Jesús Jover

Computational characterization of a mechanism for the copper-catalyzed aerobic oxidative trifluoromethylation of terminal alkynes.

A reaction mechanism for the copper(i)-catalyzed oxidative aerobic trifluoromethylation of terminal alkynes has been determined by DFT calculations. The transmetalation of CF3(-) to copper appears to be a ligand replacement process independent of the metal. The dioxygen activation follows the sequence η(1)-superoxocopper(ii), μ-η(2):η(2)-peroxodicopper(ii) and bis(μ-oxo)-dicopper(iii).

Toward a mechanistic understanding of oxidative homocoupling: the Glaser–Hay reaction

The copper-catalyzed oxidative homocoupling of terminal alkynes has been studied with DFT methods. The role of Cu(I) or Cu(II) as the initial oxidation state as well as the effect of the changes in the substrate and the base have been examined. Oxidants responsible for outer- and inner-sphere electron transfer processes have also been investigated. The Cu/O2 interactions, which arise when dioxygen is employed as the oxidant, have been studied explicitly to fully describe the 4-electron reduction process, providing a plausible mechanism that could serve as a model for other aerobic oxidative couplings. The obtained results completely agree with the reported experimental data: the computed free energy barriers are low enough for the reactions to proceed at room temperature, and electron-poor alkynes and stronger bases lead to faster reactions.

Computational Characterization of the Mechanism for Coinage-Metal-Catalyzed Carboxylation of Terminal Alkynes

Several experimentally reported copper-, silver-, and gold-catalyzed carboxylation processes of terminal alkynes are studied with DFT methods to find out the mechanism ruling these transformations. The computational results indicate that the reaction follows a very similar pathway for all three metals: the crucial step involves the electrophilic attack of an unactivated carbon dioxide unit on a metal-σ-acetylide complex. The calculations lead to the proposal of additional silver and gold catalytic systems that could perform this reaction at mild temperatures.

Modulation of single-molecule magnet behaviour via photochemical [2+2] cycloaddition

The first example of phototunable SMMs has been reported. Upon UV irradiation, variations of the coordination sphere around Dy(III) ions actually affect the magnetic behaviour of the compound via [2+2] cycloaddition reaction, leading to a magnetic transformation from the SMM behaviour to a field-induced slow relaxation.

Ruthenium-Catalyzed O- to S-Alkyl Migration: A Pseudoreversible Barton–McCombie Pathway

A practical ruthenium-catalyzed O- to S-alkyl migration affords structurally diverse thiooxazolidinones in excellent yields. Our studies suggest this catalytic transformation proceeds through a pseudoreversible radical pathway drawing mechanistic parallels to the classic Barton-McCombie reaction.

Quantitative structure-property relationship estimation of cation binding affinity of the common amino acids.

The quantitative structure-property relationship (QSPR) methodology is applied to estimate the binding affinity of lithium, sodium, potassium, copper, and silver cations to the 20 common amino acids. The proposed model, nonlinearly derived from computational neural networks (CNN), contains seven descriptors and was validated by an external prediction set. Good results are obtained with correlation coefficients, R(2), and root-mean-square errors (rms) (kJ/mol) of 0.998 (3.89), 0.999 (2.86), and 0.997 (3.90) for the training, prediction, and validation sets, respectively. Five of the descriptors of the model correspond to the amino acids and the other two to the cations; they encode information clearly related to the cation-amino acid interactions responsible for the binding affinity values analyzed. A detailed analysis of results shows that, despite the different nature of the bonding between the metal cations and the amino acids, the neural networks used are capable of predicting accurately the property studied.

Single-molecule magnetism arising from cobalt(II) nodes of a crystalline sponge

The remarkable Metal–Organic Framework (MOF), {[(Co(NCS)2)3(κ3-TPT)4]·a(H2O)·b(MeOH)}n (1), which is used in the revolutionary crystalline sponge method, displays characteristic Single-Molecule Magnet (SMM) behaviour under applied static fields. We report the subtle effects of changes in the coordination environment of the CoII ions in 1, leading to drastically different magnetic behaviors of two additional related compounds, {[(Co(NCS)2)3(κ0–3-TPT)4]·c(H2O)}n (2) and {[(Co(NCS)2(H2O)0.65(MeOH)0.35)3(κ3-TPT)2]·2.4(H2O)}n (3). Magnetic measurements reveal unquenched first order orbital angular momentum, leading to significant magnetic anisotropy in all compounds, which was corroborated through CASSCF-type calculations. Notably, the crystalline sponge is the first example of a 3D network built from CoII Single-Ion Magnets (SIMs) as nodes.

Magnetic Behavior of Heterometallic Wheels Having a [MnIV6M2O9]10+ Core with M = Ca2+ and Sr2+

Two new heterometallic Mn(IV)-M(2+) compounds with formula [Mn6M2O9(4-(t)BuC6H4COO)10(4-(t)BuC6H4COOH)5] (M = Ca(2+) (1), Sr(2+) (2)) have been crystallized. The core of both compounds consists of a planar Mn6 ring, where the Mn(IV) ions are alternatively bridged by (μ3-O)2(μ-RCOO) and (μ4-O)(μ-RCOO)2 ligands, and the two alkaline earth ions are located to both sides of the wheel, linked to the oxo bridges, generating three fused [Mn2M2O4](4+) cuboids. These compounds show a net antiferromagnetic behavior, more important for 2 (Sr(2+)) than for 1 (Ca(2+)). The fitting of the experimental data was performed with the support of DFT calculations, considering four different exchange pathways: two between adjacent Mn(IV) ions (J1 and J2) and two between nonadjacent Mn(IV) ions (J3 and J4). The results of the analysis show that J1 and J2 are of the opposite sign, the ferromagnetic contribution corresponding to the [Mn2(μ4-O)(μ-RCOO)2](4+) unit (J2). The influence of the M(2+) ions in the magnetic behavior is analyzed for 1 and 2 and for three hypothetical models with the structural parameters of 1 containing Mg(2+), Sr(2+) or without the M(2+) ions. In spite of the diamagnetic character of the alkaline earth ions, their influence on the magnetic behavior has been evidenced and correlated with their polarizing effect. Moreover, the magnetic interactions between nonadjacent ions are non-negligible.

Tunable Magnetization Dynamics through Solid-State Ligand Substitution Reaction

The dimeric molecule [Dy2(acac)6(MeOH)2(bpe)]·bpe·2MeOH (1, acac = acetylacetonate, bpe = 1,2-bis(4-pyridyl)ethylene) undergoes a solid-state ligand substitution reaction upon heating, leading to the one-dimensional chain [Dy(acac)3(bpe)]n (2). This structural transformation takes advantage of the potential coordination of the guest bpe molecules present in 1. In both complexes the Dy(III) ions adopt similar octacoordinated D4d geometries. However, the different arrangement of the negatively charged and neutral ligands alters the direction of magnetic anisotropy axis and the energy states, thus resulting in largely distinct magnetization dynamics, as revealed by the CASSCF/RASSI calculations.

A Pseudo‐Octahedral Cobalt(II) Complex with Bispyrazolylpyridine Ligands Acting as a Zero‐Field Single‐Molecule Magnet with Easy Axis Anisotropy

The homoleptic mononuclear compound [Co(bpp-COOMe)2 ](ClO4 )2  (1) (bpp-COOMe=methyl 2,6-di(pyrazol-1-yl)pyridine-4-carboxylate) crystallizes in the monoclinic C2/c space group, and the cobalt(II) ion possesses a pseudo-octahedral environment given by the two mer-coordinated tridentate ligands. Direct-current magnetic data, single-crystal torque magnetometry, and EPR measurements disclosed the easy-axis nature of this cobalt(II) complex, which shows single-molecule magnet behavior when a static field is applied in alternating-current susceptibility measurements. Diamagnetic dilution in the zinc(II) analogue [Zn(bpp-COOMe)2 ](ClO4 )2  (2) afforded the derivative [Zn0.95 Co0.05 (bpp-COOMe)2 ](ClO4 )2  (3), which exhibits slow relaxation of magnetization even in zero field thanks to the reduction of dipolar interactions. Theoretical calculations confirmed the overall electronic structure and the magnetic scenario of the compound as drawn by experimental data, thus confirming the spin-phonon Raman relaxation mechanism, and a direct quantum tunneling in the ground state as the most plausible relaxation pathway in zero field.