Search for new potential NLO crystalline materials: Chiral derivatives of (2S)-2-(methoxymethyl)pyrrolidine

In the course of searching for new acentric NLO crystalline materials, three chiral (2S)-2-(methoxymethyl)pyrrolidine derivatives were synthesized. The introduction of chiral fragments into the structures of NLO chromophores was expected to bring acentricity to the resulting crystalline materials. The presence of intermolecular H-bonds in the crystal structures of two of the compounds was expected to elevate their melting points compared to the third one and to facilitate crystallization with orientation of molecules in the crystals favorable for SHG. Three compounds of this type have been prepared and for all of them single crystals have been grown and characterized by X-ray analysis. Indeed, all investigated compounds crystallized in acentric space groups. Significant elevation of melting temperatures was found for the two compounds possessing intermolecular H-bonds. In the two compounds molecules form one-dimensional H-bonded associates (ribbons). These ribbons are located in parallel planes in one structure and go along two different crystallographic directions in the other one. The third compound does not form any supramolecular aggregates in crystals.