Crystal Engineering of Nonlinear Optical Materials Based on Interpenetrated Diamondoid Coordination Networks

Zinc(II) and cadmium(II) coordination networks with p -pyridinecarboxylate bridging ligands, Zn(4-pyridylacrylate) 2 ( 3), [Cd(4-pyridylacrylate) 2 ]·H 2 O ( 4), Cd[4-(4-pyridyl)benzoate] 2 ·H 2 O (5), and [Zn 2 (μ-OH)(4-pyridylbenzoate) 3 ]·EtOH (6), have been synthesized under hydro(solvo)thermal conditions. Despite very different metal coordination environments, compounds 3, 4, and 6 all adopt 5-fold interpenetrated diamondoid structures, while compound 5 adopts a 7-fold interpenetrated diamondoid structure. The use of unsymmetrical p -pyridinecarboxylate bridging ligands in 3 − 5 has ensured their acentricity. Compounds 3 − 5 show significant powder second-harmonic-generation efficiencies. Compound 6, however, adopts a centrosymmetric structure because of the presence of symmetrical bis[4-(4-pyridyl)benzoate] double bridges. Compounds 4 − 6 also exhibit open channels that are occupied by removable included guest molecules. The present work illustrates the potential of rational synthesis of NLO-active acentric solids based on interpenetrated diamondoid structures. Crystal data for 3: monoclinic space group Cc, a = 10.352(1) Å, b = 22.413(2) Å, c = 8.319(1) Å, β = 126.149(1)°, and Z = 4. Crystal data for 4: monoclinic space group Cc, a = 12.013(1) Å, b = 22.344(1) Å, c = 7.774(1) Å, β = 123.509(1)°, and Z = 4. Crystal data for 5: monoclinic space group Ia, a = 22.92(2) Å, b = 28.74(2) Å, c = 23.00(2) Å, β = 94.908(8)°, and Z = 4. Crystal data for 6: monoclinic space group P 2 1 / n, a = 22.028(1) Å, b = 6.780(1) Å, c = 24.399(1) Å, β = 105.096(1)°, and Z = 4.