DOI: 10.1002/asia.201000738 Chiral Bis(oxazoline) Ruthenium Complexes with Bipyridyl-Type N-Heteroaromatics: Comparative Stereochemical and Photochemical Characterization of their L- and D-Diastereomeric Geminate Isomers Masayoshi Onishi,* [a] Yoko Tashiro, [a] Yasuhiro Arikawa, [b] Junko Nagaoka, [a] Keisuke Umakoshi, [a] Yusuke Sunada, [c] and Koichi Nozaki* [d] Introduction Chiral nitrogen-based auxiliary reagents have vastly aroused the interest of synthetic chemists because of their high asymmetric induction performance in many enantioselective metal-assisted organic transformations. [1, 2] Development and utilization of diverse chiral nitrogen-based metal-coordinate systems have been well realized, [1, 3] including C 2 -symmetric (4S,4’S)-disubstituted bis(2-oxazoline) (R-biox)chelates [4] as one typical representative. Whilst tris(a-diimine)ruthen- ium(II), [RuACHTUNGTRENNUNG(bpy) 3 ] 2 + (bpy = 2,2’-bipyridyl), has been one of the most-extensively investigated coordination compounds, because of its interesting luminescent and electrochemical properties and also because of the various chemical reactivi- ties of the photogenerated metal-to-ligand charge-transfer ( 3 MLCT) species. [5] Furthermore, in the last few decades, from the spur of widely awakened interest in arranging ap- propriately functionalized molecular building-block variants to assemble new supramolecular architectures and also to make up their polymer or metal oxide-supported devices Abstract: Diastereomeric geminate pairs of chiral bis(2-oxazoline) rutheni- um complexes with bipyridyl-type N- heteroaromatics, L- and D-[RuACHTUNGTRENNUNG(L-L) 2 - ACHTUNGTRENNUNG(iPr-biox)] 2 + (iPr-biox = (4S,4’S)-4,4’- diisopropyl-2,2’-bis(2-oxazoline); L-L = 2,2’-bipyridyl (bpy) for 1 L and 1 D, 4,4’-dimethyl-2,2’-bipyridyl (dmbpy) for 2 L and 2 D, and 1,10-phenanthroline (phen) for 3 L and 3 D), were separated as BF 4 and PF 6 salts and were subject- ed to the comparative studies of their stereochemical and photochemical characterization. DFT calculations of 1 L and 1 D electronic configurations for the lowest triplet excited state re- vealed that their MO-149 (HOMO) and MO-150 (lower SOMO) characters are interchanged between them and that the phosphorescence-emissive states are an admixture of a Ru-to-biox charge-transfer state and an intraACHTUNGTRENNUNGliACHTUNGTRENNUNGgand excited state within the iPr-biox. Fur- thermore, photoluminescence proper- ties of the two L,D-diastereomeric series are discussed with reference to [RuACHTUNGTRENNUNG(bpy) 3 ] 2 + . Keywords: bis(oxazoline)s · chiral complexes · density functional calculations · photoluminescence · ruthenium [a] Prof. Dr. M. Onishi, Y. Tashiro, J. Nagaoka, Prof. Dr. K. Umakoshi Department of Applied Chemistry Faculty of Engineering, Nagasaki University Nagasaki 852-8521 (Japan) Fax: (+ 81) 95-819-2684 E-mail : onishi@nagasaki-u.ac.jp [b] Dr. Y. Arikawa Graduate School of Science and Technology Nagasaki University Nagasaki 852-8521 (Japan) [c] Dr. Y. Sunada Institute for Materials Chemistry and Engineering Kyushu University, Kasuga Fukuoka 816-8580 (Japan) [d] Prof. Dr. K. Nozaki Graduate School of Science and Engineering University of Toyama Toyama 930-8555 (Japan) Fax: (+ 81) 76-445-6549 E-mail : nozaki@sci.u-toyama.ac.jp Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000738. Chem. Asian J. 2011, 6, 1405 – 1415 # 2011 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 1405