New layered double hydroxides intercalated with substituted pyrroles. 1. In situ polymerization of 4-(1H-pyrrol-1-yl)benzoate Jairo Tronto a , Fabrice Leroux b , Eduardo Luis Crepaldi a , Zeki Naal c , Stanlei Ivair Klein d , Joa ˜o Barros Valim a, * a Departamento de Quı ´mica, Faculdade de Filosofia Cie ˆncias e Letras de Ribeira ˜o Preto, Universidade de Sa ˜o Paulo, Av. dos Bandeirantes 3900, 14040-901 Ribeira ˜o Preto, SP, Brazil b Laboratoire des Mate ´riaux Inorganiques, Universite ´ Blaise Pascal, UMR-CNRS no. 6002, 63177 Aubie `re cedex, France c Departamento. de Fı ´sica e Quı ´mica, Faculdade de Cie ˆncias Farmace ˆuticas de Ribeira ˜o Preto, Universidade de Sa ˜o Paulo, Av. dos Bandeirantes 3900, 14040-903 Ribeira ˜o Preto, SP, Brazil d Departamento de Quı ´mica Inorga ˆnica, Instituto de Quı ´mica de Araraquara, Universidade Estadual Paulista, R. Francisco Degni, s/n, 14800-090 Araraquara, SP Brazil Abstract The two-dimensional hybrid organic–inorganic materials Zn 2 –Cr and Zn 2 –Al-LDHs (Layered Double Hydroxides) containing 4-(1H-pyrrol- 1yl)benzoate anions as the interlayer anions were synthesized by the co-precipitation method at constant pH followed by subsequent hydrothermal treatment for 72 h. The materials were characterized by PXRD, 13 C CP-MAS NMR, ESR, TGA, and TEM. The basal spacing found by the X-ray diffraction technique is coincident with the formation of bilayers of the intercalated anions. Solid-state 13 C NMR and ESR data strongly suggest the partial in situ polymerization of the 4-(1H-pyrrol-1yl)benzoate anions during coprecipitation. q 2006 Elsevier Ltd. All rights reserved. Keywords: A. Nanostructures; Polymers; C. X-ray diffraction; D. Nuclear magnetic resonance (NMR); Electron paramagnetic resonance (EPR) 1. Introduction The combination of (conducting) polymers and inorganic materials is a very promising research field [1–5]. Particularly, Layered Double Hydroxides (LDHs) are intercalation-type materials whose lamellar architecture provides the opportunity of separating, periodically and in the nanoscale (1–2 nm), the inorganic and organic counterparts of the hybrid composite [6–10]. The structure of LDHs can be described considering the brucite-like structure, Mg(OH) 2 , where M(II) cations are in the centre of edge-sharing octahedra, which results in an overall planar structure. A part of the divalent cations is isomorphously replaced by trivalent cations, positively charged layers are formed and the excess of positive charge is compensated by interleaved anions. A large variety of anions, such as, heteropolyacids, metallo-organic complexes, and also poly- mers, can be intercalated into LDH layers [6–13]. Some of the resulting materials are extensively studied for their potential applications in the fields of catalysis and catalyst supports, matrices for the controlled release of drugs, plastic additives, adsorbents, flame retardants, ion exchangers, batteries, and (bio)sensors [14–22]. Moreover, synergistic interaction between the organic and inorganic parts may happen, reinforcing the interest of such organic inorganic assemblies. In the wide branch of the hybrid polymer LDH materials, the incorporation of organic moiety is performed using functionalized monomers taking into account the anionic exchange capacity of the LDH host structure. Although to the best of our knowledge, pyrrole derivatives have not been incorporated into LDH gap so far. We now report the synthesis and characterization of Zn 2 –Al- and Zn 2 –Cr-LDH intercalated with 4-(1H-pyrrol-1-yl)benzoate and its polymer obtained in situ, which belongs to the ever-growing class of two- dimensional inorganic organic hybrid materials. 2. Experimental methods The LDHs hybrid materials with a metal ratio Zn:Cr or Zn:Al of 2:1, were synthesised by coprecipitation at constant pH followed by a hydrothermal treatment. A solution contain- ing 1.92!10 K3 mol of Zn(NO 3 ) 2 $6H 2 O and 9.60!10 K4 mol of Cr(NO 3 ) 3 $9H 2 O or Al(NO 3 ) 3 $9H 2 O in 18 mL of water was Journal of Physics and Chemistry of Solids 67 (2006) 968–972 www.elsevier.com/locate/jpcs 0022-3697/$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2006.01.012 * Corresponding author. Tel.: C55 16 602 3766; fax: C55 16 633 8151. E-mail address: jobvalim@usp.br (J.B. Valim).