Molecular complexes of crown ethers, part 4: Complexes of crown ethers with picric acid

The intermolecular charge-transfer spectra of seven crown ethers (CE), viz, 15C5, 18C6, B15C5, B18C6, DC18C6, and DB24C8, with picric acid (PA) were studied in the UV-visible region in 1,2-dichloroethane (DCE) at 298.2 K. The complex formation equilibrium constant values,Kc, suggest that many factors contribute toKc, among them crown ether conformation, size and the presence of an aromatic ring in the CE.