Polyhedron最新文献

Spherical mesoporous silicas of MCM-41 type modified with titanium, iron or both these metals were prepared by co-condensation method and tested in the role of catalysts for selective oxidation of diphenyl sulphide with H₂O₂ to diphenyl sulphoxide and diphenyl sulphone. The monometallic catalysts containing titanium or iron were found to be active catalysts of diphenyl sulphide mainly to diphenyl sulphoxide. A very significant increase in catalytic activity was observed for the bimetallic samples, containing both titanium and iron. Moreover, in the case of bimetallic catalysts with higher titanium loading, diphenyl sulphone is a dominating reaction product. The increased activity of the bimetallic catalysts has been related to the synergistic operation of titanium and iron in conversion of hydrogen peroxide into reactive species, which in the next step oxidise diphenyl sulphoxide.

Coordination-driven self-assembly, particularly, helical metal complexes are quite interesting considering their distinctive architectures. Herein, we assemble new Fe(II) compounds namely, [Fe₂(L1)₂](BF₄)₄·2H₂O, 1 and [Fe₂(L2)₂](BF₄)₄, 2 from flexible glutarohydazide ligands featuring helical-like di-nuclear arrays. Structurally, in all the compounds, the two chelating ligands were arranged differently, i.e. inverted U-shaped conformation for 1 and a twisted spiral arrangement for 2 were observed respectively. Interestingly, the observed structural variations of all compounds are a result of the ligand substituents in the six positions of the pyridyl moiety in which the relatively bulky methyl group substituted ligand resists the spiral arrangement which was observed in the Br substituted analog. Magnetic investigations revealed that compounds 1 and 2 are in the high spin state at all the measured temperature ranges. Further ligand fine-tunings in the pyridyl-aldehyde moiety for the presented helical-like arrays bearing relatively strong ligand field strength are suggested for achieving the spin crossover (SCO) event.

Cupric oxide (CuO) nanostructures were directly grown on copper substrate via a simple one step solution-immersion process. The films were formed by the direct oxidation of copper in aqueous solution containing sodium hydroxide (NaOH) and ammonium persulfate (NH₄)₂S₂O₈. The influence of the reaction temperature on the structural, morphological, optical and photoelectrochemical (PEC) properties of the formed copper compounds nanostructures was investigated. The XRD and Raman spectroscopy results revealed the formation of Cu(OH)₂/CuO composite for the samples prepared at 3 and 25 °C, and pure CuO was obtained for the samples prepared at 45 and 55 °C. The SEM micrographs showed that the formed Cu(OH)₂ and CuO present a nanowire bundles and nanosheet morphology, respectively. The increase of the reaction temperature enhanced the absorbance of the CuO samples in the entire visible region. According to the photoelectrochemical measurements, the increase of the reaction temperature resulted in an improvement of the PEC response. The CuO nanosheets synthesized at 55 °C presents the highest and the most stable PEC response. A reasonable mechanism describing the formation of nanostructured copper compounds at different reaction temperatures is discussed in this paper.

Four new Zn(II)-, Cd(II)-, Mn(II)-, and Co(II)-based 1D to 2D coordination polymers (CPs) were synthesized from metal salts and 1,4-di(1-imidazol-1-yl)naphthalene (DIN) ligand via the coordination reaction under hydrothermal conditions with quantitative yields, namely, [Zn(SO₄)(DIN)(H₂O)] (CP-1), [Cd(NO₃)₂(DIN)] (CP-2), [Mn(SO₄)(DIN)(H₂O)₃] (CP-3), and [Co(NO₃)₂(DIN)₂(H₂O)₄] (CP-4). The CPs were analyzed and characterized using FT-IR, Elemental Analysis, TGA, SC-XRD, and PXRD. CP-1 was selected as a model sensor for fluorescence detection, and the sensor exhibited high quenching rates at two excitation wavelengths of λ_ex = 230 and 290 nm, and at a single emission wavelength of λ_em = 350 nm. At these two different excitation wavelengths, CP-1 behaved differently during the sensing of pesticides, and the highest quenching rate was achieved by the sensor for nitenpyram (λ_ex = 230 nm) and imidacloprid (λ_ex = 290 nm). Furthermore, during the sensing of vitamins, CP-1 encountered a strong quenching effect toward vitamin B2. During the sensing processes, the inner filter effect (for nitenpyram, imidacloprid, and vitamin B2), fluorescence resonance energy transfer (for nitenpyram, imidacloprid, and vitamin B2), and photo-induced electron transfer (for vitamin B2) were the mechanisms responsible for fluorescence quenching.

This paper reports a novel crystallographically characterized Eu³⁺ complex, [Eu(fod)₃(terpy)] (fod = anion of 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and terpy = terpyridine). The single crystal XRD result shows that the Eu ion have a nine-coordinated structure where Eu is attached to six oxygen atoms of three fod ligand and three nitrogen atoms of one terpyridine ligand with a coordination polyhedron as EuO₆N₃. The paramagnetic NMR result is in line with SC-XRD and confirms the same coordination structure of the complex in solution as well. The photophysical properties were studied in solid state, solution and as a thin film. The band gap value of the complex is determined which is found to be in the range of semiconductors, suggesting application of complex in optoelectronics. Upon excitation with UV-radiation, the complex displays characteristic emission transitions of europium ion. The complex shows high experimental emission lifetime in solid state which suggests that the antenna affect is effective in the present complex. Finally, various color parameters of the complex were calculated and the CCT value reveals the complex as a warm light source.

Oxidation of a bis-stibinoaryl amine (2) with chloranil leads first to formation of a crystallographically observed bis-stiboranoraryl amine (3a) which then undergoes isomerization to an ionic tetraarylstibonium antimonate (3b). The isomerization proceeds at different rates in different solvents, but a univariate explanation of solvent effects is not evident. The antimonate anion in 3b can be exchanged for a fluoride, resulting in a neutral fluorostiborane (4), and further to a triflate in an ionic tetraarylstibonium triflate (5). Compound 5 displays strong binding of fluoride in tetrahydrofuran. Structures of 3a, 3b, 4, and 5 were determined by single-crystal X-ray diffraction.

Mixed-ligand 2,2′-bipyridine, 1,10-phenanthroline based copper(II) complexes are often considered as potential antitumor agents. This research was aimed at synthesis and finding the cytotoxic potential of copper(II) complexes with diphenylphosphinic acid (HL) and 2,2′-bipyridine, 1,10-phenanthroline derivatives – [Cu(phen)(H₂O)L₂]·H₂O (1), [Cu(dmphen)(H₂O)L₂] (2), [Cu(Cl-phen)(H₂O)₂L]L·EtOH (3), [Cu(bipy)(H₂O)L₂] (4) and Cu(dmbipy)(H₂O)L₂ (5) (phen – 1,10-phenanthroline, dmphen – 4,7-dimethyl-1,10-phenanthroline, Cl-phen – 5-chloro-1,10-phenanthroline, bipy – 2,2′-bipyridine, dmbipy – 4,4′-dimethyl-2,2′-bipyridine). Obtained mononuclear compounds have been characterized by EPR and IR-spectroscopy, elemental, thermogravimetric, single-crystal and powder X-ray diffraction analyses. According to single-crystal X-ray diffraction data, complexes possess distorted trigonal bipyramidal or square pyramidal geometry. 2,2′-Bipyridine and 1,10-phenanthroline derivatives have been shown to be chelating agents in these complexes, while anion of diphenylphosphinic acid acts as a monodentate ligand. Complexes 1–5 have been monitored for their solution stability using UV–vis spectroscopy. In the present study, cytotoxic activity of the complexes has been investigated on 2D human cell culture models (larynx carcinoma Hep2, hepatocellular carcinoma HepG2, breast carcinoma MCF-7 and non-tumor lung fibroblasts MRC5) and 3D HepG2 human cell model. 1,10-Phenanthroline based complexes have demonstrated the highest cytotoxicity superior to the reference drug cisplatin. The level of reactive oxygen species generation in Hep2 cells has been shown to increase after incubation with complexes.

Coordination polymers have been proven to be research hotspots for their fascinating structure and functional properties. In this work, four new Cu(II)-based CPs, namely [Cu(L)(H₂O)]_n (1), [Cu(L)(phen)(H₂O)]·1.5H₂O (2), {[Cu(L)(bimb)_0.5]·H₂O}_n (3) and {[Cu(L)(dib)_0.5(H₂O)]·1.5H₂O}_n (4) [H₂L=3-carboxy-1-(3′-carboxy-benzyl)-2-oxidopyridinium, 1,10-phenanthroline (phen), 1,4-bis-((1H-imidazol-1-yl)methyl)benzene (bimb) and 1,4-di(1H-imidazol-1-yl)butane (dib)], were synthesized under hydrothermal conditions. These four compounds show different structures defined by single-crystal X-ray diffraction. In addition, these compounds are characterized by powder X-ray diffraction (PXRD), infrared spectra (IR), elemental analyses, thermogravimetric analyses, Hirshfeld surface analyses and UV–vis absorption spectra.

The present study explores the potential of six NHC-palladium(II) complexes derived from N-cinnamyl-N’-alkylbenzimidazolium salts, namely trans-dichloro[1,3-dicinnamyl-benzimidazol-2-yliden]pyridine palladium(II) (3a), trans-dichloro[1-cinnamyl-3-benzyl-benzimidazol-2-yliden]pyridine palladium(II) (3b), trans-dichloro[1-cinnamyl-(fluorobenzyl)-benzimidazol-2-yliden]pyridine palladium(II) (2-fluorobenzyl 3c, 3-fluorobenzyl 3d and 4-fluorobenzyl 3e,) and trans-dichloro[1-cinnamyl-(4-nitrobenzyl)-benzimidazol-2-yliden]pyridine palladium(II) (3f), as precatalyst for the cross-coupling reactions between furanyl and thiofuranyl derivatives and arylbromides via CH activation of the heterocycles. The structure of the six palladium(II) complexes has been elucidated through the use of multinuclear NMR, FT-IR and mass spectroscopy. Furthermore, the square-planar geometry of the organometallic ion was confirmed by single crystal X-ray diffraction study carried out on complex 3c. The latter complex proved to be the most effective precatalyst agent, with observed conversions higher than 78% when 4-bromoacetophenone and 1-bromonaphthalene were employed.

The singlet oxygen quantum yield is a valuable parameter for assessing the ability of a photosensitizer to generate radical oxygen. This value is influenced by the photo-physicochemical characteristics of the sensitizer molecule. Phthalocyanines are among these complexes and as the central metal atoms and substituent groups on the phthalocyanine ring are modified, the therapeutic effects required for photodynamic therapy (PDT) can be enhanced. For this purpose, 5-bromo-2-hydroxypyridine substituted zinc phthalocyanine and its biocompatible quaternized structure are synthesized and shown to exhibit singlet oxygen efficiency with Φ_Δ values reaching 0.65 in DMSO and 0.39 in water in photochemical studies. The obtained fluorescence quantum yields (Φ_F) for the compounds are 0.17 in DMSO and 0.06 in water, while the photodegradation (Φ_d) values are 9.1 x 10^-3 in DMSO and 5.3 x 10^-3 in water. This research offers valuable insights into developing water-soluble and targeted photodynamic therapies for combating cancer using photochemical applications.