Ionic liquid-supported chiral saldach with tunable hydrogen bonding: synthesis,metalation with Fe(III) and in vitro antimicrobial susceptibility

New water-soluble methylimidazolium ionic liquids (MIILs) bearing N,N′-bis-(salicylidene)-R,R-1,2-diaminocyclohexane (saldach) scaffold, H₂(R¹)₂saldach(2-MeIm⁺X⁻)₂ (4a: R¹=H, X=Cl^–; 4b: R¹=H, X=PF₆^–; 4c: R¹=H, X=BF₄^–; 4d: R¹=ⁱPr, X=Cl^–; 4e: R¹=ⁱPr, X=PF₆^–; 4f: R¹=ⁱPr, X=BF₄^–), and their Fe(III) complexes have been synthesized and structurally characterized as well as their profile of antimicrobial susceptibility was identified. The new saldach-supported MIILs demonstrated a distinctly enhanced biocidal effect toward methicillin resistant Staphylococcus aureus (MRSA) and multidrug-resistant Escherichia coli (MDREC). Compound 4d is the most potent antibacterial agent and could inhibit the growth of all micro-organisms, except A. flavus, more effectively than standard antibiotics.     

Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst

Fe(Cp)₂BF₄ is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)₂BF₄ as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.     

碱性电解液中K3[Fe(CN)6]在锌阳极上的自发还原和吸附延长锌镍电池的循环寿命

采用K₃[Fe(CN)₆]作为锌镍电池的电解液添加剂,克服了锌阳极的变形。此外,通过一系列实验设计和表征,探索了电解液中金属锌与K₃[Fe(CN)₆]的反应机理。通过XRD (X-ray diffraction)和XPS (X-ray photo-electron spectroscopy)测试,我们发现金属锌在KOH水溶液中能够与K₃[Fe(CN)₆]反应,将[Fe(CN)₆]^3–还原为[Fe(CN)₆]⁴⁻。添加K₃[Fe(CN)₆]的锌镍电池实现了更长的循环寿命,比不添加K₃[Fe(CN)₆]的锌镍电池长3倍以上。在相同循环次数下,改性电解质中锌阳极循环不仅形状变化较小,而且没有出现“死”锌现象,电极添加剂和粘结剂也没有发生偏析。此外,不同于一般的有机添加剂,K₃[Fe(CN)₆]的加入不仅不会增大电极的极化,还能够提高锌镍电池的放电容量和倍率性能。因此,考虑到这一改性策略有着较高的可行性和较低的成本,K₃[Fe(CN)₆]添加剂在锌镍电池的实际应用中具有极大的推广潜力。     

Ru掺杂对Fe催化剂上酚类化合物加氢脱氧影响的密度泛函理论研究北大核心CSCD

采用密度泛函理论(DFT)计算研究了苯酚、邻甲酚、愈创木酚在不同结构Ru-Fe(211)表面上吸附活化性能和加氢脱氧反应路径.结果表明,Ru掺杂能促进H2分子在Fe(211)表面上解离,提高加氢脱氧反应速率.酚类在1Ru_(ads)-Fe(211)表面上吸附比在1Ru_(sub)-Fe(211)表面上更稳定,苯酚和邻甲酚脱羟基步骤能垒分别降低0.13和0.28 eV,有利于生成芳烃.愈创木酚在1Ru_(sub)-Fe(211)表面上加氢脱氧优势路径是先脱甲氧基生成苯酚,苯酚再加氢脱氧生成产物苯(速控步骤能垒1.16 eV);而在1Ru_(ads)-Fe(211)表面上愈创木酚先脱羟基再脱甲基生成苯酚的路径更具有动力学优势(速控步骤能垒1.21 eV).计算结果表明Ru掺杂方式影响Fe催化剂对酚反应分子的吸附稳定性以及加氢脱氧反应路径和性能.与1Ru掺杂Fe(211)催化剂相比,增加Ru原子数形成4Ru_(ads)-Fe(211),能够进一步提高酚类反应物的吸附强度,但导致加氢脱氧反应能垒升高.因此,在Fe催化剂上以表面吸附的形式掺杂少量贵金属Ru更利于酚类加氢脱氧生成芳烃.     

Rational Design of Ratiometric Fe3+ Fluorescent Probes Based on FRET Mechanism

As the most abundant transition metal element in mammals, iron(Fe) plays a vital role in life activities. It is of great significance to study the variation of Fe³⁺ level in living organisms. In virtue of the advantages of high sensitivity, good selectivity and low damage to living systems, the fluorescence detection of Fe³⁺ has attracted much attention. Compared with the intensity-based fluorescent probe, the ratiometric fluorescent probe has less interference of environmental and can realize quantitative detection. In this study, four ratiometric Fe³⁺ fluorescent probes, R1, R2, R3 and R4_, were designed and synthesized using fluorescence resonance energy transfer(FRET) mechanism to achieve quantitative detection of Fe³⁺. In the FRET systems, 1,8-naphthalimide fluorophore derivatives were adopted as donors while rhodamine B derivatives were selected as receptors. The connection sites of the donor and acceptor in R3 and R4 are different from those in R1 and R2. All the four probes showed good response and selectivity to Fe³⁺. The energy transfer efficiencies of R3 and R4 were obviously higher than those of R1 and R2. This work provided a promising strategy for the development of fluorescent ratiometic Fe³⁺sensors.     

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal’s intake and/or its removal in living organisms.     

Calcium Sulfite Solids Activated by Iron for Enhancing As(III) Oxidation in Water

Desulfurized gypsum (DG) as a soil modifier imparts it with bulk solid sulfite. The Fe(III)–sulfite process in the liquid phase has shown great potential for the rapid removal of As(III), but the performance and mechanism of this process using DG as a sulfite source in aqueous solution remains unclear. In this work, employing solid CaSO₃ as a source of SO₃²⁻, we have studied the effects of different conditions (e.g., pH, Fe dosage, sulfite dosage) on As(III) oxidation in the Fe(III)–CaSO₃ system. The results show that 72.1% of As(III) was removed from solution by centrifugal treatment for 60 min at near-neutral pH. Quenching experiments have indicated that oxidation efficiencies of As(III) are due at 67.5% to HO^•, 17.5% to SO₅^•− and 15% to SO₄^•−. This finding may have promising implications in developing a new cost-effective technology for the treatment of arsenic-containing water using DG.     

Sequential separation of Cu(II)/Ni(II)/Fe(II) from strong-acidic pickling wastewater with a two-stage process based on a bi-pyridine chelating resin

A self-synthesized bi-pyridine chelating resin (PAPY) could separate Cu(II)/Ni(II)/Fe(II) sequentially from strong-acidic pickling wastewater by a two-stage pH-adjusted process, in which Cu(II), Ni(II), and Fe(II) were successively preferred by PAPY. In the first stage (pH 1.0), the separation factor of Cu(II) over Ni(II) reached 61.43 in Cu(II)-Ni(II)-Fe(II) systems. In the second stage (pH 2.0), the separation factor of Ni(II) over Fe(II) reached 92.82 in Ni(II)-Fe(II) systems. Emphasis was placed on the selective separation of Cu(II) and Ni(II) in the first-stage. The adsorption amounts of Cu(II) onto PAPY were 1.2 mmol/g in the first stage, while those of Ni(II) and Fe(II) were lower than 0.3 mmol/g. Cu(II) adsorption was hardly affected by Ni(II) with the presence of dense Fe(II), but Cu(II) inhibited Ni(II) adsorption strongly. Part of preloaded Ni(II) could be replaced by Cu(II) based on the replacement effect. Compared with the absence of Fe(II), dense Fe(II) could obviously enhance the separation of Cu(II)-Ni(II). More than 95.0% of Cu(II) could be removed in the former 240 BV (BV for bed volume of the adsorbent) in the fixed-bed adsorption column process with the flow rate of 2.5 BV/h. As proved by X-ray photoelectron spectrometry (XPS) and density functional theory (DFT) analyses, Cu(II) exerted a much stronger deprotonation and chelation ability toward PAPY than Ni(II) and Fe(II). Thus, the work shows a great potential in the separation and purification of heavy metal resources from strong-acidic pickling wastewaters.     

Structural and magnetic studies on spark plasma sintered SmCo5/Fe bulk nanocomposite magnets

SmCo₅+x wt% Fe (x=0$x=0$, 5 and 10) nanocomposite powders were synthesized by mechanical milling and were consolidated into bulk shape by spark plasma sintering (SPS) technique. The evolution of structure and magnetic properties were systematically investigated in milled powders as well as in SPS samples. A maximum coercivity of 8.9 kOe was achieved in spark plasma sintered SmCo₅+5 wt% Fe sample. The exchange spring interaction between the hard and soft magnetic phases was evaluated using δM–H measurements and the analysis revealed that the SPS sample containing 5 wt% Fe had a stronger exchange coupling between the magnetic phases than that of the sample with10 wt% Fe.     

A Molecular Low-Coordinate [Fe-S-Fe] Unit in Three Oxidation States

A [Fe-S-Fe] subunit with a single sulfide bridging two low-coordinate iron ions is the supposed active site of the iron-molybdenum co-factor (FeMoco) of nitrogenase. Here we report a dinuclear monosulfido bridged diiron(II) complex with a similar complex geometry that can be oxidized stepwise to diiron(II/III) and diiron(III/III) complexes while retaining the [Fe-S-Fe] core. The series of complexes has been characterized crystallographically, and electronic structures have been studied using, inter alia, ⁵⁷Fe Mössbauer spectroscopy and SQUID magnetometry. Further, cleavage of the [Fe-S-Fe] unit by CS₂ is presented.