Supramolecular Lanthanide Complexes with Cucurbituril: Luminescence and Logic Devices

Complexes of the composition [{DyLn(HO)(NO)}CB[6]] (NO) · HNO · 6HO (x = 1, Ln = Eu; x = 0.8, Gd, Ho) (I–III) were obtained from a mixture of lanthanide nitrates and cucurbit[6]uril (CHNO, CB[6]) in nitric acid upon heating at 100°C. According to X-ray diffraction analysis (XRD), the lanthanide cation in compounds I–III coordinates two oxygen atoms of the CB[6] molecule, HO molecules, and nitrate ions. Compounds I–III were characterized by XRD, IR and ICP-OES spectroscopy, and elemental analysis. Based on the luminescence spectra, the chromaticity coordinates were determined, with values very close to those of white light. This feature results from the presence of two Dy-centered emission bands of comparable intensity, one of which — the hypersensitive transition F → H — is due to the relatively high symmetry of the lanthanide coordination environment, close to C. Additionally, a distinctive feature of compounds I–III is the strong dependence of their luminescence spectra on the excitation wavelength. Based on this phenomenon, models of molecular logic devices have been proposed, capable of switching the luminescent signal upon irradiation with light of different wavelengths.