Synthesis, X‐ray characterization and density functional theory studies of N 6 ‐benzyl‐N 6 ‐methyladenine–M(II) complexes (M = Zn, Cd): The prominent role of π–π, C–H···π and anion–π interactions

We report the synthesis and X‐ray characterization of the N 6 ‐benzyl‐N 6 ‐methyladenine ligand (L) and three metal complexes, namely [Zn(HL)Cl 3 ]·H 2 O ( 1 ), [Cd(HL) 2 Cl 4 ] ( 2 ) and [H 2 L] 2 [Cd 3 (μ‐L) 2 (μ‐Cl) 4 Cl 6 ]·3H 2 O ( 3 ). Complex 1 consists of the 7 H ‐adenine tautomer protonated at N3 and coordinated to a tetrahedral Zn(II) metal centre through N9. The octahedral Cd(II) in complex 2 is N 9 ‐coordinated to two N 6 ‐benzyl‐N 6 ‐methyladeninium ligands (7 H ‐tautomer protonated at N3) that occupy apical positions and four chlorido ligands form the basal plane. Compound 3 corresponds to a trinuclear Cd(II) complex, where the central Cd atom is six‐coordinated to two bridging μ‐L and four bridging μ‐Cl ligands. The other two Cd atoms are six‐coordinated to three terminal chlorido ligands, to two bridging μ‐Cl ligands and to the bridging μ‐L through N3. Essentially, the coordination patterns, degree of protonation and tautomeric forms of the nucleobase dominate the solid‐state architectures of 1 – 3 . Additionally, the hydrogen‐bonding interactions produced by the endocyclic N atoms and NH groups stabilize high‐dimensional‐order supramolecular assemblies. Moreover, energetically strong anion–π and lone pair (lp)–π interactions are important in constructing the final solid‐state architectures in 1 – 3 . We have studied the non‐covalent interactions energetically using density functional theory calculations and rationalized the interactions using molecular electrostatic potential surfaces and Bader's theory of atoms in molecules. We have particularly analysed cooperative lp–π and anion–π interactions in 1 and π + –π + interactions in 3 .