Spectroscopic and Electrochemical Characterization of Langmuir−Blodgett Films of (2,3,9,10,16,17,23,24-Octakis((2-benzyloxy)ethoxy)phthalocyaninato)copper and Its Metal-free Analogue

Spectroscopic, electrochemical and spectroelectrochemical, and scanning probe microscopic characterization of thin films of (2,3,9,10,16,17,23,24-Octakis((2-benzyloxy)ethoxy)phthalocyaninato)copper, and its dihydrogen analogue, in contact with aqueous electrolytes is described. These materials form highly ordered Langmuir−Blodgett (LB) thin films, where the phthalocyanine (Pc) rings orient with the plane of the ring nearly perpendicular to the compression direction on the LB trough. The resultant thin films show remarkable mechanical stability on the trough, and atomic force microscopy studies show that the transferred thin films, in their fully compressed states, consist of stable bilayers of the Pc. X-ray diffraction studies indicate partial overlap of the benzyl-terminated side chains in adjacent Pc columns. While the DMF solution electrochemical behavior of these molecules showed a single quasi-reversible oxidation process, LB thin films showed two poorly resolved oxidation processes. Two electrochemically distinct domains in these thin films are indicated, which are a function of the aggregation behavior of these materials, and result from electrochemically driven changes in film morphology.