Hydrogen Bonding Patterns and Supramolecular Structure of 4,4′-Bipyrazolium Salts

The crystal structures of 18 inorganic salts of 4,4′-bipyrazolium [H2bpz]2+ and 3,3′,5,5′-tetramethyl-4,4′-bipyrazolium [H2Me4bpz]2+ (bpz = 4,4′-bipyrazole; Me4bpz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole) involving Cl−, I−, I3−, PdCl42−, Cu2Cl62−, Re2Cl82−, SiF62−, TaF6−, Zr2F124−, (BeF3−)n, IO3−, ClO4−, S2O62−, HSO4−, and H2PO4− ions were determined by X-ray diffraction. Primary supramolecular organization of the bipyrazolium salts originates in strong hydrogen bonding between multiple NH cationic donors and O, F, Cl, I anionic acceptors following three main modes, which support linear joints of the cationic moieties: {(Hpz+)2(A−)2}, {(Hpz+)2(AX2−)2}- two pyrazolium moieties joined by a one-atom and three-atom bridging fragment respectively, and {(Hpz+)(AX2−)} - a single pyrazolium moiety “capped” by a three-atom anionic fragment. These modes provide suitable and characteristic supramolecular synthons for the rational design of hydrogen bonded pyrazolium frameworks. The control over dimensionality of the...