Experimental and theoretical study of the compound [Pd(dmba)(NCO)(imz)] Oswaldo Treu-Filho a , Jose ´ C. Pinheiro b, * , Edson B. da Costa b , Joa ˜o E.V. Ferreira b , Antonio F. de Figueiredo b , Roge ´rio T. Kondo c , Vicente A. de Lucca Neto a , Rodrigo A. de Souza a , Alexandre O. Legendre a , Antonio E. Mauro a a Instituto de Quı ´ mica, UNESP, CP 335, 14800-900 Araraquara, SP, Brazil b Laborato ´rio de Quı ´ mica Teo ´ rica e Computacional, Departamento de Quı ´ mica, Centro de Cie ˆncias Exatas e Naturais, Universidade Federal do Para ´, CP 101101, 66075-110 Bele ´m, PA, Amazo ˆnia, Brazil c Sec ¸a ˜o de Suporte, Centro de Informa ´ tica de Sa ˜o Carlos, Universidade de Sa ˜o Paulo, 13560-970 Sa ˜o Carlos, SP, Brazil Received 2 January 2006; received in revised form 16 June 2006; accepted 21 June 2006 Available online 4 August 2006 Abstract The compound [Pd(dmba)(NCO)(imz)] (dmba = N,N-dimethylbenzilamine; NCO = cyanate; imz = imidazole) was studied through experimental and theoretical methods. The complex was synthesized and characterized by IR and NMR spectroscopy. To an appropriate representation of the molecular environment, Gaussian basis sets for the constituent atoms of the compound were built and, after ade- quate supplementation with polarization and diffuse functions, they were used to study the molecule. Calculations of electronic and vibrational structure of two possible isomers were carried out, showing that the compound, which contains the NCO GROUP trans to the Pd–C bond, is 4.29 kcal/mol more stable than the analogous one, where the imz ligand is trans to the Pd–C bond. The calculated molecular parameters, bond distances, and bond angles showed that the geometry around the metallic center is square-planar with the cyanate being linear. The theoretical infrared spectrum of C 1 symmetry (electronic state 1 A) is in accordance with the experimental one. It also verified the contribution of Pd (4d xz + 4d yz ) and Pd (4d xy ) in the HOMO and LUMO orbitals, respectively. Ó 2006 Elsevier B.V. All rights reserved. Keywords: GCHF method; DFT; Total atomic charges; Infrared spectroscopy; Palladium 1. Introduction Cyclometallated compounds constitute an important class of compounds within the organometallic chemistry, largely investigated nowadays. Particularly, there has been great interest in those compounds due to their application in a variety of fields such as catalysis [1], metallomesogens [2], synthesis of supramolecules [3] and in medical area as antitumor agents [4]. Cope and Friedrich [5] were the pio- neers in the late 1960s to synthesize cyclopalladated com- pounds using the N,N-dimethylbenzilamine as ligand. The metal–carbon bond presented in these compounds can suffer alkenes, alkynes, CO, CO 2 , isocyanide, and hal- ogens insertion, as well as alkylation, arylation, and acyla- tion reactions, according to a revision work by Caires and Mauro [6]. Palladium and platinum cyclometallated compounds [7] have been studied in recent years considering their cytotox- ic activity against tumor cells, comparable with cisplatine and carboplatine, which are recognized drugs clinically applied in cancer therapy [8]. In particular, cyclopalladated compounds have been the subject of intensive investiga- tions as anticancer agents not only for being stable enough to permit an efficient action drug, at low concentration in the organism, but also for having a considerable smaller cytotoxicity than the platinum analogue [9]. 0022-2860/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2006.06.018 * Corresponding author. Fax: +55 91 31831606. E-mail address: ciriaco@ufpa.br (J.C. Pinheiro). www.elsevier.com/locate/molstruc Journal of Molecular Structure 829 (2007) 195–201