Stabilizing molecular pairs
The intermolecular interaction energies for the stabilizing molecular pairs formed by cation and anion species of the type [+1···-1] ranging from -462.8 to -250.4 kJ mol-1. These molecular pairs are depicted in Fig. 2. The molecular dimer D1 is stabilized by three intermolecular interactions (N–H···O, C–H···O and C–H···C(π)). The lysinium acts as donors for N–H···O and C–H···C(π) interactions, whereas mandelate anion is involved as a donor for the C–H···O interaction and one of the oxygens (O4) of the carboxylate group of lysinium cation acts as an acceptor for this interaction. The D2 dimer is formed by N–H···O (involving side chain N2 of the cation and hydroxy group of the anion) and C–H···C(π) interactions. The D1 dimer is flanked on the both sides molecules formed by the motif D2. Motifs D1 and D2 are combined to form a layer which runs parallel to the crystallographic b axis. In this layer, lysinium and mandelate ions are alternately arranged and forming the –D2-D1-D2-D1- sequence as shown in Fig. 2. Dimer D3 is generated by three-centered intermolecular interactions (C–H···O and a short Csp 3–H···H–Csp 2contact formed formed between cation and anion with a distance of 1.98 Å). The least stabilizing dimer D4 which belongs to [+1···-1] type is formed by intermolecular N–H···O (involving backbone amino group of the lysinium and carboxylate group of the anion), O–H···O (involving hydroxy of the anion and carboxylate of the cation). It should be noted that there is a short contact formed between C1···O3 which provides additional stability to the dimer D4. Further, the adjacent layers of –D2-D1-D2-D1- supramolecular motifs are interconnected by the motif D4 as shown in Fig. 2.