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 (XPh4 )2 [M(CN)4 ][HAT(CN)6 ]⋅3 MeCN (X=P, M=NiII (1), PdII (3), PtII (5); X=As, M=NiII (2), PdII (4), PtII (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.