PACKING RELATIONS IN SOLID INCLUSIONS OF NOVEL ROOF-SHAPED HYDROXY HOSTS. Ingeborg Csöregh, Department of Structural Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden; Edwin Weber, Institut fur Organische Chemie, TU Bergakademie Freiberg, Leipziger Str. 29, D-09596 Freiberg/Sachsen, Germany.

Intermolecular interactions play a crucial role in molecular recognition and in packing relations of organic crystal structures.The success of crystal engineering seems to lie in understanding the crystal packing forces.

Host Ar Host Ar

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1 C₆H₅ 3 4-CH₃C₆H₄

2 4-ClC₆H₄ 4 4-C(CH₃)₃C₆H₄

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Systematic X-ray analyses of cocrystals of synthetic host molecules, such as hosts 1-4, provide excellent opportunities for investigation of noncovalent interactions between different groups in various environments.

Host *Guest Stoichiometry Space group Host *Guest Stoichiometry Space group

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2*2-pentanol l : 1 Fddd 3*methanol 2:1 P-1

2*2,4-dioxane 2: 5 P2₁/ n 3*toluene 1:1 Fddd

2*o-xylene 1: 2 Pc2₁n 4*pyridine 2:3 P-1

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The compounds listed above exhibit various sizes and polarities of the hosts and/or different H bonding abilities and polarities of the guests, resulting in different crystalline architectures with a variety of symmetries and host-guest stoichiometries. However, remarkable features repeatedly appearing in different compounds were also observed. Noteworthy is the isostructurality of two, in many respect different compounds, namely 2*2pentanol (1:1) and 3*toluene (1:1). Structural details with emphasis on the balance of intermolecular interactions will be discussed.