Pyrazole-4-sulfonate networks of alkali and alkaline-earth metals. Effect of cation size, charge, H-bonding and aromatic interactions on the three-dimensional supramolecular architecture

Variation of cation size and/or charge produces profound structural changes in the networks formed by pyrazole-4-sulfonate (L) with alkali and alkaline-earth metal cations. The zwitterionic ligand (HL) itself forms a robust three-dimensional H-bonded network: tetragonal P4(2)/mbc, a = 10.863(1) Angstrom, c = 9.195(1) Angstrom, V = 1085.0(2) Angstrom(3), Z = 8. The Na, K, Ca and Ba salts described herein are the first structurally characterized networks formed by L. NaL(H2O)(2), orthorhombic Pbca, a = 9.979(3) Angstrom, b = 7.848(3) Angstrom, c = 20.583(7) Angstrom, V = 1612.0(9) Angstrom, Z = 8; KL(H2O), orthorhombic Pbca, a = 8.174(1) Angstrom, b = 8.972(1) Angstrom, c = 19.912(3) Angstrom, V = 1460.4(4) Angstrom, Z = 8; CaL(H2O)(3), triclinic P (1) over bar, a = 5.9972(6) Angstrom, b = 9.2102(9) Angstrom, c = 12.957(1) Angstrom, alpha = 76.536(2)degrees, beta = 89.264(2)degrees, gamma = 79.057(2)degrees, V = 683.0(1) Angstrom, Z = 2; BaL(H2O).H2O, monoclinic P2(1)/c, a = 11.386(1) Angstrom, b = 4.9098(6) Angstrom, c = 24.348(3) Angstrom, beta = 90.702(2)degrees, V = 1361.0(3) Angstrom, Z = 4. All four metal sulfonate networks have an alternating inorganic-organic layered structure, reinforced by multiple H-bonding within the inorganic layer as well as between the organic and inorganic layers; extended pi-pi stacking and edge-to-face aromatic interactions within the organic layer provide further lattice strength.