Rational design of two bpy-bridged 3D and 2D Co(II) open frameworks with similar amino-acid-based Schiff bases.

Two novel bpy-bridged Co(II) Schiff base complexes have been synthesized by the hydro(solvo)thermal reactions of corresponding amino-acid-based Schiff bases, bpy and Co(NO(3))(2)·6H(2)O. The following formulae identify the two complexes: {[Co(napala)(bpy)(0.5)]·H(2)O}(n) (1) and [Co(napgly)(bpy)(0.5)](n) (2) [H(2)napala = N-(2-hydroxy-1-naphthylmethylidene)-D/L-alanine, H(2)napgly = N-(2-hydroxy-1-naphthylmethylidene)-glycine and bpy = 4,4'-bipyridine]. These two compounds have been characterized using single-crystal X-ray diffraction, infrared, powder X-ray diffraction, thermogravimetric analysis, optical spectra analysis, and magnetic measurement. Complex 1 features an unprecedented threefold interpenetrated diamond network based on the fan-shaped Co(II)(4)(µ(2)-napala)(4) molecular square node and bpy linker, which represents the first example of 3D framework among the amino-acid-based Schiff base complexes with salicylaldehyde or its derivatives. In 2, adjacent Co(II) ions are bridged by µ(2)-napgly(2-) to form left- and right-handed [Co(II)(µ(2)-napgly)](n) helical chains. These two types of helical chains are sustained alternately by a symmetrical bpy co-ligand into a 2D grid-based layer. The solid-state fluorescence of complexes 1 and 2 are quenched almost completely compared with free mixed-ligands at room temperature. Moreover, magnetic studies show the dominant antiferromagnetic coupling between the Co(II) centers mediated by the syn-anti-COO(-)-bridges in both complexes.

Diaqua-bis-(benzoato-κO)bis-[4,4,5,5-tetra-methyl-2-(pyridin-4-yl-κN)imidazoline-1-oxyl 3-oxide]cobalt(II).

The title compound, [Co(C(7)H(5)O(2))(2)(C(12)H(16)N(3)O(2))(2)(H(2)O)(2)], was obtained from a conventional solvent evaporation method. The complex mol-ecule is centrosymmetric, so pairs of equivalent ligands lie trans to each other in a slightly distorted octa-hedral CoN(2)O(4) geometry. The Co(II) ion is coordinated by the pyridine N atoms from NITpPy ligands [NITpPy is 4,4,5,5-tetra-methyl-2-(pyridin-4-yl)imidazoline-1-oxyl 3-oxide), water O atoms and two monodentate benzoate O atoms. The complex mol-ecules are connected by O-H⋯O hydrogen bonds between water mol-ecules and benzoate ligands, forming chains parallel to [100]. π-π stacking inter-actions between the benzoate ligands with centroid-centroid distances of 3.752 (2) Šconnect the chains into layers parallel to (10-1).