Syntheses, crystal structures and Hirshfeld surface analyses of bis-(2-mercaptobenzimidazole)-bromo- and iodo-copper(I) complexes

The title complexes, bromidobis(2,3-dihydro-1H-1,3-benzodiazole-2-thi-one)copper(I), [CuBr(C7H6N2S)2] (1), and bis(2,3-dihydro-1H-1,3-benzodiazole-2-thione)iodidocopper(I) acetone monosolvate, [CuI(C7H6N2S)2]·CH3COCH3 (2), were prepared by the reaction of copper(I) bromide/iodide with 2-mercaptobenzimidazole. Both complexes have mononuclear structures with the copper atom coordinated by two 2-mercaptobenzimidazole mol-ecules via their S atoms and one halide atom in an approximate trigonal-planar arrangement. In their extended structures, N-H⋯S hydrogen bonds and π-π contacts are found in both complexes; as a result of the acetone solvent mol-ecule in (2), N-H⋯O contacts are also observed. Hirshfeld surface analyses were carried out to aid in the visualization of these inter-actions, which showed that H⋯H contacts contribute 34.6% for (1) and 34.1% for (2) to the overall surface, followed by contributions from H⋯S/S⋯H, H⋯C/C⋯H and C⋯C contacts, respectively. As expected, H⋯O/O⋯H contacts are observed only in (2). The IR and 1H and 13C NMR spectra of (1) and (2) are described.

Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso-Scale Aggregates

Operando characterization of working catalysts, requiring per definitionem the simultaneous measurement of catalytic performance, is crucial to identify the relevant catalyst structure, composition and adsorbed species. Frequently applied operando techniques are discussed, including X-ray absorption spectroscopy, near ambient pressure X-ray photoelectron spectroscopy and infrared spectroscopy. In contrast to these area-averaging spectroscopies, operando surface microscopy by photoemission electron microscopy delivers spatially-resolved data, directly visualizing catalyst heterogeneity. For thorough interpretation, the experimental results should be complemented by density functional theory. The operando approach enables to identify changes of cluster/nanoparticle structure and composition during ongoing catalytic reactions and reveal how molecules interact with surfaces and interfaces. The case studies cover the length-scales from clusters via nanoparticles to meso-scale aggregates, and demonstrate the benefits of specific operando methods. Restructuring, ligand/atom mobility, and surface composition alterations during the reaction may have pronounced effects on activity and selectivity. The nanoscale metal/oxide interface steers catalytic performance via a long ranging effect. Combining operando spectroscopy with switching gas feeds or concentration-modulation provides further mechanistic insights. The obtained fundamental understanding is a prerequisite for improving catalytic performance and for rational design.

Vapochromism and Magnetochemical Switching of a Nickel(II) Paddlewheel Complex by Reversible NH3 Uptake and Release

Reaction of [NiCl2 (PnH)4 ] (1) (PnH=6-tert-butyl-pyridazine-3-thione) with NiCl2 affords the binuclear paddlewheel (PW) complex [Ni2 (Pn)4 ] (2). Diamagnetic complex 2 is the first example of a PW complex capable of reversibly binding and releasing NH3 . The NH3 ligand in [Ni2 (Pn)4 (NH3 )] (2⋅NH3 ) enforces major spectroscopic and magnetic susceptibility changes, thus displaying vapochromic properties (λmax (2)=532 nm, λmax (2⋅NH3 )=518 nm) and magnetochemical switching (2: S=0; 2⋅NH3 : S=1). Upon repeated adsorption/desorption cycles of NH3 the PW core remains intact. Compound 2 can be embedded into thin polyurethane films (2P ) under retention of its sensing abilities. Therefore, 2 qualifies as reversible optical probe for ammonia. The magnetochemical switching of 2 and 2⋅NH3 was studied in detail by SQUID measurements showing that in 2⋅NH3 , solely the Ni atom coordinated the NH3 molecule is responsible for the paramagnetic behavior.

Heavy chalcogenide-transition metal clusters as coordination polymer nodes

While metal-oxygen clusters are widely used as secondary building units in the construction of coordination polymers or metal-organic frameworks, multimetallic nodes with heavier chalcogenide atoms (S, Se, and Te) are comparatively untapped. The lower electronegativity of heavy chalcogenides means that transition metal clusters of these elements generally exhibit enhanced coupling, delocalization, and redox-flexibility. Leveraging these features in coordination polymers provides these materials with extraordinary properties in catalysis, conductivity, magnetism, and photoactivity. In this perspective, we summarize common transition metal heavy chalcogenide building blocks including polynuclear metal nodes with organothiolate/selenolate or anionic heavy chalcogenide atoms. Based on recent discoveries, we also outline potential challenges and opportunities for applications in this field.

Structural characterization and magnetic property studies of a mixed-valence {CoIIICo} complex with a μ4-oxo tetrahedral {Co} motif

We have synthesized and structurally characterized a new mixed valence pentanuclear Co complex, bearing a rare μ4-O-tetrahedral CoII4 unit, by employing a pyridine-like Schiff base ligand. We have performed DC magnetic susceptibility and magnetization measurements over polycrystalline samples and chemical quantum computations in order to understand the exchange interaction pattern within Co(ii) sites and ground state magnetic anisotropy. This new complex shows an overall antiferromagnetic exchange interaction whose strength strongly depends on the local symmetry of Co(ii) sites. Also, local ion magnetic anisotropy reveals a strongly axial behaviour with the lowest Kramers doublet (KD) at each Co(ii) ion sufficiently isolated from excited states at low temperatures. Two Co(ii) sites show tetrahedral symmetry and the spin only formalism including axial zero-field splitting (ZFS) term properly described them; on the other hand, the other two Co(ii) sites have distorted octahedral and square base pyramidal coordination spheres, and a strong orbital contribution leads to a failure of the spin only formalism. A model of four Seff = 1/2 exchange interacting sites is necessary in order to account for low temperature magnetization behaviour. In view of the strongly anisotropic KD states, the exchange interactions are forced to be modelled as anisotropic ones. Overall, experimental data and quantum chemical computations are in good agreement, supporting the proposed model for magnetic behaviour.

Photocatalytic H2-Evolution by Homogeneous Molybdenum Sulfide Clusters Supported by Dithiocarbamate Ligands

Irradiation at 460 nm of [Mo₃(μ₃-S)(μ₂-S₂)₃(S₂CNR₂)₃]I ([2a]I, R = Me; [2b]I, R = Et; [2c]I, R = ⁱBu; [2d]I, R = CH₂C₆H₅) in a mixed aqueous-polar organic medium with [Ru(bipy)₃]²⁺ as photosensitizer and Et₃N as electron donor leads to H₂ evolution. Maximum activity (300 turnovers, 3 h) is found with R = ⁱBu in 1:9 H₂O:MeCN; diminished activity is attributed to deterioration of [Ru(bipy)₃]²⁺. Monitoring of the photolysis mixture by mass spectrometry suggests transformation of [Mo₃(μ₃-S)(μ₂-S₂)₃(S₂CNR₂)₃]⁺ to [Mo₃(μ₃-S)(μ₂-S)₃(S₂CNR₂)₃]⁺ via extrusion of sulfur on a time scale of minutes without accumulation of the intermediate [Mo₃S₆(S₂CNR₂)₃]⁺ or [Mo₃S₅(S₂CNR₂)₃]⁺ species. Deliberate preparation of [Mo₃S₄(S₂CNEt₂)₃]⁺ ([3]⁺) and treatment with Et₂NCS₂^1- yields [Mo₃S₄(S₂CNEt₂)₄] (4), where the fourth dithiocarbamate ligand bridges one edge of the Mo₃ triangle. Photolysis of 4 leads to H₂ evolution but at ∼25% the level observed for [Mo₃S₇(S₂CNEt₂)₃]⁺. Early time monitoring of the photolyses shows that [Mo₃S₄(S₂CNEt₂)₄] evolves H₂ immediately and at constant rate, while [Mo₃S₇(S₂CNEt₂)₃]⁺ shows a distinctive incubation prior to a more rapid H₂ evolution rate. This observation implies the operation of catalysts of different identity in the two cases. Photolysis solutions of [Mo₃S₇(S₂CNⁱBu₂)₃]⁺ left undisturbed over 24 h deposit the asymmetric Mo₆ cluster [(ⁱBu₂NCS₂)₃(μ₂-S₂)₂(μ₃-S)Mo₃](μ₃-S)(μ₃-η²,η¹-S',η¹-S″-S₂)[Mo₃(μ₂-S)₃(μ₃-S)(S₂CNⁱBu₂)₂(μ₂-S₂CNⁱBu₂)] in crystalline form, suggesting that species with this hexametallic composition and core topology are the probable H₂-evolving catalysts in photolyses beginning with [Mo₃S₇(S₂CNR₂)₃]⁺. When used as solvent, N,N-dimethylformamide (DMF) suppresses H₂-evolution but to a greater degree for [Mo₃S₄(S₂CNEt₂)₄] than for [Mo₃S₇(S₂CNEt₂)₃]⁺. Recrystallization of [Mo₃S₄(S₂CNEt₂)₄] from DMF affords [Mo₃S₄(S₂CNEt₂)₄(η¹,κO-DMF)] (5), implying that inhibition by DMF arises from competition for a Mo coordination site that is requisite for H₂ evolution. Computational assessment of [Mo₃S₄(S₂CNMe₂)₃]⁺ following addition of 2H⁺ and 2e^- suggests a Mo(H)-μ₂(SH) intermediate as the lowest energy species for H₂ elimination. An analogous pathway may be available to the Mo₆ cluster via dissociation of one end of the μ₂-S₂CNR₂ ligand, a known hemilabile ligand type, in the [Mo₃S₄]⁴⁺ fragment.

Syntheses, structures, and magnetic properties of mixed-ligand complexes based on 3,6-bis(benzimidazol-1-yl)pyridazine

Six new metal-organic coordination polymers (CPs) [Ni(L)(2,5-TDC)(H2O)] n (1), [Ni(L)(1,3-BDC)(H2O)] n (2), [Ni(L)(1,4-BDC)(H2O)] n (3), [Mn(L)(2,5-TDC)(H2O)] n (4), [Mn(L)(2,6-PYDC)(H2O)] n (5) and [Mn(L)(1,4-NDC)] n (6) were achieved by reactions of the corresponding metal salt with mixed organic ligands (L = 3,6-bis(benzimidazol-1-yl)pyridazine, 2,5-H2TDC = thiophene-2,5-dicarboxylic acid, 1,3-H2BDC = isophthalic acid, 1,4-H2BDC = terephthalic acid, 2,6-H2PYDC = pyridine-2,6-dicarboxylic acid, 1,4-H2NDC = naphthalene-1,4-dicarboxylic acid) under solvothermal condition. CPs 1-6 were characterized by single-crystal X-ray diffraction, IR, TG, XRD and elemental analyses. Their structures range from the intricate 3D CPs 1, 3, 4 and 6 to the 2D coordination polymer 2 and the infinite 1D chain 5. The CPs 1-4 and 6 underlying networks were classified from the topological viewpoint, disclosing the distinct sql (in 1), pcu (in 3 and 6), new topology (in 2), and dia (in 4) topological nets. Moreover, analysis of thermal stability shows that they had good thermal stability. Finally, magnetic properties of CPs 1-6 have been studied, the results showed that complex 2 had ferromagnetic coupling and complexes 1, 3-6 were antiferromagnetic.

A Highly Efficient Oxygen Evolution Catalyst Consisting of Interconnected Nickel-Iron-Layered Double Hydroxide and Carbon Nanodomains

In this work, a one-pot solution method for direct synthesis of interconnected ultrafine amorphous NiFe-layered double hydroxide (NiFe-LDH) (<5 nm) and nanocarbon using the molecular precursor of metal and carbon sources is presented for the first time. During the solvothermal synthesis of NiFe-LDH, the organic ligand decomposes and transforms to amorphous carbon with graphitic nanodomains by catalytic effect of Fe. The confined growth of both NiFe-LDH and carbon in one single sheet results in fully integrated amorphous NiFe-LDH/C nanohybrid, allowing the harness of the high intrinsic activity of NiFe-LDH due to (i) amorphous and distorted LDH structure, (ii) enhanced active surface area, and (iii) strong coupling between the active phase and carbon. As such, the resultant NiFe-LDH/C exhibits superior activity and stability. Different from postdeposition or electrostatic self-assembly process for the formation of LDH/C composite, this method offers one new opportunity to fabricate high-performance oxygen evolution reaction and possibly other catalysts.

Multivariant synthesis, crystal structures and properties of four nickel coordination polymers based on flexible ligands

Four new Ni(ii) metal–organic frameworks with diverse structures have been synthesized under different conditions. The structural transformation from compound 4 to 3 has also been investigated.

Two new metal–organic frameworks based on tetrazole–heterocyclic ligands accompanied by in situ ligand formation

Two new MOFs have been constructed by the Dimroth rearrangement of the in situ generated organic ligand 5-((2H-tetrazol-5-yl)amino)isophthalic acid (H₃L).

A simultaneous disulfide bond cleavage, N,S-bialkylation/N-protonation and self-assembly reaction: syntheses, structures and properties of two hybrid iodoargentates with thiazolyl-based heterocycles

Unprecedented multiple in situ reactions were found during preparation of hybrid iodoargentates.