MOLECULAR RESOLUTION IMAGES OF A CALIX[6]ARENE FROM ATOMIC-FORCE MICROSCOPY

To obtain atomic force microscopy (AFM) images of 5,11,17,23,29,35-hex a-tert-butyl-37,38,39,40,41, 42-hexakishydroxycalix[6]arene, a monolay er containing this macrocycle as well as octadecanol for monolayer sta bilization was formed at the air/water interface by means of the Langm uir-Blodgett (LB) technique. The appropriate choice of the substrate o nto which this monolayer was transferred for AFM observation was found to be crucial for high-resolution AFM. Whereas no images of the calix [6]arene deposited onto octadecyltrichlorosilane-treated mica could be obtained, FTS (1H,1H,2H,2H-perfluorodecyltrichlorosilane) treated mic a was found to be an ideal substrate for the deposition and AFM observ ation. The large influence of the substrate on the resolution may be e xplained by the rigidness of the FTS layer as well as by the fact that the fee lattice of the chemisorbed FTS monolayer is commensurate with the arrangement of tert-butyl groups of the calix[6]arene. This metho d of sample preparation made possible the first AFM images of a macroc yclic host compound with molecular resolution and may prove to be of g eneral applicability.