Guest charge transfer systems

In Fig. 3, the values for the electron-number-related static hyperpolarizability fiJN312 obtained for these ionic chromophores (open symbols) have been compared with the same values for the best dipolar, neutral chromophores reported so far (diamonds).31 32 These chromophores, with a reduced number of electrons N equal to 20, have dynamic first hyperpolarizabilities approaching 3000 x 10 30 esu at a fundamental wavelength of 1.064 pm, in combination with a charge transfer (CT) absorption band around 650 nm. It is clear that at this point, the neutral NLOphores surpass the available ionic stilbazolium chromophores for second-order NLO applications, however, only at the molecular level. The chromophore number density that can be achieved in ionic crystals is larger than the optimal chromophore density in guest-host systems. 

Fig. 10A, B. A redox-switchable supramolecular system based on charge-transfer interactions which can be read by spectroscopic means. A Redox switching of the host compound 22. B Redox switching of the guest 24. The absorbance spectra in A and B are adapted from [42] and [43], respectively, with permission...

Liquid chromatographic resolutions based on highly selective host-guest, metal chelate and charge-transfer com-plexations have been described (1,2). Recently, a chiral diamide-bonded stationary phase (I) has been prepared, which relies entirely on hydrogen bond associations for the material to be resolved. Despite the weak and flexible interaction in this system, direct resolution of enantiomeric N-acyl-fl-amino acid esters (II) was accomplished with the advent of a highly efficient column technology (2- ). 

---