pH-Dependent Assembly of Supramolecular Architectures from 0D to 2D Networks

Five Cu(II)/benzoate/4,4‘-bipy complexes, namely, [Cu(H2O)(benzoate)2(4,4‘-bipy)2](benzoic acid)2·(4,4‘-bipy) (1),
[Cu2(H2O)2(benzoate)4(4,4‘-bipy)3]·(H2O)9 (2), [Cu2(benzoate)4(4,4‘-bipy)3] (3), [Cu3(H2O)4(benzoate)6(4,4‘-bipy)4.5]·(4,4‘-bipy)·(H2O)5 (4), and [Cu3(OH)2(H2O)2(benzoate)4(4,4‘-bipy)2] (5) (4,4‘-bipy = 4,4‘-bipyridine), have been synthesized through hydrothermal
reaction of copper(II) nitrate, benzoic acid, and 4,4‘-bipyridine under different pH conditions. The diverse product structures show
the marked sensitivity of the structural chemistry of the aromatic carboxylate ligand to synthesis conditions. Complex 1, which
exhibits a zero-dimensional (0D) structure of mononuclear copper(II), is formed at pH = 5.5. At pH = 6.0, dimeric copper(II)
complexes of 2 and 3 are formed. Reaction at pH = 7 leads to a one-dimensional (1D) structure of 4. A further increase of the pH
to 8.0 results in a two-dimensional (2D) structure of 5. Crystal data are monoclinic, space group P2/n, a = 13.992(4) Å, b =
5.7153(14) Å, c = 31.126(8) Å, β = 100.513(5)°, Z = 2 for 1, monoclinic, space group C2/c, a = 30.283(5) Å, b = 15.139(2) Å,
c = 14.457(2) Å, β = 112.776(3)°, Z = 4 for 2, monoclinic, space group P21/c, a = 5.8317(12) Å, b = 21.157(4) Å, c = 20.679(4)
Å, β = 94.343(3)°, Z = 2 for 3, triclinic, space group P1̄, a = 14.016(3) Å, b = 18.492(4) Å, c = 19.353(4) Å, α = 66.220(3)°,
β = 79.948(4)°, γ = 88.390(3)°, Z = 2 for 4, and monoclinic, space group P21/c, a = 5.6880(16) Å, b = 17.917(5) Å, c =
20.904(6) Å, β = 92.959(5)°, Z = 2 for 5.