Polar ordering of guest molecules in host-guest inclusion complexes

[摘要] ENGLISH ABSTRACT: 2,7-dimethylocta-3,5-diyne-2,7-diol forms inclusion complexes with various guests molecules, where the guest molecules are polar-ordered. A Cambridge Structural Database (CSD) search revealed ten inclusion complexes where the guest molecules were polar-ordered. Using Density Functional Theory (DFT) computational methods (in the absence of the host), we evaluated the intra-channel and lateral guest-guest interactions between the guest molecules.Two polar-ordered inclusion complexes ((1,4,7-cyclohexane-1,2,4,5,7,8-hexaoxonane)·CHCl3 and (2,4,6-(endolongifolyl)-1,3,5-trioxane)·CDCl3) were singled out in the CSD search for further studies along with 2,7-dimethylocta-3,5-diyne-2,7-diol. Synthesis of any 1,2,4,5,7,8-hexaoxonane and 1,3,5-trioxane derivatives was attempted to establish whether the polar-ordering ability extends into the family of compounds. We managed to produce three new polar-ordered inclusion complexes with 2,7-dimethylocta-3,5-diyne-2,7-diol (ClC(CH3)3, BrC(CH3)3 and IC(CH3)3), thus extending the series to six guest polar-ordered systems. We were only able to synthesise 1,4,7-cyclohexane-1,2,4,5,7,8-hexaoxonane and produce the CHCl3 inclusion complex and one new polar-ordered inclusion complex (CHBr3). Three 1,3,5-trioxanes was synthesised (the cyclohexyl, cyclohex-3-en-1-yl and cyclopentyl derivatives), which did not include any solvents. However, these 1,3,5-trioxanes also form polar-ordered crystals.These compounds and inclusion complexes were analysed by means of single crystal X-ray diffraction to determine their crystal structures. All the crystal structures could be solved and refined to adequate accuracy (except for 2,4,6-tri(cyclopentyl)-1,3,5-trioxane) with no disorder of the guest molecules (where applicable) and their polar-ordering property investigated. Due to their vast molecular differences, these compounds were studied separately by means of visual crystal structure analysis and computational modelling techniques (Density functional theory, molecular mechanics, molecular dynamics and molecular quench dynamics).

[发布机构] Stellenbosch University