A comparison of the intramolecular and intermolecular hydrogen bonding of N,N′-ethylenebis(aminobenzylidene) in the solid state with its salen analogue

The crystal structure of H₂amben has been elucidated for the first time. The close NH?N contact between neighbouring molecules supports strongly the notion that intermolecular hydrogen bonding exists within the crystal lattice, creating a series of molecular chains, which are crosslinked in a three-dimensional array. This intermolecular bonding is suggested to account for the anomalously high melting point of H₂amben (176-178 °C) compared to its H₂salen counterpart (126-128 °C). Although strong intramolecular forces are present in both ligands, H₂salen contains no intermolecular hydrogen bonds.     

Fluorous biphasic hydrolytic kinetic resolution of terminal epoxides

Although application of light-fluorous techniques facilitates the isolation of reaction products from the hydrolytic kinetic resolution (HKR) of terminal epoxides catalysed by cobalt complexes of salen ligands, the extension of the original fluorous biphasic approach to this reaction is far from being a trivial exercise. The nature of the counter anion has a dramatic effect on the catalytic activity of heavily fluorinated chiral (salen) cobalt(III) complexes. Excellent enantioselectivities are obtained in the fluorous biphasic HKR of 1,2-hexene oxide when fluorinated anions are introduced (e.e.s up to 99% both for the diol and the epoxide), with C₈F₁₇COO^- affording reaction rates even higher than those observed with non-fluorous systems.     

Y型分子筛中对称与不对称Co(II)Salen型席夫碱配合物的结构和催化性能

用自由配体法将对称、不对称Co(II)Salen型席夫碱配合物封装于Y型沸石分子筛的超笼中,并采用FTIR、UV-Vis、热分析和催化技术研究了其空间结构和催化性能.结果表明,被封装于分子筛超笼中的Salen型席夫碱配合物,同样具有未封装配合物的物理化学性能,也没有影响分子筛的框架结构;在以O2作氧化剂,催化苯乙烯环氧化反应中表现了非常高的反应活性和稳定性;金属配合物的量子化学密度泛函计算结果揭示了配合物的催化性能与轨道能量密切相关.     

新型手性双核Salen Mn的分子识别研究

合成了新型手性双Salen配体1及双核锰配合物2,并进行了表征.用紫外-可见光谱滴定法研究了主体双核Salen Mn（2）与咪唑、吡啶类客体的分子识别行为.结果表明:对咪唑类客体的缔合常数顺序为K(Im) > K(2-MeIm) > K(N-MeIm);对吡啶类客体缔合常数顺序为K(4-MePy) > K(3-MePy)> K(Py).主体与所有客体的配位数均为2.测定了识别过程的热力学函数ΔrHmθ, ΔrSmθ, 发现反应为放热、熵减过程.利用圆二色光谱研究了识别过程的Cotton效应.用分子力学方法研究了主客体的最低能量构象,结合量化计算结果对实验事实做了进一步解释.     

Synthesis and characterization of tetra-armed-thiosemicarbazone and its salen/salophen capped transition metal complexes: Investigation of their thermal and magnetic properties

In this work, we aimed to synthesize and characterize a novel tetra-directional ligand, (2E,2′E)-2,2′-((((2-(1,3-bis(4-((E)-(2-carbamothioylhydrazono)methyl)phenoxy)propan-2-ylidene)propane-1,3-diyl)bis(oxy))bis(4,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (5), including thiosemicarbazone group and its novel tetra-directional-tetra-nuclear Schiff base complexes. For this purpose, we used 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) as starting material. 4,4′-((2-(1,3-Bis(4-formylphenoxy)propan-2-ylidene)propane-1,3-diyl) bis(oxy))dibenzaldehyde (3) was synthesized by the reaction of an equivalent 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) and 4 equivalents of 4-hydroxybenzaldehyde. Then, compound 5 was synthesized in high yield (86%) by a condensation reaction of compound 3 with thiosemicarbazide (4). Finally, four novel tetra-nuclear Cr(III) or Fe(III) complexes of compound 5 were synthesized. The synthesized compounds were characterized using elemental analyses, ¹H NMR, Fourier transform–infrared spectrometry, liquid chromatography–mass spectrometry (ESI⁺), and thermal analyses. The metal ratios of the prepared complexes were determined using an atomic absorption spectrophotometer. We also investigated their effects on the magnetic behaviors of [salen, salophen, Cr(III)/Fe(III)] capped complexes. The complexes were found to be low-spin distorted octahedral Fe(III) and distorted octahedral Cr(III), all bridged by thiosemicarbazone.     

Preconcentration Ultra Trace of Cd(II) in Water Samples Using Dispersive Liquid‐Liquid Microextraction with Salen(N,N′‐Bis(Salicylidene)‐Ethylenediamine) and Determination Graphite Furnace Atomic Absorption Spectrometry

Dispersive liquid–liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 μL methanol (disperser solvent) containing 34 μL carbon tetrachloride (extraction solvent) and 0.00010 g Salen(N,N′‐bis(salicylidene)ethylenediamine) (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with Salen(N,N′‐bis(salicylidene)‐ethylenediamine), and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25 ± 1 μL). Then a 20 μL of sedimented phase containing enriched analyte was determined by GF AAS. Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 122 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the range of 2‐21 ng L^?1 with a detection limit of 0.5 ng L^?1. The relative standard deviation (R.S.D._s) for ten replicate measurements of 20 ng L^?1 of cadmium was 2.9%. The relative recoveries of cadmium in tap, sea and rain water samples at a spiking level of 5 and 10 ng L^?1 are 99, 94, 97 and 96%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on‐line liquid‐liquid extraction, single drop microextraction (SDME), on‐line solid phase extraction (SPE) and co‐precipitation based on bibliographic data. Therefore, DLLME combined with GF AAS is a very simple, rapid and sensitive method, which requires low volume of sample (5.00 mL).     

Enantioselective Synthesis of β‐Blockers via Hydrolytic Kinetic Resolution of Terminal Oxiranes by Using Bimetallic Chiral {{2,2′‐[Cyclohexane‐1,2‐diylbis(nitrilomethylidyne)]bis[phenolato]}(2−)}cobalt ([Co(salen)])‐Type Complexes

The synthesis of chirally pure β‐blockers was successfully achieved via hydrolytic kinetic resolution of butyl (±)‐4‐(oxiran‐2‐ylmethoxy)benzeneacetate ((±)‐ 1 ) and (±)‐4‐(oxiran‐2‐ylmethoxy)benzeneacetonitrile ((±)‐ 2 ) in the presence of bimetallic chiral [Co(salen)]‐type complexes. The newly synthesized bimetallic chiral [Co(salen)]‐type complexes exhibited excellent enantioselectivities of up to >98% ee in good yields (Tables 1–3).     

Salen-decorated Periodic Mesoporous Organosilica: From Metal-assisted Epoxidation to Metal-free CO2 Insertion

We clicked a salen ligand onto a thiol-ethane bridged periodic mesoporous organosilica (Salen-PMO) using a photo-initiated thiol-ene click reaction. This process resulted in a covalently bonded salen ligand on the PMO material. The final BET surface area amounts 511 m²/g and the pore size diameter is approximately 7 nm. The functionalized PMO material showed an excellent carbon dioxide uptake capacity of 1.29 mmol/g at 273 K and 1 bar. More importantly, by coordinating a MoO₂²⁺ complex onto the Salen-PMO material, we obtained a heterogeneous catalyst with a good catalytic performance for the epoxidation of cyclohexene. The catalyst was highly reusable, as no decrease in its activity was observed for at least four runs (99% conversion). Finally, the metal-free Salen-PMO showed an exceptional catalytic performance in the cycloaddition of CO₂ to epoxides. The obtained results clearly demonstrate the versatility of the Salen-PMO material not only as metal-free catalyst but also as a support material to anchor metal complexes for specific catalytic applications. With the same catalytic platform, we were able to firstly create epoxides out of alkenes, and subsequently turn these epoxides into cyclic carbonates, consuming CO₂.     

双水杨醛缩乙二胺烷基钴(Ⅲ)配合物的电化学行为及光谱电化学表征

用循环伏安法研究了双水杨醛缩乙二胺烷基钴(Ⅲ)配合物[RCo(Salen),R=CH₃,C₂H₅,n-C₄H₉,i-C₄H₉]在热解石墨电极上的电化学行为。RCo(Salen)的电化学氧化或还原均为可逆的单电子过程;氧化时钴的价态变化为Co^Ⅲ→Co^Ⅳ,还原时为Co^Ⅲ→Co^Ⅱ→Co^Ⅰ,并伴有Co─C键的断裂和R·自由基的产生。氧化产物和还原产物均不稳定,R影响电化学性质,随着R给电子能力的增强,氧化反应的电位和还原反应的电位均负移。光谱电化学实验的结果提供了进一步的验证。     

微波辅助原位生成水溶性Salen-Cu(II)配合物催化水中的两步一锅法click反应

本文报道原位生成的水溶性Salen-Cu(II)配合物(N,N’-双(亚甲基-2-羟基-5-苯磺酸钠)缩-N,N’-二甲基乙二胺合铜)催化微波加热的水中的两步一锅法click反应。在优化反应条件之后，对碘苯及其衍生物、叠氮化钠与苯乙炔及其衍生物的两步一锅法click反应和卤代烷、叠氮化钠与苯乙炔的三组分两步一锅法click反应进行了考察。在所选择的条件下，这两类click反应都能获得很好的收率，与常规加热模式的三组分两步一锅法click反应相比较，微波加热的显示出了特别高的反应效率。