Single-step biocatalytic synthesis of sexithiophene

POLY 529

Subhalakshmi Nagarajan, mailtosubha@yahoo.com1, Ramaswamy Nagarajan, ram@uml.edu2, Mario Cazeca, mariocazeca@yahoo.com2, Jayant Kumar, Jayant_Kumar@uml.edu2, Ferdinando Bruno, Ferdinando_Bruno@uml.edu3, and Lynne A. Samuelson4. (1) Department of Chemistry, Center for Advanced Materials, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, (2) Department of Physics, Center for Advanced Materials, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, (3) U.S Army Natick Soldier Center, RDECOM, Kansas street, Natick, MA 01760, (4) Nanomaterials Science Team, U.S. Army Natick Soldier, RDECOM, Natick, MA 01760
Conjugated molecules, like thiophene oligomers, are important organic semiconductors with applications in photovoltaics and thin-film transistors. Among oligothiophenes,sexithiophene (a-6T) has been reported to have mobilities greater than 0.02 cm2/Vs which are only attainable if the compounds are pure. The conventional methods for synthesizing a-6T involve use of ferric/cupric chloride as catalysts which result in a-6T with metal impurities that require extensive purification. Here we report a unique method for the one-pot synthesis of a-6T involving enzyme catalyzed coupling of terthiophene(a-3T). The reaction is carried out in acetone-water or water-dimethylsulfoxide (DMSO) solvent systems in presence of sulfonated polystyrene and catalyzed by the enzyme horseradish peroxidase. a-3T is soluble in acetone and DMSO, while a-6T is insoluble in them and this difference in solubility causes precipitation of a-6T, while the catalyst (HRP) remains soluble in the reaction mixture. Matrix Assisted Laser Desorption Ionization spectroscopy clearly indicates the formation of a-6T.