{Insert Figure 2}
As mentioned earlier, relatively weak stabilizing molecular dimers are
formed between cation-water and anion-water dimeric complexes in the
solid state. Both water molecules (O1W and O2W) interact with lysinium
and mandelate ions forming [0···-1] and [0···+1] molecular
species with stabilizing in nature. There are five such molecular types
observed in which cation-water complex makes four molecular dimers
(motifs D5, D7-9 and [0···+1] type) and anion-water complex forms
only one dimer (motif D6 and [0···-1] type).
As shown in Fig. 3, water molecules bridge the adjacent cations and
adjacent anion in the solid state. We note that the lysinium side chain
amino group (via H2A) interacts with water molecule (O2W) through
N–H···O interaction and found to be stronger dimer (motif D5,E tot: -86.4 kJ mol-1) among
four [0···+1] type molecular dimers. The backbone amino group
(via H1B) also interacts with the water molecule (O1W) through
intermolecular N–H···O interaction (motif D9,E tot: -21.4 kJ mol-1). This
dimer is relatively weaker than that of the dimers formed by water
molecules and oxygens of the carboxylate group of the lysinium (motif
D7, E tot: -32.8 kJ mol-1 and
motif D8, E tot: -22.4 kJ
mol-1). The water molecule (O2W) interacts with
carboxylate group of the anion forming a molecular dimer D6. The
strength of this dimer (E tot: -51.4 kJ
mol-1) is found to be stronger than the dimer formed
by intermolecular N–H···O interaction involving backbone nitrogen and
water molecule (motif D9). From the energetic point of view, one can see
that water molecules in the complex make stronger interactions with side
chain N of the cation and carboxylate group of the anion.