Salts of the scissor-shaped racemic host 1,1′- binaphthyl-2,2′-dicarboxylic acid with amines: structure and thermal stability

Abstract

The salts formed between racemic 1,1′-binaphthyl-2,2′-dicarboxylic acid (BNDA) and the amines diethylamine (DEA), di-n-butylamine (DBA), cyclohexylamine (CHA) and dicyclohexylamine (DCHA) are reported. Structure 1, (BNDA2− )(2DEA+), and 2a, (BNDA2− )(2DBA+ ), resulted from slow evaporation of a solution of BNDA in the respective amine. A competition experiment whereby BNDA was dissolved in a mixture of 60% DEA and 40% DBA resulted in a polymorph of 2a, namely 2b. Slow evaporation of dilute solutions of BNDA with CHA and DCHA resulted in a mixed salt solvate 3, (BNDA2− )(3CHA+)(C7NO2H11 − )·CHA·H2O, and a salt solvate, 4, (BNDA2− )(2DCHA+)·CH3OH·H2O, respectively. For all the experiments methanol was used as a co-solvent due to BNDA insolubility with the amines. In structure 3 one of the CHA guests reacted with carbon dioxide in the atmosphere to form a carbamate anion, C7NO2H11 − . The kinetics of desolvation for salts 1, 2a and 2b were also determined.