Two new silicate hydrates (C20H30N2)(8) center dot [Si8O20](2) center dot 110H(2)O and (C20H30N2)(4) center dot [Si8O20] center dot 42H(2)O, and their implications for the role of non-covalent interactions in high-silica zeolite synthesis

Two new silicate hydrates, (C20H30N2)(8) . [Si8O20](2) . 110H(2)O (1) and ( C20H30N2)(4) . [Si8O20] . 42H(2)O (2) have been prepared and their structur es determined using single-crystal X-ray diffraction. The structures of 1 a nd 2 are formed from silicate octameric cubes bridged by hydrogen-bonded wa ter molecules. Crystal data for 1. P-1, Z = 1, a = 18.508(1) Angstrom, b = 20.393(1) Angstrom, c = 20.784(1) Angstrom, alpha = 97.747(4)degrees, beta = 92.249(5)degrees, gamma = 116.396(3)degrees; 2. P-1, Z = 1, a = 14.345(1) Angstrom, b = 14.855(1) Angstrom, c = 16.162(1) Angstrom, alpha = 80.339(5 )degrees, beta = 84.916(5)degrees, gamma = 67.805(5)degrees. Both 1 and 2 h ave apertures formed by hydrogen-bonded water molecules which are approxima tely 9.5 x 5.5 and 12.0 x 9.0 Angstrom in 1 and 2, respectively. The struct ures of both hydrates have numerous weak C-H . . .O hydrogen bonds between the organic cations and water molecules. The importance of these and organi c-inorganic electrostatic forces are discussed in the context of zeolite sy nthesis. (C) 2001 Elsevier Science B.V. All rights reserved.