Fullerene derivatives fluorescence

The lifetimes of the singlet excited states are only partly influenced the values range from 1.1 to 1.8ns [61,66,84,85,89-92], and for C6o a value ofabout 1.3 ns was estimated. As for the fluorescence quantum yields, there is also a solvent dependence of the fluorescence lifetimes for fullerene derivatives with electron-... 

Table 2 Fluorescence Properties of Fullerene Derivatives Compared to Those of C oK-io...

Figure 19 (a) Optical and AFM images and (b) fluorescence and SEM images of the honeycomb structure of PPV-polystyrene copolymer film. AFM images of the morphology of (c) PPV-polystyrene copolymer and (d) PPV-polystyrene-fullerene derivatives. The chemical structure formula for the two copolymers are also reported. Reprinted figures with permission from B. de Boer, U. Stalmach, P.F. van Hutten, C. Melzer, V.V. Krasnikov, and G. Hadziioannou, Polymer42 (2001) 9097. Figure 1,6, 7. Copyright 2001 Elsevier.

A similar approach was used in grafting Cjq onto a pregenerated lithiated polyethylene surface [121]. A polyethylene film with terminal diphenylmethyl groups was deprotonated with BuLi to yield an anionic polyethylene surface that was treated with Cg0 and quenched with methanol. The incorporation at the polyethylene surface was determined by XPS, UV/Vis and fluorescence spectroscopy. This reaction also works for polyisopropene, polybutadiene [69], poly(vinylbenzyl chloride) or poly(N-vinylcarbazole) PVK [54] with BuLi or NaH as a base. Charge-transfer interactions in the soluble fullerene-PVK derivative between the positively charged carbazole and Cjq lead to an enhanced photoconductivity compared with PVK [54]. 

The pseudorotaxane self-assembles through hydrogen bonding, and the binding constant, calculated using steady-state fluorescence, is 1.4 x 10. The zinc phthalocyanine derivative exhibited an excited-state lifetime of approximately 3.1 ns. The fast decay of the excited state of 1 ZnPc upon complexation with the fullerene... 

Figure 3 Comparison of absorption and fluorescence (inset) spectra of different classes of C6oderivatives themethano-C6oderivative l -carboxy-l,2-methano[60]fullerene the pyrrolidino-C6o derivative N-ethyl-trans-2, 5 -dimethylpyrrolidino[3, 4 l,2][60] fullerene 33 (Fig. 24) (- - -),[B14al the C60 derivative 2-hydroxy-tetrahydrofu-ran[4, 5 l,2] [60]fullerene (—), and the amino-C60 derivative 3 (Fig. 4) AW -dimethyl-piperazine [2, 3 l,2][60]fullerene (-). (From Ref. 65.)...

Unlike the reversed shift of the emission band compared to the dihydrogen addend type, the singlet lifetime in the bis- and tris(bis-(ethoxycarbonyl)-methylene) derivatives is increased comparable to the former multiple adducts. The values range from 1.7 to 3.1 ns (tris-adduct), depending on the distorted T7-electron system of the fullerene core [67,108], In comparison to C6o, the fluorescence quantum yield for the malonic ester hexaadduct is increased by the factor 10 (30 X 10 4) [67,111], In the case of both pyrrolidino hexa-adducts (Th 14 and D3 15, Fig. 13), the effect is remarkably higher. The fluorescence quantum yields are increased about 100-fold (-0.02) compared to C6o. On the other hand, the singlet lifetime is only partly increased with -3.5 ns [111,112],... 

The nature of the lowest-lying excited states of the fullerenes has been difficult to identify with much certainty. From Shpol skii-type luminescence spectra recorded at 1.5 K it has been concluded that the first-excited singlet state in C70 is of A 2 character. The origins of the lowest energy transitions in Ceo, namely Si(T]g) and S2(Gg), have been assigned on the basis of fluorescence and excitation spectra, supported by theoretical calculations. " The luminescence properties and relaxation dynamics of single crystals of Qo have been described while related measurements have been made for solid films of Ceo " Similar studies have reported the luminescence spectral properties of 50 trapped inside the cavities of NiY zeolites. An analysis of the fine structure of electron-vibrational spectra has been made for 50 and its derivatives in a solid toluene matrix. The rate of triplet energy transfer between fullerenes in toluene solution has been measured as a function of temperature and used to derive thermodynamic parameters for the transfer process. ... 

There have been only a few reports of emission properties of functionalized fullerenes. A systematic fluorescence study of four derivatives... 

Fluorescence quantum yields of the C o derivatives were quantitatively determined. For the mono-functionalized Cgo derivatives, the compound with a (5-6)-open fulleroid addition pattern on the fullerene cage appeared to be considerably less fluorescent than those with a [6,6]-closed cage addition pattern. Despite the disturbance of the electronic structure via multiple additions to the fullerene cage, the multiple-functionalized Cgo derivatives exhibited no dramatic changes in fluorescence quantum yields in... 

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