Monoclinic nanoporous crystal structures for l-valyl–l-alanine acetonitrile solvate hydrate and l-valyl–l-serine trifluoroethanol solvate

Abstract

Crystal structures of dipeptides with hydrophobic channels presented in the past all have hexagonal symmetry. The compounds L-valyl–L-alanine acetonitrile solvate hydrate and L-valyl–L-serine trifluoroethanol solvate represent the first examples of structures with monoclinic symmetry, which has the effect of changing the shape of the pores to accommodate the specific guest molecules. The co-crystallized solvent molecules of L-valyl–L-alanine can be removed by drying, giving a shift of space group from P2₁ with Z′ = 3 to P6₁ with Z′ = 1. During this process the cell volume increases by 6.5%. A similar shift was not observed for L-valyl–L-serine, for which the trifluoroethanol solvent is less easily removed from the pores.