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.
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.
UV-Vis spectrum was utilized to study the aggregation behaviors of H4THPP2+ inDMF-chloroform mixture and water. It was found that J-aggregation of H4THPP2+ was formed inDMF-chloroform mixture and H-aggregate was formed in aqueous solution with highionic-strength, as indicated by different spectral characteristics of different H4THPP2+ aggregates.
The aggregation of meso-tetrakis(4-hydroxyphenyl)porphyrin (H2THPP) in dimethyl- formamide (DMF)-water solution and in DMF-chloroform solution was studied by UV-vis absorption spectroscopy. The red shift of Soret band indicates the formation of J-type aggregates of H2THPP in these two solutions. However, different shift extent of Soret band, 12 nm in DMF-water solution and 32 nm in DMF-chloroform solution, implies structural difference between these two J-type aggregates. The hydrogen bond between hydroxyl group and N-H bonds in porphyrin ring is thought as the main cause to the formation of J-type aggregate in DMF- chloroform solution, whereas the π?σ interaction between two adjacent porphyrin cores is thought as the main cause of the formation of J-type aggregate in DMF-water solution
