Supramolecular gas–solid reaction between formic acid vapours and solid [CoIII5-C5H4COOH)(η5-C5H4COO)]

Abstract
Exposure of the solid zwitterion [CoIII5-C5H4COOH)(η5-C5H4COO)] to vapours of formic acid quantitatively produces the co-crystal [CoIII5-C5H4COOH)(η5-C5H4COO)] [HCOOH] without proton transfer from formic acid to the deprotonated –COO group on the zwitterion; formic acid can be quantitatively removed by mild thermal treatment, regenerating the starting material.