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