Unusual Ni⋯Ni interaction in Ni(ii) complexes as potential inhibitors for the development of new anti-SARS-CoV-2 Omicron drugs

Two nickel(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) of a tetradentate Schiff base ligand (H2L) derived from 2-hydroxy-1-naphthaldehyde with ethylenediamine were synthesized, designed, and characterized via spectroscopic and single crystal XRD analyses. Both nickel(ii) complexes exhibited unusual Ni⋯Ni interactions and were fully characterized via single-crystal X-ray crystallography. Nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) crystallize in monoclinic and triclinic crystal systems with P21/c and P1̄ space groups, respectively, and revealed square planar geometry around each Ni(ii) ion. The structure of both the complexes have established the existence of a new kind of metal system containing nickel(ii)-nickel(ii) interactions with a square planar-like geometry about the nickel(ii) atoms. Both square planar Ni(ii) complexes were often stacked with relatively short Ni⋯Ni distances. The non-bonded Ni-Ni distance (Ni⋯Ni separation) seems to be 3.356 Å and 3.214 Å from the nickel atoms of [Ni(L)]2(1) and [Ni(L)]n(2), respectively. These distances are shorter than the sum of their van der Waals radii (4.80 Å) but longer than the sum of their covalent radii (2.50 Å), indicating that there is a Ni⋯Ni interaction but not a Ni-Ni bond. The discrete molecules are π-stacked and connected via weak intermolecular interactions (C-H⋯O and C-H⋯N). Cyclic voltammetry measurements were obtained for both the complexes, and their pharmacokinetic and chemoinformatics properties were also explored. Detailed structural analysis and non-covalent supramolecular interactions were investigated using single-crystal structure analysis and computational approaches. Both the unique structures show good inhibition performance for the Omicron spike proteins of the SARS CoV-2 virus. To gain insights into potential SARS-CoV-2 Omicron drugs and find inhibitors against the Omicron variants of SARS-CoV-2, we examined the molecular docking of the nickel(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron spike protein (PDB ID: 7WK2 and 7WVO). A strong binding was predicted between Ni(ii) coordination complexes [Ni(L)]2(1) and [Ni(L)]n(2) with the SARS-CoV-2 Omicron variant receptor protein through the negative value of binding affinity. Molecular docking of Nil(ii) complexes [Ni(L)]2(1) and [Ni(L)]n(2) with a DNA duplex (PDB ID: 7D3T) and RNA (PDB ID: 7TDC) binding protein was also studied. Overall, this study suggests that Ni(ii) complexes can be considered as drug candidates against the Omicron variants of SARS-CoV-2.

A turn-off Eu-MOF@Fe2+ sensor for the selective and sensitive fluorescence detection of bromate in wheat flour

A new europium metal-organic framework (Eu-MOF) was prepared by simple hydrothermal method. The product exhibited intense red fluorescence, long fluorescence lifetime (0.454 ms) and excellent fluorescence stability. The fluorescence titration result showed that Fe³⁺ could completely quench the fluorescence of Eu-MOF, while the fluorescence quenching effect of Fe²⁺ or bromate was negligible. Considering the strong oxidizing property of bromate, a "turn off" Eu-MOF@Fe²⁺ sensor toward bromate was designed by generating Fe³⁺ due to the redox reaction. The results showed that the sensor displayed a wide linear range (0-0.2 mM), high sensitivity (LOD = 3.7 × 10^-6 mol/L), good selectivity and resistant to possible interferences in real four sample. Furthermore, the detection mechanism was investigated by PXRD, XPS and UV-Vis methods. More importantly, the Eu-MOF@Fe²⁺ sensor was further applied to detect bromate in wheat flour with satisfactory recovery (95.30%-104.38%) and accuracy (RSD < 2.85%). These results suggest that Eu-MOF@Fe²⁺ can be used as a potential sensor to detect bromate in food industry.

Crystal structure of diaqua-bis(μ2-2-carboxy-3,4,5,6-tetrafluorobenzoato-κ2 O:O′)-bis(phenanthroline-κ2 N,N′)-bis(μ2-3,4,5,6-tetrafluorophthalato-κ3 O:O,O′)dieuropium(III) – phenanthroline (1/2), C40H19EuF8N4O9

C40H19EuF8N4O9, triclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 11.3326(4) Å, b = 12.7652(4) Å, c = 13.2629(4) Å, α = 102.266(2)°, β = 97.689(2)°, γ = 105.630(3)°, V = 1767.93(10) Å3, Z = 2, R gt (F) = 0.0329, wR ref (F 2) = 0.0648, T = 293(2) K.

Crystal structure of poly[diaqua-(μ3-fumarato)-(μ3-maleato)-(μ4-1,2,4,5-tetrakis((1H-1,2,4-triazol-1-yl)methyl)benzene)tetracadmium(II)] dihydrate, C34H32N12O9Cd4

C34H32N12O9Cd4, monoclinic, P 1 ‾ $P\overline{1}$ (no. 2), a = 9.894(2) Å, b = 9.942(2) Å, c = 10.896(2) Å, α = 94.35(3)°, β = 96.80(3)°, γ = 93.35(3)°, V = 1058.7(4) Å3, Z = 1, R gt (F) = 0.0406, wR ref(F 2) = 0.0984, T = 293(2) K.

Structural Diversities of a Series of Cd(II) Coordination Complexes Based on a Flexible Tripodal N-donor Ligand

Three Cd(II) coordination complexes with unique structures and topologies, namely, {[Cd(tttmb)(Hbtc)]·5H2O}n (1), {[Cd(tttmb)(m-phda)(H2O)]·2H2O}n (2), and {[Cd(tttmb)(o-cpla)]·(CH3CN)·(H2O)1.5}n (3), have been successfully synthesized under hydro(solvo)thermally condition based on a flexible tripodal N-contained ligand 1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (tttmb) and aromatic polycarboxylate acids (H3btc = 1,2,4-benzenetricarboxylic acid, m-H2phda = 1,3-phenylenediacetic acid and o-H2cpla = Homophthalic acid). Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray single-crystal diffraction and thermogravimetric analyses. 1 crystallize in the orthorhombic chiral space group P212121 and feature 3D coordination networks. 2 reveals a 2D ladder-like structure with (4,4) topology containing alternating Cd(II)/m-phda2− left- and right-handed helical motifs. 3 exhibits a 3D net with (63)(66)(7·82) topology. The structural and dimensional diversity of these complexes not only indicates that the flexible ligand tttmb exhibits strong coordination ability and diverse coordination modes, but also shows that aromatic polycarboxylates play important roles in constructing the frameworks of complexes. Moreover, the different photoluminescence behaviors of 1–3 have been studied in the solid state.