A study on the molecular complexes of crown ethers with polynitro fluorenones

The interaction of four crown ethers, benzo-15-crown-5, dibenzo-18-crown-6, dicyclohexyl-18-crown-6 and dibenzo-24-crown-8 with three nitrofluorenones has been studied using electronic absorption, infrared, 1H NMR and 13C NMR spectral methods. It is shown that association constants of 1 :1 complexes vary linearly with the number of oxygen's in the ethers. The molecular binding properties are discussed collectively in terms of association constants, charge transfer transition energies, intensities of these bands, enthalpies of complexation and electron affinities of the acceptors. Evidence has been presented that the dominant contributions to charge transfers arise from π — π interaction. Possible overlap structures have been proposed based on infrared, and NMR spectra of the complexes