Crystal Engineering Using Bisphenols and Trisphenols. Complexes with Hexamethylenetetramine (HMTA): Strings, Multiple Helices and Chains-of-Rings in the Crystal Structures of the Adducts of HTMA with 4,4'-Thiodiphenol (1/1), 4,4'-Sulfonyldiphenol (1/1), 4,4'-Isopropylidenediphenol (1/1), 1,1,1-Tris(4-hydroxyphenyl)ethane (1/2) and 1,3,5-Trihydroxybenzene (2/3)

The 4,4′-bisphenols (1), X(C₆H₄OH)₂ [a, X = nil; b, X = O; c, X = S; d, X = 502; e, X = CO; f, X = CH₂; g, X = CMe₂; h, X = C(CF₃)₂], when co-crystallized from alcoholic solutions with hexamethylenetetramine, (CH₂)₆N₄ (HMTA), form 1:1 adducts (4a)–(h). 4,4′-Thiodiphenol–hexamethylenetetramine (1/1), (4c), C₁₂H₁₀O₂S.C₆H₁₂N₄, and 4,4′- sulfonyldiphenol–hexamethylenetetramine (1/1), (4d), C₁₂H₁₀O₄S.C₆H₁₂N₄, are orthorhombic, Pmn2₁, (4c) a = 15.029 (2), b = 9.7954 (8), c = 5.9817 (11) Å and (4d) a = 14.779 (2), b = 10.2558 (15), c = 5.9817 (8) Å, with Z = 2, and the structures consist of zigzag chains comprising strings of alternating bisphenol and HMTA units, each lying across mirror planes and linked by O—H...N hydrogen bonds. In addition, both (4c) and (4d) exhibit C—H...(arene) hydrogen bonds with one CH₂ group of the HMTA unit acting as a donor to two different arene rings; (4d) also exhibits multiple C—H...O=S hydrogen bonds with three C—H bonds in each HMTA unit acting as donors towards a single sulfone O atom. 4,4′-Isopropylidenediphenol–hexamethylenetetramine (1/1), (4g), C₁₅H₁₆O₂.C₆H₁₂N₄, is monoclinic, C2/c, a = 25.093 (6), b = 7.1742 (13), c = 23.612 (7) Å, = 110.42 (2)°, with Z = 8, and again the structure is built from chains of alternating bisphenol and HMTA units linked by O—H...N hydrogen bonds, but these now form double helices around twofold rotation axes; the double helices are themselves linked into sheets by C—H...O hydrogen bonds. The trisphenol (2), CH₃C(C₆H₄OH)₃, forms three adducts (5a)–(c) with HMTA, having trisphenol:HMTA ratios of 1:2 (5a), 2:3 (5b) and 1:1 (5c). 1,1,1-Tris(4-hydroxyphenyl)ethane–hexamethylenetetramine (1/2), (5a), C₂₀H₁₈O₃.(C₆H₁₂N₄)₂, is orthorhombic, P2₁2₁2₁, a = 6.9928 (10), b = 14.0949 (15), c = 30.999 (4) Å, with Z = 4, and the trisphenol units and half the HMTA units form a triple helix around a 2₁ axis, in which each strand consists of alternating phenol and HMTA units, linked as usual by O—H...N hydrogen bonds. The remaining HMTA units, which are external to the triple helix, are connected to it by O—H...N hydrogen bonds and are formed into externally buttressing stacks. The triol (3), 1,3,5-C₆H₃(OH)₃, forms a 2:3 adduct (6) with HMTA. 1,3,5-Trihydroxybenzene–hexamethylenetetramine (2/3), (6), C₆H₆O₃.(C₆H₁₂N₄)_1.5, is monoclinic, C2/c, a = 23.598 (2), b = 7.136 (2), c = 19.445 (3) Å, = 96.822 (11)°, with Z = 8, and the dominant structural motif consists of centrosymmetric rings containing two molecules each of (3) and HMTA, connected by O—H...N hydrogen bonds; these rings are themselves linked into a chain-of-rings by further HMTA units lying on twofold rotation axes. The hydrogen-bonding patterns are codified using the graph-set approach.

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