羧酸桥联的四核镧系簇合物的磁热效应和慢磁弛豫

在水热条件下,通过使用羧酸和螯合配体得到了一个系列的四核镧系簇合物,即[Ln₄(mnba)₁₂(tzp)₂(H₂O)₂](Ln=Gd(1),Tb(2),Er(3);Hmnba=间硝基苯甲酸;tzp=2-(1H-1,2,4-三唑-3-基)吡啶))。这3个化合物是同构的,且具有线性的四核簇结构。磁性研究表明,化合物1和3中簇内镧系离子之间是弱铁磁耦合的,但化合物2中铽离子之间是弱的反铁磁相互作用和(或)铽离子激发的斯塔克能级的去布居。化合物1具有较大的磁热效应(-ΔS_m^max=20.6J·kg^-1·K^-1)。交流磁化率测试表明化合物3展现出频率和温度依赖的虚部信号,这是慢磁弛豫的典型特征,原因是铒离子的强各向异性和铁磁耦合的存在。     

异金属簇{LnCu3}低温磁制冷性能

基于对已报道Gd-Cu配合物的文献调研,发现一类{LnCu₃}簇合物(Ln=Gd(1),Tb(2),Dy(3)),其Cu^Ⅱ离子被Gd^Ⅲ离子有效分隔且分子内部仅拥有铁磁相互作用,因而对其进行了低温磁制冷性能研究。在已报道实验方法上加以改进,用一锅法制备出一系列异金属{LnCu₃}簇合物(Ln=Gd(1),Tb(2),Dy(3)),并运用元素分析、红外、单晶/粉末X-射线衍射等方法对其进行表征,以证明其同构性及相纯度。低温磁热效应的研究结果表明簇合物1-3在ΔH=0~7T下的最大磁熵变值(-ΔS_m)分别为16.1(2K),6.9(5K)和8.1(5K)J·kg^-1·K^-1。簇合物1与已报道的Gd-Cu簇合物的磁熵变对比再次证明了弱铁磁相互作用在3d-4f分子磁制冷剂设计中起到重要的作用。     

异金属簇{LnCu3}低温磁制冷性能

基于对已报道Gd-Cu配合物的文献调研,发现一类{LnCu₃}簇合物(Ln=Gd(1), Tb(2), Dy(3)),其Cu^II离子被Gd^III离子有效分隔且分子内部仅拥有铁磁相互作用,因而对其进行了低温磁制冷性能研究。在已报道实验方法上加以改进,用一锅法制备出一系列异金属{LnCu₃}簇合物(Ln=Gd(1), Tb(2), Dy(3)),并运用元素分析、红外、单晶/粉末X-射线衍射等方法对其进行表征,以证明其同构性及相纯度。低温磁热效应的研究结果表明簇合物1-3在ΔH=0~7 T下的最大磁熵变值(-ΔS_m)分别为16.1(2 K), 6.9(5 K)和8.1(5 K)J·kg^-1·k^-1。簇合物1与已报道的Gd-Cu簇合物的磁熵变对比再次证明了弱铁磁相互作用在3d-4f分子磁制冷剂设计中起到重要的作用。     

基于四甲基取代胍环的四核稀土镝簇合物的慢磁弛豫

报道了2个基于四甲基取代胍环的三明治型四核稀土簇合物, [Ln₄(μ₃-OH)₄(μ₂-OH)₂(H₂O)₄(NO₃)₂(TMeQ[6])₂]·(NO₃)₄·26H₂O(Ln=Dy, 1; Ln=Tb, 2)。晶体结构分析显示2个簇合物包含2个四甲基取代胍环夹心的四核稀土立方烷结构, [Ln₄(μ₃-OH)₄]⁸⁺。磁性研究显示化合物1显示了慢磁弛豫行为。由于胍环配体可以有效的传递能量给稀土铽离子, 化合物2具有较好的发光性能。     

基于四甲基取代六元瓜环的四核稀土镝簇合物的慢磁弛豫

报道了2个基于四甲基取代六元瓜环的三明治型四核稀土簇合物,[Ln₄(μ₃-OH)₄(μ₂-OH)₂(H₂O)₄(NO₃)₂(TMeQ[6])₂]·(NO₃)₄·26H₂O(Ln=Dy,1;Ln=Tb, 2)。晶体结构分析显示2个簇合物包含2个四甲基取代瓜环夹心的四核稀土立方烷结构,[Ln₄(μ₃-OH)₄]⁸⁺。磁性研究显示化合物1显示了慢磁弛豫行为。由于六元瓜环配体可以有效的传递能量给稀土铽离子,化合物2具有较好的发光性能。     

含大环[Ni([15]aneN5]2+氰基桥联四核簇合物的合成、结构和磁性质

用1,4,7,10,13-五氮十五烷(cpad)作为端基配体,合成了2个同构化合物[{Ni(cpad)}₃M(CN)₆]₂[M(CN)₆](ClO₄)₃·6H₂O (M=Cr³⁺,1;Fe³⁺,2),其中[M(CN)₆]^3-通过氰基桥联配位,4个[Ni(cpad)]²⁺阳离子形成四核簇[{Ni(cpad)}₃M(CN)₆]³⁺,游离的[M(CN)₆]^3-和ClO₄^-为平衡阴离子。晶体参数如下：1,三方晶系,P3c1空间群,a=1.5144 1(18) nm,c=3.080 7(6) nm,V=6.118 9(15) nm³,Z=2;2,三方晶系,P3c1空间群,a=1.4976 2(17) nm,c=3.087 8(5) nm,V=5.997 6(14) nm³,Z=2。变温磁化率显示在四核簇内氰基桥联的金属离子之间存在铁磁相互作用。     

一例四核Gd(Ⅲ)簇的结构、磁性、抑菌活性及大的磁热效应

以多齿配体1,3-二（三（羟甲基）甲胺基）丙烷（H₆L）为原料,采用溶剂热法合成了一例有趣的多核Gd（Ⅲ）簇合物1,分子式为[Gd₄（CH₃COO）₆（H₃L）₂]·2CH₃OH。系统地研究了簇1的结构、磁性及抑菌活性。结构分析表明,簇1包含一个蝴蝶形的Gd₄核,且Gd（Ⅲ）离子中心存在2种不同的配位环境。磁性研究表明,簇1中存在反铁磁相互作用,并且表现出显著的低温磁制冷性能（T=2.0 K和ΔH=7.0 T时,-ΔS_m=40.6 J·kg^-1·K^-1）。同时,簇1对5种常见细菌均具有抑菌活性,其中对藤黄微球菌的抑菌效果最好。     

O—P—O桥联锰-席夫碱配合物的合成、结构和磁性质

采用溶液法合成了2例由O—P—O单元桥联的锰-席夫碱(SB)新型三核配合物,即[Mn₃(salen)₃(L)]ClO₄·H₂O (1)和[Mn₃(salpn)₃(L)]ClO₄(2),其中salen^2-=N,N''-乙二胺缩双水杨醛,salpn^2-=N,N''-丙二胺缩双水杨醛,H₂L=(5-(乙氧基羰基)萘-1-基)膦酸。通过单晶X射线衍射、红外光谱、粉末X射线衍射对其进行了表征。配合物1和2是同构的,均是由膦酸酯配体中的O—P—O桥联3个[Mn (SB)]+构成一个三核结构单元[Mn3(SB)3(L)]⁺,一个无序的ClO₄^-作为平衡阴离子存在。这些[Mn₃(SB)₃(L)]⁺三聚体通过π-π相互作用和相邻的分子形成超分子一维波形链。配合物1和2的磁性研究表明,不对称结构中的3个Mn(Ⅲ)离子分别是2个高自旋和1个低自旋,而Mn(Ⅲ)离子之间主要存在反铁磁相互作用。     

含樟脑衍生物氰基桥联双金属配合物的合成、结构及磁性质

采用樟脑衍生物为配体，分别合成了氰基桥联Cu(Ⅱ)-Fe(Ⅲ)-Cu(Ⅱ)三核配合物[{Cu(D,L-La)₂}₂Fe(CN)₆](ClO₄) (1)和Mn(Ⅲ)-Fe(Ⅲ)双核配合物[Mn(D,L-Lb)(DMF)(Tp)Fe(CN)₃]·(H₂O)₆ (2)。晶体结构分析表明，化合物1中Cu(Ⅱ)离子处于五配位的配位环境，分别和1个D-La，1个L-La及[Fe(CN)₆]^3-中的1个氰基配位，2个Cu(Ⅱ)离子通过[Fe(CN)₆]^3-桥联。通过分子间氢键作用，化合物1形成二维超分子网络结构。化合物2中，[(Tp)Fe(CN)₃]^-通过其中的1个氰基与[Mn(D，L-Lb)]⁺桥联，其中Mn(Ⅲ)离子为六配位，分别和四齿配体Lb的2个氧原子和2个氮原子、DMF的1个氧原子及[(Tp)Fe(CN)₃]^-中的氰基氮原子配位。磁性研究表明，在化合物1中，Cu(Ⅱ)离子与Fe(Ⅲ)离子之间表现出铁磁相互作用，用哈密顿函数H=-2J(S₁·S₂+S₂·S₃)对其χ_MT-T曲线进行拟合，得到1的朗日因子g为2.190，交换常数J为0.55 cm^-1。     

基于多齿希夫碱配体的四核和十核锰簇合物的合成、结构和磁性

合成了一种具有{NO₄}给电子组成的多齿水杨醛希夫碱配体,3,5-二-叔丁基水杨醛-三(羟甲基)氨基甲烷(H₄L),并利用元素分析、红外光谱以及核磁共振氢谱表征其结构。Mn(ClO₄)₂或MnCl₂·4H₂O分别与该配体在溶液中反应生成了一个四核锰簇合物[Mn₄^Ⅲ(HL)₂(H₂L)₂(MeCN)₄](ClO₄)₂·2MeCN(1)和一个十核锰簇合物[Mn₆^ⅢMn₄^Ⅱ(bz)₁₀(L)₄(H₂O)₂]·10MeCN(2)。X-射线衍射分析表明化合物1的晶体结构空间群为三斜P1,而化合物2为正交Aba2。2~300K温度区间的磁性测量数据表明化合物2中存在反铁磁相互作用。     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.