By Kristen Limbert
Catenanes are mechanically interlocked structures usually in a chain like formation. To assemble these structures, usually a metal template is required. The majority of metal templates are d-block, transition metals, however research has been conducted into the use of f-metal compounds, such as Lanthanides to produce catenanes. The difficulty to produce catenanes with f metal templates comes from the loosely defined coordination sphere of the Lanthanide.
Lanthanides offer photophysical properties that enable the production of optical anion sensors. For the complex to be successful, it will need to be thermodynamically and kinetically stable to withstand ions so it can detect the desired anions.
A previous example of a Lanthanide-template catenane was produced by Christophe Lincheneau, Bernard Jean-Denisa and Thorfinnur Gunnlaugsson who produced - and  catenanes using Europium(III) for the template.
The aim of this project was to produce a ligand metal complex similar to the diagram below.
There were 2 approaches to achieve this goal.
For approach 1, step 1 was unsuccessful, yielding only starting material. Step 2 was attempted using compound (1), however the desired compound was not obtained (compound (3)).
For approach 2, step 1 was successful, this was confirmed by NMR and Mass Spec. However, step 2 was not successful.
Due to some of the experiments being unsuccessful, a new approach was required to progress the project. Step 2 of approach 1 using compound (1) as the starting material yielded an unexpected compound.
This molecule (compound 10) was then used to produce a potential ligand for a ligand-metal complex (compound 11).
The (S,S) enantiomer of the diamine was also used to form an enantiomeric ligand.
A variety of metals were used to try and form a metal-ligand. Luthenium, zinc (acetate and triflate), nickel (nitrate and chloride), lanthanum and silver (tetrafluoro-borate) were used to form the metal-ligand complex.
To characterise the compounds produced at each step, NMR, Mass Spectroscopy and UV-Vis were used. The data obtained confirmed the production of compounds (10) and (11), and showed that the formation of the ligand-metal complex was unsuccessful with all the metal complexes attempted. The potential reason for the unsuccessful formation of the ligand-metal complex is the hydrolysis of the C=N bond, forming the starting materials. To achieve success, the experiment would need to be carried out again in anhydrous conditions.
In conclusion, the desired compound was not achieved due to the planned reactions being unsuccessful, even after adaptations of the conditions used. However, a new compound was discovered and testing as to whether it will be a successful ligand for a metal ligand complex is underway.
1) C. Lincheneau, B. Jean-Denisa, T. Gunnlaugsson, Chem. Commun., 2014,50, 2857-2860
*To view Kristen’s project poster, please click on the thumbnail below