A Macrocycle with a Pair of Endo‐Isocyanides and its Affinity to Gold(I)

A pair of isocyanides pointing towards each other are fixed in a macrocyclic scaffold. The arrangement not only increases their local concentration, it should also enable their linear arrangement in coordination compounds. The macrocyclic diisocyanide ligand 1 is synthesized and fully characterized. Its interaction with gold(I) ions is investigated. While IR- and $^1$H-NMR-based titration experiments unraveled a stoichiometry of 2 Au(I) ions per macrocycle 1, the corresponding association constants are studied by UV-Vis titration experiments. However, the values are above the method’s detection limits and only a lower boundary of an over-all association constant is determined to be 3.0x10$^7$ M$^{-1}$. The kinetics of the complex formation is further analyzed by NMR titration experiments and in spite of a change in the solvent, association constants about one order of magnitude larger than the lower limit determined by the UV-Vis experiments are obtained.