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Research Article

Electrostatic Self-Organization of Robust Porphyrin−Polyoxometalate Films

Supporting Info

Giorgio Bazzan,^† Wendy Smith,^† Lynn C. Francesconi,^† and Charles Michael Drain*^†^‡

Department of Chemistry and Biochemistry, Hunter College and Graduate Center of the City University of New York, 695 Park Avenue, New York, New York 10065, The Rockefeller University, 1230 York Avenue, New York, New York 10065

Langmuir, 2008, 24 (7), pp 3244–3249

DOI: 10.1021/la7031658

Publication Date (Web): March 6, 2008

†

City University of New York.

Author to whom correspondence should be addressed. E-mail: cdrain@hunter.cuny.edu.

‡

Rockefeller University.

Abstract

Strategies to create thin films using layer-by-layer methods use oppositely charged polymeric polyelectrolytes for both or at least one component to beneficially exploit multitopic electrostatic interactions between the deposited layers with opposite charges. In contrast, the electrostatic deposition of tetracationic 5,10,15,20-tetrakis(1‘-methyl-4‘-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP⁴⁺) with tetraanionic polyoxometalates such as EuPW₁₁O₃₉^4- or SiW₁₂O₄₀^4- onto charged substrates, such as mica, or polar substrates, such as glass and indium−tin oxide (ITO), demonstrates that the use of polymeric components is not a priori necessary. The use of molecules in sequential dipping approaches requires a careful balance in the interaction energies between the oppositely charged molecules, as demonstrated by the observation that a tetraanionic porphyrin such as 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin does not form layers with TMPyP⁴⁺. In the present case, these systems require several rounds of dipping to obtain films of uniform coverage and durability. The thin films deposited onto glass, quartz, ITO, and mica are surprisingly robust, since they are not removed by sonication in either organic solvents or 100 mM NaCl.

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