Tao Liu's research while affiliated with University of Science and Technology of China and other places

A series of adamantanamine-(OCH2CH2)n -phenothiazine (n = 0, 1, 2, 3) electron donors was synthesized. Photoinduced electron transfer was observed in the supramolecular complex of the phenothiazine derivatives with p-nitrobenzoyl-β-cyclodextrin (NBCD) through binding of the adamantyl group by the NBCD cavity, which is stabilized clearly via hydrophobic interactions in aqueous solution. Detailed Stern–Volmer constants were measured and they were partitioned into dynamic Stern–Volmer quenching constants and static binding constants. The results revealed an efficient electron transfer process inside the supramolecular systems compared to that controlled by diffusion. This observation also indicates that the chain length will influence the electron transfer efficiency of a supramolecular donor–acceptor system.

A series of N-bonded donor-acceptor derivatives of phenothiazine containing phenyl (PHPZ), anisyl (ANPZ), pyridyl (PYPZ), naphthyl (NAPZ), acetylphenyl (APPZ), and cyanophenyl (CPPZ) as an electron acceptor have been synthesized. Their photophysical properties were investigated in solvents of different polarities by absorption and emission techniques. These studies clearly revealed the existence of an intramolecular charge transfer (ICT) excited state in the latter four compounds. The solvent dependent Stokes shift values were analyzed by the modified Lippert-Mataga equation to obtain the excited state dipole moment values. The large excited state dipole moment suggests that the full (or nearly full) electron transfer take place in the A-D systems. In the system of A-D phenothiazine derivatives, the transition dipole moments Mflu were determined mainly by direct interactions between the solvent-equilibrated fluorescence 1CT state and ground state because of their lack of significant change with increase of the solvent polarity. The electron structure and molecular conformation of phenothiazine derivatives will be significantly changed with the increase of the electron affinity of the N-10 substituent.

The interactions of β-cyclodextrin (β-CD) with N-phenylphenothiazine (1), N-benzylphenothiazine (2) and N-phenethylphenothiazine (3) were studied by cyclic voltammetry. In aqueous solutions, increasing the amount of β-CD caused negative shifts in the anodic peaks and an increase in the current of the 1/1 +• and 3/3 +• couples owing to the fact that more 1 and 3 were included in the β-CD cavities. However, compound 2 neither gave an anodic nor a cathodic wave in the presence of β-CD because the oxidization reactions on the surface of electrode were controlled by the conformations of the N-substituted phenothiazines in the cavity of β-CD. In 1:9 methanol/water binary solutions, 1 and 3 were investigated by fast scan cyclic voltammetry which showed that the irreversible waves became quasi-reversible waves in the presence of β-CD, confirmed the stabilization of cation radical intermediates by β-CD. The electrochemical and absorption spectral data indicated 1:1 inclusion complex formation of β-CD with 1 and 3 cation radicals in methanol/water binary solutions and the binding constants of 1 +• and 3 +• were very large under this condition.