Crystallization and Single crystal X-ray diffraction
Analytical reagent grade L–Lysine (Merck) and L–mandelic acid (Lobachemie) were taken in a stoichiometric proportion (1:1) and dissolved in double distilled water. The resultant solution was filtered and evaporated at room temperature. Transparent needle-shaped single crystals were obtained after a week and used for X-ray diffraction analysis.
A good quality single crystal was chosen for X-ray intensity data collection. The intensity data were collected at room temperature (293 K) on a Bruker Kappa APEX3 CMOS diffractometer equipped with graphite monochromated Mo K α radiation (λ = 0.71073 Å) using ω/2θ scan mode. The structure was solved with the SHELXT program.25 All the non-hydrogen atoms were refined anisotropically using the program SHELXL-2018/3.26 The positions of H atoms of the ammonium groups and the water molecules were located from a difference Fourier map and the N–H and O–H distances were restrained to 0.85(2) Å. The remaining H atoms were positioned by riding model approach. Since absence of significant anomalous scatterers in the title complex, the absolute configuration was not established. However, the absolute configuration of L-lysine and L-mandelic acid from the starting materials was assumed. The Friedel pairs were merged during the final cycle of the refinement. The refined coordinates belong to (S )-lysine and (S )-mandelate configurations. The crystal data and refinement parameters of the title complex are presented in Table 1. The thermal ellipsoidal plot and dimeric motifs were produced using the program MERCURY.27