Abstract. 25,16,. ~ i]_ heptacosa-I (25), 2,4,6(27),7,9,11 (26),21,23-nonaene perchlorate-ethanol-water (1 / 1 / 1), C33H36NO~ -.-C104.C2HsOH.H20, Mr = 690-2, orthorhombic, Pca2~, a = 27.747 (5), b = 9.572 (3), c = 12.866 (4) A,, V= 3417 (3) A 3, Z = 4, Dx = 1-39 g cm-3, a(Mo Ka)=0"7107A, #=1.69cm-~, F(000)=1464, T= 100 (5)K, final R = 6.5% for 2915 observed reflections. The water molecule is complexed in the cavity of the macrocycle with hydrogen bonds to the polyethylene oxy atoms adjacent to the outer phenyl rings of the terphenyl unit. The O atom of the water molecule accepts hydrogen bonds from the pyridinium proton and the OH proton of the ethanol molecule. The HC104 proton is transferred to the pyrido nitrogen.Experimental. The title compound was prepared by dissolving 50 mg (0-09 mmol) of the 4-phenylpyridohemispherand (Dijkstra, den Hertog, van Steen, Zijlstra, Skowronska-Ptasinska, Reinhoudt, van Eerden & Harkema, 1987) in 2 ml of ethanol and the slow addition of 0.5 ml of 70% HC104. Slow evaporation of solvent afforded colorless crystals of the complex suitable for X-ray diffraction, m.p. 496 K (dec.).Intensities were measured at 100 (5)K on an Enraf-Nonius CAD-4 diffractometer using graphite- H atoms of the macrocycle were placed in calculated positions and treated as riding on their parent atoms (bond distance 0.95/k, B~so = 4.0 A2), with the exception of the methyl hydrogens. These atoms and the H atoms of the water molecule were found from a difference Fourier synthesis. Positions of these atoms were refined. Hydrogens of the ethanol group could not be located (probably due to the large thermal motions). These hydrogens were not included in the refinement. In order to fix the origin in the c direction, the z parameter of the C1 atom has been fixed.The structure was solved with MULTAN (Germain, Main & Woolfson, 1971) and refined by full-matrix least squares. Weights for each reflection in the refinement (on F) were calculated from w = 4Fo2/0.2(Fo2), ov2(Fo2) = 0"2(/)+ (pFo2)2; the value of the instability factor p was determined as 0.04. The number of parameters refined was 457: scale factor, isotropic extinction factor [final value 2.4 (7) x 10-9], positional and anisotropic thermal parameters for the non-H atoms positional parameters of some H atoms.Refinement converged at R = 6-5%, wR = 6.3%, S = 1.64, (A/o')max = 0"2. Largest peak on the final difference Fourier map 0.54 e A -3 (in the perchlorate ion). All calculations were performed using SDP