Studies On Synthesis, Monooxygenase-mimic And Hydrolase-mimic Performances Of Benzo-10-aza-15-crown-5 Substituted Salicylaldimine Schiff Bases

One of the chief purpose of enzyme-mimic researches is to design and synthesize low molecular weight compound which have no peptide bone of the macromolecule, but possess reactive site similar to that of enzyme and can catalyze common chemical reaction with high capability and selectivity. Synzymes are a kind of compound to mimic partial structure and function of enzyme, they generally possess both associate site and catalytic site within the molecule. Crown ethers, as the first generation of enzyme-mimic base compounds, are a category of cyclic compounds which are constructed by hydrophobic outer ethylene groups and hydrophilic inner oza or aza atoms. They can associate with many guest molecules, mimic and control the microenviroment around the reactive site to improve the reactivity of synzymes. Thus, to design and synthesis crown ether substituted functional molecule is a trend of current Crown Chemistry and Biomimetic Chemistry. However, by now the crown ether substituted Schiff base-type enzyme-mimic models remain rather seldom. The report of benzoaza crown-Schiff bases as monooxygenase-mimic and hydrolase-mimic have not been found yet. For the purpose to employ the cooperativity of the azacrown ethers in enzyme-mimic aspects, we design and synthesis benzo-10-aza-15-crown-5 substituted mono, bis and asymmetric salicylaldimine Schiff bases and their transition-metal complexes, and systematically study the influences of azacrown ether substituentes as well as their bonding sites, and the alkali metal ions complexed with the crown ethers on the dioxygen affinities, monooxygenase-mimic and hydrolase- mimic performances of these complexes, and moreover, discover some regulations among them. As a result, we have gained a series of new results which will supply many valuable information for the design an synthesis of new monooxygenase- mimic and hydrolase-mimic models. Considering that the reactivity of the N atom of the crown ether or morpholino ring and the modifiability of the Schiff base ligand, 3 series of benzo- 10-aza-15-crown-5 or morpholino substituted new salicylaldimine Schiff bases and their transition-metal [Co(II), Mn(III)] complexes have been designed and successfully synthesized. Thy all have been characterized by IR,1HNMR,MS,and elemental analyse.The Co(II) complexes have been employed as synthetic oxygen carriers. Their equilibrium constants Ko2 and thermodynamic parameters ΔHo and ΔSo for oxygenation in the presence of diethyleneglycol dimethy ether (as solvent) and pyridine (as axial lingand) over a range of –5oC to 25 oC have been determined and calculated. The results indicate that: 1. the dioxygen affinities of all the crown ether-Schiff base Co(II) complexes are superior to their crown-free analogues, and the former also obviously possess macrocyclic effect. The dioxygen affinities are follow the order: double azacrown ether substituted bis-Schiff base > single azacrown ether substituted bis-Schiff base > single azacrown ether substituted mono-Schiff base> morpholino substituted species> the simple analogues. 2. the bonding sites of the crown ether in the complexes visibly influence the dioxygen affinities of the complexes. 3. the benzoaza crown ether substituted species can attune well many factors of the ligands such as π-donating ability, hydrophobicity, steric block and hydrogen bond between azacrown ether and nearby hydroxyl to effectively control the reactive center and improve the dixygen affinities. 4.The ESIMS spectra confirm the existence of K(I)/Co(II) dinuclear sandwich type complexes in the oxygenation reaction, which can much enhance the O2-binding abilities of the complexes.The Mn(III) complexes have been employed as cytochrome P-450 artificial models to catalyze epoxidation of styrene under ambient temperature and pressure using PhIO and NaClO as oxygen source. The results reveal that, as compared with the crown-free analogues, the crown ether substituted species show much higher catalytic activities. Their catalytic capabilities also follow a...