Assembly And Performance Of Metal-Organic Polyhedra Containing Hydrogen Bonding Groups

Hydrogen bonding plays an important role in supramolecular recognition and catalysis, as well as the electron and proton delivery in these systems. Metal-organic polyhedra (MOPs) have shown excellent advantages in the rational building of microenvironments isolated from bulk solution, with size and shape-selective recognition of the substrates. The introducing of hydrogen bonding groups into the well-defined cavities of MOPs would expand their application in the filed such as bio-molecule recognition, size-selective catalysis, electron and proton delivery in light driven proton reduction.In this thesis, through the rational designing of ligands, several metal-organic polyhedra were constructed with the incorporating of different kinds of hydrogen bonding groups into their cavity to enrich the chemical properties of the MOPs. With the cooperation of hydrogen bonding groups and the well-defined cavities of the MOPs, the obtained compounds could achieve the specific recognition and catalysis properties with high efficiency and selectivity.(1) Metal-organic tetrahedrons Ce-TBMN and Ce-TBAS were achieved via self-assembly by incorporating triamine-triazine and amide groups as hydrogen bonding groups into the fragments of the ligands containing three ONO tridentate coordination sites, respectively. The tetrahedron Ce-TBMN has630A3internal cavity,18.0×7.65A2opening windows with totally twelve Watson-Crick type and twelve coordinated amide hydrogen bonding groups, and could selectively recognized guanosine molecule over other ribonucleosides. The tetrahedron Ce-TBAS has1000A3internal cavity and21.0×8.05A2opening windows, with totally twelve uncoordinated and twelve coordinated amide hydrogen bonding groups, could selectively recognize sucrose over other related natural mono-and disaccharides.(2) The presence of hydrogen donor and acceptor in their cavity allowed the Ce-TBMN and Ce-TBAS to act as molecular flasks to prompt the Knoevenagel condensation reactions of salicylaldehyde derivatives and Cyanosilylation reactions of aromatic aldehydes. Ce-TBMN showed remarkable size-selectivity in catalyzing2-hydroxy-3-methoxybenzaldehyde Knoevenagel condensation reaction with95%conversion in3h and2-nitrobenzaldehyde or3-nitrobenzaldehyde Cyanosilylation reaction with97%conversions in1h. Ce-TBAS showed better conversions to the larger size substrates than Ce-TBMN in the promotion of Knoevenagel condensation reaction and greater catalysis ability to the larger-sized3-nitrobenzaldehyde and4-nitrobenzaldehyde Cyanosilylation reaction than the smaller-sized2-nitrobenzaldehyde. Experiments of substrates with different size and shape, as well as competitive experiments using the nonreactive guests as inhibitions demonstrated that the tetrahedrons exhibited enzymatically catalytic behavior and the catalytic reactions were occurred in the "molecular flasks". Control experiments with the ligand H6TMBN or H6TBAS themselves as the catalyst for the Knoevenagel condensation were carried out in the same condition. For the smaller substrates, their conversions catalyzed by the ligands were obviously lower than those catalyzed by Ce-TBMN or Ce-TBAS, respectively, suggesting that metal-organic polyhedra could effectively fix multi hydrogen bonding groups to avoid the "self-quenching" effect, enhancing the catalytic activity of the multi hydrogen bonding groups in homogeneous state.(3) A cobalt-based redox active triangular prism Co-ZJ with the large opening windows (9.25×9.25A2) and internal cavity (450A3) was obtained by the self-assembly of the well-designed ligand ZJ and Co2+. The coordination configurations of cobalt centres in Co-ZJ were similar with that of metalloenzyme VB12, which could work as catalyst for light driven H+reduction in the presence of Ru(bpy)3(PF6)2as photosesitizer and H2A as electron sacrifice during10hours. The volume of the H2was0.09mL and the TON (turnover number) of this system was calculated as326. The Co-ZJ could also encapsulate the hydroquinone/benzoquinone(QHQ) redox couples to accelerate the electron and proton delivery, and improved the catalytic efficiency about11times, with the volume of the H20.92mL and the TON3471.