Hosseini, Seyed MohammadDehghan, HosseinSafarifard, Vahid
7页
查看更多>>摘要：In this work to introduce Co(II) ions into TMU-22(Zn) metal-organic framework (MOF), we report a post-synthetic exchange (PSE) approach. Several analytical methods were employed to examine the exchange between Co2+ ions and Zn2+ ions in TMU-22(Zn) for the formation of the mixed-metal TMU-22(Zn/Co). It was found that the introduction of active Co2+ ions into the TMU-22(Zn) framework leads to the photocatalytic activity of TMU-22(Zn/Co) for benzyl alcohol oxidation. Since Co2+ ions were favorably substituted at positions more accessible to the substrate, the TMU-22(Zn/Co) showed superior catalytic performance. This study provides a facile method to develop mixed-metal MOFs for photocatalysis performance.
查看更多>>摘要：Four new acyloxy bridged Ln(2)(III) compounds [Ln(2)(L)(2)(acac)(2)(EtOH)(2)] (Ln(III) = Gd (1), Tb (2), Dy (3), and Ho (4), Hacac = acetylacetone, and H2L = pyridine-2-carboxylic acid (3-ethoxy-2-hydroxy-benzylidene)-hydrazide) have been prepared by a polydentate Schiff base ligand under solvothermal condition. The single-crystal X-ray structure study reveals that 1-4 are isostructural and contain a parallelogram Ln(2)O(2) core. Magnetic study reveals that antiferromagnetic interaction exists in compound 1. More importantly, compound 1 displays well cryogenic magnetic refrigeration property (-& UDelta;S-m = 28.2 J kg(-1) K-1, T = 2.0 K and & UDelta;H = 70 kOe); while compound 3 exhibits evident single-molecule magnet behavior under zero-field condition (& UDelta;E/k(B) = 26.8 K, tau(0) = 1.05 x 10(-7) s).
Zaguzin, Alexander S.Sukhikh, Taisiya S.Kolesov, Boris A.Sokolov, Maxim N....
5页
查看更多>>摘要：[Zn2(2-I-bdc)2dabco]n metal-organic framework (2-I-bdc = 2-iodoterephtalate, dabco = 1,8-diazabicyclooctane] (1) was prepared and structurally characterized as a superstructure of one of conventional [Zn2(bdc)2(dabco)]n (2) modicifactions. Selectivity of sorption of various organic substrates, as well as I2 uptake, was compared for 1 and 2, demonstrating remarkable differences which can be related to different patterns of non-covalent bonding of guest molecules in MOF pores.
查看更多>>摘要：New chromium phthalocyanine complex peripherally substituted with 8-quinolinoxy group was synthesized from modified precursor 4-(8-quinolinoxy) phthalonitrile in presence of CrCl3 center dot 6H(2)O in DMAE, using zinc dust as the reducing agent. The product mu-oxodimer of Cr(III)QPc [Cr(III)QPc-O-Cr(III)QPc] exhibited green florescence, in contrary to the typical red emissive behaviour of phthalocyanines. The detailed study on the emission spectrum of Cr(III)QPc-O-Cr(III)QPc revealed dual peaks with abroad band situated at 510 nm and a narrow peak situated at 686 nm, where the former broad band was found to be responsible for the intense green emission. The emission at 686 nm was the expected ligand based transition of Pc core from excited state singlet to ground state, S-1 -> S-0, while the abnormal peak at 510 nm was found to be due to the combined effect of radiative relaxation of second excited singlet state to ground state (S-2 -> S-0) and the LMCT of Pc2- to Cr(III) metal center. The emission spectra of Cr(III)QPc-O-Cr(III)QPc also exhibited a reciprocal relationship in the intensity of the dual peaks when the excitation wavelength was varied from 350 to 440 nm. The presence of an isoemission point at 648 nm indicated that two emission bands were brought about by two different excitonic transitions. Substituted chromium phthalocyanines are very less reported to date with remarkable fluorescent features, and in this work, the modified cyclotetramerization method applied by using zinc dust have paved new ways for their preparation. The preparation of unstable manganese phthalocyanine, MnQPc, was also rarely reported owing to its aerobic oxidation to the more stable and often synthesized analogue, MnQPc(CH3COO). Here, the synthesis of MnQPc was achieved under normal cyclization conditions and the effect of acetic acid and chlorinated solvents on the oxidative stability of MnQPc were also studied.
Motimani, Nozuko M.Ngubane, SiyabongaSmith, Gregory S.
10页
查看更多>>摘要：Polynuclear heteroleptic ruthenium(II) photosensitisers combining either imine or amine-functionalised bipyridyl ligands were synthesised (via Schiff-base condensation/reductive amination reactions), characterised and investigated for their photoreactivity in the hydrothiolation reaction. Furthermore, electrochemical, electronic absorption and emission studies of the complexes were conducted. All the ligand-modified, heteroleptic complexes show red-shifted emission spectra (614-633 nm) relative to the canonical [Ru(bpy)(3)](PF6)(2) complex (609 nm), attributed to the transition from the triplet MLCT excited state ((MLCT)-M-3) to the ground state. The complexes were evaluated as visible-light photoredox catalysts in the radical hydrothiolation reaction of olefins (thiol-ene coupling) to afford thioethers. Control reactions performed in the absence of the photocatalyst resulted in either significantly lower yields (6%) or no product formation, demonstrating the role of the complexes as photoredox catalysts. The reactions carried out using trinuclear complexes (E-red (Ru2+*/+) = +0.300 V vs Ag/Ag+) resulted in increased yields in comparison with their respective mononuclear congeners and greater than those reported for [Ru(bpy)(3)](PF6)(2), demonstrating the benefits of using polynuclear photocatalysts for photoinitiated redox catalysis reactions.
查看更多>>摘要：A series of novel cationic ruthenium half-sandwich complexes, bearing 1-substituted-4-pyridyl-1H-1,2,3-triazole ligands, were synthesized and fully characterized by a range of analytical techniques. The complexes were found to be efficient catalyst precursors for transfer hydrogenation reactions using ketones as substrates. We demonstrated that the complexes could hydrogenate acetophenone in excellent conversions (similar to 75 %) within 3 h, employing a low concentration of base of only 2 mol %. Extending the reaction time to 6 h gave near quantitative conversions for both catalysts employed. In addition to this, the transfer hydrogenation of acetophenone was also found to proceed even at low catalyst loadings (0.025-0.05 mol%) and low base concentrations (0.25-1.0 mol%). Under these conditions substrate conversion was moderate (22-60 %). The catalytic efficiency of the most effective catalyst was then evaluated in the transfer hydrogenation of a small library of aromatic and aliphatic ketones. It was shown that more challenging substrates such as benzophenone and 2-octanone could be hydrogenated to the corresponding secondary alcohols in conversions > 90 %. Finally, based on several experimental observations, a possible mechanism for the process is proposed.
查看更多>>摘要：Density functional theory (DFT) has been used to determine the geometric and electronic structure of the series [cis-{(eta(5)-C5H3)(2)(CMe2)(2)}-Ru-2(CO)(4)(mu-H)(n)](n+) (n = 0, 1, 2) and their di-tert-butyl-bipyridine (bipy) analogs ((CO)(2) = bipy). The results have been analyzed by using natural bond orbitals (NBO) and quantum theory of atoms in molecules (QTAIM). This series provide a thorough description of the changes in the bonding that occur as the Ru-Ru bond in the n = 0 complexes is first protonated to form the 18-electron hydrogen bridged com-plexes, which each has a 3-center/2-electron Ru-H-Ru bond but not a direct Ru-Ru bond, and then protonated again to form dibridged complexes, which have two 3-center/2-electron Ru-H-Ru bonds and even without a direct Ru-Ru bond have an electron count of 19 electrons, which is compensated by having one more antibonding than bonding Ru-Ru molecular orbitals.
查看更多>>摘要：Two new iron(III) complexes, (TrBA)[Fe(azp)(2)] (1) and (TrPA)[Fe(azp)(2)] (2) (H(2)azp = 2,2' - dihydrox-yazobenzene, TrBA = tributylammonium and TrPA = tripropylammonium) were prepared by reaction of the azo dye H(2)azp, tributylamine (or tripropylamine) and FeCl3 in methanolic solution. The crystal structure of 1 was determined by single-crystal X-ray analysis. The asymmetric unit contains one tributylamonnium cation and one [Fe(azp)(2)](-) anion with an octahedrally coordinated Fe(III) ion with an FeN2O4 chromophore - the tridentate ligand azp(2-) is coordinated by two deprotonated phenolic oxygen atoms and one nitrogen atom from the azo group. The single-crystal X-ray analysis of 1 suggests that an N-H center dot center dot center dot O hydrogen bonding interaction between the TrBA cation and the [Fe(azp)(2)](-) anion may induce distortion of the coordination polyhedron resulting in a highspin complex. Magnetic investigation (DC magnetic data) revealed a high-spin state in the studied temperature range (2-300 K) for both 1 and 2. AC susceptibility measurements for 1 showed a field-induced slow relaxation of magnetization with an atypical temperature dependence of the relaxation time. Moreover, the cryogenic and room temperature Fe-57 Mossbauer spectroscopy parameters confirmed the high-spin state of 1. The study was also supported by theoretical calculations at the DFT level of theory.
Pham Van ThongNguyen Thi Thanh ChiAzam, MohammadCu Hong Hanh...
7页
查看更多>>摘要：The NMR spectra of five diplatinum(II) complexes, Pt(mu-Cl)(arylolefin)](2) [arylolefin = Eug (1), (i)PrEug (2), Meug (3), EtEug (4), Saf (5)], in CDCl3 are studied. All the five complexes are formed by the reaction of K[PtCl3(arylolefinH)] with Ag2O in the mixture of alcohol-water. A mononuclear platinum complex, PtCl(Saf)(CH3CN)], which is formed by the crystallization of a dimeric complex 5 in acetonitrile is also investiated. The mononuclear platinum complex is characterized by elemental analysis, ESI mass spectrometry, infrared and NMR spectroscopic studies and single crystal X-ray crystallography. The single X-ray crystal structure reveals the coordination of Pt(II) ion to Saf via C = C-allyl and the carbon of the benzene ring. DFT calculations are also performed to collect information about the structural parameter and stability of mononuclear platinum complexes. The findings reveal that the theoretical data agree with the experimental findings of single crystal X-ray structure. In addition, Hirshfeld surface analysis is also carried out to investigate various intermolecular interactions in the crystal structure of mononuclear platinum complex.
查看更多>>摘要：A series of tetranuclear [Ni(II)2Ln(III)2] complexes of general formula [Ni2Ln2(L)(H2O)9(OH)4Cl]center dot 3H2O center dot Cl (1, 2, 5) (Ln = Dy (1), Tb (2), Ho (5)) and [Ni2Ln2(L)(H2O)12Cl] center dot 3H2O center dot 5Cl (3, 4, 6, 7) (Ln = Gd (3), Sm (4), Nd (6), Pr (7)); H4L = N,N',N'',N"'-tetra(3-methoxysalicylidene)-pentaerythritol) have been synthesized. The molecular structures and magnetic properties of 1-7 are reported. Structural analysis indicated that this family of clusters consists of a tetranuclear [Ni(II)2Ln(III)2] core, supported by a tetrapodal Schiff base ligand. Both Ni(II) ions adopt a distorted octahedral coordination environment, whilst the two terminal Ln(III) ions exhibit distorted tricapped trigonal prismatic geometries and are coordinated by eight or nine oxygen donor atoms. Magnetic measurements revealed that the Dy derivative of complex 1 displays typical d single-molecule magnet behaviour with the presence of slow magnetic relaxation. By contrast, complexes 2-7, no obvious SMM behaviour was exhibited, however for the Gd derivative 3, a significant magnetocaloric effect was observed.
NSTL
Elsevier