ELSEVIER Synthetic Metals 101 (1999) 762-763 Aniline and aminonaphthalenesulfonic acid-based materials: optimization of magnetic properties at ambient temperature F. Tsobnang*, C. ChalliouP, A. Wang”, I. Lado-TouriEo”, D. Cottevieilleb and A. Le Mehautk’ aInstitut Sup&ieur des Materiaux duMans,44, avenue F.A. Bartholdi,72000 Le Mans (France) b Alcatel Al&horn CRC,Alcatel UT Branche CRCRoute deNozay, 91460 Marcoussis (France) Abstract Computational andexperimental studies on aniline andaminonaphthalenesulfonic acid-based materials were carried out in order to solvequestions relatedto the reproducibilityof results, influenceof pollution and correlation between magnetism and chemistry encountered in previous workson this type of materials. Thestrictly organic originof the magnetic properties as well as its potentialapplications will be discussed. Keywords: molecular magnetism, DensityFunctional Theory 1. Introduction During the last 10 years, the synthesis of magnetic materials containing only light elements (C, N, 0, S and H), the so-called organic magnets, has been the subject of a considerable amount of work, both theoretically and experimentally [l, 2, 31. As a result, today a few organic materials [4, 5, 6, 71 are known to display ferromagnetic or ferromagnetic-like properties, but their transition temperatures are still too low for practical applications. Reports of high- temperatureorganic magnets have been controversialand linked to pollutionby transition metals [l, 21. This work is focused on the magnetic characterization of materials based on aniline and aminonaphthalenesulfonic acid [2, 8] by means of -several experimental andtheoretical studies. 2. Experimental The moleculeshownin figure 1 was prepared by mixing 0.03 mol of l-chloro-2,4dinitrobenzene with 0.02mol of 1-aminonaphthalensulfonic acid in a DMF/pyridine solution. After 24 h of stirring a solidprecipitated, which was filtered off. Thefiltrate was evaporated and crystallized at low temperature before being dissolved in acetic acid and precipitated in ether. The samples were characterized by RMN’H, JR-TF and elementary analysis: RMN’H - 6 @pm):8.29 (HI); 10.55(HZ);7.6-7.8 (I+); 7.8- 7.9 (a); 6.5 (Hs); 7.5-7.7 (&) ; 7.5-7.7 (H7); 8.11 (Hz& 9.35- 9.5 (Hg); 8.1 (HK,);8.95 (-HI& IR-TF - 1196 (SO3 asp.); 1031 (SO3 sym.); 1132 (SO3 naphthalene); 1546,1339 (NO2conj.); 3288 (NH); 681 (C-S). Elementary analysis -% theoretical:C (49.4) ; H (2.9) ; N (10.8); 0 (28.7); S (8.2). % experimental: C (51.28); H (2.49) ; N (13.25) ; 0 (27.02); S (5.96). Magnetic measurements were carried out with a vibrating sample magnetometer, Saturation magnetization and coercive field obtained for two samples prepared as indicated aboveare presented in Table 1. The evolution in time (after crystallization) of magnetic properties of thesetwo samples are also shown, 6 7 NO2 Fig. 1. Molecular structure of dinitrophenyl)naphthalene-6-sulfonic acid. l-( l-amino-2,4- Table 1 Variation of magnetic properties with time of l-( l-amino-2,4- dinitrophenyl)naphthalene&.ulfonic acid. Sample ............... Hc cG> .......................................... ....... . ... MS (emu) ................ ........ ....... .......... 1 day 64 0.72*10 :3.. 1 3 days 48 o.45*10-3 7 days 0 0 2 few hours 95 3.15*10” 29 davs 0 0 0379-6779/99/$ - see front matter 0 1999 Elsevier Science S.A. All rights reserved. PII: SO379-6779(98)00653-5