As a powerful macrocyclic host molecule with unique conformation and cavity structure that are fine-tuned by the bridging nitrogen atoms, methylazacalix[4]pyridine (MACP-4) has been shown to selectively recognize Zn2+ and form stable Zn(Ⅱ)-MACP-4 complexes both in solid state and solution with an association constant up to 5.97 (logKs). The molecular recognition of Zn(Ⅱ)-MACP-4 complexes towards various amino acids and anions with different geometry was investigated by using the spectral titration methods and X-ray analysis. The Zn(Ⅱ)-MACP-4 complex was found to recognize the 17 amino acids tested with the association constant up to 3.97 (logKs). On the other hand, the Zn(Ⅱ)-MACP-4 complex selectively interacted with anions and the maximum association constant of 3.9 (logKs) was obtained.
GONG HanYuan, WANG DeXian, HUANG ZhiTang & WANG MeiXiang Beijing National Laboratory for Molecular Sciences, CAS Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
The flexible polymer dispersed liquid crystal (PDLC) film with threshold voltage V10 and saturation driving voltage V90 as low as 0.34 V/μm and 0.77 V/μm,respectively,has been prepared successfully by polymerization induced phase separation (PIPS). The surface rubbing effect on morphologies of liquid crystals (LC) droplets and electro-optic properties of PDLC films has been studied experimentally and theoretically. We use a CVC (Color Video Camera) and a SEM (Scan Electron Microscope) to detect and characterize morphologies of LC droplets in the net of polymer. The result reveals that almost all the smaller LC droplets exhibit in the rubbing direction uniformly,and the texture of PDLC is similar to that of H-PDLC. Meanwhile,compared with the sample of the non-rubbing disposal,the response time declines evidently by 11.2 ms (i.e.,the rising time τrise) and 27.2 ms (i.e.,the decaying time τdown),and the contrast ratio is improved from 18.5 to 35.9. Such a result can be attributed to the surface rubbing effect.
Achiral diacetylene 10,12-pentacosadinoic acid (PCDA) and a chiral low-molecular-weight organogelator could form co-gel in organic solvent and it could be polymerized in the presence of Zn(II) ion or in the corresponding xerogel under UV-irradiation. Optically active polydiacetylene (PDA) were subsequently obtained. Supramolecular chirality of PDA could be controlled by the chirality of gelators. Left-handed and right-handed helical fibers were obtained by using Land D-gelators in xerogels respectively, and CD spectra exhibited mirror-image circular dichroism. The PDA in xerogel exhibited typical blue-to-red transition responsive to the temperature and pH, while the supramolecular chirality of PDA showed a corresponding change.
