Crystal growth and structure of L-methionine L-methioninium hydrogen maleate—a new NLO material

A new organic nonlinear optical (NLO) crystal from the amino acid family, viz., L-methionine L-methioninium hydrogen maleate (LMMM), has been grown by slow evaporation method from aqueous solution. Bulk crystals were grown using submerged seed solution method. The structure was elucidated using the single crystal x-ray diffraction data. The compound crystallized in the space group P21 and the unit cell contains a protonated L-methioninium cation and a zwitterionic methionine residue plus a maleate anion. The backbone conformation angles Ψ1 and Ψ2 are in cis and trans configurations for both the methionine and methioninium residues, respectively. Amino and carboxyl groups of the methioninium and methionine residues are connected through N–H...O hydrogen bonds leading to a ring R22(10) motif.