Cyanamides as π-Hole Donor Components of Structure-Directing (Cyanamide)···Arene Noncovalent Interactions

Crystallization of newly prepared copper(II) clusters [Cu₄X₆O(NCNMe₂)₄] (X = Cl 1 or Br 2) from toluene and styrene solutions afforded crystalline adducts 1·4PhMe, 1·4PhCH═CH₂, 2·4PhMe, and 2·4PhCH═CH₂, which were characterized by physicochemical methods including single-crystal X-ray diffraction. Inspection of the X-ray structures of (1–2)·4(arene) and the appropriate Hirshfeld molecular surface analysis allowed the recognition of the previously unreported π-hole···arene interactions involving the cyanamide ligands. The presence of these interactions and their structure-directing character was confirmed theoretically by density functional theory calculations including molecular electrostatic potential, energy decomposition, and atoms-in-molecules analyses. The observed π-hole···π interaction between coordinated cyanamide and arene moieties in the adducts exhibits a contribution of π-hole···σ(C–H^aryl) interaction. Analysis of the Cambridge Structure Database revealed that the cyanamide···arene separations in the [Cu₄X₆O(NCNMe₂)₄]·4(arene) systems are among the shortest found for all reported cyanamide structures.