Polymorphism in co-crystals: a metastable form of the ionic co-crystal 2 HBz center dot 1 NaBz crystallised by flash evaporation

Christian Butterhof, Kilian Bärwinkel, Jürgen Senker, Josef Breu
2012 CrysteEngComm  
While polymorphism is a wide spread phenomenon, the number of reported polymorphic co-crystals is still very limited. Here we report the synthesis and structural characterisation of such a rare case of polymorphism with a co-crystal of benzoic acid (HBz) and sodium benzoate (NaBz). Flash evaporation yielded a new polymorph of this ionic co-crystal with a stoichiometry of 2 HBz?1 NaBz. The thermodynamic relationship between the known and the new polymorph was determined to be of enantiotropic
more » ... of enantiotropic nature. At room temperature, this new form B is metastable. While the known form A is composed of one dimensional tapes, form B is built from infinite rods. The coordination sphere of sodium, however, in both forms is octahedral and the packing around it is dense.
doi:10.15495/epub_ubt_00004751 fatcat:itbxm6ivyvbvnpnikfo4ywzukm