ORIGINAL RESEARCH DFT analysis: Fe 4 cluster and Fe(110) surface interaction studies with pyrrole, furan, thiophene, and selenophene molecules Rosa L. Camacho-Mendoza • Eliazar Aquino-Torres • Julian Cruz-Borbolla • Jose G. Alvarado-Rodrı ´guez • Oscar Olvera-Neria • Jayanthi Narayanan • Thangarasu Pandiyan Received: 9 January 2013 / Accepted: 7 March 2013 Ó Springer Science+Business Media New York 2013 Abstract DFT studies of both the Fe 4 cluster and the Fe(110) surface interaction with pyrrole, furan, thiophene, and selenophene showed that selenophene forms a stabler adsorbate iron complex than the other heterocyclic mole- cules; this is consistent with the binding energy data that were calculated between the Fe cluster and the Fe(110) surface with the heterocycles. Furthermore, when the adsorption of the compounds with the iron cluster was analyzed by molecular orbital studies, the orbitals of sel- enophene overlapped more strongly with the Fe atom than that of the other molecules. In TD-DFT, the p ? p* peak observed for the molecules disappeared when they formed complexes, and there appeared a charge transfer band (ligand to metal), thus confirming the coordination of these molecules with the cluster. The data suggest that the chemisorption is an exothermic process. Keywords DFT  Heterocyclic  Iron clusters  Fe(110) surface corrosion inhibition Introduction The study of small clusters is of interest because they display unusual structural, magnetic, and catalytic proper- ties; for example, pure iron nanoscaled clusters, which exhibit high magnetic moments [1], are used as efficient catalysts in the production of single-walled carbon nano- tubes [2, 3], where the activation of the C–H bond is a crucial stage in the dehydrogenation reaction [4]. In addi- tion, the small-sized metal clusters possess a high surface- to-volume ratio that maximizes the reaction rate per unit amount of catalyst [5]. These results suggest that the unusual properties are strongly dependent on the size and the electronic configuration of the metal clusters. Small clusters are generally intermediates in the path from small molecules to solids, and their atomic composition spans from a few to several hundred thousand atoms [6, 7]. Moreover, the iron clusters have attracted much interest because of their good adsorption properties for organic ligands on the surface as well as their close relation to environmental corrosion [8–10]. Furthermore, the study of the bonding nature in the clusters and in their organic sorbates is considered a challenge from the theoretical and experimental points of view. Since the corrosion inhibition generally depends on several parameters such as the nature and oxidation state of the metallic surface, corrosion media, and the nature of the organic sorbate [11–13], thus, the quest for a suitable compound that effectively inhibits the corrosion of the metallic surface has gained much attention. In previous papers, how the structural data of corrosion inhibitors are R. L. Camacho-Mendoza  E. Aquino-Torres  J. Cruz-Borbolla (&)  J. G. Alvarado-Rodrı ´guez A ´ rea Acade ´mica de Quı ´mica, Universidad Auto ´noma del Estado de Hidalgo, Unidad Universitaria, km 4.5 Carretera Pachuca–Tulancingo, Pachuca, Hidalgo C.P. 42184, Mexico e-mail: jcruz@uaeh.edu.mx O. Olvera-Neria A ´ rea de Fı ´sica Ato ´mica Molecular Aplicada (FAMA), CBI, Universidad Auto ´noma Metropolitana-Azcapotzalco, Av. San Pablo 180, Col. Reynosa, Mexico, DF C.P. 02200, Mexico J. Narayanan Divisio ´n de Ingenierı ´a en Nanotecnologı ´a, Universidad Polite ´cnica del Valle de Me ´xico, Av. Mexiquense, Tultitla ´n, Estado de Me ´xico C.P. 54910, Mexico T. Pandiyan (&) Facultad de Quı ´mica, Universidad Nacional Auto ´noma de Me ´xico, Ciudad Universitaria, Me ´xico, DF C.P. 04510, Mexico e-mail: pandiyan@unam.mx; pandiyan@servidor.unam.mx 123 Struct Chem DOI 10.1007/s11224-013-0254-9