CHARACTERIZATION OF SANDWICH CHARGE-TRANSFER COMPLEXES COMPOSED OF BIS-ANTHRACENE DONORS AND AROMATIC ACCEPTORS

Properties of 'sandwich' charge-transfer (CT) complexes composed of bi s-anthracene host compounds, in which two anthracences are connected b y an anthraquinone spacer, and various aromatic accepters have been sy stematically studied, Complexation stronger than that seen in monomer model compounds was observed in all cases, Thermodynamic analysis reve aled that this enhanced binding to accepters is due to larger enthalpi c gain accompanied by a lower entropy loss effected by preorganization of the host, The major factor that determines the association constan ts is not the strength but the steric features of acceptor, Binding co nstants for fluorenones with nitro residues in the bay region are smal ler because of the bulkiness of the substituents, It has been establis hed that the CT complexes are of the weak b(pi)-a(pi) type from the an alysis of the CT absorption energy. Complexation-induced chemical shif ts in the LH NMR spectra indicate highly oriented guest inclusion and have revealed some geometrical features of the complexes.