3d/4f Coordination Clusters as Cooperative Catalysts for Highly Diastereoselective Michael Addition Reactions

Chemical Chartographisis: a contemporary perspective in molecular design and synthesis

The use of flexible molecular systems in solution, without strictly controlling their behaviour, has frequently been productive. Their potential could increase by a more holistic view of the reaction(s) process(es) in which they are involved. In this perspective, we introduce a broader approach - "Chemical Chartographisis" - and discuss three projects in detail to illustrate its potential. The topics involve bimetallic 3d/4f species and coordination compounds built from benzotriazole-based and (a)symmetric salan ligands and focus on catalytic and, in less detail, biological-related examples.

Anion-directed structural tuning of two azomethine-derived Zn2+ complexes with optoelectronic recognition of Cu2+ in aqueous medium with anti-cancer activities: from micromolar to femtomolar sensitivity with DFT revelation

Herein, two novel mononuclear transition metal Zn2+ complexes i.e. [Zn(HL)(N3)(OAc)] (NS-1) & [Zn(HL)2(ClO4)2] (NS-2) have been synthesised using a tridentate clickable Schiff base ligand, HL (2-methyl-2-((pyridin-2-ylmethyl)amino)propan-1-ol), and the polyatomic monoanions N3- and ClO4- for NS-1 and NS-2 respectively. Interestingly, NS-1 and NS-2 have been explored for the detection of Cu2+ with an LOD of 48.6 fM (response time ∼6 s) and 2.4 μM respectively through two mutually independent pathways that were studied using sophisticated methods like UV-Vis, cyclic voltammetry, ESI-MS etc. with theoretical DFT support. Herein, both chemosensors are equally responsive towards the detection of Cu2+ in aqueous as well as other targeted real field samples with appreciable recovery percentage (74.8-102%), demonstrating their practical applicability. Moreover, the detection of unbound Cu2+ in a human urine specimen was also analysed which may be helpful for the diagnosis of Cu2+-related disorders like Wilson's disease. Taking one step ahead, TLC strips have been employed for on-field detection of the targeted analytes by contact mode analysis. Additionally, the anti-cancer activity of these complexes has also been studied on breast cancer cells with the help of the MTT assay. It has been found that at a 0.5 mM dose, both NS-1 and NS-2 could kill 81.4% and 73.2% of cancer cells respectively. However, it has been found that NS-1 destroys normal cells together with cancer cells. Hence, NS-2 could be administered as a better anticancer drug for MDA-MB-231 cancer cells in comparison with NS-1. In a nutshell, the present work describes how anion-directed synthesis of two architecturally different metal complexes leads toward the detection of the same analyte via an independent chemodosimetric pathway along with their anti-cancer activities on breast cancer cells.

Chiral Co3Y Propeller-Shaped Chemosensory Platforms Based on 19F-NMR

Two propeller-shaped chiral Co^III₃Y^III complexes built from fluorinated ligands are synthesized and characterized by single-crystal X-ray diffraction (SXRD), IR, UV-vis, circular dichroism (CD), elemental analysis, thermogravimetric analysis (TGA), electron spray ionization mass spectroscopy (ESI-MS), and NMR (¹H, ¹³C, and ¹⁹F). This work explores the sensing and discrimination abilities of these complexes, thus providing an innovative sensing method using a ¹⁹F NMR chemosensory system and opening new directions in 3d/4f chemistry. Control experiments and theoretical studies shed light on the sensing mechanism, while the scope and limitations of this method are discussed and presented.

Heteroligand α-Diimine-Zn(II) Complexes with O,N,O'- and O,N,S-Donor Redox-Active Schiff Bases: Synthesis, Structure and Electrochemical Properties

A number of novel heteroligand Zn(II) complexes (1-8) of the general type (Lⁿ)Zn(NN) containing O,N,O'-, O,N,S-donor redox-active Schiff bases and neutral N,N'-chelating ligands (NN) were synthesized. The target Schiff bases LⁿH₂ were obtained as a result of the condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with substituted o-aminophenols or o-aminothiophenol. These ligands with combination with 2,2'-bipyridine, 1,10-phenanthroline, and neocuproine are able to form stable complexes upon coordination with zinc(II) ion. The molecular structures of complexes 4∙H₂O, 6, and 8 in crystal state were determined by means of single-crystal X-ray analysis. In the prepared complexes, the redox-active Schiff bases are in the form of doubly deprotonated dianions and act as chelating tridentate ligands. Complexes 6 and 8 possess a strongly distorted pentacoordinate geometry while 4∙H₂O is hexacoordinate and contains water molecule coordinated to the central zinc atom. The electrochemical properties of zinc(II) complexes were studied by the cyclic voltammetry. For the studied complexes, O,N,O'- or O,N,S-donor Schiff base ligands are predominantly involved in electrochemical transformations in the anodic region, while the N,N'-coordinated neutral nitrogen donor ligands demonstrate the electrochemical activity in the cathode potential range. A feature of complexes 5 and 8 with sterically hindered tert-butyl groups is the possibility of the formation of relatively stable monocation and monoanion forms under electrochemical conditions. The values of the energy gap between the boundary redox orbitals were determined by electrochemical and spectral methods. The parameters obtained in the first case vary from 1.97 to 2.42 eV, while the optical bang gap reaches 2.87 eV.

Carboxylate-Decorated Aggregation of Octanuclear Co4Ln4 (Ln = Dy, Ho, Yb) Complexes from Ligand-Controlled Hydrolysis: Synthesis, Structures, and Magnetic Properties

One-pot reactions of an asymmetric carboxy-ether-phenol based Schiff base H₂L (2-((2-hydroxy-3-methoxybenzylidene)amino)benzoic acid) with selected Ln(NO₃)₃·nH₂O and [Co₂(μ-OH₂)(O₂CCMe₃)₄(HO₂CCMe₃)₄] (Co₂-Piv) in basic MeOH medium resulted in a family of three octanuclear complexes, [Co^II₄Ln^III₄L₄(μ_1,3-Piv)₄(μ_1,1,3-Piv)₂(η¹-Piv)₂(μ₃-OH)₄(MeOH)₂]·mMeOH·nH₂O (Ln = Dy; m = 3, n = 1 (1), Ho; m = 4, n = 0 (2), Yb; m = 3, n = 1 (3)). The coordination aggregates thus obtained were nicely sustained by four ligand anions and eight externally added carboxylate anions showing three different modes of intermetallic connectivity. The options for incorporating different 4f ions in an investigative synthesis, without altering the resulting intermetallic core structure, were successful for the three representative examples. Single-crystal X-ray diffraction studies revealed that the compounds are isostructural and built from two initially formed partial dicubane-type Co₂Ln₂L₂ units. In each of the tetranuclear parts, the metal ion centers are held together by two L^2-, two μ₃-HO^-, three Piv^- bridges, one terminal Piv^-, and one terminal MeOH. Four carboxylate ends of four L^2- units are responsible for connecting two Co₂Ln₂ units into octanuclear structures. The unique distortion around the Co^II centers is achieved from the facile coordination of bigger 4f ions to the adjacent hard OO sites. The distortion is further maintained by the presence of terminal COO^- groups from L^2-. The dc magnetic susceptibility data revealed ferromagnetic coupling between the Co^II and Ln^III centers within the series, whereas the ac magnetic susceptibility measurements identified only 1, having a highly anisotropic Dy^III ion, as a single-molecule magnet in the absence of any external magnetic field, with an energy barrier U_eff of 12.5 K.

The structural manipulation of a series of Ni4 defective dicubanes: Synthesis, X-ray Structures, Magnetic and Computational analyses

We report the synthesis and characterization of four new tetranuclear Ni(ii) complexes, C1-C4, all of which exhibit defective dicubane cores. C1-C4 are derived from the same salicylaldoxime derived ligand, H2L1. Complexes C1 and C4 have isostructural cores, differing in structure only by solvate molecules. Magnetic and computational analyses have revealed that complexes C1, C2, and C4 exhibit competing ferro- and antiferromagnetic interactions, however the different solvated species in C1 and C4 leads to notably different magnitudes in their magnetic coupling constants. Theoretical magneto-structural studies show that the pairwise magnetic exchange interaction is highly dependent on the Ni-X-Ni angle, as revealed by orbital overlap calculations.

Substitution Effects Regulate the Formation of Butterfly-Shaped Tetranuclear Dy(III) Cluster and Dy-Based Hydrogen-Bonded Helix Frameworks: Structure and Magnetic Properties

The generation of two types of complexes with different topological connections and completely different structural types merely via the substitution effect is extremely rare, especially for -CH₃ and -C₂H₅ substituents with similar physical and chemical properties. Herein, we used 3-methoxysalicylaldehyde, 1,2-cyclohexanediamine, and Dy(NO₃)₃·6H₂O to react under solvothermal conditions (CH₃OH:CH₃CN = 1:1) at 80 °C to obtain the butterfly-shaped tetranuclear Dy^III cluster [Dy₄(L¹)₄(μ₃-O)₂(NO₃)₂] (Dy₄, H₂L¹ = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)). The ligand H₂L¹ was obtained by the Schiff base in situ reaction of 3-methoxysalicylaldehyde and 1,2-cyclohexanediamine. In the Dy₄ structure, (L¹)^2- has two different coordination modes: μ₂-η¹:η²:η¹:η¹ and μ₄-η¹:η²:η¹:η¹:η²:η¹. The four Dy^III ions are in two coordination environments: N₂O₆ (Dy1) and O₉ (Dy2). The magnetic testing of cluster Dy₄ without the addition of an external field revealed that it exhibited a clear frequency-dependent behavior. We changed 3-methoxysalicylaldehyde to 3-ethoxysalicylaldehyde and obtained one case of a hydrogen-bonded helix framework, [DyL²(NO₃)₃]_n·2CH₃CN (Dy-HHFs, H₂L² = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-ethoxyphenol)), under the same reaction conditions. The ligand H₂L² was formed by the Schiff base in situ reaction of 3-ethoxysalicylaldehyde and 1,2-cyclohexanediamine. All Dy^III ions in the Dy-HHFs structure are in the same coordination environment (O₉). The twisted S-shaped (L²)^2- ligand is linked by a Dy(III) ion to form a spiral chain. The spiral chain is one of the independent units that is interconnected to form Dy-HHFs through three strong hydrogen-bonding interactions. Magnetic studies show that Dy-HHFs exhibits single-ion-magnet behavior (U_eff = 68.59 K and τ₀ = 1.10 × 10^-7 s, 0 Oe DC field; U_eff = 131.5 K and τ₀ = 1.22 × 10^-7 s, 800 Oe DC field). Ab initio calculations were performed to interpret the dynamic magnetic performance of Dy-HHFs, and a satisfactory consistency between theory and experiment exists.

Two 1D homochiral heterometallic chains: crystal structures, spectra, ferroelectricity and ferromagnetic properties

Two new homo chiral Cu–Ln (Ln = Gd and Ho) compounds bearing a chiral Schiff base ligand (1R,3S)-N′,N′′-bis[3-methoxysalicylidene]-1,3-diamino-1,2,2-trimethylcyclopentane (H₂L) have been synthesized and characterized by elemental analysis, IR spectroscopic and single-crystal X-ray diffraction techniques. The compounds were found to exhibit 1D zig-zag skeletons with double μ-1,5 bridging dicyanamide anions. Circular dichroism (CD) spectra have been used to verify their chiroptical activities. Magnetic studies suggest that 1 and 2 hold the same magnetic behavior with the dinuclear compounds presenting ferromagnetic interaction. Furthermore, both compounds show ferroelectricity with the remnant polarization (P_r) value of 0.23 and 0.18 μC cm⁻² at room temperature, respectively.

Two homochiral 1D heterometallic chains are potential multifunctional molecules coexisting optical activity, ferromagnetic and ferroelectric properties.

A Trinuclear Zinc Coordination Cluster Exhibiting Fluorescence, Colorimetric Sensitivity, and Recycling of Silver Ion and Detection of Cupric Ion

The detection and reusage of transition-metal ions play a crucial role in human health and environmental protection. Recently, various analytical methods and substances have been successfully applied to probe or sense silver ions; however, rare representative examples have been presented regarding the simultaneous detection of silver and silver recycling with the elemental silver powder form. Herein, an unparalleled sensing mechanism for silver ions and recycling silver in its elemental form is exemplified by a fluorescent trinuclear zinc coordination cluster possessing the dual function of colorimetric sensing of silver and responding cupric ions. A Schiff-base-based trinuclear zinc coordination cluster, 1, with formula Zn₃(L₁)₂(CH₃COO)₂(H₂O)₂, has been successfully synthesized by the initial exploration of multidentate ligand H₂L₁-((E)-2,4-di-tert-butyl-6-((2-hydroxy-3-methoxybenzy-lidene)amino)phenol) with various metal ions under self-assembly reactions. Complex 1 is highly fluorescent in solution and as a solid, in addition to acting as a fluorescence sensor toward Ag^I in ethanol media. Compound 1 displays distinctive sensing of Ag^I through the fluorescence quenching effect at 576 nm and signal augment at 446 nm over 11 kinds of cations in the absence of interference. The proposed sensing mechanism is attributed to the ligands in 1 which interact with Ag^I; the ligands undergo oxidation cyclization reaction, leading to the formation of 2 with the formula Zn₃(L₂)₄(CH₃COO)₂·2CH₃CH₂OH·H₂O, and Ag^I reduction to elemental Ag powder. Compound 1 presents specific selectivity and sensitivity for Ag^I in ethanolic solution with a detection limit of 0.1722 μM. The orange color of 1 changes to colorless during the mixing of a small amount of Ag^I, revealing its potential practical application in naked-eye detection of Ag^I. Furthermore, 2 exhibits obvious fluorescence emission at 448 nm (λ_ex = 380 nm) and selectively responds to Cu^II over 11 kinds of metal ions with the fluorescence "turn-off" owing to the formation of 3 in ethanolic solution; it also has a detection limit of 0.0226 μM.

Facile synthesis of a new Cu(ii) complex with an unsymmetrical ligand and its use as an O3 donor metalloligand in the synthesis of Cu(ii)-Mn(ii) complexes: structures, magnetic properties, and catalytic oxidase activities

A new, facile Cu(ii) template method has been employed for the unsymmetrical dicondensation of 1,2-ethylenediamine with salicylaldehyde and o-vanillin. The mononuclear complex, [CuL] (1), thus obtained, has been used as an O₃ donor metalloligand for the synthesis of four new Cu(ii)-Mn(ii) complexes, [(CuL)MnCl₂] (2), [(CuL)Mn(NO₃)₂(CH₃OH)]_n (3), {[(CuL)Mn(benz)(H₂O)]₂·(CuL)₂(ClO₄)₂} (4) and [(CuL)Mn(benz)Cl]₂ (5) (where benz = benzoate). Single-crystal structural analyses reveal that 2 is a dinuclear complex while complex 3 is polymeric with a repeating dinuclear [(CuL)Mn(NO₃)₂(CH₃OH)] unit, linked via the nitrate ion. Both 4 and 5 are discrete tetranuclear complexes, where the dinuclear units [(CuL)Mn(benz)(H₂O)] and [(CuL)Mn(benz)Cl] are connected by double benzoate and double chloride bridges, respectively. In complex 4, two monomeric [CuL] units are cocrystallized with the tetranuclear complex. An important difference in the structure of 4 from the other three complexes is that one solvent water molecule is coordinated to each Mn(ii) ion, which makes complex 4 catalytically very active towards mimicking catecholase and phenoxazinone synthase-like oxidation reactions. The turnover numbers (k_cat) for the aerial oxidation of 3,5-di-tert-butylcatechol and o-aminophenol are 399 h^-1 and 230 h^-1, respectively. The evidence of the intermediate species in the mass spectra indicates possible heterometallic cooperation where the Mn(ii) center helps in substrate binding and Cu(ii) participates in the oxidation reactions with molecular oxygen. Cyclic voltammetry measurements suggest the reduction of Cu(ii) to Cu(i) during the catalytic process. Temperature-dependent dc molar magnetic susceptibility measurements reveal that complexes 2-5 are antiferromagnetically coupled with the exchange coupling constants (J) of J = -13.5 cm^-1 and J = -13.5 cm^-1 for 2 and 3, respectively, J₁ = -12.6 cm^-1 and J₂ = -1.20 cm^-1 for complex 4 and J₁ = -13.24 cm^-1 and J₂ = 0.36 cm^-1 for complex 5 as is expected from the Cu-O-Mn bridging angles.

Trinuclear Lanthanide Coordination Clusters: Single-Molecule-Magnet Behavior and Catalytic Activity in the Friedel-Crafts Alkylation Reaction

A new multidentate ligand (H₃ L) was synthesized by the condensation reaction of 4-tert-butyl-2,6-diformylphenol and 2-amino-4-nitrophenol. The reaction of the ligand with hydrated lanthanide nitrate produced two isostructural trinuclear coordination clusters: [DyLn₃ L₃ (DMF)₃ (H₂ O)₂ ] ⋅ 3.8DMFLn=Dy (1) and Nd (2) (DMF=N, N-dimethylformamide). Single-crystal X-ray diffraction analysis revealed that there are three lanthanide ions arranged in an almost perfect linear fashion in both complexes. Magnetic studies show single-molecule-magnet (SMM) behavior in the Dy derivative with τ₀ =1.7×10^-6  s and a thermal energy barrier of 7.0 cm^-1 . Both complexes were used as catalysts towards the Friedel-Crafts alkylation reaction of indole with different aldehydes with yields varying from 59-98 %. Complex 1 showed better catalytic efficiency than complex 2. This is the first report of using trinuclear lanthanide coordination clusters as catalysts for the Friedel-Crafts alkylation reaction.

In situ selective ligand transformation from Si–H to Si–OH for synergistic assembly of hydrogen-bonded metal–organic frameworks

Two isoreticular silicon-based hydrogen-bonded metal–organic frameworks (HMOFs) have been synthesized by in situ selective transformation of the ligand from hydrosilane to silanol.

Substituents lead to differences in the formation of two different butterfly-shaped NiDy clusters: structures and multistep assembly mechanisms

The most effective way to understand reaction mechanisms and kinetics is to identify the reaction intermediates and determine the possible reaction patterns. The influencing factors that must be considered in the self-assembly of clusters are the type of ligand, metal ion, coordination anion and the pH of the solution. However, changes in ligand substituents resulting in different self-assembly processes to obtain different types of structures are still very rare, especially with -H and -CH₃ substituents, which do not exert significant steric hindrance effects. In this study, planar mononuclear Ni(L¹)₂ (L¹ = 2-ethoxy-6-(iminomethyl)phenol) was dissolved in methanol and combined with Dy(NO₃)₃·6H₂O for 48 h at room temperature to obtain a butterfly-like Ni₂Dy₂ cluster ([Dy₂Ni₂(L¹)₄(CH₃O)₂(NO₃)₄], 1). The Dy(iii) ions in cluster 1 are in an O₈N coordination environment, and the Ni(ii) ions are in an O₅N coordination environment. High-resolution electrospray ionization mass spectrometry (HRESI-MS) was used to track species changes during the formation of cluster 1. Six key intermediate fragments were screened, and the self-assembly mechanism was proposed as Ni(L¹)₂→ HL¹ + NiL¹→ DyL¹/Ni(L¹)₂'→ DyNi(L¹)₂→ Dy₂Ni₂(L¹)₄. Through this assembly mechanism, we found that Ni(L¹)₂ was first cleaved into HL¹ + NiL¹ and then further assembled to obtain 1. Another butterfly-like tetranuclear heterometallic cluster ([Dy₂Ni₂(L²)₄(CH₃O)₂(NO₃)₄], 2) was obtained using planar mononuclear Ni(L²)₂ (L² = (E)-2-ethoxy-6-((methylimino)methyl)phenol) with -CH₃ substitution on the nitrogen atom under the same reaction conditions. The structural analysis of cluster 2 showed that the Dy(iii) ions are in an O₉ coordination environment, and the Ni(ii) ions are in an O₄N₂ coordination environment. HRESI-MS was used to trace species changes during the formation of 2, and the assembly mechanism was proposed as Ni(L²)₂→ DyNi(L²)₂→ Dy₂Ni(L²)₂→ Dy₂Ni₂(L²)₄. Analysis of the assembly mechanism of 2 showed that Ni(L²)₂ was twisted during the reaction, and its coordination point was exposed to capture the Dy(iii) ions. Finally, Dy(NO₃)₃·6H₂O was replaced with NaN₃ to obtain a [Ni₂Na₂(L²)₄(N₃)₄] cluster (3) under the same reaction conditions and verify the above-mentioned torsion step. HRESI-MS was also used to trace the assembly process, and the assembly mechanism was proposed as Ni(L²)₂→ NiNa(L²)₂→ NiNa₂(L²)₂→ Ni₂Na₂(L²)₄. Herein, the effect of interference from substitution and the regulation self-assembly process were discovered in the formation of 3d-4f heterometallic clusters, and different types of coordination clusters were obtained.

Zinc-dysprosium functionalized amyloid fibrils

The heterometallic Zn2Dy2 entity bearing partially saturated metal centres covalently decorates a highly ordered amyloid fibril core and the functionalised assembly exhibits catalytic Lewis acid behaviour.

Effect of coordination anion substitutions on relaxation dynamics of defect dicubane Zn2Dy2 tetranuclear clusters

We showcase the coordination anion substitution effect on the relaxation dynamics of defect dicubane Zn₂Dy₂ tetranuclear clusters.

Bottom-Up Assembly of a Highly Efficient Metal-Organic Framework for Cooperative Catalysis

In this study, we demonstrate a bottom-up assembly of a monomeric copper complex and a two-dimensional (2-D) heterometallic metal-organic framework (MOF) from a carboxylate-functionalized tridentate Schiff base ligand and metal ions. The obtained 2-D MOF features a unique bimetallic copper center which is different from its monometallic precursor and acts as an efficient heterogeneous catalyst for the Friedel-Crafts reaction and Henry reaction. The MOF catalyst shows a remarkably superior activity compared to its homogeneous counterparts in a wide range of substrates. It is presumably ascribed to the dual activation of the substrates by the active bimetallic copper center confined in the MOF network, which is supported by the significant changes in catalytic activity at low catalyst/substrates ratios when using the 2-D MOF and its precursor as catalysts, respectively. Moreover, the MOF catalyst also shows an excellent stability and recyclability. Our work, therefore, provides a stepwise strategy to design a heterogeneous cooperative catalyst, by taking advantage of the modulated structure of MOF and tunable functionality of the tridentate Schiff base, with high performance in a variety of organic synthesis.

Transformative 3d-4f coordination cluster carriers

The aim of this perspective is to summarise the use of the reported 3d-4f Coordination Clusters (CCs) in catalytic reactions and to demonstrate the potential of this emerging field. The pioneering work of Shibasaki, Matsunaga and others, demonstrated the use of 3d-4f in situ systems to catalyse asymmetric organic transformations. Our recent studies show that well characterised 3d-4f CCs catalyse numerous organic transformations and useful mechanistic aspects of their catalysis can be obtained. Furthermore, we have shown that by manipulation of the metal ion coordination environment; the nature of the 3d and lanthanide ions and the organic periphery of the ligand can all improve the efficacy of a 3d-4f CC catalyst. All in situ formed and well characterized 3d-4f CCs involved in catalysis are discussed.

The modular synthesis of rare earth-transition metal heterobimetallic complexes utilizing a redox-active ligand

We report a robust and modular synthetic route to heterometallic rare earth-transition metal complexes. We have used the redox-active bridging ligand 1,10-phenathroline-5,6-dione (pd), which has selective N,N' or O,O' binding sites as the template for this synthetic route. The coordination complexes [Ln(hfac)₃(N,N'-pd)] (Ln = Y [1], Gd [2]; hfac = hexafluoroacetylacetonate) were synthesised in high yield. These complexes have been fully characterised using a range of spectroscopic techniques. Solid state molecular structures of 1 and 2 have been determined by X-ray crystallography and display different pd binding modes in coordinating and non-coordinating solvents. Complexes 1 and 2 are unusually highly coloured in coordinating solvents, for example the vis-NIR spectrum of 1 in acetonitrile displays an electronic transition centred at 587 nm with an extinction coefficient consistent with significant charge transfer. The reaction between 1 and 2 and VCp₂ or VCp^t₂ (Cp^t = tetramethylcyclopentadienyl) resulted in the isolation of the heterobimetallic complexes, [Ln(hfac)₃(N,N'-O,O'-pd)VCp₂] (Ln = Y [3], Gd [4]) or [Ln(hfac)₃(N,N'-O,O'-pd)VCp^t₂] (Ln = Y [5], Gd [6]). The solid state molecular structures of 3, 5 and 6 have been determined by X-ray crystallography. The spectroscopic data on 3-6 are consistent with oxidation of V(ii) to V(iv) and reduction of pd to pd^2- in the heterobimetallic complexes. The spin-Hamiltonian parameters from low temperature X-band EPR spectroscopy of 3 and 5 describe a ²A₁ ground state, with a V(iv) centre. DFT calculations on 3 are in good agreement with experimental data and confirm the SOMO as the d_x²-y² orbital localised on vanadium.

Heterometallic ZnII⁻LnIII⁻ZnII Schiff Base Complexes with Linear or Bent Conformation-Synthesis, Crystal Structures, Luminescent and Magnetic Characterization

A series of racemic, heteronuclear complexes [Zn₂Nd(ac)₂(HL)₂]NO₃·3H₂O (1), [Zn₂Sm(ac)₂(HL)₂]NO₃·3CH₃OH·0.3H₂O (2), [Zn₂Ln(ac)₂(HL)₂]NO₃·5.33H₂O (3–5) (where HL is the dideprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diamino-2-propanol, ac = acetate ion, and Ln = Eu (3), Tb (4), Dy (5), respectively) with an achiral multisite coordination Schiff base ligand (H₃L) were synthesized and characterized. The X-ray crystallography revealed that the chirality in complexes is centered at lanthanide(III) ions due to two vicinally located μ-acetato-bridging ligands. The presented crystals have isoskeletal coordination units but they crystallize in monoclinic (1, 2) or trigonal crystal systems (3–5) with slightly different conformation. In 1 and 2 the Zn^II–Ln^III–Zn^II coordination core is linear, whereas in isostructural crystals 3–5 the chiral coordination cores are bent and lie on a two-fold axis. The complexes 1, 3–5 show a blue emission attributed to the emission of the ligand. For Zn^II₂Sm^III complex (2) the characteristic emission bands of f-f* transitions were observed. The magnetic properties for compounds 1, 4 and 5 are characteristic for the paramagnetism of the corresponding lanthanide(III) ions.

Influence of alcoholic solvent and acetate anion coordination mode variations on structures and magnetic properties of heterometallic Zn2Dy2 tetranuclear clusters

We clarify that slight modifications of the synthetic conditions generate two Zn₂Dy₂ clusters with acetate anion coordination mode variation and different magnetic behaviors.

Dinucleating Schiff base ligand in Zn/4f coordination chemistry: synthetic challenges and catalytic activity evaluation

Synthetic challenges and catalytic activity evaluation of Zn/(Dy,Y) coordination clusters derived from a dinucleating Schiff base ligand.

Two tetranuclear 3d–4f heterometal complexes Mn2Ln2 (Ln = Dy, Gd): synthesis, structure, magnetism, and electrocatalytic reactivity for water oxidation

The two Mn₂Ln₂ complexes can catalyze water oxidation, which may arise from the cooperative catalytic effect of the Mn/Ln ions.

Synthesis, structures and magnetic properties of linear {CoII2LnIII2} coordination clusters

A series of linear CoII2LnIII2 coordination clusters have been synthesized and their magnetic properties have been systematically studied.

A tetranuclear CuII2DyIII2 coordination cluster as a Suzuki (C–C) coupling reaction promoter

The air stable and high yielding tetranuclear coordination cluster [CuII2DyIII2L₄(NO₃)₂(CH₃CN)₂]·2(CH₃CN) promotes the Suzuki coupling reaction of phenylboronic acid with substituted aryl halides under environmentally benign conditions.