Langmuir and Langmuir-Blodgett films containing a porphyrin-ruthenium complex

• Published in: Journal of nanoscience and nanotechnology Vol. 5; no. 6; p. 909
• Main Authors: Wohnrath, Karen, Dinelli, Luis R, Mello, Sarita V, Constantino, Carlos J L, Leblanc, Roger M, Batista, Alzir A, Oliveira, Jr, Osvaldo N
• Format: Journal Article
• Language: English
• Published: United States 01.06.2005
• Subjects: Biomimetic Materials - analysis; Biomimetic Materials - chemistry; Biosensing Techniques - instrumentation; Biosensing Techniques - methods; Crystallization - methods; Electrochemistry - methods; Materials Testing; Membranes, Artificial; Nanostructures - analysis; Nanostructures - chemistry; Porphyrins - analysis; Porphyrins - chemistry; Ruthenium - analysis; Ruthenium - chemistry; Surface Properties
• ISSN: 1533-4880
• DOI: 10.1166/jnn.2005.132

The fabrication of supramolecular structures from the tetraruthenated porphyrin-containing phosphines, {TPyP[RuCl3(dppb)]4}, RuTPyP, is demonstrated with Langmuir and Langmuir-Blodgett films. The surface pressure-molecular area isotherms (pi-A) point to an edge-on arrangement for the RuTPyP molecules in the condensed state. Weak aggregation in the Langmuir films was indicated by non-zero surface potentials at large areas per molecule and a slight red shift in the ultraviolet-visible absorption spectrum in comparison to the spectrum in solution. Further aggregation occurs in the Z-type Langmuir-Blodgett films, which was confirmed with ultraviolet-visible spectroscopy of the deposited films. Fourier transform infrared and Raman spectroscopic data for powder and Langmuir-Blodgett films indicate that the RuTPyP molecules are chemically stable in Langmuir-Blodgett films regardless of the contact with water during film fabrication. The nanostructured nature of the Langmuir-Blodgett films was manifested in cyclic voltammetry due to the high sensitivity of the metallic centers in RuTPyP. Electrodes modified with Langmuir-Blodgett films exhibit an anodic peak at 100 mV and a cathodic peak at 7 mV, which is assigned to RuIII/RuII redox processes. Furthermore, Langmuir-Blodgett films from RuTPyP showed electrocatalytic activity for oxidation of benzyl alcohol, illustrated by a large shift of 100 mV in the anodic peak at 400 mV, while electropolymerized and cast films of the same compound displayed smaller and no activities, respectively.