Synthesis and electrochemistry of vanadium(IV) Schiff base complexes

The electrochemical properties of vanadyl(IV) derivatives, namely salen Schiff base complexes of the type [VO(Salen)] (5-BrSalen, 5-NO₂Salen, 5-MeOSalen, salpn (bis(salicylaldehyde)-1,3-propanediamine, 5-BrSalpn, 5-NO₂Salpn, 5-MeOSalpn, Me₂Salen, Salophen, 5-BrSalophen, and 5-MeOSalophen) were investigated. The equatorial Schiff base ligands affect the oxidation potentials via interaction with the d-orbitals of the vanadyl metal ion. The cathodic peak potential (E_pc) becomes less negative according to the sequence MeO- < H- < Br- < NO_2?.     

离子液体中Mn（Salen）催化仲醇的氧化反应研究

以PhI(OAc)2为氧化剂,考察了1,3-二烷基咪唑硫酸酯系列离子液体中Mn(Salen)催化仲醇氧化的反应. 结果表明, 在MMISM-CH2Cl2(1:4,v:v)混合溶剂中, 反应条件为n((-苯乙醇): n(醋酸碘苯): n(催化剂1c)=50: 70: 1时, (-苯乙醇的转化率可以达到97.8%, 产物苯乙酮的选择性为100%, 远高于在纯CH2Cl2中的结果, 也要好于[bmim]BF4和[bmim]PF6对该反应的促进作用. 此外, BMISM及BEISE对催化剂1c有较好的稳定作用,催化剂可以重复使用.     

链状Salen型高分子席夫碱金属配合物的合成及表征

以对苯二甲酰氯为交联剂,利用界面聚合法合成了链状Salen型高分子席夫碱金属配合物PLSBM(M:CoⅡ,MnⅡ,ZnⅡ,CuⅡ),通过元素分析、红外光谱(FT-IR)、扫描电镜(SEM)、电感耦合等离子原子发射光谱(ICP-AES)和X射线光电子能谱(XPS)对结构进行了表征,发现PLSBM呈不规则的链状结构,配位金属离子与配体形成了稳定的配合物后金属离子的结合能增加了0.5～2.1eV。     

Noncovalent secondary interactions in Co(II)Salen complexes: O2 binding and catalytic activity in cyclohexene oxygenation

The O2 affinity of Co(II)Salen complexes 1-4 and their reactivity in cyclohexene oxygenation reactions of Co(II)Salen complexes 1-4 are modulated by noncovalent interactions such as hydrogen bonding and steric hindrance using a functionalized diamino bridge. Higher O2 affinity is observed in the case of efficient hydrogen-bonding interactions (complex 1), while increased steric hindrance (cis vs trans diamino bridge) around the Co-coordinated O2 is influencing the reactivity of the complexes.     

Synthesis and thermodynamic studies of the dinuclear adducts between dimethyltin(IV) dichloride with SalenH2 and MII(Salen) complexes in chloroform

A UV-Vis spectrophotometric study of adduct formation of SalenH₂ (1) and M^II(Salen), where M?=?Mn (2), Fe (3), Co (4), Ni (5) and Cu (6) as donors with Me₂SnCl₂ as acceptor have been investigated in chloroform. Adducts (1a–6a) have been characterized by ¹H, ¹³C and ¹¹⁹Sn NMR, IR and electronic spectroscopy and microanalysis. Formation constants and thermodynamic parameters were measured for 1 : 1 and 2 : 1 adducts at various temperatures (T?=?278 to 308 K). The data refinement was carried out with the SQUAD 84 program. The trend of formation constants of M^II(Salen) complexes with Me₂SnCl₂ follows the order: Mn>Fe>Cu>Co>Ni. The formation constants for the free 1 and M^II(Salen) with Me₂SnCl₂ changes according to the following trend: M^II(Salen)>SalenH₂     

MCM-48固载手性salen Mn(III)催化苯乙烯环氧化反应

手性salenMn(III)化合物是非常有效的烯烃不对称环氧化催化剂[1],近年来对它的非均相化研究越来越受到大家的关注[2-4].以聚合物为载体固载salen Mn(III)化合物的研究已经取得了很大的进展,相对的无机载体的研究要少得多.本文首次将手性salen Mn(III)化合物固载到介孔分子筛MCM     

Europium(III) complexes containing organosilyldipyridine ligands grafted on silica nanoparticles

This work focuses on the grafting of transition metal complexes on silica surface nanoparticles. Nanoscale silica particles in aqueous sols are used as starting silicated materials. We have undertaken the synthesis of europium(III) complexes containing organosilyldipyridine ligands, (EtO)3Si(CH2)3NHCH2-bipy (1) and (EtO)(CH3)2Si(CH2) 3NHCH 2-bipy (2), in view of a direct grafting reaction on silica nanoparticles. Reaction of one molar equivalent of 1 and 2 with Eu(tmhd)3 (tmhd= 2,2,6,6-tetramethyl-3,5-heptanedionato), as precursor, leads to octacoordinated silylated europium(III) complexes [Eu(tmhd)3(1)] (3) and [Eu(tmhd)3(2)] (4) as white solids in 34-54% yields. Europium complexes were characterized by elemental analysis, mass spectrometry, FT-IR, UV, and luminescence spectroscopies. These new complexes are reacting in a 1:10 (v/v) water and ethanol mixture with silica nanoparticles colloidal sol. Elemental analysis and thermogravimetric data indicated grafting ratios of 0.41 and 0.26 mmol of europium(III) complexes per gram of silica. Functionalized silica nanoparticles were characterized by DRIFT spectroscopy and TEM microscopy. The first analysis shows that the chemical integrity of the complexes is retained on the silica surface together with the size and the monodispersity of the nanoscale particles. As expected for europium(III) complexes, luminescence is observed under UV irradiation. Emission and excitation spectra indicate that the metal coordination environment is not modified on the silica surface. Moreover, the sharpness of the luminescence bands and the strong antenna effect are maintained when complexes are covalently bonded to silica. New luminescent europium(III) complexes grafted on silica nanoparticles are therefore obtained from our approach.     

Synthesis and Crystal Structure of a New Salen Complex

Salen Schiff base complexes are some of the most important stereochemical models in transition metal coordina tion chemistry, with their ease of preparation and structural variation. [1] Salen complexes are extensively used as organic reaction catalysts, it was reported to be used in asymmetric cyclopropanation, epoxidation, aziridination, hydrolysis, alkylation, Diels-Alder reaction, reduction, oxidation etc. Here we report the synthesis and structure of a new salen nickel complex 4.     

微波固相法制备Mn(Salen)/Al-HMS催化剂

微波固相法制备Mn(Salen)/Al-HMS催化剂;Mn(Salen)络合物;Al-HMS;微波辐射;苯乙烯;环氧化反应     

Phosphorus‐containing Salen‐metal complexes investigated for enhancing the fire safety of thermoplastic polyurethane (TPU)

Three novel phosphorus‐containing Salen‐based derivatives (Salen‐DPCP‐M: M = Ni, Zn, and Mn), which include both phenyl phosphate structures (DPCP) and Salen‐metal complexes, were prepared for enhancing the fire safety of thermoplastic polyurethane (TPU). Thermogravimetric analysis (TGA) showed that Salen‐DPCP‐M altered the thermal degradation pathways of TPU probably due to the phosphorus‐containing structure of Salen‐DPCP‐M. The cone calorimeter test showed that the addition of 3 wt% of Salen‐DPCP‐Ni, Salen‐DPCP‐Zn, and Salen‐DPCP‐Mn lowered the peak of heat release rate (PHRR) from 1495 kW/m² for neat TPU to 690, 875, and 813 kW/m², respectively, for the TPU composites, which demonstrated that Salen‐DPCP‐M improved the fire safety of TPU. In addition, the release of toxic CO gas from the Salen‐DPCP‐Ni/TPU and Salen‐DPCP‐Zn/TPU composites was reduced by 78.2% and 80.0%, respectively. The results of TGA/infrared spectrometry (TG‐FTIR) showed that the incorporation of Salen‐DPCP‐Ni promoted the release CO₂, while reducing the formation of harmful gases. Laser Raman spectroscopy (LRS) and scanning electron microscopy (SEM) showed that Salen‐DPCP‐Ni/TPU and Salen‐DPCP‐Zn/TPU composites formed a dense and stable char layer. Herein, the mechanism of these flame retardants containing novel phosphorus‐containing Salen‐metal complexes is also proposed.     

Comparative Study of Aerobic Alkene Epoxidations Catalyzed by Optically Active Manganese(iii) and Cobalt(ii) Salen Complexes

A comparative study of aerobic alkene epoxidations in the presence of pivalaldehyde catalyzed by the optically active Mn(III)Salen and Co(II)Salen complexes has been performed. The nature of the asymmetric induction is discussed.     

手性Salen及Ga(Salen)催化苯基锂对环氧环己烷对映选择性开环反应

合成了14个含1,2-环己二胺、1,2-二苯基乙二胺或邻苯二胺的手性Salen化合物, 研究了手性Salen直接催化苯基锂对环氧环己烷的不对称开环反应, 结果表明二胺的结构和苯环上3,3'-位取代基对反应的对映选择性有很大的影响. 用Salen与 Me₃Ga原位生成的Ga(Salen)催化苯基锂对环氧环己烷的不对称开环反应, 与用Salen直接催化相比, 得到了更好的化学产率和对映选择性. 当用Ga(Slane) 15为催化剂时, 最佳ee值为73%.     

Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine

Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.     

(Schiff base) divalent group 14 element species: manganese and iron complexes (Salen)M=Mn(Co)2(eta 5-C5H5) (M14 = Ge, Sn, Pb) and (Salen)Sn=Fe(CO)4

Syntheses of the (divalent group 14 species)dicarbonyl(cyclopentadienyl)manganese (Salen)M=Mn(CO)2(eta 5-C5H5) [M = Ge (1), Sn (2), Pb (3)] and [(Salen)tin(II)]tetracarbonyliron (Salen)Sn=Fe(CO)4 (4) are reported. The structures of 2 and 4 were determined by X-ray crystallography. The observed Sn-Mn bond length, 2.4428(7) A, is the shortest distance observed for this type of bond and corresponds to considerable multiple bonding between these atoms. In complex 4, the iron atom has a slightly distorted trigonal-bipyramidal coordination sphere; the (Salen)tin(II) ligand occupies an axial site, indicating that it functions in this complex as a strong sigma-donor and weak pi-acceptor ligand. Crystal data for 2: orthorhombic, P2(1)2(1)2(1), a = 6.972(1) A, b = 15.678(2) A, c = 19.032(2) A, alpha = beta = gamma = 90 degrees, V = 2080.3(5) A3, T = 173(2) K, Z = 4. Crystal data for 4: triclinic, P1, a = 8.465(2) A, b = 9.795(3) A, c = 13.213(4) A, alpha = 105.55(3) degrees, beta = 105.15(3) degrees, gamma = 100.84(3) degrees, V = 978.7(5) A3, T = 173(2) K, Z = 2.     

Synthesis of tyrosine-involved corrole Cu(III), Mn(IV), and Mn(III) complexes as biomimetic models of oxygen evolving complex in photosystem II

Boc-protected tyrosine-attached corrole ligand on the “ortho” position compound 3, its corresponding copper (III) 4a, manganese (IV) 4b, and manganese (III) 4c complexes have been designed and synthesized based on the structures of active-centers of related biological systems. ¹H NMR and electronic absorption spectra of these metal complexes are investigated. The crystal structure of 4a displays the relative position of TyrOH unit to the high valent metal center. Electrochemistry investigations display the possibilities of intramolecular electron or energy transfer between TyrOH group and metal corrole group.     

Heterogenization of Salen Metal Molecular Catalysts in Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution

Integrating a molecular catalyst with a light harvester into a photocatalyst is an effective strategy for solar light conversion. However, it is challenging to establish a crystallized framework with well-organized connections that favour charge separation and transfer. Herein, we report the heterogenization of a Salen metal complex molecular catalyst into a rigid covalent organic framework (COF) through covalent linkage with the light-harvesting unit of pyrene for photocatalytic hydrogen evolution. The chemically conjugated bonds between the two units contribute to fast photogenerated electron transfer and thereby promote the proton reduction reaction. The Salen cobalt-based COF showed the best hydrogen evolution activity (1378 μmol g⁻¹ h⁻¹), which is superior to the previously reported nonnoble metal based COF photocatalysts. This work provides a strategy to construct atom-efficient photocatalysts by the heterogenization of molecular catalysts into covalent organic frameworks.     

Tetranuclear polybipyridyl complexes of Ru(II) and Mn(II), their electro- and photo-induced transformation into di-mu-oxo Mn(III)Mn(IV) hexanuclear complexes

Three heterotetranuclear complexes, [{Ru(II)(bpy)(2)(L(n))}(3)Mn(II)](8+) (bpy = 2,2'-bipyridine, n = 2, 4, 6), in which a Mn(II)-tris-bipyridine-like centre is covalently linked to three Ru(II)-tris-bipyridine-like moieties using bridging bis-bipyridine L(n) ligands, have been synthesised and characterised. The electrochemical, photophysical and photochemical properties of these complexes have been investigated in CH(3)CN. The cyclic voltammograms of the three complexes exhibit two successive very close one-electron metal-centred oxidation processes in the positive potential region. The first, which is irreversible, corresponds to the Mn(II)/Mn(III) redox system (E(pa) approximately 0.82 V vs Ag/Ag(+) 0.01 M in CH(3)CN-0.1 M Bu(4)NClO(4)), whereas the second which is, reversible, is associated with the Ru(II)/Ru(III) redox couple (E(1/2) approximately 0.91 V). In the negative potential region, three successive reversible four electron systems are observed, corresponding to ligand-based reduction processes. The three stable dimeric oxidized forms of the complexes, [Mn(2)(III,IV)O(2){Ru(II)(bpy)(2)(L(n))}(4)](11+), [Mn(2)(IV,IV)O(2){Ru(II)(bpy)(2)(L(n))}(4)](12+) and [Mn(2)(IV,IV)O(2){Ru(III)(bpy)(2)(L(n))}(4)](16+) are obtained in fairly good yields by sequential electrolyses after consumption of respectively 1.5, 0.5 and 3 electrons per molecule of initial tetranuclear complexes. The formation of the di-micro-oxo binuclear complexes are the result of the instability of the {[Ru(II)(bpy)(2)(L(n))](3)Mn(III)}(9+) species, which react with residual water, via a disproportionation reaction and the release of one ligand, [Ru(II)(bpy)(2)(L(n))](2+). A quantitative yield can be obtained for these reactions if the electrochemical oxidations are performed in the presence of an added external base like 2,6-dimethylpyridine. Photophysical properties of these compounds have been investigated showing that the luminescence of the Ru(II)-tris-bipyridine-like moieties is little affected by the presence of manganese within the tetranuclear complexes. A slight quenching of the excited states of the ruthenium moieties, which occurs by an intramolecular process, has been observed. Measurements made at low concentration (<1 x 10(-5) M) indicate that some decoordination of Mn(2+) arises in 1a-c. These measurements allow the calculation of the association constants for these complexes. Finally, photoinduced oxidation of the tetranuclear complexes has been performed by continuous photolysis experiments in the presence of a large excess of a diazonium salt, acting as a sacrificial oxidant. The three successive oxidation processes, Mn(II)--> Mn(III)Mn(IV), Mn(III)Mn(IV)--> Mn(IV)Mn(IV) and Ru(II)--> Ru(III) are thus obtained, the addition of 2,6-dimethylpyridine in the medium giving an essentially quantitative yield for the two first photo-induced oxidation steps as found for electrochemical oxidation.     

Thermodynamics of Cobalt(III) Schiff base complexes in various solvents

The electronic and steric effects of some Schiff bases and the solvent on the thermodynamic parameters of the pentacoordinate Co(III) Schiff base complexes were studied. The formation constants and the thermodynamic parameters were measured spectrophotometrically for 1:1 adduct formation of the complexes as acceptors with tributylphosphine (PBu₃) as donor, in some solvents (acetonitrile, tetrahydrofuran, butanol, ethanol and N,N-dimethylformamide) in constant ionic strength (I = 0.01 M, sodium perchlorate) and at various temperatures. The trend of the reactivity of the pentacoordinate cobalt(III) Schiff base complexes toward tributylphosphine according to the solvent is as follows: acetonitrile > tetrahydrofuran > butanol > ethanol > N,N-dimethylformamide. The trend of the reactivity of pentacoordinate cobalt(III) Schiff base complexes toward the donor in a given solvent according to the equatorial Schiff base is as follows: BBE > BAE > Salen.     

The synthesis and characterization of single substitute melamine cored Schiff bases and their [Fe(III) and Cr(III)] complexes

In this study, firstly, two single substitute novel ligands have been synthesized by reacting melamine with 3,4,-dihydroxybenzaldeyhde or 4-carboxybenzaldehyde. Then, eight new mono nuclear single substitute [Salen/Salophen Fe(III) and Cr(III)] complexes have been synthesized by reacting the ligands [2-(3,4-dihydroxybenzimino)-4,6-diamimo-1,3,5-triazine and 2-(4-carboxybenzimino)-4,6-diamimo-1,3,5-triazine)] with tetradentate Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(salophen H₂). And then, all ligands and complexes have been characterized by means of elementel analysis, FT-IR spectroscopy, ¹H NMR, LC–MS, thermal analyses and magnetic suscebtibility measurements. Finally, metal ratios of the prepared complexes were determined using AAS. The complexes have also been characterized as disorted octahedral low-spin Fe(III) and Cr(III) bridged by catechol and COO^? groups.     

手性双核Salen配合物的谱学性质

合成了四个新型的手性双核(R,R)Salen配合物[(Cu)2L•H2O(2), (Ni)2L(3), (Zn)2L•H2O(4), (MnCl)2L•2H2O(5)], (其中L是由(R,R)环己二胺、 3,5-叔丁基水杨醛、 5,5’-亚甲基二水杨醛为原料合成的手性二聚Salen配体(1)).用元素分析、NMR、FT-IR、UV-Vis、CD光谱对配体和配合物进行了表征.在与单核的Salen配体和配合物比较的基础上，详细讨论了红外光谱、电子吸收光谱、圆二色光谱性质.发现双核配体和配合物的电子吸收光谱吸收峰的位置和形状与单核的配体和配合物基本一致，而吸收峰的强度有近似两倍的关系.另外， 用激子偶合理论解释了此类手性化合物圆二色谱的Cotton效应和Cotton分裂. Cotton分裂的方向依赖于环己二胺的构象.(R,R)环己二胺决定了Salen化合物的手征性为负， Cotton分裂的正负两部分分别处于高能区和低能区.