Introducing A Picket Fence Porphyrin Derivatives And Their Molecular Recognition Role

"Picket Fence" porphyrin with functional groups positioned above the prophyrin plane constructed a special binding model. For the binding of an axial ligand to a protected porphyrin complex, some interaction between the axial ligand and the cavity can be regarded as the extra recognition factor in addition to the coordination bond, which could strength molecular recognition ability. Previous results have shown that this cavity structure can recognize not only neutral molecular, but also anions. Amino acids as ingredient of protein have good biocompatibility and special biological functions. So conjugated these amino acids with prophyrins can form the amino acid "picket fence" structure, which will also have good biocompatibility. Based upon these consideration in this thesis, we synthesized some amino acid "picket fence" porphyrins and studied anions recognition ability.In this article, five "picket fence" porphyrins were synthesized by DCC condensation with Boc protected amino acids as fence structure. Seven anions (F^-,Cl^-,Br^-,I^-,H₂SO₄^-,AcO^-,H₂PO₄^-) were used as guest to study molecular recognition of these five "picket fence" porphyrins. Results showed that this kind of compounds had strong binding ability to anions, and the association constants reached up to 10⁵. Among anions for F^- and Cl^-, they showed some selectivity.Metal ions insertion into porphyrin core will bring out very important physiological activity. Five metal compounds based upon Boc-Gly "picket fence" porphyrin were synthesized. As their free base counterpart, these metal porphyrins also showed anion recognition ability (except Cu porphyrin). In order to explore the binding mechanism, solvent effect was explored. Because the Cl^- channels are unique anion channels, they play crucial roles in physiological process. So chloride ions were chosen as guest to study solvent effects in six different polar solvents (toluene, THF, CH₂Cl₂, CH₃CN, EtOH, THF-H₂O (1:1 v/v)). Results showed that binding was strong in aprotonic solvents like CH₃CN, CH₂Cl₂, THF and toluene, and nonbinding occurred in protonic solvents like EtOH and THF-H₂O (1:1 v/v). The reason for this phenomenon was that either EtOH or H₂O in THF-H₂O (1:1 v/v) mixture provided over excess hydrogen-bond donor, which instead of Cl^- interact with amide functional group resulted in blocking the interaction of Cl^- with amide. These results suggested that the interaction between amino acid fence porphyrins and Cl^- was dominated by hydrogen-bond.Meanwhile, "picket fence" porphyrins are also better model for mimic myoglobin and hemoglobin. One synergistical dioxygen binding model correlated with biology will reveal the most important structure, which can satisfy the coordinated dioxygen binding. And it will be helpful for understanding the energy requirement controlled by hemoglobin allosterism.So, here one kind of multi-porphyrin system was synthesized by esteratic link four "picket fence" porphyrins together. And two kinds of porphyrins with multiple basic ligands were synthesized, too. This multi-porphyrin will make the present synthetic model compound more close to the mechanism of hemoglobin binding dioxygen. And it could tentatively simulate hemoglobin to cooperate with dioxygen, which would more meaningful to provide theoretical base for researches of artificial blood substitutes.