Conformations of calix[4]arenes-an investigation based on CSD data. Part II. Partial cone, 1,2-alternate and 1,3-alternate conformers of methyleneand heteroatom-bridged calix[4]arenes In the first part of this investigation (Part I), cone conformers of calix[4]arenes with methylene and heteroatom bridges from the Cambridge Structural Database (CSD) were investigated. Previously introduced parameters α, β and δ were utilized in describing the conformations of the hydrocarbon base frame of the above mentined compounds. In this part of the investigation, partial cone, 1,2-and 1,3-alternate conformers of methylene-and heteroatom-bridged calix[4]arenes are studied and the influence of inter-and intramolecular interactions on the conformations of these compounds is evaluated.

Conformations of calix[4]arenes -an investigation based on CSD data. Part I. Cone conformers of methylene-and heteroatom-bridged calix[4]arenesConformations of calix[4]arenes with methylene and heteroatom bridges from the Cambridge Structural Database (CSD) were investigated with the help of the previously introduced parameters α, β and δ. The usefulness of these parameters in describing the conformations of the scaffolds of the above mentioned compounds was demonstrated. The dependence of the values of these parameters on inter-and/or intramolecular interactions present in the structure was investigated in order to discover how the geometry of the calix[4]arene moiety depends on the above listed effects. Structures with C 4v symmetry in the cone group have both β and δ close to 0°. With deformation of the calix[4]arene symmetry towards C 2v (flattened cone structures), the β parameter increases. Deformation towards C s symmetry is best reflected by increase of the parameter δ. Parameter α reflects the degree of 'opening' of the calix[4]arene cavity; structures with four OH groups at the lower rim tend to have lower α and therefore more open structure.