Sh. Lee et al., CHARACTERIZATION OF SANDWICH CHARGE-TRANSFER COMPLEXES COMPOSED OF BIS-ANTHRACENE DONORS AND AROMATIC ACCEPTORS, Perkin transactions. 2, (5), 1996, pp. 847-852
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.