J O U R N A L O F C H E M I S T R Y Materials Communication Molecular tectonics: design, synthesis and structural analysis of a molecular network based on inclusion processes using a doubly fused p-isopropylcalix[4]arene Julien Martz,a Ernest Graf,a Mir Wais Hosseini,a* Andre� De Cianb and Jean Fischer aLaboratoire de Chimie de Coordination Organique and bLaboratoire de Cristallochimie et Chimie Structurale, Universite� Louis Pasteur, UMR CNRS 7513, F-67000 Strasbourg, France.E-mail: hosseini@chimie.u-strasbg.fr Received 31st July 1998, Accepted 1st September 1998 The synthesis of a hollow molecular module (koiland) possessing two divergent cavities was achieved by double fusion of two p-isopropylcalix[4]arenes in cone conformation by two silicon atoms. The formation of either a discrete binuclear inclusion complex in the presence of CH2Cl2 acting as stopper or of an infinite 1-D inclusion network (koilate) in the presence of hexadiyne acting as connector was demonstrated in the solid state by singlecrystal diffraction studies.The inclusion network was based on the interconnection of consecutive koilands by connector molecules. Over the last ten years much attention has been focused on molecular crystal engineering and the design of molecular networks in the solid state is still a subject of current interest.1 The majority of reported molecular networks are either based on hydrogen bonding2,3 or on coordination bonds.4,5 However, we have proposed that one may use inclusion processes based on van der Waals interactions as a construction principle to design molecular networks in the solid state.6 Thus, we demonstrated that 1-D molecular networks (koilates)7 may be generated under self-assembly conditions using hollow molecular receptors (koilands)8 possessing at least two divergent cavities Scheme 1 Structures of p-isopropylcalix[4]arene 1 and of hexadiyne 3 and connector molecules capable of bridging by double as welle as schematic representations of 1 in cone conformation and inclusion consecutive koilands (Fig. 1). of the koiland 2 obtained upon fusion of two units 1 by two Here we describe the synthesis of a new koiland as well as silicon atoms. its use in the formation of either a discrete exobinuclear inclusion complex or an infinite 1-D molecular network in the solid state. obtained in 9% yield by crystallisation from a 159 mixture of The design of the koiland 2 is based on the double fusion CH2Cl2–hexane.by two silicon atoms of two p-isopropylcalix[4]arenes 1 The synthesis of 2 (Scheme 1) was achieved in 39% yield (Scheme 1). The latter appeared to be an interesting backbone upon treatment of 1 in dry THF by NaH followed by addition since it has been shown that in the presence of p-xylene it of SiCl4.7 Compound 2 was obtained as colourless crystalline forms (151) and (251) inclusion complexes in the solid state.9 material after crystallisation from a CH2Cl2–MeOH mixture.Although the preparation of 1 based on Ni catalysed direct In addition to 1H and 13C NMR spectroscopy, mass specisopropylation of calix[4]arene using propene was recently trometry and elemental analysis, compound 2 was also reported,10 for the sake of experimental simplicity, we modified characterised by 29Si NMR in CDCl3 which revealed, as the reported Zinke–Conforth procedure11 by heating at 110 °C expected, a signal at -112.48 ppm.† for 2 h a 50575510 mixture of p-isopropylphenol, formal- In order to study the inclusion ability of 2, the latter was dehyde and sodium hydroxide.The pure compound 1 was crystallised from solvents capable of acting as stoppers. Thus, in the presence of CH2Cl2, 2, possessing two divergent cavities, formed indeed a discrete exobinuclear inclusion complex in the solid state. Single crystals (air stable rod-type morphology) were obtained upon slow diVusion of MeOH into a CH2Cl2 solution of 2.The X-ray analysis‡ (Fig. 2) revealed the following features: (i) 2 possessing a centre of symmetry was indeed composed of two p-isopropylcalix[4]arene units in cone conformation fused by two Si atoms adopting a tetrahedral coordination geometry with an average Si–C distance of ca. Fig. 1 Schematic representation of a discrete exobinuclear inclusion 1.61 A° and OSiO angle of ca. 109.4°; (ii) a discrete binuclear complex (a) and of an infinite inclusion network (b) formed between inclusion complex was formed between 2 and two CH2Cl2 an hollow molecular module and a stopper or connector units respectively. molecules; (iii) each cavity of the koiland was occupied by J. Mater. Chem., 1998, 8(11), 2331–2333 2331Fig. 2 Crystal structure of the exobinuclear inclusion complex formed between 2 and CH2Cl2 molecules acting as stoppers.For sake of clarity, H atoms are not presented. one solvent molecule with the shortest distance of ca. 3.68 A° between the carbon atom of the solvent and one of the carbon Fig. 3 A portion of the crystal structure showing the formation of an atoms of the koiland; (iv) whereas hydrogen atoms of the infinite inclusion network between koilands 2 and connectors 3.For sake of clarity, CHCl3 molecules present in the lattice and H atoms solvent were oriented towards the interior, the chlorine atoms are not presented. were facing the exterior of the cavity. The ability of 2 to form linear molecular networks based on inclusion processes was studied using as connector 3 possessing a cylindrical shape.Upon slow diVusion at 21 °C Notes and references of MeOH into a CHCl3 solution of 2 and 3 in large excess †1H NMR: (CDCl3, 300 MHz; 25 °C): d 1.07 (d, CH3, 12H, 6.8 Hz), (200-fold), suitable colourless single crystals (rhombic mor- 1.13 (d, CH3, 12H, 6.8 Hz), 1.22 (d, CH3, 24H, 6.8 Hz), 2.74 (m, isopr., phology) were obained after 8 h. The crystals, unstable outside 8H); 3.31 (d, CH2, 4H, 13.4 Hz), 3.39 (d, CH2, 4H, 13.9 Hz), 4.48 (d, the solution, thus obtained were studied by X-ray diVraction§ CH2, 4H, 13.6 Hz), 4.58 (d, CH2, 4H, 13.4 Hz), 6.79 (s, arom., 4H), 6.89 (s, arom., 4H), 6.91 (s, arom., 8H), 13C NMR: (CDCl3, which revealed the following features: (i) the crystals (mono- 50.32 MHz, 25 °C): d 23.67, 23.83, 24.12, 32.73, 33.15, 33.54, 34.44, clinic, P21/a space group) were compared of 2, 3 and CHCl3 126.04, 126.12, 127.19, 127.29, 129.14, 130.13, 132.66, 142.36, 145.02, molecules; (ii) as predicted, a 1-D network was formed between 148.44; 29Si NMR: (CDCl3, 59.63 MHz, 25 °C): d -112.48; 2 and 3 (Fig. 3), the solvent molecules were not participating FAB+ (meta-nitrobenzyl alcohol matrix) m/z 1232.7 (M·+, 100%), directly in the formation of the network; (iii) the observed 1217.6 (M·+ -CH3, 25%); Found: C 73.35, H 6.70; Calc.for network resulted from the interconnection, through inclusion C80H88O8Si2·CH2Cl2 (1232.60) C 73.78, H 6.88%. ‡Crystal data for 2·2CH2Cl2: (colorless, 173 K): C80H88O8Si2· processes, of 2 by 3; (iv) the assembling core leading to the 2CH2Cl2, M=1403.63, triclinic, a=11.6667(4), b=13.0829(5), formation of the 1-D network by translational symmetry could c=13.8915(5) A° , a=108.628(9), b=110.871(9), c=91.648(9)°, be identified as the inclusion of one of the methyl groups of 3 U=1852.9(5) A° 3, space group P19, Z=1, Dc=1.26 g cm-3, Nonius within a cavity of 2; (v) both the connector and the koiland CCD, Mo-Ka, m=0.244 mm-1, 4741 data with I>3s(I ), R=0.066, were centrosymmetric; (vi) the coordination geometry around Rw=0.081.§Crystal data for (2,3)n network (colorless, 173 K): C80H88O8Si2· the silicon atoms was tetrahedral with an average Si–O distance C6H6·2CHCl3, M=1550.63, monoclinic, a=13.6981(3), b= of 1.60 A° and an average OSiO angle of 109.4°; (vii) the 19.7336(6), c=15.3589(4) A° , b=95.721(9), U=4131.0(4) A° 3, space shortest C–C distance of 3.56 A° between the CH3 group of group P21/a, Z=2, Dc=1.25 g cm-3, Nonius CCD, Mo-Ka, m= connector and one of the carbon atoms bearing the phenolic 0.289 mm-1, 4567 data with I>3s(I ), R=0.065, Rw=0.081.Full crysgroup at the bottom of the cavity indicated a high degree of tgraphic details, excluding structure factors, have been deposited at inclusion.the Cambridge Crystallographic Data Centre (CCDC). See Information for Authors, Issue 1. Any request to the CCDC for this In conclusion, a molecular module possessing two divergent material should quote the full literature citation and the reference cavities was shown to form in the crystalline phase either a number 1145/116. discrete exobinuclear inclusion complex in the presence of solvent molecules acting as stoppers, or an infinite inclusion 1 M.C. Etter, Acc. Chem. Res., 1990, 23, 120; J. D. Dunitz, Pure molecular network in the presence of connector molecules. Appl. Chem., 1991, 63, 177; A. Gavezzotti, Acc. Chem. Res., 1994, 27, 309; G. R. Desiraju, Angew. Chem., Int. Ed. Engl., 1995, 34, Thus, one may use as a construction principle inclusion 2311; G.M. Whitesides, J. P. Mathias and T. Seto, Science, 1991, processes between hollow molecular modules and full connec- 254, 1312; M. Simard, D. Su and J. D. Wuest, J. Am. Chem. Soc., tor units to design molecular networks in the solid state. 1991, 113, 4696; F. W. Fowler and J. W. 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