DOI: 10.1002/chem.200601813 Organogels of 8-Quinolinol/Metal(II)–Chelate Derivatives That Show Electron- and Light-Emitting Properties Michihiro Shirakawa, [a] Norifumi Fujita, [a] Takahiro Tani, [a] Kenji Kaneko, [b] Masayoshi Ojima, [c] Akihiko Fujii, [c] Masanori Ozaki, [c] and Seiji Shinkai* [a, d] Introduction Spontaneous, but programmed self-assembly of low-molecu- lar-weight compounds is an essential concept to construct distinct supramolecules for nanotechnology by the bottom- up method. Among various supramolecular architectures de- veloped thus far, low-molecular-weight gel systems have become a topic of growing interest because they are expect- ed to be useful not only as novel functional soft materials, but also as well-defined nanostructured assemblies. [1] In par- ticular, p-block-based low-molecular-weight gels have re- ceived much attention, because they have great potential in applications for nanoscale molecular electronics. [2,3] In the last several years, low-molecular-weight organogels with metal–chelate moieties, namely metallogels, have been widely investigated to explore advanced soft and nanomate- rials. [4] Metal chelates are favorable from a viewpoint of gel functionality because they have not only various electronic states arising from inorganic metal elements, but also limit- less possibilities of molecular design arising from organic li- gands. Until now, metallogels with various features of metal chelates have been reported to show unusual functional properties such as redox responsiveness, [5] catalytic action, [6] phosphorescence behavior, [7] spin-crossover phenomena, [8] conductivities, [9] and so on. [10] Among the numerous metal chelates, 8-quinolinol/metal–chelate derivatives are known to possess attractive electronic and luminescent properties. For instance, tri(8-quinolinol)aluminum (Alq 3 ) has become one of the most efficient electron transport and emitting materials for organic light-emitting diode devices. [11] Fur- thermore, Alq 3 nanowires and nanobelts are utilized as field emission materials. [12] Here, we report on gel formation and electron- and light- emitting properties of 8-quinolinol copper(II)–, palladi- Abstract: 8-Quinolinol/copper(II)-, pal- ladium(II)-, and platinum(II)-chelate- based organogelators (1M) and their nongelling reference compounds (2 M) were synthesized. Complexes 1 M could gelate various organic solvents at very low concentrations. Electron micro- scope measurements gave visual images of well-developed fibrous struc- tures characteristic of low-molecular- weight organogels. UV/Vis and FTIR spectroscopy revealed that the good gelation ability of 1 M arises from the p–p interactions of the chelate moieties and the hydrogen-bond interactions among the amide groups. Very interest- ingly, field emission performances of the nanofibers prepared from the 1M gels are evidently different depending on the electronic states of the three kinds of central metals. In addition, the 1Pt gel shows unique thermo- and sol- vatochromism of visible and phosphor- escent color in response to a sol–gel phase transition. Furthermore, the 1Pt gel possesses an attractive ability to in- hibit dioxygen quenching of excited triplet states, which increases the phos- phorescence quantum yield of this gel. This effect is attributed to the isolation effect of the phosphorescent chelate moiety from the dioxygen-containing solution phase. Keywords: chelates · field emission · gels · phosphorescence · self-assembly [a] Dr. M. Shirakawa, Dr. N. Fujita, T. Tani, Prof. S. Shinkai Department of Chemistry & Biochemistry Graduate School of Engineering Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan) Fax: (+ 81)92-802-2820 E-mail: seijitcm@mbox.nc.kyushu-u.ac.jp [b] Prof. K. Kaneko HVEM Laboratory, Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan) [c] M. Ojima, Prof. A. Fujii, Prof. M. Ozaki Division of Electrical, Electronic, and Information Engineering, Graduate School of Engineering Osaka University Suita Osaka 565-0871 (Japan) [d] Prof. S. Shinkai Center for Future Chemistry, Kyushu University 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan) Chem. Eur. J. 2007, 13, 4155–4162 # 2007 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 4155 FULL PAPER