B Carries a Single-n-Pair

Fig. 28 Photoinduced electron transfer studies carried out on 6-mer (not shown) and 7-mer hairpin DNA duplexes capped by a stilbene acceptor chromophore.31 167 168 The duplexes contain A-T base pairs and a single G-C base pair, whose position in the duplex is varied, (a) The photoinduced ET process is illustrated for 3G C, in which the G-C base pair is third removed from the stilbene (St) group. The stilbene fluorescence is quenched by electron transfer from the G donor, (b) Damping factors for charge separation, /3(CS), and subsequent charge recombination, /3(CR), for n G C, in which the G base is connected to the T-bearing strand, (c) Damping factors, /3(CS) and /3(CR), for n C G, in which the G base is connected to the A-bearing strand.

Figure 5.11 reproduces the results of the curve-fitting carried out in the FT-Raman SjCFs/v SNS band of LiTFSI-doped di-ureasils and the composition dependence of the area of the resolved components, respectively. At n > 40 the band was decomposed into a single component at 739 cm" due to free TFSI" ions, ° whereas at n = 20 it was resolved into two peaks at 743 and 739 cm". The former component is ascribed to the occurrence of contact ion pairs. Figure 5.11(b) shows that, while the concentrations of free anions and coordinated anions remain essentially constant at 40 < n < 8, at n = 5 the fraction of free anions decreases significantly and the proportion of associated species increases concomitantly. 

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