On the design of a planar oxo matrix for binding transition metals: a density functional approach P. Belanzoni, M. Rosi, A. Sgamellotti * Centro di Studio CNR per il Calcolo Intensivo in Scienze Molecolari, c/o Dipartimento di Chimica, Universita Á di Perugia, via Elce di Sotto 8, I-06123 Perugia, Italy Received 25 July 2001; revised 13 November 2001; accepted 23 November 2001 Abstract Density functional theory method is applied to investigate the geometry and electronic structure of a molecular system considered as a model of a metal±oxo surface. Vanadyl cation complexed by 2-hydroxyisonaphthalic acid is chosen as a building block, which gives an extended layer-type structure where planar, dimeric units are held together by a platinum or zirconium atom. The resulting two metal-linked two-dimer systems can be used as suitable model systems for polyoxomatrices, where the coordination around both platinum and zirconium atoms is square-planar. The electronic structures point out unpaired electrons which are responsible for magnetic interactions occurring mainly within isolated dimeric units for platinum system and with a more complicated spin distribution between adjacent dimers in the plane for zirconium system. q 2002 Elsevier Science B.V. All rights reserved. Keywords: Molecular modeling; Planar oxo matrix; Transition metals; Density functional theory method 1. Introduction The design of building blocks for the construction of two- and three-dimensional arrays of oxygen atoms suitable for binding transition metals is particularly challenging [1,2]. This paper deals with the molecular modeling of a bidimensional extended metal±oxo structure. Such a kind of material can have, depending on the nature of the metal to which the oxo matrix is ®xed, some desired chemical and physical properties [3]. In particular, for the construction of planar oxo matrices, it is possible to use the anion derived from 2-hydroxyisonaphthalic acid as a building block which, composed only of sp 2 carbons, has a rigorously planar geometry [4]. The material structure consists of in®nite chains of molecules linked together by a network of hydrogen bonds involving carboxylic oxygen atoms and water molecules. The complexa- tion with vanadium gives rise to extended structures of layer-type where planar dimeric units are linked by potassium countercations. The coordination around vanadium on a single isolated dimeric unit of the matrix is pyramidal, with the two metal atoms protruding from the basal plane in opposite directions. Magnetic susceptibility data show strong antiferro- magnetic interactions between the two metal atoms within the dimeric unit. A theoretical study of these systems must necessarily start from a characterization of the models which can be appropriate for their description, in connection with the extensive use in the ®eld of catalysis. We selected the vanadium-containing Journal of Molecular Structure Theochem) 583 2002) 73±79 0166-1280/02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved. PII: S0166-128001)00805-3 www.elsevier.com/locate/theochem * Corresponding author. Tel.: 139-05-585-5516; fax: 139-05- 585-5606. E-mail address: sgam@thch.unipg.it A. Sgamellotti).