Synthesis, X‐ray characterization and density functional theory studies of N⁶‐benzyl‐N⁶‐methyladenine–M(II) complexes (M = Zn, Cd): The prominent role of π–π, C–H···π and anion–π interactions

Abstract

We report the synthesis and X-ray characterization of the N 6 -benzyl-N 6methyladenine 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 7H-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 (7H-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.

Noncovalent Sulfoxide–Nitrile Coupling Involving Four-Center Heteroleptic Dipole–Dipole Interactions between the Sulfinyl and Nitrile Groups

“…Two theoretical approaches for studies of noncovalent interactions in the solid state are widespread . The first is the “molecular” approach that is typically applied for molecular crystals and includes cutting a molecular cluster (MC) from the crystal without taking into account the neighboring molecular environment (i.e., the most important intramolecular and intermolecular interactions) and periodicity of the real crystal (see reviews − and other recent works − ). This cut is not unambiguous, and it requires accounting the most important intramolecular and intermolecular interactions.…”

New Type of Aromatic π‐Systems for Anion Recognition: Strong Anion‐π and C−H⋅⋅⋅Anion Interactions Between Halides and Aromatic Ligands in Half‐Sandwich Compounds

“…[9] Anion-π interactions are shown to be of great importance in systems containing coordination and organometallic compounds. [32,33] Transition metal coordination is known to enhance the strength of various interactions, most notably hydrogen bonding [34] and stacking interactions. [35,36] Theoretical and experimental studies have also shown that pyridine can form anion-π interactions only if its nitrogen is coordinated with silver(I), [37] while silver(I) coordination of all nitrogen atoms of pyrazine and s-tetrazine dramatically strengthens their anionπ interactions.…”

Unexpectedly Long Lifetime of the Excited State of Benzothiadiazole Derivative and Its Adducts with Lewis Acids

“…The possible chelate coordination of the amino-benzothiadiazole moiety via N 3 and N 4 atoms is unfavorable, as discussed earlier for archetype 4-amino-2,1,3-benzothiadiazole [ 34 ]. Thus, in the case of the N 5 site occupied by H + , the ZnCl 3 – fragment prefers to attach one more Cl – from HCl to form ZnCl 4 2– rather than coordinate to PyH-btd + , although such complexes with positively charged N-donor ligands are quite common [ 35 , 36 ].…”