.Name/describe 4 examples of “Supramolecular Chemistry and Supermolecules” that we might encounter in our daily lives, for example in consumer products , medicines or nature. [10%]2.Consider the molecule 1below. (i)Explain why compound 1is expected to be a good host for copper ions over sodium ions.[8%](ii)Copper salts can be toxic. Suggest a potential application of a compound like 1.[2%](iii)Suggest a modified structure that is expected to be selective for potassium ions over copper ions. Give brief reasoning.[5%](iv)Outline a synthetic scheme for synthesis of your suggested host, starting from catechol (1,2-dihydroxybenzene). You may useany other simple reactants or reagents. Make sure you clearly describe any special conditions you would employ to achieve a good yield of your macrocyclic product.[20%]3.The structure of zinc tetrakis(4-hexyloxyphenyl)porphyrin4is shown below. It can be synthesised by reaction of pyrrole with 4-hexyloxybenzaldehyde in refluxing propionic acid, followed by reaction of the porphyrin with zinc acetate.
a)Draw the important mechanistic steps for the sequence that gives intermediate 2.[15%]b)The overall yield for the reaction to porphyrin 3is typically around 15%. What side products are expected from this reaction?[5%]c)The overall yield ofzinc porphyrin 4is increased significantly when the reaction is performed in a single operation (i.e. when pyrrole, aldehyde and zinc acetate are reacted in refluxing in propionic acid). Explain this observation.[5%]d)Do you expect porphyrins 3and 4to show a liquid crystal phase? Briefly explain your answer.[5%]e)Synthesis of porphyrin derivatives requires both the 2 and 5-positions of the pyrrole to beunsubstituted. When one position is “blocked” (see scheme, where there is an “R” substituent on the pyrrole) the reaction stops after formation of a dipyrromethane. These compounds are themselves important because they can be oxidised (using “DDQ”) to the corresponding dipyrromethene which is a good, chelating ligand (e.g for Zn2+, Cu+). Reaction with boron trifluoride yield the important “BODIPY” materials (highly fluorescent compounds used in applications such as sensors and photosensitising).
Using this information and the your knowledge of supramolecular assembly approaches, design a synthesis of a catenane that incorporates a dipyromethene unit in each ring,represented by the general structure below. Your synthesis should start usingthe substituted pyrroleshown (using any other reactants and reagents).
