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Supramolecular structures of Ni^II and Cu^II with the sterically demanding Schiff base dyes driven by cooperative action of preagostic and other non-covalent interactions.

ABSTRACT: This work reports on synthesis and extensive experimental and theoretical investigations on photophysical, structural and thermal properties of the Ni^II and Cu^II discrete mononuclear homoleptic complexes [Ni(L ^I,II)₂] and [Cu(L ^I,II)₂] fabricated from the Schiff base dyes o-HOC₆H₄-CH=N-cyclo-C₆H₁₁ (HL ^I) and o-HOC₁₀H₆-CH=N-cyclo-C₆H₁₁ (HL ^II), containing the sterically crowding cyclo-hexyl units. The six-membered metallocycles adopt a clearly defined envelope conformation in [Ni(L ^II)₂], while they are much more planar in the structures of [Ni(L ^I)₂] and [Cu(L ^I,II)₂]. It has been demonstrated by in-depth bonding analyses based on the ETS-NOCV and Interacting Quantum Atoms energy-decomposition schemes that application of the bulky substituents, containing several C-H groups, has led to the formation of a set of classical and unintuitive intra- and inter-molecular interactions. All together they are responsible for the high stability of [Ni(L ^I,II)₂] and [Cu(L ^I,II)₂]. More specifically, London dispersion dominated intramolecular C-H⋯O, C-H⋯N and C-H⋯H-C hydrogen bonds are recognized and, importantly, the attractive, chiefly the Coulomb driven, preagostic (not repulsive anagostic) C-H⋯Ni/Cu interactions have been discovered despite their relatively long distances (∼2.8-3.1 Å). All the complexes are further stabilized by the extremely efficient intermolecular C-H⋯π(benzene) and C-H⋯π(chelate) interactions, where both the charge-delocalization and London dispersion constituents appear to be crucial for the crystal packing of the obtained complexes. All the complexes were found to be photoluminescent in CH₂Cl₂, with [Cu(L ^II)₂] exhibiting the most pronounced emission - the time-dependent density-functional-theory computations revealed that it is mostly caused by metal-to-ligand charge-transfer transitions.

SUBMITTER: Shiryaev AA

PROVIDER: S-EPMC8086159 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV-Vis-NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML2]∙nH2O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.

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Supramolecular structures of Ni^II and Cu^II with the sterically demanding Schiff base dyes driven by cooperative action of preagostic and other non-covalent interactions.

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Supramolecular structures of NiII and CuII with the sterically demanding Schiff base dyes driven by cooperative action of preagostic and other non-covalent interactions.

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OmicsDI is part of the ELIXIR infrastructure

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Supramolecular structures of Ni^II and Cu^II with the sterically demanding Schiff base dyes driven by cooperative action of preagostic and other non-covalent interactions.