Reyes Jiménez-Aparicio

The article dealt with the structurally validated L²⁻ (H₂L=epindolidione=5,11‐dihydroquinolino[3,2‐b]quinoline‐6,12‐dione, a heteroatom‐modified tetracene and a structural isomer of indigo dye) bridged {(acac)₂Ru^III}₂(μ‐L²⁻) 1/2 (S=1, acac=acetylacetonate) and [{(bpy)₂Os^II}₂(μ‐L²⁻)](ClO₄)₂ [3](ClO₄)₂/[(pap)₂Os^II}₂(μ‐L²⁻)](ClO₄)₂ [4](ClO₄)₂ (S=0, bpy=2,2′‐bipyridine, pap=2‐phenylazopyridine). 1/2 and [3](ClO₄)₂/[4](ClO₄)₂ with a metal‐metal separation of ≈7 Å stabilized selectively in meso(ΔΛ)/rac(ΔΔ/ΛΛ) and meso diastereomeric forms, respectively, in spite of calculated minor difference in energy between the diastereomers in each case. Though 2, [3](ClO₄)₂/[4](ClO₄)₂) exhibited intermolecular π–π interactions, no such non‐covalent interaction was perceived in 1. Ru^IIIRu^III derived 1/2 (S=1, 2.63/2.57 μ_B at 300 K) attributed to non‐interacting two Ru(III) (S=1/2) spins with an intermolecular through space weak antiferromagnetic exchange interaction below 12 K and its variable temperature ¹H NMR revealed Fermi and pseudo‐contact shifts. Multiple redox steps of the complexes varied as a function of metal ion (Ru versus Os), its oxidation state (III versus II) and ancillary ligand (acac versus bpy versus pap). A collective consideration of DFT calculated MOs and Mulliken spin densities suggested delicate electronic forms along the redox chain due to the participation of bridge largely in the oxidation processes as a consequence of its redox non‐innocent feature. Reductions were however mostly centered around the metal (Ru^III to Ru^II) and ancillary ligands (bpy/pap) in 1/2 and 3²⁺/4²⁺, respectively. 1ⁿ/2ⁿ, [3]²⁺/[4]²⁺ displayed mixed metal/ligand based weak low‐energy (800‐1400 nm) transitions in addition to intense visible bands as corroborated by TD‐DFT calculations.

The synthesis, characterization and structural determination of four complexes with formula (PPh4)n[Rh2(µ–O2CPh)4Au(CN)2]n (1) and Kn[Rh2(µ–O2CR)4M(CN)2]n (M = Au, R = OEt (2), OMe (3); M = Ag, R = OMe (4)) are described. In all cases, the [CN-M-CN]– (M = Au, Ag) group is bridging the axial positions of the dirhodium units giving one-dimensional chains. The packing of the chains in the solid state depends on the nature of the carboxylate group of the dimetallic unit, the counterion present in the complex and the metal itself. The most striking change is observed in the Kn[Rh2(μ-O2CCH2OMe)4Au(CN)2]n complex (3) where the chains are positioned perpendicular to each other with an Au···Au interchain distance of 2.963 Å. The emission studies of this complex upon excitation at 350 nm show a clear broad emission band centered at 430 nm, while no luminescence is observed for the other compounds. The appearance of emission properties only in the case of complex 3 can be explained by its short aurophilic inter-actions.

The present work aimed to obtain discrete heavier metal complexes of unperturbed deprotonated bis-lawsone (hinge-like H₂L = 2,2′-bis(3-hydroxy-1,4-napthoquinone). This is primarily due to its limited examples with lighter metal ions (Co, Zn, and Ga) and the fact that our earlier approach with the osmium ion facilitated its functionalisation. Herein, we demonstrated the successful synthesis and structural characterisation of L²⁻-derived diruthenium [(bpy)₂Ru^II(μ-L²⁻)Ru^II(bpy)₂](ClO₄)₂ [1](ClO₄)₂ (S = 0), (acac)₂Ru^III(μ-L²⁻)Ru^III(acac)₂2 (S = 1) and monoruthenium (pap)₂Ru(L²⁻) 3 (S = 0) derivatives (bpy = 2,2′-bipyridine, acac = acetylacetonate, and pap = 2-phenylazopyridine). The crystal structures established that (i) O,O⁻/O,O⁻ donating five-membered bis-bidentate and O⁻,O⁻ donating seven-membered bidentate chelating modes of deprotonated L²⁻ in rac (ΔΔ/ΛΛ) diastereomeric [1](ClO₄)₂, 2 and 3, respectively. (ii) The L²⁻ bridging unit in [1](ClO₄)₂, 2 and 3 underwent twisting its two naphthoquinone rings with respect to the ring connecting C–C bond by 73.01°, 62.15° and 59.12°, respectively. (iii) Intermolecular π–π interactions (∼3.5 Å) between the neighbouring molecules. The paramagnetic complex 2 (S = 1) with two non-interacting Ru(III) (S = 1/2) ions exhibited weak antiferromagnetic coupling only at very low temperatures. In agreement with the magnetic results, 2 displayed typical Ru^III-based anisotropic EPR in CH₃CN (<g>/Δg: 2.314/0.564) but without any forbidden g_1/2 signal at 120 K. The complexes exhibited multiple redox processes in CH₃CN in the experimental potential window of ± 2.0 V versus SCE. The analysis of the redox steps via a combined experimental and theoretical (DFT/TD-DFT) approach revealed the involvement of L²⁻ to varying extents in both the oxidative and reductive processes as a consequence of its bidirectional redox non-innocent feature. The mixing of the frontier orbitals of the metal ion and L²⁻ due to their closeness in energy indeed led to the resonating electronic form in certain redox states instead of any precise electronic structural state.

Synthesis of [Ru₂Cl(Dp-FPhF)_x(O₂CCH₃)_4−x] compounds and the study of how electronic density variation of the Ru₂⁵⁺ core affects their physicochemical properties.

Conventional heating and solvothermal synthetic methods (with or without microwave activation) have been used to study the reaction of o-, m- and p-methoxybenzoic acid with [Ru₂Cl(μ-O₂CMe)₄]. The tetrasubstituted series [Ru₂Cl(µ-O₂CC₆H₄-R)₄], with R = o-OMe, m-OMe and p-OMe, has been prepared by the three procedures. Depending on the synthetic method and the experimental conditions, three compounds have been isolated (1a, 1b, 1c) with the o-methoxybenzoate ligand. However, with the m- and p-methoxybenzoate ligands, only the complexes 2 and 3 have been obtained, respectively. Compound 1a, with stoichiometry [Ru₂Cl(µ-O₂CC₆H₄-o-OMe)₄]_n, shows a polymeric structure with the chloride ions bridging the diruthenium units to form linear chains. Compounds 2 and 3, with the same stoichiometry, predictably form zig-zag chains in accordance with their insolubility and their magnetic measurements. Compound 1b, [Ru₂Cl(µ-O₂CC₆H₄-o-OMe)₄(EtOH)], is a discrete molecular species with a chloride ion and one ethanol molecule occupying the axial positions of the dimetallic unit. Compound 1c is a cation-anion complex, [Ru₂(µ-O₂CC₆H₄-o-OMe)₄(MeOH)₂][Ru₂Cl₂(µ-O₂CC₆H₄-o-OMe)₄]. The cationic complex has two solvent molecules at the axial positions whereas the anionic complex has two chloride ligands at these positions. Complexes have been characterized by elemental analyses, mass spectrometry and IR and UV-vis-NIR spectroscopies. A magnetic study of complexes 1a, 1b, 2 and 3 have also been carried out. The crystal structure of compounds 1b and 1c have been solved by single X-ray crystal methods.

In this article, we report on the synthesis and characterization of the tetracarboxylatodirhodium(II) complexes [Rh₂(μ–O₂CCH₂OMe)₄(THF)₂] (1) and [Rh₂(μ–O₂CC₆H₄–p–CMe₃)₄(OH₂)₂] (2) by metathesis reaction of [Rh₂(μ–O₂CMe)₄] with the corresponding ligand acting also as the reaction solvent. The reaction of the corresponding tetracarboxylato precursor, [Rh₂(μ–O₂CR)₄], with PPh₄[Au(CN)₂] at room temperature, yielded the one-dimensional polymers (PPh₄)_n[Rh₂(μ–O₂CR)₄Au(CN)₂]_n (R = Me (3), CH₂OMe (4), CH₂OEt (5)) and the non-polymeric compounds (PPh₄)₂{Rh₂(μ–O₂CR)₄[Au(CN)₂]₂} (R = CMe₃ (6), C₆H₄–p–CMe₃ (7)). The structural characterization of 1, 3·2CH₂Cl₂, 4·3CH₂Cl₂, 5, 6, and 7·2OCMe₂ is also provided with a detailed description of their crystal structures and intermolecular interactions. The polymeric compounds 3·2CH₂Cl₂, 4·3CH₂Cl₂, and 5 show wavy chains with Rh–Au–Rh and Rh–N–C angles in the ranges 177.18°–178.69° and 163.0°–170.4°, respectively. A comparative study with related rhodium-silver complexes previously reported indicates no significant influence of the gold or silver atoms in the solid-state arrangement of these kinds of complexes.

The controlled release of functionally active compounds is important in a variety of applications. Here, we have synthesized, characterized, and studied the magnetic properties of three novel metal–metal-bonded tris(formamidinato) Ru₂⁵⁺ complexes. We have used different auxin-related hormones, indole-3-acetate (IAA), 2,4-dichlorophenoxyacetate (2,4-D), and 1-naphthaleneacetate (NAA), to generate [Ru₂Cl(μ-DPhF)₃(μ-IAA)] (RuIAA), [Ru₂Cl(μ-DPhF)₃(μ-2,4-D)] (Ru2,4-D), and [Ru₂Cl(μ-DPhF)₃(μ-NAA)] (RuNAA) (DPhF = N,N′-diphenylformamidinate). The crystal structures of RuIAA, RuIAA·THF, Ru2,4-D·CH₂Cl₂, and RuNAA·0.5THF have been determined by single-crystal X-ray diffraction. To assess the releasing capacity of the bound hormone, we have employed a biological assay that relied on Arabidopsis thaliana plants expressing an auxin reporter gene and we demonstrate that the release of the phytohormones from RuIAA, Ru2,4-D, and RuNAA is pH- and time-dependent. These studies serve as a proof of concept showing the potential of these types of compounds as biological molecule carriers.

In this article, we describe the preparation of anionic heteronuclear one-dimensional coordination polymers made by dirhodium paddlewheels and tetracyanido-metallatate building blocks. A series of complexes of (PPh₄)_2n[{Rh₂(µ-O₂CCH₃)₄}{M(CN)₄}]_n (M = Ni (1), Pd (2), Pt (3)) formulae were obtained by reaction of [Rh₂(μ-O₂CCH₃)₄] with (PPh₄)₂[M(CN)₄] in a 1:1 or 2:1 ratio. Crystals of 1−3 suitable for single crystal X-ray diffraction were grown by slow diffusion of a dichloromethane solution of the dirhodium complex into a chloroform solution of the corresponding tetracyanido–metallatate salt. Compounds 1 and 2 are isostructural and crystallize in the triclinic P-1 space group, while compound 3 crystallizes in the monoclinic P2₁/n space group. A detailed description of the structures is presented, including the analysis of the packing of anionic chains and PPh₄⁺ cations.