Communications 1458 Ó WILEY-VCH Verlag GmbH, D-69469 Weinheim,1998 0935-9648/98/1712-1458 $ 17.50+.50/0 Adv. Mater. 1998, 10, No. 17 Experimental All chemicals used were from Aldrich and were used as received. PEG- 200 solutions of bpy and metal ions were easily obtained by direct mixing of the components. A few minutes of stirring was necessary only in the case of the metal salts. We used Eu(NO 3 ) 3 ×5H 2 O for Eu 3+ and Tb(NO 3 ) 3 ×5H 2 O for Tb 3+ . In the present work, the bpy concentration was always 0.1 M and the lanthanide ion concentration was 0.02 M. Sol-gel matrices containing PEG and luminophores were created as fol- lows: TMOS was partially hydrolyzed by mixing with acidified water (HCl, pH 3.0) at a molar ratio of 1:2 [14]. The mixture was continuously stirred for 1 h. At first it was turbid, but in the course of hydrolysis it became clear. Then 1 mL of this original sol was combined with 5 mL of the PEG solution. The mixture was stirred for a further 30 min, poured into PMMA cuvettes, covered with perforated aluminum foil, and left to dry at 50 C. The gel was ready after about 1 week. When the mixture is still fluid, thin films can also be made by dip-coating. Absorption spectra were made using a Cary 1E spectrophotometer; the luminescence spectra were made with a home-assembled spectrofluorom- eter using Oriel parts and employing a 150 W Xe lamp. All measurements were made under ambient conditions. Received: May 13, 1998 Final version: June 22, 1998 ± [1] N. Sabbatini, M. Guardigli, J.-M. Lehn, Coord. Chem. Rev. 1993, 123, 201. [2] T. Jin, S. Tsutsumi, Y. Deguchi, K.-I. Machida, G.-Y. Adachi, J. Elec- trochem. Soc. 1995, 142, L195. [3] T. Jin, S. Inone, S. Tsutsumi, K.-I. Machida, G.-Y. Adachi, J. Non- Cryst. Solids 1998, 223, 123. [4] Y. Zhao, D. Zhou, G. Yao, C.-H. Huang, Langmuir 1997, 13, 4060. [5] R.-J. Zhang, K.-Z. Yang, Langmuir 1997, 13, 714. [6] C. A. Vincent, in Electrochemistry, Science and Technology of Poly- mers-2 (Ed: R. G. Linford), Elsevier Applied Science, London 1990, p. 47. [7] H. Cai, G. C. Farrington, J. Electrochem. Soc. 1992, 139, 744. [8] M. S. Mendolia, G. C. Farrington, Solid State Ionics 1992, 53, 1059. [9] L. D. Carlos, Solid State Ionics 1996, 85, 181. [10] V. Bekiari, P. Lianos, J. Non-Cryst. Solids 1998, 226, 200. [11] M. Denjeka, E. Snitzer, R. E. Riman, J. Lumin. 1995, 65, 227. [12] B. C. Joshi, J. Non-Cryst. Solids 1995, 180, 217. [13] D. Segal, Chemical Synthesis of Advanced Ceramic Materials, Cam- bridge University Press, Cambridge 1989. [14] M. Ferrer, P. Lianos, Langmuir 1996, 12, 5620. FT-Raman Studies of Charged Defects Created on Methyl End-Capped Oligothiophenes by Doping with NOBF 4 ** By Juan Casado, Víctor Hernµndez, Shu Hotta, and Juan T. López Navarrete* Oligothiophenes have been investigated extensively in recent years as models of polythiophenes with defect-free chemical structures. [1±3] The ease of controlling their elec- tronic structure and properties by simply varying the de- gree of polymerization is one of the advantages of this class of organic electrical conductors. These materials have rap- idly been applied to a wide range of technical devices, in- cluding nonlinear optics, [4] Schottky diodes, [5] light-emitting diodes (LEDs), [6] and thin-film field effect transistors (FETs). [7] A few articles have been published recently on the synthesis of various families of a,a¢-end-capped oli- gothiophenes with variable chain length. [8±12] Processability of the oligomers is generally better than that of the poly- mers. As an example, the replacement by methyl groups of the a-hydrogens at both ends of the oligothiophene intro- duces ordering in the crystal. [13,14] The a,a¢-methyl end-capped oligothiophenes are particu- larly useful for obtaining information on the nature of the charge carriers in doped polythiophene, since the blocking of the a-positions prevents further undesired reactions upon doping. In the present communication, we report on the FT-Raman spectra of two a-methyl-substituted oligo- mers of polythiophene (see Scheme 1), which have been doped with a relatively strong acceptor such as NOBF 4 . These new experimental data are compared with those pre- viously obtained for the pristine materials, and they are in- terpreted on the basis of the effective conjugation coordi- nate theory. Evidence is found for the first time that the Raman spectra of the second oxidized species for longer ± [*] Prof. J. T. López Navarrete,Prof. V. Hernµndez, Dr. J. Casado Departamento de Química Física Facultad de Ciencias, Universidad de Mµlaga E-29071 Mµlaga (Spain) Dr. S. Hotta Matsushita Research Institute Tokyo, Inc. Advanced Materials Research Laboratory 3-10-1 Higashimita, Tama-ku, Kawasaki 214-8501 (Japan). [**] This work was supported in part by the DGES (Dirección General de Enseæanza Superior, MEC, Spain) through the research project PB96- 0682, and made use of the Junta de Andalucía shared facilities (group no. FQM-0159). The authors also thank the Servicio Central de Apoyo a la Investigación (SCAI) of the University of Mµlaga, for the use of the scientific instrumentation and the technical facilities. J.C. is grate- ful to the MEC (Spain) for a personal grant. _______________________ See page 1411 for ordering details. Scheme 1. Chemical structure of the a,a¢-dimethyl end-capped pentamer.