Conformations of calix[4]arenes — an investigation based on CSD data. Part II. Partial cone, 1,2-alternate and 1,3-alternate conformers of methylene- and heteroatom-bridged calix[4]arenes

Abstract

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 III. Calix[4]resorcinarenes

“…The group of calix [4]resorcinarenes is smaller than the group of calix [4]arenes with methylene bridges but significantly larger than the group of calix [4]arenes with heteroatom bridges (see [7,8]). There are altogether 551 cif files belonging to this group (23.2 % from the total of 2377 cif-files in [9] belonging to calix [4]arenes with methylene and heteroatom bridges and calix [4]resorcinarenes); the number of 218 cif files for calix [4]arenes with heteroatom bridges amounts to 9.2 % and for calix [4]arenes with methylene bridges (1610 cif files) to 67.7 %.…”

“…In the preceding two papers [7,8]), the previously introduced parameters α, β and δ [11,12] have been utilized to describe the geometry of the calix [4]arene base frame. Furthermore, the utility of the parameters α, β and δ to describe the influence of inter/intramolecular interactions on the geometry of the calix [4]arene scaffold in all conformers of methylene-and heteroatom-bridged calix [4]arenes was demonstrated.…”

“…Duplicite hits not excluded from Table 2; seven structures with incomplete cif files, where conformations were impossible to determine, are not included in the total number in Table 2. Unlike previously discussed calix [4]arenes [7,8], there are substituents present on the methylene bridges of calix [4]resorcinarenes; the positions (axial/equatorial with regard to the macrocycle) of these groups significantly affect the geometry of the resorcinarene scaffold [1]. However, because of the presence of two hydroxyl groups at the m-positions of the upper rim (and in some cases a third hydroxyl group at the p-position of the upper rim), several substitution patterns not observed in the group of calix [4]arenes are possible with calix [4]resorcinarenes (e.g.…”

“…In the previous two parts, of this work [7,8], influence of inter/intramolecular interactions and substitition patterns on the geometry of methylene-and heteroatom-bridged calix [4]arenes has been investigated. To enable comparison between calix [4]arene and calix [4]resorcinarene molecules, the system of ca-Вестник Карагандинского университета lix [4]resorcinarene and calix [4]arene conformations has been unified so the conformations of calix [4]resorcinarenes are reported as cone, partial cone, 1,2-alternate and 1,3-alternate.…”

“…In the group of calix [4]resorcinarenes, there is a relatively large percentage of cone-structures (over 82 %) and of symmetrically substituted structures with the exception of partial cone conformers (see Table 2). In the large number of symmetrically substituted structures, the resorcinarene group resembles the group of heteroatom-bridged calix [4]arenes described in previous papers [7,8]. Duplicite hits not excluded from Table 2; seven structures with incomplete cif files, where conformations were impossible to determine, are not included in the total number in Table 2.…”