Correction: Effect of non-covalent self-dimerization on the spectroscopic and electrochemical properties of mixed Cu(i) complexes

[This corrects the article DOI: 10.1039/D2RA05341A.].

Effect of non-covalent self-dimerization on the spectroscopic and electrochemical properties of mixed Cu(i) complexes

A series of six new Cu(i) complexes with ([Cu(N-{4-R}pyridine-2-yl-methanimine)(PPh₃)Br]) formulation, where R corresponds to a donor or acceptor p-substituent, have been synthesized and were used to study self-association effects on their structural and electrochemical properties. X-ray diffraction results showed that in all complexes the packing is organized from a dimer generated by supramolecular π stacking and hydrogen bonding. ¹H-NMR experiments at several concentrations showed that all complexes undergo a fast-self-association monomer-dimer equilibrium in solution, while changes in resonance frequency towards the high or low field in specific protons of the imine ligand allow establishing that dimers have similar structures to those found in the crystal. The thermodynamic parameters for this self-association process were calculated from dimerization constants determined by VT-¹H-NMR experiments for several concentrations at different temperatures. The values for K _D (4.0 to 70.0 M^-1 range), ΔH (-1.4 to -2.6 kcal mol^-1 range), ΔS (-0.2 to 2.1 cal mol^-1 K^-1 range), and ΔG ₂₉₈ (-0.8 to -2.0 kcal mol^-1 range) are of the same order and indicate that the self-dimerization process is enthalpically driven for all complexes. The electrochemical profile of the complexes shows two redox Cu(ii)/Cu(i) processes whose relative intensities are sensitive to concentration changes, indicating that both species are in chemical equilibrium, with the monomer and the dimer having different electrochemical characteristics. We associate this behaviour with the structural lability of the Cu(i) centre that allows the monomeric molecules to reorder conformationally to achieve a more adequate assembly in the non-covalent dimer. As expected, structural properties in the solid and in solution, as well as their electrochemical properties, are not correlated with the electronic parameters usually used to evaluate R substituent effects. This confirms that the properties of the Cu(i) complexes are usually more influenced by steric effects than by the inductive effects of substituents of the ligands. In fact, the results obtained showed the importance of non-covalent intermolecular interactions in the structuring of the coordination geometry around the Cu centre and in the coordinative stability to avoid dissociative equilibria.

Photocatalytic reactions of a nickel(ii) annulene complex incorporated in polymeric structures

A study of the structural and chemical processes of a new polymeric photocatalyst containing a Ni(ii) macrocyclic complex and its application to the solar reduction of CO₂ in aqueous homogeneous solution.

Crystal lattice effect on the quenching of the intracluster magnetic interaction in [V12B18O60H6]10− polyoxometalate

Quenching effect of the intracluster antiferromagnetic coupling by alkaline ions of the crystalline packing.

Resolution and characterization of helicate dimer and trimer complexes of 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane with copper(I)

Complexation of copper(I) with the binucleating ligand, 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane, mphenpr, result in formation of helical dimers, [Cu2(mphenpr)2](2+). The resolution of the enantiomeric forms of the dimers has been carried out with Δ-[As(cat)3](-) as resolving agent and X-ray structures for two compounds, P-[Cu2(mphenpr)2](Δ-[As(cat)3])2 and P-[Cu2(mphenpr)2](Δ-[As(cat)3])2·4(CH3CN), are reported. The rate of racemization in poorly-coordinating solvents has been examined by (1)H NMR, and is slow. At saturating concentrations of [[Cu2(mphenpr)2](2+)] in acetonitrile, crystals of the helical trimeric complex [Cu3(mphenpr)3](ClO4)3 are obtained. The X-ray structure of the trimer is reported. This species has also been resolved. As with the helical dimer, racemization in poorly-coordinating solvents is slow, and circular dichroism and (1)H NMR spectra are reported. The absolute configuration of the resolved complex, P-[Cu3(mphenpr)3](Δ-[As(cat)3])3, has been determined by X-ray crystallography.

Theoretical Modeling of the Oxidation of Hydrazine by Iron(II) Phthalocyanine in the Gas Phase. Influence of the Metal Character

The hydrazine oxidation by iron(II) phthalocyanine (Fe(II)Pc) has been studied using an energy profile framework through quantum chemistry theoretical models calculated in the gas phase at the density functional theory B3LYP/LACVP(d) level. We applied two models of charge-transfer mechanisms previously reported (J. Phys. Chem. A 2005, 109, 1196) for the hydrazine oxidation mediated by Co(II)Pc. Model 1 consists of an alternated loss of one electron and one proton, involving anionic and neutral species. Model 2 considers an alternated loss of two electrons and two protons and includes anionic, neutral, and cationic species. Both applied models describe how the charge-transfer process occurs. In contrast with the obtained results for Co(II)Pc, we found that the hydrazine oxidation mediated by Fe(II)Pc is a fully through-bond charge-transfer mechanism. On the other hand, the use of different charge-transfer descriptors (spin density, electronic population, condensed Fukui function) showed a major contribution of the iron atom in comparison with the cobalt atom in the above-mentioned process. These results could explain the higher catalytic activity observed experimentally for Fe(II)Pc in comparison with Co(II)Pc. The applied theoretical models are a good starting point to rationalize the charge-transfer process of hydrazine oxidation mediated by Fe(II)Pc.

Through-Space and Through-Bond Mixed Charge Transfer Mechanisms on the Hydrazine Oxidation by Cobalt(II) Phthalocyanine in the Gas Phase

Two quantum chemistry theoretical models in the gas phase at the density functional theory B3LYP/LACVP(d) level of calculation are proposed to rationalize the hydrazine oxidation by cobalt(II) phthalocyanine (Co(II)Pc). This oxidation reaction involves the net transfer of four electrons. These theoretical models that are described in terms of energy profiles include a through-space mechanism for the transfer of the first electron of the hydrazine and a through-bond mechanism proposed for the transfer of the three electrons remaining. The main difference between both models arises from a one-electron and one-proton alternate transfer for model 1 and a two-electron and two-proton alternate transfer for model 2. The main problem for experimental studies is to determine if the first transfer corresponds to an electron or a chemical transfer. Under this point of view, we proposed two models which deal with this problem. We conclude that model 1 is more reasonable than model 2 because the whole oxidation process is always exergonic.

Ni(II) complexes with Schiff bases derived from amino sugars

It was found by 1H and 13C NMR spectroscopy that the Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose exhibits enol-imine-keto-amine and anomeric equilibria in methanolic, and in dimethyl sulfoxide solutions. The reaction of the Schiff base with nickel acetate gave the bidentate, mononuclear Ni(II) complex that was characterized by spectroscopic methods and by cyclic voltammetry. The coordination of the Schiff base to the metal is through the enol-imine tautomeric form, and the anomeric equilibrium remains in dimethyl sulfoxide solutions. This complex was also obtained by reaction of D-glucosamine with Ni(II) salicylaldehydate. The same reaction was employed for the synthesis of bis-N-[2-deoxy-D-galactopyranosyl-2-(2-hydroxybenzaldiminate)]Ni(II). The small paramagnetic shifts of the 1H NMR resonances of the complexes suggest that paramagnetic species are present in low proportions.

(Acetonitrile-N)(o-benzoquinone diimine-N,N′)chloro-trans-bis(triphenylphosphine-P)ruthenium(II) hexafluorophosphate 0.25-hydrate

The Ru atom in the title compound, [RuCl(CH(3)CN){P(C(6)H(5))(3)}(2){C(6)H(4)(NH)(2)}]PF(6).0.25H(2)O, has a six-coordinate octahedral geometry, with a trans arrangement of the triphenylphosphine groups. The asymmetric unit contains two complex molecules and a partially occupied water site. Principal dimensions include Ru-N 1.958 (4)-2.044 (5), Ru-P 2.3897 (16)-2.4092 (15), and Ru-Cl 2.4280 (15) and 2.4295 (16) A

(o-Benzoquinone diimine-N,N′)dichlorobis(triphenylphosphine-P)ruthenium(II) 1.33-methanol 0.33-dichloromethane solvate

The Ru atom in the title compound, [RuCl(2){P(C(6)H(5))(3)}(2){C(6)H(4)(NH)(2)}].1.33CH(3)OH.0.33CH(2)Cl(2), shows a six-coordinate octahedral geometry, with a trans arrangement of the triphenylphosphine groups. One and a half molecules of complex, two molecules of methanol and a half molecule of dichloromethane form the asymmetric unit, with crystallographic twofold rotation symmetry for the complex molecule in a special position.