Rational design of two bpy-bridged 3D and 2D CoII open frameworks with similar amino-acid-based Schiff bases

Abstract

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.

Nanoflakes of an aminoacid-based chiral coordination polymer: Synthesis, optical and electrochemical properties, and application in electrochemical sensing of H2O2

“…2B). The emission bands of tyr [15] around 400, 420, and 450 nm (λ ex ¼306 nm) and those of bipy [14,16] around 400, 420, 450 and 480 nm (λ ex ¼270 nm) can be assigned to the intra ligand π n -π charge transfer transition. The emission peaks around 420, 450, and 480 nm (λ ex ¼275 nm) for [Cu 2 (tyr) 2 (bipy)] n may be assigned to the ligand-centered π n -π transition of tyr and bipy [17].…”

Three new 3D metal-organic frameworks based on the tetrakis(imidazol-1-ylmethyl)methane and 1,4-benzenedicarboxylic acid ligands with transition metal (Zn/Cd/Co) and properties research

“…In recent years, metal-organic frameworks (MOFs) have received much attention not only due to structural diversity, but also their great potential application value in many fields, such as, ion exchange [1,2], catalysis [3][4][5], gas adsorption and separation [6][7][8], luminescence [9][10][11], magnetism [12,13] etc. To date, though lots of MOFs have been reported and studied within the past decades, the establishment of novel structures remain a big challenge in the long term [14].…”

A pair of novel helical Zn(II) enantiomers constructed from l- and d-threonine Schiff bases: Synthesis, crystal structures and properties

“…It is believed that chirality and helicity are intimately associated with the living processes even though their origin remains unclear [16]. Therefore, research on the correlation between the chirality of molecular building blocks and the helicity of polymer could help us to better realize the origin of the DNA and proteins in biological systems [17].In previous works, our group has successfully obtained two 3D and 2D Co(II) complexes based on the D/L-alanine and glycine Schiff bases in 2012 [18], and two 2D grid-based Co(II) amino acid Schiff base complexes with left-and right-handed helical chains in 2014 [19]. As our continuous work, L-threonine and D-threonine are used as Schiff-base ligands for construction the helical coordination polymers.…”

“…In previous works, our group has successfully obtained two 3D and 2D Co(II) complexes based on the D/L-alanine and glycine Schiff bases in 2012 [18], and two 2D grid-based Co(II) amino acid Schiff base complexes with left-and right-handed helical chains in 2014 [19]. As our continuous work, L-threonine and D-threonine are used as Schiff-base ligands for construction the helical coordination polymers.…”

“…Herein, only complex 1 will be discussed as an example because both absorption spectra are very similar by judging from the two figures. Schiff base H 2 nap-L-thr shows intense absorption bands in the 250 nm, corresponding to a π-π* transition of the naphthyl group [18], other two absorption bands at~300 and~400 nm were assigned imine and keto form, respectively, according to the work of Heinert and Martell [35]. The corresponding bands of complex 1 are shifted slightly compared with H 2 nap-L-thr, suggesting that the coordination of the zinc ion influence the intrinsic electronic property of ligand.…”