Synthesis, thermal properties and X-ray structural study of weak C-H⋯O=C hydrogen bonding in aliphatic polyester dendrimers

Dendritic polyester compounds based on polyol with three, four and six reactive hydroxy groups as a molecular core, chloroacetyl chloride (or bromoacetyl bromide) and sodium metal enolate were prepared by a simple two-step synthetic procedure. The compounds were characterised by using the NMR and MS techniques, and the thermal properties were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The structures of the crystalline compounds were determined by X-ray single crystal diffraction. Detailed analysis of the structures showed that the self-complementarity of the molecules together with a multitude of weak C-H⋯O=C hydrogen bonding results in crystalline dodecamethyl and dodecaethyl esters 9a and 9b, whereas slight modification in the structure of nonaethyl ester 8 renders it viscous oil.