core distyryl-BODIPY was observed as the number of terminal BODIPY donors was increased, as expected. ... 

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