Preparation and ESR characterization of polyalkyl-s-indacenyl anion-radicals from polyalkyl-1,5-dilithio-s-indacenes C. Adams a , J. Araneda a , C. Morales a , I. Chavez a , J.M. Manriquez a , D. Mac-Leod Carey b , N. Katir c , A. Castel c , P. Rivière c,⇑ , M. Rivière-Baudet c , M. Dahrouch d , N. Gatica d a Facultad de Química, Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago de Chile, Chile b Departamento de Química, Universidad Andres Bello, República 275, Santiago de Chile, Chile c Laboratoire d’Hétérochimie Fondamentale et Appliquée, UMR 5069 du CNRS, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex 94, France d Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile article info Article history: Received 9 June 2010 Accepted 6 October 2010 Available online 13 October 2010 Keywords: Polyalkyl-(or chloropolyalky)l-s-indacenyl anion radicals ESR 1,1 0 ,2,2 0 -Tetramethyl-2,2 0 -bisimidazolidine Polyalkyl-lithio-s-indacenylimidazolidinium salt abstract Polyalkyl-(or chloropolyalkyl)-s-indacenyl anion radicals were obtained from the organodilithium deriv- atives of the corresponding substituted-1,5-dihydro-s-indacenes by three different methods: (i) UV pho- tolysis, (ii) oxidation by a ferrocenium salt, (iii) single electron transfer reaction from an electron rich olefin. The last reaction (iii) involves transient formation of an unstable polyalkyl-lithio-s-indacenyl imi- dazolidinium salt. The same salt, obtained by another way by reacting 1,3-dimethylimidazolidinium chloride with the polyalkyl-1,5-dilithio-s-indacene, also leads to the corresponding lithium polyalkyl-s- indacenyl anion radical. All lithium polyalkyl-s-indacenyl anion radicals studied were characterized from their ESR spectra. They present a characteristic symmetrical spin distribution. On the contrary a Rho- dium-COD polyalkyl-s-indacene radical presents a non symmetrical spin distribution. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Because of their potential use as ligands or spacers in the syn- thesis of binuclear complexes, conducting polymers and biological compounds, polyalkyl-s-indacenes and polyalkyl-1,5-dihydro-s- indacenes, as well as some of their radical anions, radical cations or radicals have been prepared and studied [1–10]. Here we report the lithium anion-radicals (Ar) ÀÅ Li + of various polyalkyl-s-indacenes or halopolyalkyl-s-indacenes which have been prepared by three different ways and then characterized by ESR. 2. Experimental section All reactions were performed under nitrogen using standard Schlenk tube and dry solvents. NMR spectra were recorded on Bru- ker AC 80 ( 1 H, 80 MHz), ARX400 ( 1 H, 400.13 MHZ); AC 200 ( 13 C, 50.32 MHz), ARX 400 ( 13 C, 100.62 MHz) spectrometers. Mass and gas chromatography (GC/mass) and mass spectra were recorded with a Hewlett Packard HP5989 in electron impact mode (Ei, 70 Ev), or a Rybermag R10-10 spectrometer operating in Ei mode, or by chemical desorption (DCi/CH 4 or NH 3 ). Infrared spectra were recorded on a Perkin–Elmer 1600FT spectrometer. ESR spectra were recorded on a Brüker spectrometer EPR ELFXSYS E 500. g Val- ues were calculated by the Brüker Xepr software using the fre- quencemeter integrated to the ER049X microwave bridge. The magnetic field was controlled by the NMR teslameter Brüker and verified against dpph. Elemental analyses were done by the ‘‘Cen- tre de Microanalyses de l’Ecole Nationale Supérieure de Chimie de Toulouse”. All Density Functional (DF) calculations reported here were performed with the Amsterdam Density Functional package, ADF 2006.01 [11]. All the structures were fully optimized (without any geometry constrain) via analytical energy gradient techniques employing the Local Density Approximation [12] (LDA), and the Generalized Gradient Approximation (GGA) method using Vosko, Wilk and Nusair’s local exchange correlations [13], with nonlocal exchange corrections by Becke [14], and non local electronic corre- lations by Perdew [15]. We used uncontracted type IV basis set used Triple-n accuracy sets of Slater-Type Orbitals [16] (STO) with a single polarization function added for the main group elements (2p on H and 3d on C). Frozen Core approximation [17] was applied to the inner orbitals of the constituent atoms: the C core up to 1s, Cl up to 2p and Rh up to 3d. For recrystallized compounds, melting points were measured on a Leitz microscope. 0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2010.10.002 ⇑ Corresponding author. Tel.: +33 5 61 55 83 48; fax: +33 5 61 55 82 04. E-mail address: riviere@chimie.ups-tlse.fr (P. Rivière). Inorganica Chimica Acta 366 (2011) 44–52 Contents lists available at ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica