Ademir Neves

Catecholase activity of dicopper(II) complexes containing different numbers of chelate members in the pyridine groups of the ligand was studied to identify a functional model for copper enzyme catechol oxidase. Complexes [Cu^II(μ‐OH)Cu^II(L₁)](ClO₄) (1), [Cu^II(μ‐OH)Cu^II(L₂)](ClO₄) (2), and [Cu^II(μ‐OH)Cu^II(L₃)](ClO₄) (3) were synthesized and characterized by elemental analysis, FTIR, UV–Vis spectroscopy, mass spectrometry, and electrochemistry. Their catalytic activity in the oxidation of 3,5‐di‐tert‐butylcatechol was determined. Changing the number of members of the chelate rings altered the catalytic activity. Complex 2 showed the highest catalytic activity due to a high turnover rate, with efficiency of 3.40±0.61. Mechanistic investigations indicate that the catalytic reaction occurs through the reduction of Cu(II) to Cu(I) with formation of hydrogen peroxide. The spectroscopic and catecholase activity were further rationalized through DFT and TD‐DFT calculations. Interestingly, all three complexes also showed DNA binding properties, which were also corroborated via molecular docking studies.

Herein, we present three new binuclear copper(II) complexes containing different polycyclic aromatic hydrocarbons, able to catalyze the oxidation of 3,5-di-tert-butylcathecol, a model substrate for catechol oxidase. The ligands and complexes were successful characterized in solid and solution states. The structure of C1 was determined by X-ray crystallography and it contains a [CuII2(L1-μ-phenoxo)(OAc)(H2O)2] unit, with two coppers in a pyramidal square geometry and a large distance of 3.715 Å between the copper(II) centers. All complexes (C1, C2 and C3) were found to be effective catalysts in the oxidation of 3,5-di-tert-butylcathecol to its quinone and C1 provided the highest catalytic constants at the three pH values studied. In addition to their potential use as a biomimetic catalyst in catechol oxidation, the interaction of these complexes with deoxyribonucleic acid from calf thymus (CT-DNA) was also studied, and C3 showed the greatest affinity with nucleic acids.

Two new copper(II) mononuclear complexes (C_Se and C_S) were synthesized and characterized by the following techniques: X-ray crystallography, elemental analysis, IR, EPR and UV-vis spectroscopies, conductimetric analysis and mass spectrometry. The crystalline structures of both complexes revealed two neutral complexes pentacoordinated with their chalcogenated ligands coordinating to the copper(II) center in a tridentate way with Se, N, Se and S, N, S as donor atoms and two cis-chloro ions completing the coordination structures. The hydrolytic activity in phosphate diester cleavage of C_Se and C_S was investigated using 2,4-BDNPP as a substrate, and applying the Michealis–Menten approach, giving the kinetics parameters (C_Se/C_S): k_cat (s⁻¹) = 1.17 × 10⁻⁴/1.97 × 10⁻⁴; K_M (mol L⁻¹) = 3.13 × 10⁻³/5.58 × 10⁻³. Both complexes also catalyze the oxidation of the 3,5-di-tert-butylcatechol (3,5DTBC) substrate with turnover numbers of 4.32 × 10⁻² s⁻¹ for C_Se and 4.87 × 10⁻² for C_S.

Herein, we report the CO-releasing activity of three new photoCORMs, two with nonbonding pyridine moieties and one with a benzyl group. Compounds [MnBr(CO)₃(bpa-κ²)] (2, where bpa = N-benzyl(2-pyridylmethyl)amine); [MnBr(CO)₃(pmpea-κ²)] (3, where pmpea = N-(2-pyridylmethyl)-N′-(2-pyridylethyl)amine) and [MnBr(CO)₃(bpea-κ²)] (4, where bpea = N-bis(2-pyridylethyl)amine) were synthesized and characterized by common spectroscopic techniques (UV-Vis and IR). Density functional theory studies were also performed to provide new insights into the M–C bond and to assume the orbitals involved in the absorption transitions. Their CO-releasing activities were measured both in organic and in physiological media and compared to that of a previously published compound [Mn(CO)₃(dpa-κ³)]Br (1, where dpa = N-bis(2-pyridylmethyl)amine). An increase in the number of members of the chelate from five to six influenced the release of CO, affecting both the binding mode of the ligand and the CO-release process and affecting their potential use as CO-release carriers and therapeutic agents.