Photoinduced recoordination of metal cations in complexes with chromogenic crown ethers

A fast photochemical process, namely, photoinduced recoordination of a metal cation in the cavity of a chromogenic crown compound is considered. The photoinduced recoordination of cations is an efficient intramolecular adiabatic relaxation process resulting in the decrease in the excited-state energies of metal complexes, which in some cases may precede the complete release of the cation to the solution. The principles of molecular design of optical sensors based on crown ethers and the photoinduced recoordination and cation photoejection mechanisms are discussed. The attention is focused on the effect of photoinduced recoordination on the spectral luminescence properties of the complexes of crown-containing dyes, on the effect of complexation on the intramolecular charge transfer and cation recoordination in nonexcited complexes and on theoretical methods for investigation of these processes.