Journal of Chemical Crystallography, Vol. 30, No. 11, November 2000 ( c  2001) Crystal structure of diethoxynitrobenzene-p-tert-butylcalix [4]arene·2(CH 3 ) 2 C O: evidence of intra- and intermolecular CH/π interactions forced by crystal packing Nongnuj Jaiboon, (1) * Narongsak Chaichit, (2) Bongkot Pipoosananakaton, (1) Thawatchai Tuntulani, (1) and Mongkol Sukwattanasinitt (1) Received October 5, 2000 Diethoxynitrobenzene-p-tert-butylcalix[4]arene·2(CH 3 ) 2 C O crystallized in the monoclinic system, space group P 2 1 /c, with cell dimensions a = 16.1437(2) ˚ A, b = 21.0292(2) ˚ A, c = 18.9685(3) ˚ A and β = 110.308(1) ◦ . The asymmetric unit consists of a diethoxynitrobenzene-p- tert-butylcalix[4]arene molecule and two solvated acetone molecules. Besides the usual CH/π interaction between p-tert-butylcalix[4]arene π cavity and a solvated acetone, this structure shows the intra- and intermolecular CH/π interactions among a nitrobenzene ring, ethylene bridge of the ethoxynitrobenzene side chain and a solvated acetone molecule. KEY WORDS: Calix[4]arene; CH/π interaction; crystal structure. Introduction Interactions between C H groups and pi-elec- tron systems were found to be highly important driv- ing forces in conformation of organic compounds 1 and in supramolecular host–guest complexation. 2 Aoyama and co-workers demonstrated that com- plexes between calix[4]resorcarene and alcoholic guests in chloroform involve a substantial contribu- tion of the CH/π interaction between the alkyl groups of the guest and the polyhydroxy aromatic cavity of the host. 3,4 Thus far only CH/π interactions of the alkyl groups and π cavities of the macrocycles have been reported. In this article we report CH/π interactions between diethoxynitrobenzene-p-tert- butylcalix[4]arene and solvated acetone molecules in which CH/π interactions can be observed inside and outside the p-tert-butylcalix[4]arene cavity. (1) Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. (2) Department of Physics, Faculty of Science, Thammasart Univer- sity at Rangsit, Pathumthani 12121, Thailand. * To whom correspondence should be addressed. Experimental section The synthesis of diethoxynitrobenzene-p-tert- butylcalix[4]arene has been reported by Pipoosana- nakaton et al. 5 The compound can be crystallized as pale yellow prisms by addition of acetone into its CH 2 Cl 2 solution. Diffraction data were collected at room temperature on a Bruker SMART CCD area detector diffractometer. The collected data were re- duced using the program SAINT, 6 and the empirical absorption correction was done using the SADABS program. 7 The structure was solved by direct methods and all nonhydrogen atoms were refined anisotropi- cally based on full-matrix least-square methods us- ing SHELX-97 package for PC. 8 The O10 and O12 were refined disordered and were determined the s.o.f. using free variable. All hydrogen atoms except hydroxyl hydrogen atoms were geometrically calcu- lated using a riding model. The hydroxyl hydrogen atoms at O2 and O4 were found from difference Fourier maps and refined with isotropic displacement parameters. The final R 1 factor of 0.1105 is rather high because of vibrational disorder of the solvated ace- tone molecules. Summaries of crystal and experimen- tal data are given in Table 1. Final atomic coordinates 717 1074-1542/01/1100-0717$18.00/0 C  2001 Plenum Publishing Corporation