Copper localization in cucurbit[8]uril

The CuK EXAFS, XANES and EPR spectra of the cucurbit[8]uril (Q8) samples containing Cu have been measured at the different stages of their preparation. The electron state of Cu atoms has been characterized. The composition of their closest environment, coordination numbers and interatomic distances have been determined. It has been found out, that during processing cucurbit[8]uril with copper acetylacetonate vapor at the first stage, Cu atoms of Cu(acac)2 molecules are coordinated by nitrogen (or oxygen) atoms of cucurbit[8]uril. It was also determined for certain that at the second stage there arise Cu–Cu bonds than the metallic copper phase in samples annealed at 250 °C in an H2 atmosphere. The process of copper atom clusterization depends on the preparation conditions and is more pronounced for samples that were processed in Cu(acac)2 vapor for a longer time and thus have higher copper concentration.