Structure of poly-1,5-diaminonaphtalene) 1,5-DAN). A theoretical approach Roberto Salcedo a, * , Manuel Salmo Ân b , Martha Aguilar b , Toma Âs Herna Ândez-Perez b , Miguel Saloma c a Departamento de Polõ Âmeros, Instituto de Investigaciones en Materiales, Circuito Exterior s/n, Ciudad Universitaria, Universidad Nacional Auto Ânoma de Me Âxico, Coyoaca Ân 04510, Mexico b Instituto de Quõ Âmica, Circuito Exterior, Ciudad Universitaria, Universidad Nacional Auto Ânoma de Me Âxico, Coyoaca Ân, 04510, Mexico c Facultad de Quõ Âmica, Divisio Ân de Estudios de Posgrado, Universidad Nacional Auto Ânoma de Me Âxico, Coyoaca Ân 04510, Mexico Received 17 October 2000; received in revised form 5 March 2001; accepted 5 March 2001 Abstract The polymer of 1,5-diaminonaphtalene 1,5-DAN) was studied in several ways but there are still many doubts about its exact molecular structure and associated behaviour. We carried out a theoretical simulation of different proposed structures in order to elucidate the correct one. We obtained interesting results that showed some characteristics of the macroscopic behaviour. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Hydrocarbon; Polymerisation; Energy 1. Introduction The electrosynthesis of conducting polymer thin ®lm electrodes is an interesting research area, because they have many applications in several scienti®c and techno- logical ®elds. For example, electrodes coated with poly- aniline ®lms are used in batteries [1,2], gas separating membranes [3], biosensors [4] and electronic devices [5]. In addition, polypyrrole ®lms have been used as transparent anodes for diodes [6], as ¯uorophore [7], and they have also been used in metal-oxide-semiconductor devices [8]. These applications have prompted studies of the electropolymerisation of mono- and polynuclear aromatic hydrocarbons containing hydroxy or amino groups such as o-amino phenol [9,10], 5-amino-1-naphthol [11], 1-pyren- amine [12] and naphthylamine [13±16]. Other aromatic compounds containing two ±NH 2 groups such as o-phenyl- enediamine [17], 2,3-DAN [18], 1,8-DAN [19] and 1,5- DAN [20,21] have also been studied. Conducting ®lms of these materials can be obtained potentiodynamically by oxidation of monomers in acetonitrile or aqueous solutions. Jackowska and co-workers [20,21] performed electro- polymerisation of 1,5-DAN and proposed several possible molecular structures for the polymer that was formed. They support their conclusions mainly by IR analysis. Previously, we had carried out some experimental work along the same lines and had obtained some interesting results that comple- ment the work of the above authors. This information was used in the theoretical calculation study of the molecular structure and IR spectra. The aim of this contribution is to afford new suggestions about the molecular structure of these polymeric materials. 2. Methodology All calculations were performed using the hybrid B3LYP/ 6-31G pp method [22], which combines the exact Hartree± Fock exchange with Becke's [23] and uses the Lee±Yang± Parr correlation function [24] in order to include the most important correlation effects. The version used was that included in the gaussian98 [25] package. The IR spectra simulation and thermochemistry data were obtained by frequency calculations at the same level. Initial geometries were obtained using the Universal 1.01 Molecular Mechanics method [26] from the cerius software [27]. This choice of calculus was based because recent inves- tigations have demonstrated that the DFT-B3LYP method leads to excellent results for geometries and energies [28,29]. We performed a test and found the results to agree well with the previously obtained results for a similar Polymer 42 2001) 8737±8742 0032-3861/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S0032-386101)00200-2 www.elsevier.com/locate/polymer * Corresponding author. Tel.: 152-622-46-00; fax: 152-5-616-1201. E-mail address: Salcedo@servidor.unam.mx R. Salcedo).