Energy transfer efficiency, shells

Fig. 12 Schematic representation of the fast and the slow component of energy transfer in the co-doped system. The fat arrow indicates a transfer process between a donor (in black) with an acceptor (in grey) in its nearest neighbour shell attributed to the fast component, the thin arrows indicate that for donors which do not happen to have an acceptor in the nearest neighbour shell, the energy transfer is less efficient...

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. 

M solution in THF) is efficiently quenched by the addition of micromolar amounts of 43 or 44, which is assigned to singlet energy transfer on the basis of the favorable overlap between the emission spectrum of 42 and the absorption shell of... 

PMl-substituted hexa-peri-hexabenzocoronene (HBC) 35 was designed as model compound for intermolecular energy and electron transfer studies because of its Dgh symmetry, electronic and self-assembling properties [33-35]. The multichromophore (HBC-6PM1) 35 has six PMl chromophores attached to HBC via a 3 -dodecyl-4, 5, 6 -triphenyl-1,l 2, l"-terphenyl spacer unit (Scheme 8). HBC-6PM1 35 was obtained by Diels-Alder reaction of hexa-[4-(tetradec-l-yn-l-yl)phenyl]-HBC 34 [36] and well-established building block PMI-decorated Cp 29 (as discussed above) in diphenyl ether at 250°C in 58% yield [33-35]. Indeed, electronic excitation of the HBC core of this molecule resulted in efficient energy transfer to the PMl shell [37, 38]. 

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