DFT studies for three Cu(II) coordination polymers: Geometrical and electronic structures, g factors and UV–visible spectra

Synthesis, characterization, PXRD studies, and theoretical calculation of the effect of gamma irradiation and antimicrobial studies on novel Pd(II), Cu(II), and Cu(I) complexes

The main objective of this study is to synthesize and characterize of a new three complexes of Pd (II), Cu (II), and Cu (I) metal ions with novel ligand ((Z)-2-(phenylamino)-N'-(thiophen-2-ylmethylene)acetohydrazide) H2LB. The structural composition of new compounds was assessed using several analytical techniques including FT-IR, 1H-NMR, electronic spectra, powder X-ray diffraction, and thermal behavior analysis. The Gaussian09 program employed the Density Functional Theory (DFT) approach to optimize the geometry of all synthesized compounds, therefore obtaining the most favorable structures and crucial parameters. An investigation was conducted to examine the impact of γ-irradiation on ligands and complexes. Before and after γ-irradiation, the antimicrobial efficiency was investigated for the activity of ligands and their chelates. The Cu(I) complex demonstrated enhanced antibacterial activity after irradiation, as well as other standard medications such as ampicillin and gentamicin. Similarly, the Cu(I) complex exhibited superior activity against antifungal species relative to the standard drug Nystatin. The docking investigation utilized the target location of the topoisomerase enzyme (2xct) chain A.

Unraveling the Major Differences between the Trinuclear Cyclopentadienylmetal Carbonyl Chemistry of Cobalt and That of Nickel-A Theoretical Study

The geometries and energetics of the trinuclear cyclopentadienylmetal carbonyls Cp₃M₃(CO)_n (Cp = η⁵-C₅H₅); M = Co, Ni; n = 3, 2, 1, 0) have been investigated by density functional theory. The cobalt and nickel systems are found to be rather different owing to the different electronic configurations of the metal atoms. For cobalt, the small calculated energy separation of 5.0 kcal/mol between the two lowest-energy singlet Cp₃Co₃(μ₃-CO)(μ-CO)₂ and Cp₃Co₃(μ-CO)₃ tricarbonyl structures accounts for the experimental results of both isomers as stable species that can be isolated and structurally characterized by X-ray crystallography. The corresponding Cp₃Ni₃(CO)₃ species in the nickel system are predicted not to be viable owing to exothermic CO dissociation to give the experimentally observed very stable Cp₃Ni₃(μ-CO)₂, which is found to be the lowest-energy isomer by a substantial margin of ∼25 kcal/mol. In all of the low-energy Cp₃M₃(CO)_n (n = 2, 1) structures, including that of the experimentally known triplet spin state Cp₃Co₃(μ₃-CO)₂, all of the carbonyl groups are face-bridging or face-semi-bridging μ₃-CO groups bonded to all three metal atoms of the M₃ triangle. In the lowest-energy carbonyl-free Cp₃M₃ (M = Co, Ni) structures, agostic C-H-M interactions are found using hydrogens of the Cp rings. In addition, the lowest-energy Cp₃Ni₃ is the only structure among all of the low-energy Cp₃M₃(CO)_n (M = Co, Ni; n = 3, 2, 1, 0) structures in which each Cp ring is a bridging rather than terminal ligand.

Investigations of the temperature-dependent electron paramagnetic resonance spectra and local structures for a cobalt(II) porphyrin complex within a metal-organic framework

The interaction between an adsorbed CO molecule and the unsaturated coordinated Co²⁺ center in the metal-organic framework (MOF) PCN-224 is investigated by analyzing the electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) and the adsorption energies at various temperatures. Six- and five-coordinated octahedral models (four planar N with two and one axial CO molecules, respectively) are constructed to simulate the local structures of the Co²⁺ centers at different temperatures. Because of the Jahn-Teller effect of the Co²⁺ centers, the C₂-Co-N₄ and C-Co-N₄ combinations undergo different tetragonal elongation distortions along the C₄ axis, characterized by the relative elongation ΔZ and displacement ΔZ' of Co²⁺ at different temperatures. Given the agreement between the calculated and experimental EPR parameters, as well as the adsorption properties, the six- and five-coordinated models are regarded as suitable for low- and high-temperature systems, respectively. These studies may be helpful to understand the properties of similar MOFs with adsorbed molecules under the effect of ambient temperature.