Exploration of Br⋯O halogen bonding interactions in dinuclear vanadium(V) complexes with Schiff base ligands

Designing metal chelates of halogenated sulfonamide Schiff bases as potent nonplatinum anticancer drugs using spectroscopic, molecular docking and biological studies

In this contribution, five Ni(II) complexes have been synthesized from sulfonamide-based Schiff bases (SB¹-SB⁵) that comprise bromo or iodo substituents in the salicylidene moiety. The chemical structures of these compounds were extensively elucidated by different analytical and physicochemical studies. All ligands act as bidentate chelators with ON binding mode yielding octahedral, square planar, or tetrahedral geometries. The phenolic OH at δ 12.80 ppm in the free Schiff base SB² vanishes in the ¹H NMRspectrum of diamagnetic complex [Ni(SB²-H)₂] favoring the OH deprotonation prior to the chelation with Ni(II) ion. The appearance of twin molecular ion peaks ([M - 1]⁺ and [M + 1]⁺) is due to the presence of bromine isotopes (⁷⁹Br and ⁸¹Br) in the mass spectra of most cases. Also, the thermal decomposition stages of all complexes confirmed their high thermal stability and ended with the formation of NiO residue of mass 6.42% to 14.18%. Besides, antimicrobial activity and cytotoxicity of the ligands and some selected complexes were evaluated. Among the ligands, SB⁴ showed superior antimicrobial efficacy with MIC values of 0.46, 7.54, and 0.95 µM against B. subtilis, E. coli, and A. fumigatus strains, respectively. The consortium of different substituents as two bromine atoms either at positions 3 and/or 5 on the phenyl ring and a thiazole ring is one of the reasons behind the recorded optimal activity. Moreover, there is a good correlation between the cytotoxicity screening (IC₅₀) and molecular docking simulation outcomes that predicted a strong binding of SB² (16.0 μM), SB⁴ (18.8 μM), and SB⁵ (6.32 μM) to the breast cancer protein (3s7s). Additionally, [Ni(SB⁴-H)₂] (4.33 µM) has nearly fourfold potency in comparison with cisplatin (19.0 μM) against breast carcinoma cells (MCF-7) and is highly recommended as a promising, potent, as well as low-cost non-platinum antiproliferative agent after further drug authorization processes.

Transition metal(ii) complexes of halogenated derivatives of (E)-4-(2-(pyridin-2-ylmethylene)hydrazinyl)quinazoline: structure, antioxidant activity, DNA-binding DNA photocleavage, interaction with albumin and in silico studies

Six transition metal(ii) complexes with halogenated quinazoline derivatives as ligands were characterized and evaluated for interaction with calf-thymus DNA, photocleavage of plasmid-DNA, affinity for bovine serum albumin, and antioxidant activity.

Role of hydrogen bonds and weak non-covalent interactions in the supramolecular assembly of 9-hydroxyeucaliptol: crystal structure, Hirshfeld surface analysis, and DFT calculations

The compound 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-9-ol (9-hydroxyeucaliptol) has been prepared and characterized by single-crystal X-ray diffraction analysis, infrared, Raman, and UV-visible spectroscopies. The molecular geometry of the title compound was also investigated theoretically by density functional theory (DFT) calculations to compare with the experimental data. The substance crystallizes in the trigonal crystal system, space group P3₂ with Z = 9 molecules per unit cell. There are three independent molecules in the crystal asymmetric unit having the same chirality and showing some differences in the orientation of the H-atom of the hydroxyl group. The crystal structure of 9-hydroxyeucaliptol shows that the hydroxyl group presents an anti-conformation with respect to the O-atom of the ether group. The crystal packing of 9-hydroxyeucaliptol is stabilized by intermolecular O-H···O hydrogen bonds involving the hydroxyl groups of different molecules, which play a decisive role in the preferred conformation adopted in solid state. The intermolecular interactions observed in solid state were also studied through the Hirshfeld surface analysis and quantum theory of atoms in molecules (QTAIM) approaches. Energy framework calculations have also been carried out to analyze and visualize the topology of the supramolecular assembly, and the results indicate a significant contribution from electrostatic energy over the dispersion.

A first exploration of isostructurality in transition metal nitroprussides: X-ray analysis, magnetic properties and DFT calculations

Transition metal M(ii) (M = Mn, Fe, Cu, Zn, Cd) nitroprussides with 1-methyl-imidazole were prepared and characterized by spectroscopic techniques, thermal analysis, and powder (Fe complex) and single-crystal XRD.

Differentiating intramolecular spodium bonds from coordination bonds in two polynuclear zinc(ii) Schiff base complexes

Two new zinc(ii) complexes have been synthesized and characterized. Theoretical study is devoted to distinguish between conventional coordination bonds and spodium bonds between the zinc and oxygen centers.

One-Dimensional Diiodine-Iodobismuthate(III) Hybrids Cat3{[Bi2I9](I2)3}: Syntheses, Stability, and Optical Properties

One-dimensional iodine-rich iodobismuthates(III), Cat₃{[Bi₂I₉](I₂)₃} [Cat = 1,4-MePy (1) and 1-EtBMAP (2)], feature the highest amount of "trapped" diiodine units in polyhalogen-halometalates of p-block elements. Both complexes have narrow optical band gaps (1.55 and 1.63 eV, respectively) and moderate thermal stability.

Intramolecular Spodium Bonds in Zn(II) Complexes: Insights from Theory and Experiment

Two new dinuclear zinc(II) complexes, [Zn₂(µ_1,3-OAc)(L¹)₂]I·MeOH (1) and [Zn₂(µ_1,3-OAc)(L²)(NCS)] (2), (where HL¹ = 2-(((3-(dimethylamino)propyl)amino)methyl)-6-methoxy-phenol and H₂L² = 2,2′-[(1-Methyl-1,2-ethanediyl)bis(iminomethylene)]bis[6-ethoxyphenol]) have been synthesized and characterized by elemental and spectral analysis. Their X-ray solid state structures have been determined, revealing the existence of intramolecular Zn···O spodium bonds in both complexes due to the presence of methoxy (1) or ethoxy (2) substituents adjacent to the coordinated phenolic O-atom. These noncovalent interactions have been studied using density functional theory (DFT) calculations, the quantum theory of “atoms-in-molecules” and the noncovalent interaction plot. Moreover, a search in the Cambridge structure database (CSD) has been conducted in order to investigate the prevalence of intramolecular spodium bonds in Zn complexes. To our knowledge this is the first investigation dealing with intramolecular spodium bonds.