Peroxido Complexes of Vanadium(V) as Ligands. Crystal Structures of [Cd(NH3)6][{VO(O2)2(OH)}2{μ-Cd(NH3)4}] and [{VO(O2)2(Im)}2{μ-Cu(Im)4}] (Im = Imidazole)

Organic ligands regulate the environmental impacts of metal-organic frameworks on nitrogen-fixing bacterium Azotobacter vinelandii

Metal-organic frameworks (MOFs) are rapidly developed materials with fantastic properties and wide applications. The increasing studies highlighted the potential threats of MOF materials to the environment. Comparing to the limited species of metal elements, the organic ligands have much higher diversity, but the influence of organic ligands on the environmental impacts of MOFs has not been revealed. Herein, we synthesized three Cu-MOFs with different organic ligands, namely Cu-BDC (1,4-terephthalic acid), Cu-IM (imidazole) and Cu-TATB (2,4,6-tris(4-carboxyphenyl)- 1,3,5-triazine), and evaluated their environmental toxicity to the nitrogen-fixing bacterium Azotobacter vinelandii. Cu-BDC inhibited the bacterial growth at lower concentrations than Cu-IM and Cu-TATB. The transcriptomes suggested the changes of membrane components by Cu-MOFs, consistent with the membrane leakage and cell wall damages. Cu-MOFs inhibited the nitrogen fixation activity through energy metabolism disturbance according to Gene Ontology functional annotation of ATP binding, Ca²⁺Mg²⁺-ATPase activity and ATP content. Only Cu-IM lowered the nitrogen fixation related nif genes, and affected the ribosome, purine metabolism and oxidative phosphorylation pathways. Otherwise, Cu-BDC and Cu-TATB mainly affected the flagellar assemblies and bacterial chemotaxis pathways. Our results collectively indicated that organic ligands regulated the environmental toxicity of MOFs through different metabolism pathways.

Oxoperoxovanadium Complexes of Hetero Ligands: X-Ray Crystal Structure, Density Functional Theory, and Investigations on DNA/BSA Interactions, Cytotoxic, and Molecular Docking Studies

Oxoperoxovanadium (V) complexes [VO (O)₂ (nf) (bp)] (1) and [VO (O)₂ (ox) (bp)] (2) based on 5-nitro-2-furoic acid (nf), oxine (ox) and 2, 2′ bipyridine (bp) bidentate ligands have been synthesized and characterized by FT-IR, UV-visible, mass, and NMR spectroscopic techniques. The structure of complex 2 shows distorted pentagonal-bipyramidal geometry, as confirmed by a single-crystal XRD diffraction study. The interactions of complexes with bovine serum albumin (BSA) and calf thymus DNA (CT-DNA) are investigated using UV-visible and fluorescence spectroscopic techniques. It has been observed that CT-DNA interacts with complexes through groove binding mode and the binding constants for complexes 1 and 2 are 8.7 × 10³ M⁻¹ and 8.6 × 10³ M⁻¹, respectively, and BSA quenching constants for complexes 1 and 2 are 0.0628 × 10⁶ M⁻¹ and 0.0163 × 10⁶ M⁻¹, respectively. The ability of complexes to cleave DNA is investigated using the gel electrophoresis method with pBR322 plasmid DNA. Furthermore, the cytotoxic effect of the complexes is evaluated against the HeLa cell line using an MTT assay. The complexes are subjected to density functional theory calculations to gain insight into their molecular geometries and are in accordance with the results of docking studies. Furthermore, based on molecular docking studies, the intermolecular interactions responsible for the stronger binding affinities between metal complexes and DNA are discussed.

Heterometallic Copper-Vanadium Compounds: Crystal Structures of Polymers [Cu(im)4(V2O4(mand)2)] n and [Cu(im)4(V2O4((S)-mand)2)] n ·2nH2O (im = imidazole, mand = mandelato2-)

ABSTRACT

Two new 1D polymeric heterometallic copper-vanadium compounds were prepared. The polymers are constructed from [Cu(im)₄]²⁺ cations that are coordinated to two terminal oxido ligands of [V₂O₄(mand)₂]^2- anions. The stronger coordination in [Cu(im)₄V₂O₄(mand)₂] _n (1) that contains the racemic mandelato ligand is manifested by a shorter Cu‒O bond distance 2.4095(12) Å, while the weaker interaction in [Cu(im)₄(V₂O₄((S)-mand)₂)] _n ·2nH₂O (2) is exhibited by Cu‒O bond distances 2.4547(16) Å and 2.5413(16) Å. The vanadate anion in compound 2 carries only the (S)-enantiomer of the initial mandelic acid and differs from the anion in 1 in parallel cis orientation of the phenyl groups of the mandelato ligand. FT-IR spectroscopy was used for the confirmation of the coordination mode of mandelato ligand. Strong bands corresponding to the vibrations of carboxyl groups can be observed around 1650 and at 1344 cm^-1. The stretching vibration of deprotonated hydroxyl group in the mandelato ligand occurs at 1045 and 1065 cm^-1 for 1 and 2, respectively. In addition, the very strong, characteristic band corresponding to ν(V=O) vibration can be observed at 931 cm^-1 for 1 and 925 cm^-1 for 2, as well as in Raman spectrum.

GRAPHIC ABSTRACT

The polymeric structures of two new vanadium-copper heterometallic complexes are constructed from [Cu(imidazole)₄]²⁺ cations that are coordinated to two terminal oxido ligands of [V₂O₄(mandelato)₂]^2- anions with different orientation of the phenyl groups depending on the chirality of the mandelato ligand.