A novel porphyrin-salen compound and corresponding zinc（Ⅱ） porphyrin-salen compound （ZnPSC10） covalently linked by a flexible alkoxy chain （-O（CH）10O--） have been synthesized and characterized. Molecular recognition of three N-heterocyclic guests, pyridine, 1,4-diazobycyclo[2,2,2]octane （DABCO） and pyrazine, with the host ZnPSC10 was investigated. Binding constants were determined by means of UV-vis titration method. The binding mode of ZnPSC10 with DABCO has been discussed in detail by using ^1H NMR. It was found that the conformations of the recognition system changed from closed to open with the adding of DABCO.
Molecular Recognition of α,α,α,β-ZnT（o-BocThr）APP （1） toward a series of imidazole derivatives and amino acid esters was investigated. Association constants were determined in chloroform by means of UV-Vis titration method. The association constants of 1 with imidazole derivatives are larger than those of 1 with amino acid esters. 1H NMR spectra were investigated to describe the binding mode of the recognition system, showing that all the protons of the guests were shifted to upfield. The circular dichroism spectra of 1-L-/D-ValOMe showed a split cotton effect in Soret region, while those of 1-L-/D-PheOMe showed no split cotton effect. Molecular modeling was performed to understand chiral recognition on a molecular level. Quantum chemical calculation was carried out based on the stable conformations of these recognition systems, which gave a reasonable explanation for the behavior of molecular recognition. The results indicated that the conformation of 1-D-ValOMe was more stable than that of 1-L-ValOMe.
