Phenylalanine-Based Co2+ and Cd2+ 1D Coordination Polymers: Structural Properties and Catalytic Application for Solvent-Free Aerobic Oxidation of Cycloalkene

Two 1D coordination polymers (CPs) with general formula [M(L)(H2O)(AcO)]n, (M = Co (1) or Cd (2), AcO = acetate anion and L denotes l-phenylalanine based ligand), were synthesized and fully characterized by various spectroscopies (UV-vis, FTIR, and NMR), thermal techniques, magnetic measurements (for 1), and single-crystal and powder X-ray diffraction studies. They can be described as "ribbon-like" 1D polymers constructed through a zigzag arrangement. The polymeric structure is developed due to the coordination mode adopted by the amino acid ligand, classified as μ3-N1O1:O1:O2, which simultaneously links three metal centers. This moiety also plays an important role as a magnetic coupler between metal centers in the cobalt system, which shows a weak antiferromagnetic interaction. Both CPs have also been used in the catalytic oxidation of cyclohexene with molecular oxygen (O2) as an oxidant. Under mild conditions, both compounds demonstrated remarkable catalytic activity, with the cobalt system being more efficient than the cadmium analogue (conversion: 73 and 58% and selectivity for the major product, 2-cyclohexanone: 63 and 55%, for 1 and 2, respectively). Leaching experiments and the results obtained using a radical quencher are consistent with a radical-mediated mechanism for the Co compound. The presence of the superoxide radical was also confirmed using EPR spectroscopy and DMPO as a spin trap, which was further validated by DFT calculations. The activity observed for the Cd analogue is attributed to the organic scaffold assisted by the templating effect of the metal ion.

Five Porous Complexes Constructed from a Racemic Ligand: Synthesis, Chiral Self-Assembly, Iodine Adsorption, and Desorption Properties

Herein, a chiral bispyridyl ligand (L) was designed and synthesized using a Schiff base condensation reaction, followed by a 1,3-H shift. Five complexes, [Zn₂L₂(OAc)₄] (1), {[CdLCl₂(DMF)]·4H₂O}_n (2), [Cd₂L₂I₄]·4H₂O (3), {[CdL₂(H₂O)₂](NO₃)₂·2CH₃OH}_n (4), and [Hg₂L₂Cl₄]·2DMF (5), were synthesized and characterized upon its reaction with Zn(II), Cd(II), or Hg(II) ions, respectively. X-ray crystallography shows that the organic compound exists as a racemic ligand with equal amounts of its R- and S-isomers, and all of the synthesized complexes exhibit heterochiral self-assembly via a chiral self-discrimination process. Complexes 1, 3, and 5 exist as centrosymmetric binuclear metallamacrocycles, while complexes 2 and 4 exist as 1D looped-chain coordination polymers. Inspired by the assembled structures of the five complexes, I₂ adsorption/desorption measurements for the complexes were carried out. The results show that complexes 1 and 5 exhibit good adsorption capacities toward I₂ in n-hexane and in water, respectively.

Crystal structure of poly[diaqua-(μ3-3,4,5,6-tetrafluoro-phthalato-κ3O:O′:O′′)-(μ2-1,2-bis(4-pyridyl)ethene-κ2 N:N′)cobalt(II)], C14H9CoF4NO6

C14H9CoF4NO6, monoclinic, P21/n (no. 14), a = 6.1183(2) Å, b = 7.5688(2) Å, c = 32.5016(7) Å, β = 90.672(2)°, V = 1504.99(7) Å3, Z = 4, R gt(F) = 0.0398, wR ref(F 2) = 0.1037, T = 293 K.

Crystal structure and photocatalytic degradation properties of a new two-dimensional zinc coordination polymer based on 4,4ʹ-oxy-bis(benzoic acid)

A new two-dimensional ZnII coordination framework [Zn(1,3-BMIB) (OBA)] n (1) (where H2OBA is 4,4ʹ-oxy-bis(benzoic acid) and 1,3-BMIB is 1,3-bis(2-methyl-1-imidazolyl)benzene) has been prepared and characterized through IR spectroscopy, elemental and thermal analysis, and single-crystal X-ray diffraction. Complex 1 is a (4, 4) grid coordination polymer with a layer structure. It exhibits high photocatalytic degradation effects upon UV irradiation of methylene blue and methylene orange aqueous solutions.

A series of helical coordination polymers based on two racemic bis(pyridylmethylene) propane-1,2-diamine ligands: relationship of conformations, structures and properties

The self-assembly of d¹⁰ metal salts and two racemic bis(pyridyl) diamine ligands generates ten complexes, showing diverse helical and wavelike chains, (4,4) layers, as well as 3D sqc and uog nets.