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

The synthesis, crystal structures, spectroscopic characterization, and comprehensive quantum-chemical calculations for a novel series of anion-pi hybrid salts (XPh4)(2)[M(CN)(4)][HAT(CN)(6)]center dot 3MeCN (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)]}(infinity) 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)]}(infinity) 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-pi 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-pi [M(CN)(4)](2-)/HAT(CN)(6) adducts in MeCN is proposed.