Molecular Deformation, Charge Flow, and Spongelike Behavior in Anion–π {[M(CN) 4 ] 2− ;[HAT(CN) 6 ]} ∞ (M=Ni, Pd, Pt) Supramolecular Stacks

The synthesis, crystal structures, spectroscopic characterization, and comprehensive quantum‐chemical calculations for a novel series of anion–π hybrid salts (XPh 4 ) 2 [M(CN) 4 ][HAT(CN) 6 ] ⋅ 3 MeCN (X=P, M=Ni II ( 1 ), Pd II ( 3 ), Pt II ( 5 ); X=As, M=Ni II ( 2 ), Pd II ( 4 ), Pt II ( 6 ); HAT(CN) 6 =1,4,5,8,9,11‐hexaazatriphenylenehexacarbonitrile) are presented. The systems comprise 1D {[M(CN) 4 ] 2− ;[HAT(CN) 6 ]} ∞ stacks, in which the electron‐rich metal complexes adjust their orientation to match the electron‐deficient areas of HAT(CN) 6 . Electronic charge‐transfer interactions along the stacks result in polarization of electron density within HAT(CN) 6 and in perturbations along the {[M(CN) 4 ] 2− ;[HAT(CN) 6 ]} ∞ contacts. Electronic structure analysis suggests, for example, a relocation of 0.1–0.2  e per molecule from [M(CN) 4 ] 2− to HAT(CN) 6 and anion–π interaction energies of around −65 kcal mol −1 . A reversible structural single‐crystal‐to‐single‐crystal transformation, through desolvation/resolvation processes in the solid state, is also reported and a scheme for the formation of anion–π [M(CN) 4 ] 2− /HAT(CN) 6 adducts in MeCN is proposed.