DOI: 10.1002/chem.200500565 A Highly Directional Fourfold Hydrogen-Bonding Motif for Supramolecular Structures through Self-Assembly of Fullerodendrimers Uwe Hahn, [a] JuanJ. Gonzµlez, [b] Elisa Huerta, [b, c] Margarita Segura, [b, c] Jean-FranÅois Eckert, [a] FranÅois Cardinali, [a] Javier deMendoza,* [b, c] and Jean-FranÅois Nierengarten* [a] Dedicated to Professor David I. Schuster on the occasion of his 70th birthday Introduction Since the pioneering work of Vçgtle in the late 1970s, [1] the synthetic concept based on repetitive growth with branching units has been investigated extensively, and has lead to a wide range of core-shell macromolecular structures, now recognized as dendrimers . [2] In recent years, the rapid advan- ces in dendrimer synthetic chemistry have focussed on the creation of functional systems, with increased attention being given to potential applications. [3] Among the large number of molecular subunits used for dendrimer chemistry, C 60 has proven to be a versatile building block and fuller- ene-functionalized dendrimers, that is, fullerodendrimers , [4] have generated significant research activities in the past few years. [5] In particular, the peculiar physical properties of full- erene derivatives make fullerodendrimers attractive candi- dates for a variety of interesting features in supramolecular chemistry and materials science. [6] C 60 itself is a convenient core for dendrimer chemistry [5a] and the functionalization of C 60 with a controlled number of dendrons improves dramatically the solubility of the fuller- enes. [7] Furthermore, variable degrees of addition within the fullerene core are possible and its almost spherical shape leads to globular systems even with low-generation den- drons. [8] On the other hand, specific advantages are gained by the encapsulation of a fullerene moiety in the middle of a dendritic structure. [9] The shielding effect resulting from the presence of the surrounding shell has been useful in op- timizing the optical limiting properties of C 60 derivatives, [10] to obtain amphiphilic derivatives with good spreading char- acteristics, [11] or to prepare fullerene-containing liquid-crys- talline materials. [12] The use of the fullerene sphere as a pho- toactive core unit has also been reported. [9] In particular, the Abstract: Supramolecular dendrimers resulting from the dimerization of full- erene-functionalized dendrons through a quadruple hydrogen-bonding motif were prepared. The synthetic strategy is based on the esterification of a tert- butoxycarbonyl (Boc)-protected 2- ureido-4-[1H]pyrimidinone precursor possessing an alcohol function with fullerodendrons bearing a carboxylic acid unit at the focal point. Subsequent acidic treatment to cleave the protect- ing group and reaction of the resulting amine with octylisocyanate affords the targeted compounds. As demonstrated by the results of MALDI-TOF mass spectrometry and 1 H NMR spectrosco- py, both of the 2-ureido-4-[1H]pyrimi- dinone derivatives form self-assembled dimers spontaneously through hydro- gen-bonding interactions, thus leading to supramolecular structures containing two or ten fullerene moieties. Keywords: aggregation · dendrim- ers · fullerenes · hydrogen bonds · self-assembly [a] Dr. U. Hahn, Dr. J.-F. Eckert, F. Cardinali, Dr. J.-F. Nierengarten Groupe de Chimie des Fullernes et des Systmes ConjuguØs Laboratoire de Chimie de Coordination du CNRS 205 route de Narbonne, 31077 Toulouse Cedex 4 (France) Fax: (+ 33)561-553-003 E-mail: jfnierengarten@lcc-toulouse.fr [b] Dr. J. J. Gonzµlez, E. Huerta, Dr. M. Segura, Prof. Dr. J. de Mendoza Departamento de Química Orgµnica Universidad Autónoma de Madrid Cantoblanco, 28049 Madrid (Spain) Fax: (+ 34)914-973-966 E-mail: javier.demendoza@uam.es jmendoza@iciq.es [c] E. Huerta, Dr. M. Segura, Prof. Dr. J. de Mendoza Institute of Chemical Research of Catalonia (ICIQ) 43007 Tarragona (Spain) Fax: (+ 34)977-920-226 # 2005 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim Chem.Eur.J. 2005, 11, 6666–6672 6666