Phase characterization using fluorescence spectroscopy

Dendrimers have precise compositional and constitutional aspects, but they can exhibit many possible conformations. Thus, they lack long-range order in the condensed phase, which makes it inappropriate to characterize the molecular-level structure of dendrimers by X-ray diffraction analysis. However, there have been many studies performed using indirect spectroscopic methods to characterize dendrimer structures, such as studies using photophysical and photochemical probes by UV-Vis and fluorescence spectroscopy, as well as studies using spin probes by EPR spectroscopy. 

In addition to the techniques previously mentioned, a wide variety of methods has been used to characterize the new inclusion compounds in solution and in the solid state, in both directly practice-oriented and theoretical papers, to elucidate the relationship between the relative strength of interaction and some surface parameters of the guest molecules. Complexes obtained in solution are frequently studied by phase-solubility, to obtain the stoichiometric ratio for the complex and an apparent stability constant [12-14], but spectral studies including UV, infrared, fluorescence, and NMR spectroscopy (see Section 10.3 and Chapter 9) can also be used for characterization [6, 15-17]. Inclusion compounds obtained in the sohd state are frequently characterized using infrared spectroscopy, X-ray diffraction (Chapter 7), scanning electron microscopy techniques [18, 19] (Section 10.6), differential scanning calorimetry (DSC) (Chapter 8) [20, 21], and/or fluorescence (Section 10.3) and voltammetric measurements (Section 10.5) [16, 22]. 

The Miller group also reported the synthesis of nonacene derivatives 75 and 76 using their thioaryl approach discussed above in the context of substituted heptacenes [62]. The synthesis is reminiscent of that of heptacene derivatives [58], with the key step being the Diels-Alder reaction between anthracenequinone 72 and the bis-ortho-quinodimethane precursor 73 (Fig. 35). The persistence of the less substituted derivative 76 is insufficient for characterization by solution phase methods. Derivative 75, however, could be investigated by NMR, UV/vis-NIR, and fluorescence spectroscopies as well as by LDI-TOF-MS [62]. 

In the preceding chapter it had already been discussed that it is less the synthesis itself which may be the bottleneck in high-throughput zeolite science but rather the analysis of the solids formed in a high-throughput program. There are several standard characterization techniques which are typically employed to characterize zeolitic materials. These include powder XRD for phase identification, X-ray fluorescence analysis (XRF) or atomic absorption spectrometry to analyze elemental composition, sorption analysis to study the pore system, IR-speclroscopy, typically using adsorbed probe molecules to characterize the acid sites, NMR spectroscopy and many others. For some of these techniques parallelized solutions have been developed and described in the literature, other properties are more difficult to assess in a parallelized or even a fast sequential fashion. 

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