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1.
The sequential reaction of a multisite coordinating compartmental ligand [2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino)‐2‐methylpropane‐1,3‐diol] (LH4) with appropriate lanthanide salts followed by the addition of [Mg(NO3)2] ? 6 H2O or [Zn(NO3)2] ? 6 H2O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg2Ln]3+ (Ln=Dy, Gd, and Tb) and [Zn2Ln]3+ (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X‐ray crystallography as well as ESI‐MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg2Ln]3+ and [Zn2Ln]3+ heterometallic complexes. [Mg2Dy]3+ and [Zn2Dy]3+ show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole–dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single‐molecule magnet behavior of complexes [Mg2Dy]3+ and [Zn2Dy]3+.  相似文献   

2.
[CrIII8MII6]12+ (MII=Cu, Co) coordination cubes were constructed from a simple [CrIIIL3] metalloligand and a “naked” MII salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior.  相似文献   

3.
A series of new tetranuclear heterometallic ZnII‐EuIII complexes have been synthesized, that is, (bpy)2Zn2Eu2(naph)10 ( 1 ), (bpy)2Zn2Eu2(naph)8(NO3)2 ( 2 ), and (phen)2Zn2Eu2(naph)8(NO3)2 ( 3 ), and other ones, where naph? is the 1‐naphthoate anion, bpy=2,2′‐bipyridyl, and phen=1,10‐phenanthroline. The solid‐phase complexes consist of large supramolecular ensembles due to stacking interactions between the aromatic ligands. Photoluminescence (PL) measurements were carried out to study PL spectra, lifetimes and quantum yields (QY) of the synthesized complexes at different temperatures. The external QY for the solid phases of complexes under UV excitation was found to exceed 20 %. It has been shown that partial replacement of naphthoate ligands in the coordination environment of Eu3+ by NO3? anions influences the PL properties. To investigate the behavior of these complexes in solvent, we dissolved complex 3 in MeCN, put it on a transparent glass as a substrate, and studied the PL properties at room temperature.  相似文献   

4.
5.
A series of heterometallic 3d–Gd3+ complexes based on a lanthanide metalloligand, [M(H2O)6][Gd(oda)3] ? 3 H2O [M=Cr3+ ( 1‐Cr )] (H2oda=2,2′‐oxydiacetic acid), [M(H2O)6][MGd(oda)3]2 ? 3 H2O [M=Mn2+ ( 2‐Mn ), Fe2+ ( 2‐Fe ) and Co2+ ( 2‐Co )], and [M3Gd2(oda)6(H2O)6] ? 12 H2O [M=Ni2+ ( 3‐Ni ), Cu2+ ( 3‐Cu ), and Zn2+ ( 3‐Zn )], are reported. Magnetic and heat‐capacity studies revealed a significant impact on the magnetocaloric effect depending on the anisotropy of the 3d transition metal ions, as confirmed by comparison of the observed maximum values of ?ΔSm between complexes 2‐Co and 1‐Cr . In these two complexes, the 3d metal ions have the same spin (S=3/2 for Co2+ and Cr3+ ions), and the theoretical calculation suggested a larger ?ΔSm value for 2‐Co (47.8 J K?1 kg?1) than 1‐Cr (37.5 J K?1 kg?1); however, the significant anisotropy of Co2+ ions in 2‐Co , which can result in smaller effective spins, gives a smaller value of ?ΔSm for 2‐Co (32.2 J K?1 kg?1) than for 1‐Cr (35.4 J K?1 kg?1) at ΔH=9 T.  相似文献   

6.
We report the synthesis, crystal structures, and spectral, thermal, and magnetic properties of a family of metal–organic perovskite ABX3, [C(NH2)3][MII(HCOO)3], in which A=C(NH2)3 is guanidinium, B=M is a divalent metal ion (Mn, Fe, Co, Ni, Cu, or Zn), and X is the formate HCOO?. The compounds could be synthesized by either diffusion or hydrothermal methods from water or water‐rich solutions depending on the metal. The five members (Mn, Fe, Co, Ni, and Zn) are isostructural and crystallize in the orthorhombic space group Pnna, while the Cu member in Pna21. In the perovskite structures, the octahedrally coordinated metal ions are connected by the antianti formate bridges, thus forming the anionic NaCl‐type [M(HCOO)3]? frameworks, with the guanidinium in the nearly cubic cavities of the frameworks. The Jahn–Teller effect of Cu2+ results in a distorted anionic Cu–formate framework that can be regarded as Cu–formate chains through short basal Cu? O bonds linked by the long axial Cu? O bonds. These materials show higher thermal stability than other metal–organic perovskite series of [AmineH][M(HCOO)3] templated by the organic monoammonium cations (AmineH+) as a result of the stronger hydrogen bonding between guanidinium and the formate of the framework. A magnetic study revealed that the five magnetic members (except Zn) display spin‐canted antiferromagnetism, with a Néel temperature of 8.8 (Mn), 10.0 (Fe), 14.2 (Co), 34.2 (Ni), and 4.6 K (Cu). In addition to the general spin‐canted antiferromagnetism, the Fe compound shows two isothermal transformations (a spin‐flop and a spin‐flip to the paramagnetic phase) within 50 kOe. The Co member possesses quite a large canting angle. The Cu member is a magnetic system with low dimensional character and shows slow magnetic relaxation that probably results from the domain dynamics.  相似文献   

7.
Mixed 3d–4f 12‐azametallacrown‐4 complexes, [Mn2Ln2(OH)2(hppt)4(OAc)2(DMF)2] ? 2 DMF ? H2O [Ln=Dy ( 1 ), Er ( 2 ), Yb ( 3 ), Tb ( 4 ) and Y ( 5 ), H2hppt=3‐(2‐hydroxyphenyl)‐5‐(pyrazin‐2‐yl)‐1,2,4‐triazole)], were synthesized by reactions of H2hppt with Mn(OAc)2 ? 4 H2O and Ln(NO3)3 ? 6 H2O. This is the first 3d–4f azametallacrown family to incorporate Ln ions into the ring sets. These isostructural complexes exhibit alternating arrangements of two Mn and two Ln ions in the rings with each pair of metal centers bound by an N?N group and μ2‐O bridging. Magnetic measurements revealed dominant antiferromagnetic interactions between metal centers, and frequency‐dependent out‐of‐phase (${\chi {^\prime}{^\prime}_{\rm{M}} }$ ) signals below 4 K suggest slow relaxation of magnetization.  相似文献   

8.
Two Dy–Mn polymers, {[Dy(L1)3Mn1.5(H2O)3]?3.125 H2O}n ( 1 , L1=pyridine‐2,6‐dicarboxylic acid) and {[Dy(L2)3Mn1.5(H2O)6]?8.25 H2O}n ( 2 , L2 = 4‐hydroxylpyridine‐2,6‐dicarboxylic acid), with high symmetry (S6) have been prepared. Polymer 1 has a nanoporous 3D framework with channel of about 17.6 Å diameter, while 2 has a honeycomb‐type 2D structure with the cavity of approximately 14.4 Å diameter. In the construction of multidimensional porous polymers with 3d–4f mixed metals, it is the first observation that a ligand substituent effect leads to dramatic differences in the structures formed. Luminescent studies reveal that the emission intensities of 1 and 2 increase significantly upon the addition of Mg2+, whereas the introduction of other metal ions leaves the intensity unchanged or even weakens it; hence, both of them may serve as good candidates of Mg2+ luminescent probes. To our knowledge, complex 1 is also the first example of a 3d–4f metal‐based nanoporous polymer to exhibit luminescent selectivity for Mg2+. Magnetic susceptibility measurements reveal a rather rare ferromagnetic interaction in 2 . Thermal gravimetric analyses and powder X‐ray diffraction investigations have also been performed, suggestive of high thermal stability of 1 .  相似文献   

9.
Single‐crystal X‐ray diffraction measurements have been carried out on [Nd(dmf)4(H2O)3(μ‐CN)Fe(CN)5]?H2O ( 1 ; dmf=dimethylformamide), [Nd(dmf)4(H2O)3(μ‐CN)Co(CN)5]?H2O ( 2 ), [La(dmf)4(H2O)3(μ‐CN)Fe(CN)5]?H2O ( 3 ), [Gd(dmf)4(H2O)3(μ‐CN)Fe(CN)5]?H2O ( 4 ), and [Y(dmf)4(H2O)3(μ‐CN)Fe(CN)5]?H2O ( 5 ), at 15(2) K with and without UV illumination of the crystals. Significant changes in unit‐cell parameters were observed for all the iron‐containing complexes, whereas 2 showed no response to UV illumination. Photoexcited crystal structures have been determined for 1 , 3 , and 4 based on refinements of two‐conformer models, and excited‐state occupancies of 78.6(1), 84(6), and 86.6(7) % were reached, respectively. Significant bond‐length changes were observed for the Fe–ligand bonds (up to 0.19 Å), the cyano bonds (up to 0.09 Å), and the lanthanide–ligand bonds (up to 0.10 Å). Ab initio theoretical calculations were carried out for the experimental ground‐state geometry of 1 to understand the electronic structure changes upon UV illumination. The calculations suggest that UV illumination gives a charge transfer from the cyano groups on the iron atom to the lanthanide ion moiety, {Nd(dmf)4(H2O)3}, with a distance of approximately 6 Å from the iron atom. The charge transfer is accompanied by a reorganization of the spin state on the {Fe(CN)6} complex, and a change in geometry that produces a metastable charge‐transfer state with an increased number of unpaired electrons, thus accounting for the observed photomagnetic effect.  相似文献   

10.
采用[(Tp)Fe(CN)3]-(Tp=hydrotris(pyrazolyl)borate)与Mn(Ac)2·4H2O反应,合成了氰根桥联的异金属三核配合物[Mn(phen)2][(Tp)Fe(CN)3]2·5H2O (1)(phen=1,10-phenanthroline),并对其结构和磁性进行了研究。晶体结构分析结果表明该化合物晶体属于三斜晶系,P1空间群。在该配合物中,Mn(Ⅱ)与2个phen分子及2个[(Tp)Fe(CN)3]-配位,形成一种弯曲的三核结构。磁性测量结果表明,Mn(Ⅱ)和Fe(Ⅲ)之间通过氰根桥联产生弱的反铁磁相互作用。  相似文献   

11.
采用[(Tp)Fe(CN)3]-(Tp=hydrotris(pyrazolyl)borate)与[NiL](ClO4)2(L=3,10-bis(2-bydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetra-decane)反应,合成了氰根桥联的异金属三核配合物[NiL][(Tp)Fe(CN)3]2·4H2O(1),并对其结构和磁性进行了研究.该化合物晶体属于正交晶系,Pbca空间群.配合物1中,Ni(Ⅱ)大环与2 [(Tp)re(CN)3]-通过氰根桥联,形成近似直线的三核结构.Ni原子的配位采取六配位稍畸变的八面体构型.其中大环配体上的4个N原子占据赤道平面而桥联氰根的2个N原子占据轴向位置.磁性测定表明在2-300 K的温度范围内,Ni(Ⅱ)和Fe(Ⅲ)之间通过桥联的氰根产生弱的铁磁相互作用.用哈密顿函数H=-2J(SFel·SNi SFe2·SNi)对其XMT-T曲线进行了拟合,得到1的朗德因子g=2.35和交换常数J=8.13 cm-1.最后,对配合物的结构与磁性的关系进行了讨论.  相似文献   

12.
在溶剂热条件下,基于芳香四羧酸合成了2种新颖的配位聚合物:{[Zn2(tptc)(1,4-bimb)2]·H2O}n(1)和{[Ni(tptc)0.5(1,2-bimb)(H2O)]·H2O}n(2),其中,tptc为对-三联苯-3,3″,5,5″-四羧酸,1,4-bimb为1,4-二(咪唑-1-亚甲基)苯,1,2-bimb为1,2-二(咪唑-1-亚甲基)苯。结构分析表明,1为三维结构,拓扑符号为(86);2为二维层状网络,通过氢键相互作用进一步扩展为三维超分子结构。此外,我们还研究了1对阳离子、阴离子的荧光感应以及2的磁性质。  相似文献   

13.
Complexes formed between metal dications, the conjugate base of uracil, and uracil are investigated by sustained off‐resonance irradiation collision‐induced dissociation (SORI‐CID) in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Positive‐ion electrospray spectra show that [M(Ura?H)(Ura)]+ (M=Zn, Cu, Ni, Co, Fe, Mn, Cd, Pd, Mg, Ca, Sr, Ba, or Pb) is the most abundant ion even at low concentrations of uracil. SORI‐CID experiments show that the main primary decomposition pathway for all [M(Ura?H)(Ura)]+, except where M=Ca, Sr, Ba, or Pb, is the loss of HNCO. Under the same SORI‐CID conditions, when M is Ca, Sr, Ba, or Pb, [M(Ura?H)(Ura)]+ are shown to lose a molecule of uracil. Similar results were observed under infrared multiple‐photon dissociation excitation conditions, except that [Ca(Ura?H)(Ura)]+ was found to lose HNCO as the primary fragmentation product. The binding energies between neutral uracil and [M(Ura?H)]+ (M=Zn, Cu, Ni, Fe, Cd, Pd ,Mg, Ca, Sr Ba, or Pb) are calculated by means of electronic‐structure calculations. The differences in the uracil binding energies between complexes which lose uracil and those which lose HNCO are consistent with the experimentally observed differences in fragmentation pathways. A size dependence in the binding energies suggests that the interaction between uracil and [M(Ura?H)]+ is ion–dipole complexation and the experimental evidence presented supports this.  相似文献   

14.
在空气中采用高温固相反应方法合成的17MO-(8-x-y)-75B2O3-xGd2O3(MLBEG,M-Mg,Ca,Sr,Ba)玻璃,在紫外光(λex=350nm)激发下发射蓝光和红光,在绿色光(λex=532nm)激发下发射红光,电子自旋共振谱研究表明玻璃体系中有Eu^2 离子存在,蓝色区的宽带发射是Eu^2 离子的5d-4f跃迁发射:红色区的窄带发射是Eu^3 离子的5Do-7FJ(J=1,2,3,4)跃迁发射,发现玻璃中的碱土金属离子对Eu^3 /Eu^2 离子的比例有很大影响,选择不同的碱土金属离子可以调节玻璃蓝色光和红色光的相对发射强度,MLBEG玻璃的发光性质可用于转换太阳能,增强植物的光合作用。  相似文献   

15.
We report the synthesis and spectroscopic identification of the trisbenzene complexes of strontium and barium M(Bz)3 (M=Sr, Ba) in low‐temperature Ne matrix. Both complexes are characterized by a D3 symmetric structure involving three equivalent η6‐bound benzene ligands and a closed‐shell singlet electronic ground state. The analysis of the electronic structure shows that the complexes exhibit metal–ligand bonds that are typical for transition metal compounds. The chemical bonds can be explained in terms of weak donation from the π MOs of benzene ligands into the vacant (n?1)d AOs of M and strong backdonation from the occupied (n?1)d AO of M into vacant π* MOs of benzene ligands. The metals in these 20‐electron complexes have 18 effective valence electrons, and, thus, fulfill the 18‐electron rule if only the metal–ligand bonding electrons are counted. The results suggest that the heavier alkaline earth atoms exhibit the full bonding scenario of transition metals.  相似文献   

16.
The synthesis and structural characterization of three heterometallic rings templated about imidazolium cations is reported. The compounds are [2,4‐DiMe‐ImidH][Cr7NiIIF8(O2CtBu)16] 1 (2,4‐DiMe‐ImidH=the cation of 2,4‐dimethylimidazole), [ImidH]2[Cr6NiII2F8(O2CCtBu)16] 2 (ImidH=the cation of imidazole), and [1‐Bz‐ImidH]2 [Cr7NiII2F9(O2CtBu)18] 3 (1‐Bz‐ImidH=the cation of 1‐benzylimidazole). The structures show the formation of octagonal arrays of metals for 1 and 2 and a nonagon of metal centers for 3 . In all cases the edges of the polygon are bridged by a single fluoride and two pivalate ligands, and the position of the divalent metal centers cannot be distinguished by X‐ray diffraction. Magnetic studies combined with EPR spectroscopy allow the characterization of the magnetic states of the compounds. In each case the exchange is antiferromagnetic with a magnetic exchange parameter J≈?5.8 cm?1, and it is not possible to differentiate the exchange between two CrIII centers (JCrCr) from the exchange between a CrIII and a NiII center (JCrNi). For 2 there is evidence for the presence of at least two, possibly four, linkage isomers of the heterometallic ring, caused by the presence of two divalent metal centers in the ring. The EPR spectroscopy of 3 suggests an S=1/2 ground state of the ring and that it is likely that only one linkage isomer is present.  相似文献   

17.
Sequential reaction of a multisite LH4 ligand {2‐[2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino]‐2‐methylpropane‐1,3‐diol} with appropriate lanthanide salts followed by the addition of Ni(NO3)2 ? 6 H2O in a 4:1:2 stoichiometric ratio in the presence of triethylamine afforded four heterobimetallic trinuclear complexes [Ni2Gd(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 1 ), [Ni2Tb(LH3)4] ? 3 NO3 ? 3 MeOH ? CH3CN ( 2 ), [Ni2Dy(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 3 ), and [Ni2Ho(LH3)4] ? 3 NO3 ? 3 MeOH ? H2O ? CH3CN ( 4 ). Complexes 1 – 4 possess linear trimetallic cores with a central lanthanide ion. Magnetic studies revealed a predominant ferromagnetic interaction between the Ni and Ln centers. Alternating current susceptibility measurements of complex 3 showed a small frequency dependence of the out‐of‐phase signal, χ′′M , under zero direct current field, but without achieving a net maximum above 2 K. Magnetic studies on 1 revealed that it has a significant magnetocaloric effect.  相似文献   

18.
Single crystals of tetrakis(thiadiazole)porphyrazine and the corresponding metal(II) derivatives, MTTDPz (M=H2, Fe, Co, Ni, Cu, and Zn) were grown by sublimation under reduced pressure with continuous N2 gas flow. Their structures, obtained by X-ray crystallographic analysis, depend significantly on the central metal ion, and the M=Ni and Cu derivatives exhibit polymorphism. They can be classified into three forms, alpha, beta, and gamma. The alpha form (M=H2, Ni, and Cu) is composed of two-dimensional hexagonal close packing formed by side-by-side contacts between thiadiazole rings, whereas the beta form (M=Fe, Co, and Zn) crystallizes into a one-dimensional coordination polymer. The gamma form (M=Ni and Cu) consists of a ladder structure caused by pi stacking, similar to the beta form of phthalocyanine, and by side-by-side contacts between thiadiazole rings. Although the crystal structures of the MTTDPz series exhibited multi-dimensional network structures, magnetic measurements revealed relatively weak exchange interactions, probably reflecting the long distances between the metal ions.  相似文献   

19.
用手性的V形双齿配体N,N''-((1R,2R)-1,2-二取代环己二胺)双(N-苯甲酸(3-吡啶亚甲基)酰胺(1R,2R)-3-bcpb)和不同的Cu(II)盐反应,组装成2个新的手性Cu(II)配位聚合物{[Cu((1R,2R)-3-bcpb)]Cl2}n1)和{[Cu((1R,2R)-3-bcpb)2](ClO42·2H2O·2CH3OH}n2)。其中1是一维链状结构,2具有二维(4,4)网络拓扑。溶剂热条件下,在甲醇溶剂体系中,通过引入AgClO4,1能转换成2,同时通过加入NaCl,2也能转换成1。圆二色谱和二次谐波响应测试验证了它们具有结构上的手性。  相似文献   

20.
Four new quaternary chalcogenides, Ba4AgGaS6 ( 1 ), Ba4AgGaSe6 ( 2 ), Ba4CuInS6 ( 3 ), and Ba4AgInS6 ( 4 ), were synthesized by solid‐state reactions and their structures were characterized through single‐crystal X‐ray diffraction. In spite of their similar chemical compositions, the flexible arrangement between the transition metals and the triel atoms leads to subtle differences in their polyanion structures. All structures feature similar [MTrQ6]8? 1D polyanionic chains (M=Cu, Ag; Tr=Ga, In; Q=S, Se), which are constructed from corner‐sharing MQ4 or TrQ4 tetrahedra. However, the transition metals and triels are mixed in 1 , 2 , and 3 , but they occupy independent crystallographic sites in 4 . As a result, compounds 1 – 3 belong to the known Ba2CoS3 (Pnma No. 62) or Ba2MnS3 (Pnma No. 62) class, whereas 4 crystallizes in its own structural type within the monoclinic P21/c (No. 14) space group. The structural relationship among these new phases was also studied with the aid of DFT calculations and related optical properties are presented as well.  相似文献   

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