NEWS OF THE WEEK MATERIALS
SCIENCE
SEMICONDUCTOR SWITCHEROO Scrambling molecular chain's building blocks determines p- or n-type activity unmodified sexithiophene (a chain chemistry professorTbbin of six thiophenes). The researchJ. Marks and coworkers ers also prepared thin-film tranhave synthesized a set of perflu- sistorsfromthe oligomers. oroarene-modified thiophene The oligomers with perfluooligomers that can be either p- roarenes in the inner positions of type or n-type semiconductors, the chain are p-type semicondepending on the positions of the ductors, they found—the same electron-deficient perfluoroarene as sexithiophene. But the oligbuilding blocks [Angew. Chem. bit.omer with perfluoroarene rings Ed., 42,3900 (2003)}.This is the at the ends of the chain is an nfirst known family of compounds type semiconductor. in which individual members can Marks and coworkers attribtake on different conduction ute the differences in electronic I N S I D E OUT Replacing two thiophenes of pathways, the researchers say. behavior "to a subtle interplay of sexithiophene with perfluoroarenes yields new "The achievement should aid in molecular stereoelectronic efp-type semiconductors (top and middle) and a rare the design of high-mobility n- fects on molecular energy levels." organic n-type semiconductor (bottom). type organic semiconductors," These effects are modulated by Marks adds. differences in intermolecular atoms changes in the oligomer is Because organic-based semi- packing of the oligomers that re- nice work," notes Ananth Dodconductors can be made smaller sult from interactions between abalapur, a professor of electriand are more flexible than silicon- the electron-poor perfluoroarene cal and computer engineering at based materials, they are expect- rings and electron-rich thiophene the University of Texas, Austin. ed to lie at the heart of future gen- rings, they note. "The new compounds are useful erations of thin-film transistors, "The synthesis and careful since they are based on the welllight-emitting diodes, and other mapping ofwhat happens as the known sexithiophene."—STEVE electronic devices. These "plas- number and position of fluorine RITTER tic electronics" are generally fabricated by alternating layers of p- G O V E R N M E N T type (hole-transporting) and n-type (electron-transporting) materials. A number ofp-type organic compounds have already I eremy M. Berg, professor of biophysics tells C&EN.MHe is been synthesized, but n-type orand biophysical chemistry and director an outstanding ganic compounds are more chalof the Institute for Basic Biomedical leader and one of lenging to prepare and are still Sciences at Johns Hopkins University School the bright lights of rare. of Medicine, was appointed director of the his generation." The researchers made six-ring National Institute of General Medical SciFor his part, Berg oligomers in which the two per- ences (NIGMS) last week by NIH Director tells C&EN that he fluoroarene rings are either in the Elias A. Zerhouni. Within NIH, NIGMS is the is excited to be joining the agency. "NIH has middle of the chain, next to the single largest source of funding for chembeen very good to me and very good to the ends of the chain, or in the termi- istry research. sort of science that I believe in," he says. nal positions of the chain. Solu"Having a chance to help direct it is a Berg, 45, holds B.S. and M.S. degrees in tions and thin films of the com- chemistry from Stanford University and a thrill." pounds were characterized by a Ph.D. from Harvard University. In early November, Berg will replace Judith suite of analytical methods, in"NIH and the government are very lucky to H. Greenberg, who has been acting director of chidingX-ray diffraction and cyclic have been able to attract Dr. Berg/' Zerhouni NIGMS since May 2002.—SUSAN MORRISSEY voltammetry, and compared with
N
ORTHWESTERN UNIVERSITY
Berg Named Director Of NIGMS
J
HTTP://WWW.CEN-ONLINE.ORG
C & E N / S E P T E M B E R 1. 2003
9
