Inclusion Complexation of Dimeric and Trimeric Oligo(ferrocenyldimethylsilanes) with γ-Cyclodextrin Jose ´ A. Fernandes, † Se ´rgio Lima, † Susana S. Braga, † Martyn Pillinger, † Paulo Ribeiro-Claro,* ,† Jose ´ E. Rodriguez-Borges, ‡ Andre ´ D. Lopes, § Jose ´ J. C. Teixeira-Dias, † and Isabel S. Gonc ¸ alves* ,† Department of Chemistry, CICECO, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal, CIQ, Department of Chemistry, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal, and Department of Chemistry and Biochemistry, Faculty of Science and Technology, University of the Algarve, Campus de Gambelas, 8000-062 Faro, Portugal Received July 29, 2005 The oligo(ferrocenyldimethylsilanes) FcSiMe 2 Fc and FcSiMe 2 [(η 5 -C 5 H 4 )Fe(η 5 -C 5 H 4 SiMe 2 )]- Fc [Fc ) (η 5 -C 5 H 5 )Fe(η 5 -C 5 H 4 )] were encapsulated in γ-cyclodextrin (CD) to give crystalline inclusion compounds with 2:1 and 3:1 (host-to-guest) stoichiometries, respectively. A complex between γ-CD and ferrocene was also prepared for comparison. The formation of true inclusion complexes was confirmed in the solid state by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), and 13 C/ 29 Si CP MAS NMR spectroscopy. Powder XRD reveals that the complexes containing ferrocene and the trimer 1,1′-bis(ferrocenyldimeth- ylsilyl)ferrocene have very similar solid-state structures based on channel-type packing of the host molecules. The complexes containing the oligo(ferrocenyldimethylsilanes) dehydrate up to 100 °C, after which no mass loss is registered by TGA in the temperature range 100- 225 °C. The dissociation of the complexes occurs slightly above 225 °C and is immediately followed by the simultaneous release of the guests and the decomposition of the host in the temperature range 250-310 °C. 13 C CP MAS NMR spectra of the inclusion compounds show that the encapsulation of the guest molecules in the CD cavity induces the host macrocycle to adopt a more symmetrical conformation, with each glucose unit in a more similar environment. The inclusion modes are discussed. Introduction Cyclodextrins (CDs) are cyclic oligosaccharides com- prising six (R-CD), seven (-CD), eight (γ-CD), and more D-glucose units linked by R-(1f4) glycosidic bonds. 1-3 Their shape is like a hollow truncated cone, and they have no hydroxy groups inside their cavity. Although the depths of the cavities for the three CD molecules are the same (7.9 Å), their cavity diameters are differ- ent: ca. 5.7, 7.8, and 9.5 Å for R-, -, and γ-CD, respectively. CDs are known to form inclusion com- plexes with a large number of low molecular weight organic molecules, inorganic ions, and metallo-organic species. 3-5 Since the early 1990s, the interaction of CDs with organic polymers has also been extensively inves- tigated. 6-12 Examples of polymers that have been suc- cessfully encapsulated include poly(propylene glycol), polypropylene, poly(methyl vinyl ether), polyisobutylene, polyesters, and polyamines. The resultant inclusion complexes are main-chain polyrotaxanes, which are potentially of interest as molecular machines. 12 Within this field, inorganic polymers have started to attract attention because they have excellent features such as resistance to heat and certain chemicals. Harada and co-workers have studied silicon-containing polymers and have shown that - and γ-CD form inclusion complexes with poly(dimethylsiloxanes) and poly(dimethylsilanes) of various molecular weights to give crystalline com- pounds. 13 A further, largely unexplored, approach for the for- mation of cyclodextrin-based supramolecular architec- * Corresponding authors. Fax: 00351-234-370084. E-mail: igoncalves@dq.ua.pt (I.S.G.); pclaro@dq.ua.pt (P.R.-C.). † University of Aveiro. ‡ University of Porto. § University of the Algarve. (1) Harata, K. In Comprehensive Supramolecular Chemistry; Szejtli, J., Osa, T., Eds.; Pergamon: Oxford, 1996; Vol. 3, pp 279-304. (2) Saenger, W.; Steiner, T. Acta Crystallogr. 1998, A54, 798. (3) Szejtli, J. Chem. Rev. 1998, 98, 1743. (4) Saenger, W. Angew. Chem., Int. Ed. Engl. 1980, 19, 344. (5) Fenyvesi, E.; Szente, L.; Russel, N. R.; McNamara, M. 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