Department of Chemistry Seminar Announcement Date/Time/VenueTitle/Speaker 20 Jan (Thu) 10am – S8 Level 3 Executive Classroom Directed Assembly of C 4 -Symmetric Vanadate-Centered Quadruplexes: Synergistic Ion-specific Transport and Asymmetric Catalysis Professor Chen Chien-Tien National Tsing Hua University, Taiwan Host : Asst Prof Huynh Han Vinh About the Speaker Professor Chen Chien-Tien, b 1964 in Taipei, Taiwan. National Tsing- Hua Univ. (BS 1986; MS 1988), Univ. of Illinois at Urbana-Champaign (Ph.D. 1994, Prof. S. Denmark), Scripps Research Institute (Postdoc. 1995, Prof. B. Sharpless) Associate Prof. (1995), Professor (2000-), Research Chair of NTNU ( ), Distinguished Professor of NTHU (2010-). Research filed: (synergistic) asymmetric catalysis, organic optoelectronic materials and LC-based optical switches, DNA photocleavages, and nanoparticle-encapsulated dendritic probes, directed assembly for synergistic ion-specific transport. Abstract All are Welcome We have developed a series of N-Salicylidene-based L-a-amino acids as chiral auxiliaries for chiral vanadyl(V) methoxide complex synthesis. These configurationally well-defined complexes have been examined for kinetic resolution of 2 o alcohols. They serve as efficient and highly enantioselective catalysts for asymmetric aerobic oxidation of a-hydroxy acid, phosphonic acid, and ketone derivatives at ambient temperature. The asymmetric inductions of the oxidation process are in the range of 50 - > 500 in terms of selectivity factors (k rel ) in most instances. X-ray crystallographic analysis of an adduct between N-benzyl-mandelamide and the catalyst allows for probing the origin of the nearly exclusive asymmetric control in the oxidation process. In the case of the 3,5-di-tert-butyl and 3,5-dihalo- substituted analogs, pentanuclear C 4 - symmetric complexes were formed when potassium salts were employed instead of the corresponding sodium salts. The complexes work synergistically in the asymmetric aerobic oxidations of various racemic a-hydroxy acid and ketone derivatives with excellent selectivity factors. A directed assembly process to form C 4 -symmetric, vanadate-centered helical quadruplexes, for the first time, from a given chiral oxidovanadium(V) complex allows for highly efficient K + -, Ag +, Ba 2+, Pb 2+, Hg 2+, and (chiral) ammonium ion-specific transports from aqueous phase into organic solvents, reminiscent of the K + specific transport exerted by four homochiral glycine residues of the opening site in KcsA membrane protein. References: (a) Weng, S.-S.; Shen, M.-W.; Kao, J.-Q.; Munot, Y. S.; Chen, C.-T. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, (b) Pawar, V. D.; Weng, S.-S.; Bettigeri, S.; Kao, J.-Q.; Chen, C.-T. J. Am. Chem. Soc. 2006, 128, (c) Chen, C.-T. and Lee, W.-Z. J. Org. Chem. 2007, 72, (d) Chen, C.-T.; Lin, Y.-H.; Kuo, T.-S. J. Am. Chem. Soc. 2008, 130, (e) Lee, W.-Z. and Chen, C.-T. et al. Organometallics 2009, 28, 652. (f) C.-T. Chen, J.-Q. Kao, S. B. Salunke, Y.-H. Lin; Organic Lett. 2010, 12, on web (Dec. 6).