Transition Metal Chemistry最新文献

Electrocatalytic water splitting to produce hydrogen is a promising route to provide green hydrogen on a large scale. To explore non-noble metal electrocatalysts with high performance is still a challenge. Herein, a one-step electrodeposition way is developed to construct the heterostructural (NiO-La₂O₃)/(Ni-La)/NiO/Ni electrocatalysts on Ni foam. The dark Ni-La coating was prepared by co-electrodeposition from an aqueous solution containing LaCl₃ and NiCl₂ with a molar concentration ratio of 1:5. Among these heterostructural Ni-based electrocatalysts, an excellent HER activity is achieved: an overpotential of 22 mV at the current density of 10 mA cm⁻² in 1 M KOH solution. It is demonstrated that the introduction of La significantly reduces the overpotential for HER. The higher the La content in the Ni-La coating of these electrocatalysts, the better the electrocatalytic HER performance was exhibited. This work provides a facile and inexpensive route to prepare Ni-La coating on electrodes in an aqueous solution.

A novel single-component conductor derived from neutral radical gold bis(dithiolene) complexes is prepared based on the original reactivity of tBuN-substituted 1,3-thiazoline-2-thione heterocycle to give a tBuS-substituted thiazole ring. The corresponding 2-(tert-butylthio)-1,3-thiazole-4,5-dithiolate ligand (tBuS-tzdt) forms the d⁸ anionic complex [Au(tBuS-tzdt)₂]⁻, easily oxidized through electrocrystallization into the neutral radical [Au(tBuS-tzdt)₂]^·. The effect of increasingly bulky R groups (R = Et, EtOH, tBu), in the series of such radical complexes [Au(RS-tzdt)₂]^·, is investigated, with a focus on their solid state organization, either into face-to-face dimers or into non-dimerized, uniform stacks.

Two Schiff base macrocyclic ligands (L1 and L2) were synthesized using ethylenediamine and terephthalaldehyde (or isophthalaldehyde) as raw materials in acetonitrile solvent. Surprisingly, series of Schiff base macrocyclic ligands with different combination modes (L2-1, L2-2 and L2-3) with isophthalaldehyde as raw material were synthesized. Two Schiff base macrocyclic nickel complexes (Ni-1 and Ni-2) based on L1 and L2 for ethylene oligomerization were obtained with (DME)NiCl₂. The synthesized ligands and their corresponding complexes were characterized by various analysis techniques to confirm their chemical structure and thermal stability. And the catalytic properties of the two nickel complexes were also investigated for ethylene oligomerization. When the ethylene pressure was 0.5 MPa, the Al/Ni ratio was 500:1, and the reaction time was 30 min in the presence of MAO, the catalytic activities of Ni-1 and Ni-2 were 4.53 × 10⁴ g/(mol Ni·h) and 4.73 × 10⁴ g/(mol Ni·h), respectively. Compared with PS-Ni complex based on 2,3-butanedione and p-phenylenediamine and three other nickel complexes with simpler ligand structures, Ni-1 and Ni-2 had lower catalytic activities and higher selectivity for C₄ olefin because of the higher spatial resistance of the macrocycles.

Two novel cobalt(ii) complexes [Co(HL¹)₂](NO₃)₂.2.5H₂O (1) and [Co(HL²)₂](NO₃)₂ (2) (where HL¹ = (E)-2-(1-(pyridin-2-yl)ethylidene)hydrazine-1-carboxamide and HL² = (E)-2-(pyridin-2-ylmethylene)hydrazine-1-carboxamide) have been synthesized and structurally characterized by spectroscopic techniques and single-crystal diffraction analysis. The complexes are close comparable with metals exhibiting the expected distorted octahedral geometry being chelated by two semicarbazone ligands via NNO donor set. The catecholase-like activity of complexes 1 and 2 was evaluated by using 3,5-di-tert-butylcatecholas substrate. The results showed that both the complexes are effective catalysts with K_cat values of 762 and 562, respectively. Theoretical DFT study and Hirschfeld surface analyses were also carried out to reveal the nature of intermolecular contacts and to integrate experimental observations.

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Two novel cobalt(ii) complexes [Co(HL¹)₂](NO₃)₂.2.5H₂O (1) and [Co(HL²)₂](NO₃)₂ (2) have been synthesized and structurally characterized by spectroscopic techniques and single-crystal diffraction analysis. The complexes are nearly akin with metals exhibiting the expected distorted octahedral geometry being chelated by two semicarbazone ligands via NNO donor set. The catecholase-like activity of complexes 1 and 2 was evaluated by using 3,5-DTBC as substrate. The result confirmed the formation of quinone or 3,5-DTBQ derivative and indicates that the complexes exhibit noticeable catalytic activity with K_cat values of 762 and 562, respectively. Theoretical DFT study and Hirschfeld surface analyses were also performed to reveal the nature of intermolecular contacts and to integrate experimental findings.

In this study, new 4-chloro-5-(2-isopropyl-5-methylphenoxy)phthalonitrile compound, containing bioactive thymoxy group, and its metal-free phthalocyanine and metallo-phthalocyanine derivatives were synthesized for the first time. Their structures were determined by spectroscopic methods such as FTIR, UV–Vis, ¹H-, and ¹³C-NMR (for phthalonitrile derivative), MALDI-TOF mass spectrometry (for phthalocyanine derivatives) and elemental analysis as well. The phthalocyanines showed excellent solubility in polar and nonpolar solvents without aggregation and absorb at long wavelengths with their high molar coefficient. In N,N-dimethylformamide, the effects of the type of central metal ions [metal-free, indium(III) acetate, lutetium(III) acetate, magnesium(II) or zinc(II)] in the phthalocyanine, containing bioactive thymoxy group, cavity on the spectroscopic, photophysical, and photochemical properties of the phthalocyanines were determined. These features are compared with each other. Lutetium(III) acetate phthalocyanine did not show any fluorescence, while metal-free phthalocyanine and indium(III) acetate phthalocyanine showed low fluorescence. It was determined that magnesium phthalocyanine significantly enriched the fluorescence, and zinc phthalocyanine had appropriate and sufficient fluorescence. Lutetium(III) acetate and zinc(II), especially indium(III) acetate phthalocyanines, could produce large amounts of singlet oxygen. Metal-free and magnesium phthalocyanines had the capacity to produce sufficient singlet oxygen (it means production of enough amount of singlet oxygen by a photosensitizer candidate during PDT applications). All phthalocyanines have sufficient and suitable photostability (it means an ideal photosensitizer should be stable under light irradiation until complete its PDT activation, and it should be decomposed after its PDT activation so that it does not accumulate in the body). With these determined properties, magnesium(II), especially indium(III) acetate and zinc(II) phthalocyanines, may be suitable candidates as type II photosensitizers for photodynamic therapy applications. Lutetium(III) acetate phthalocyanine may be a photosensitizer candidate in photocatalytic applications.

Rigid, dicarboxylic acid ligand 5-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid (H₃L) has been synthesized and utilized for assembling a metal organic framework [Pb₂(HL)₂]_n through the hydrothermal technique. The target complex has been described by single-crystal X-ray diffraction, powder X-ray diffraction measurement, elemental analysis and infrared spectroscopy, and proved to be a structurally novel 3D complex. The central metal ions Pb(II) of complex 1 are coordinated to the carboxyl oxygen atoms, possessing two different coordination modes, heptacoordination and octacoordination. In the case of topology, complex 1 exhibits a net topological structure of 2,3,9-c with Schläfi symbol of {3·5²}{3²·4⁴·5¹²·6¹⁴·7²·8²}{5}. The optical properties have been undertaken at room temperature, showing attractive luminescence behavior. Moreover, the electrochemiluminescent intensity of complex 1 can reach up to 1056 a.u. and maintain relatively stable after eight cycles, which could further provide ideas for building organic light-emitting diodes (OLEDs) constructed with a more affordable metal center.

A two-dimensional (2D) pillared-bilayer iron-based metal–organic framework (MOF), [Fe₂(aip)₂(bpy)₂]·(H₂O)(DMF) (1) (where H₂aip = 5-aminoisophthalic acid, bpy = 4,4'-bipyridine, DMF = N,N-dimethylformamide), was solvo/hydrothermally synthesized using H₂aip, bpy and ferrous sulfate heptahydrate as raw materials in DMF/H₂O mixed solvent. The structure and properties of 1 were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy and UV–vis diffuse reflectance spectroscopy. In 1, each Fe(II) ion exhibits a distorted octahedral geometry, while the aip²⁻ and bpy ligands adopt the chelating/bridging bis-bidentate (μ₃-η¹:η¹:η²) and bridging bidentate (μ₂-η¹:η¹) coordination modes, respectively. Infinite one-dimensional [Fe₂(aip)₂]_n chains extending along the a axis are formed through bridging and chelating carboxylate groups of aip²⁻ ligands and are further cross-linked by bpy ligands along the b axis to generate an infinite 2D pillared-bilayer framework with an interdigitated structure. Fe-MOF 1 shows both UV-light photocatalytic activity and Fenton-like catalytic activity toward the degradation of rhodamine B solution, which can be potentially applied in environmental remediation such as industrial wastewater treatment.

Three new metal organic frameworks [Zn(bipa)(suc)]_n (1), [Ni(bipa)(suc)(H₂O)₂]_n (2) and [Co(bipa)_1.5(oip)(H₂O)]_n (3) (bipa = 2,5-bis(1-imidazole)pyrazine), H₂suc = succinic acid, H₂oip = 5-hydroxy isophthalic acid) have been synthesized by solvothermal method. They were then characterized by single crystal X-ray diffraction, elemental analysis, infrared spectrum and thermogravimetric analysis. Structural analyses showed that MOFs 1 and 3 exhibited a 3D supramolecular network, while MOF 2 presented a 2D layered structure and was further assembled to a 3D architecture via intermolecular O–H···O hydrogen bond. Moreover, the luminescence sensing of MOF 1 toward nitro explosives was investigated, owing to its excellent chemical stability and luminescence properties. MOF 1 showed remarkable fluorescence quenching toward TNP with a high Ksv value of 6.48 × 10⁴ M⁻¹ and a low limit of detection of 1.4 × 10⁻⁵ M. Also, the luminescent sensing mechanism of MOF 1 was investigated.

Reaction of cis-protected [(Me₄en)Pd(SO₄)] with the newly designed C₃-symmetric Ba₃L anionic ligand produces a stable trinuclear [(Me₄enPd)₃L] in a cis-O,O′ mode. A characteristic structural feature is that [(Me₄enPd)₃L] consists of a total of 10 rings with one 6-membered central benzene ring, three 5-membered rings (PdN₂C₂), three 6-membered rings (PdO₂C₃), and three 7-membered rings. This tripalladium(II) complex shows significant multi-center catalytic efficiency in the Heck reaction with the appropriate C₃-symmetric trifunctional substrate via geometrical coincident interaction between the substrate and the catalyst. A theoretical calculation of the geometrical intermolecular interaction-behavior between the catalyst ([(Me₄enPd)₃L]) and the substrate (1,3,5-tris(4-iodophenyl)benzene) in N,N-dimethylformamide solution was carried out.

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