ELSEVIER Inorganica Chimica Acta 254 (1997) 213-217 Preliminary Communication A cationic iron(III) porphyrin encapsulated between the layered structure of MoS2. A new approach to the synthesis of an Fe-Mo-S system Shirley Nakagaki, Antonio S. Mangrich, Fernando Wypych Departamento de Quimica, UniversidadeFederaldo Paranti (LABEPR).C.P. 19081, CEP 81531.990 Curitiba. PR. Brazil Received 8 July 1996;revised11 November 1996 Abstract A new Fe-Mo-S system was obtained from the interaction of MoS2and an iron(I11) porphyrin. The products were charact~rised by X-ray diffraction, UV-Vis and EPR spectroscopies.X-ray diffraction measurements indicated the formationof two distinct productsdepending on the {iron porphyrin} / {single layer MoS2} ratio employed.The interlayerexpansions (Adt ~-.4A; Ad,=9 A) suggestedmono- and bi-tayer arrangementsof the iron porphyrin into the van der Waals gaps between the host plates. Keywords: Nanocomposites: Molybdenum disulfide complexes: Porphyrin complexes; Nitrogenase complexes: EPR spectroscopy 1. Introduction The research field of the nanocomposites has recently attracted considerable interest, particularly when two-dimen- sional inorganic host lattices and polymeric organic guests are cor~cerned [1-5]. Such systems, in which components are mixed at the molecular level, can show hybrid physical and ,::heroical properties derived both from the host frame- work and the encapsulated (guest) molecules. The interest in Fe-Mo-S systems is related to the impor- tan~.e of biological nitrogen fixation catalysed by the nilrogenases, a component of which, known as the Mole protein, contains a unique Fe--Mo-S cluster believed to be the active site for dinitrogen reduction [6,7a]. Attempts to ~ynthesize structural models of this heterometallic cluster (the FeMoco cofactor) have produced a number of linear and cubanc-like metal-sulfur assemblies [ 7b ]. In this work, we introduce a new synthetic approach to an Mo-Fe-S sys- tem. Our interest in the preparation and characterisation of a nanocomposite consisting of the encapsulation of iron(llI) porphyrin between the layers of MoS,, is in consequence of the use of solid catalytic materials on heterogeneous catalysis [8,9]. We have been able to produce nanocomposites by interacting an iron porphyrin with single layers of the com- mercial compound 2H-MoS2. Layered nanocomposites derived of two-dimensional host lattices resemble intercalation compounds; the two types of material normally differ only in the preparation methods. In intercalation compounds, the diffusion rate of the guest mol- ecules into the host lattice decreases as the size of the guest increases. As a consequence, it is not possible to prepare intercalation compounds with organic polymers. In order to overcome this problem, two procedures have been developed: (i) intercalation of the monomer followed by chemical or thermal polymerisation [1,3]; (ii) encapsulation of the polymer by exfc!iation. This consists ofobtaining single lay- ers of the host material, promoting the adsorption of the polymer to the single layers and finally allowing them to re- aggregate [4,10-12]. The second method was employed in this work, when raeso-tetrame~hylpyfidylporphyrin iron (HI) (FeTM4PyP 5+ ) was encapsulated between the layers of MoS.~. 2. Experimental To prepare the suspension of single layers of MoS:, pow- dered 2H-MoS2 (~ 100 rag, Aldrich Chemical Co.) was dried under vacuum (0.1 Torr) for 2 h and then flushed several times with dry argon. LiBu" (5 ml, 2.4 mol 1- i solu- tion in hexane, Aldrich) and hexane (5 ml) were then added. The system was allowed to react under argon at 20°(2 for 5 days, according to Eq. (I) ix-- I ) [ 13,14]. 2H-MoS,_ + xLiBu ~~x/2n-CsHxs + LidMo~ ( I ) After 5 days, tim ternary compound (Li)JloS,., ~ 20 rag) was mixed with distilled water (50 ml) and sonicated for 2 h (4 × 30 min). This procedure yieldeda colloidal suspension of single layers of MoS, (Eq. (2)). 0020-16931971517.00 Copyright © 1997Elsevier Science S.A.All fights t~sm'ved Pll $0020-1693 (96) 05563-6