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1.
Unprecedented Sensitization of Visible and Near‐Infrared Lanthanide Luminescence by Using a Tetrathiafulvalene‐Based Chromophore
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Min Feng Dr. Fabrice Pointillart Dr. Boris Le Guennic Bertrand Lefeuvre Dr. Stéphane Golhen Dr. Olivier Cador Dr. Olivier Maury Dr. Lahcène Ouahab 《化学:亚洲杂志》2014,9(10):2814-2825
Ligand L was synthesized and then coordinated to [Ln(hfac)3] ? 2 H2O (LnIII=Tb, Dy, Er; hfac?=1,1,1,5,5,5‐hexafluoroacetylacetonate anion) and [Ln(tta)3]?2 H2O (LnIII=Eu, Gd, Tb, Dy, Er, Yb; tta?=2‐thenoyltrifluoroacetonate) to give two families of dinuclear complexes [Ln2(hfac)6( L )] ? C6H14 and [Ln2(tta)6( L )] ? 2 CH2Cl2. Irradiation of the ligand at 37 040 cm?1 and 29 410 cm?1 leads to tetrathiafulvalene‐centered and 2,6‐di(pyrazol‐1‐yl)‐4‐pyridine‐centered fluorescence, respectively. The ligand acts as an organic chromophore for the sensitization of the infrared ErIII (6535 cm?1) and YbIII (10 200 cm?1) luminescence. The energies of the singlet and triplet states of L are high enough to guarantee an efficient sensitization of the visible EuIII luminescence (17 300–14 100 cm?1). The EuIII luminescence decay can be nicely fitted by a monoexponential function that allows a lifetime estimation of (0.49±0.01) ms. Finally, the magnetic and luminescence properties of [Yb2(hfac)6( L )] ? C6H14 were correlated, which allowed the determination of the crystal field splitting of the 2F7/2 multiplet state with MJ=±1/2 as ground states. 相似文献
2.
Hetero‐tri‐spin [2p‐3d‐4f] Chain Compounds Based on Nitronyl Nitroxide Lanthanide Metallo‐Ligands: Synthesis,Structure, and Magnetic Properties
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Mei Zhu Peng Hu Yungai Li Xiufeng Wang Prof. Licun Li Prof. Daizheng Liao V. M. L. Durga Prasad Goli Prof. S. Ramasesha Dr. Jean‐Pascal Sutter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13356-13365
Employing nitronyl nitroxide lanthanide(III) complexes as metallo‐ligands allowed the efficient and highly selective preparation of three series of unprecedented hetero‐tri‐spin (Cu?Ln‐radical) one‐dimensional compounds. These 2p–3d–4f spin systems, namely [Ln3Cu(hfac)11(NitPhOAll)4] (LnIII=Gd 1Gd , Tb 1Tb , Dy 1Dy ; NitPhOAll=2‐(4′‐allyloxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide), [Ln3Cu(hfac)11(NitPhOPr)4] (LnIII=Gd 2Gd , Tb 2Tb , Dy 2Dy , Ho 2Ho , Yb 2Yb ; NitPhOPr=2‐(4′‐propoxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) and [Ln3Cu(hfac)11(NitPhOBz)4] (LnIII=Gd 3Gd , Tb 3Tb , Dy 3Dy ; NitPhOBz=2‐(4′‐benzyloxyphenyl)‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide) involve O‐bound nitronyl nitroxide radicals as bridging ligands in chain structures with a [Cu‐Nit‐Ln‐Nit‐Ln‐Nit‐Ln‐Nit] repeating unit. The dc magnetic studies show that ferromagnetic metal–radical interactions take place in these hetero‐tri‐spin chain complexes, these and the next‐neighbor interactions have been quantified for the Gd derivatives. Complexes 1Tb and 2Tb exhibit frequency dependence of ac magnetic susceptibilities, indicating single‐chain magnet behavior. 相似文献
3.
《无机化学与普通化学杂志》2018,644(15):827-832
The 1:1:2 mixture of Ln(hfac)3, Zn(hfac)2, and NIT‐Pyrim (hfac = hexafluoroacetylacetonate, NIT‐Pyrim = 2‐pyrimidine‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide) afforded a series of 2p‐3d‐4f magnetic chains [Ln(hfac)3Zn(hfac)2(NIT‐Pyrim)2] [LnIII = Gd ( 1 ), Ho ( 2 ), Yb ( 3 )], in which Zn(hfac)2 and Ln(hfac)3 units are bridged by pyrimidine substituted nitronyl nitroxides through their NO moieties and pyrimidine nitrogen atoms. These complexes represent the first examples of 2p‐3d‐4f complexes with ZnII ions. Magnetic studies show that there exist ferromagnetic exchange couplings between the coordinated NO groups of radical ligands and the GdIII ions. 相似文献
4.
Xiaoling Wang Panpan Xu Xia Bao Fengwu Wang Yonghong Chen Yijun Wei 《无机化学与普通化学杂志》2013,639(1):176-180
Abstract. Two radical–LnIII–radical complexes, [Ln(hfac)3(NITPh‐Ph)2] [Ln = Gd ( 1 ) and Ho ( 2 ), hfac = hexafluoroacetylacetonate; and NITPh‐Ph = 4′‐biphenyl‐4, 4, 5, 5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide] were synthesized and characterized by X‐ray diffraction, elemental analysis, magnetic measurements, as well as IR and UV/Vis spectroscopy. X‐ray crystal structure analysis revealed that the structures of both complexes are isomorphous, the central LnIII ions are coordinated by six oxygen atoms from three hfac ligand molecules and two oxygen atoms from nitronyl radicals. The temperature dependencies of the magnetic susceptibilities were studied. They showed that in the GdIII complex, ferromagnetic interactions between GdIII and the radicals and antiferromagnetic interactions between the radicals coexist in this system (with JRad–Gd = 0.1 cm–1, JRad–Rad = –0.309 cm–1). 相似文献
5.
Three unprecedented nitronyl nitroxide radical‐bridged 3d–4f clusters, [Ln2Cu2(hfac)10(NIT‐3py)2(H2O)2](LnIII=Y, Gd, Dy), have been obtained from the self‐assembly of Ln(hfac)3, Cu(hfac)2, and the radical ligand. The Dy complex shows a slow relaxation of magnetization, representing the first nitronyl nitroxide radical‐based 3d–4f cluster with single‐molecule magnet behavior. 相似文献
6.
Haixiang Han Jesse C. Carozza Audra P. Colliton Yuxuan Zhang Zheng Wei Alexander S. Filatov Yu‐Sheng Chen Melisa Alkan Andrey Yu. Rogachev Evgeny V. Dikarev 《Angewandte Chemie (International ed. in English)》2020,59(24):9624-9630
A known trinuclear structure was used to design the heterobimetallic mixed‐valent, mixed‐ligand molecule [CoII(hfac)3?Na?CoIII(acac)3] ( 1 ). This was used as a template structure to develop heterotrimetallic molecules [CoII(hfac)3?Na?FeIII(acac)3] ( 2 ) and [NiII(hfac)3?Na?CoIII(acac)3] ( 3 ) via isovalent site‐specific substitution at either of the cobalt positions. Diffraction methods, synchrotron resonant diffraction, and multiple‐wavelength anomalous diffraction were applied beyond simple structural investigation to provide an unambiguous assignment of the positions and oxidation states for the periodic table neighbors in the heterometallic assemblies. Molecules of 2 and 3 are true heterotrimetallic rather than a statistical mixture of two heterobimetallic counterparts. Trinuclear platform 1 exhibits flexibility in accommodating a variety of di‐ and trivalent metals, which can be further utilized in the design of molecular precursors for the NaMM′O4 functional oxide materials. 相似文献
7.
Three new homodinuclear lanthanide(III) complexes [Ln2(L)6(2,2′‐bipy)2] [Ln = TbIII ( 1 ), SmIII ( 2 ), EuIII ( 3 ); HL = 3‐hydroxycinnamic acid (3‐HCA); 2,2′‐bipy = 2,2′‐bipyridine] were synthesized and characterized by IR spectroscopy, elemental analyses, and X‐ray diffraction techniques. Complexes 1 – 3 crystallize in triclinic system, space group P$\bar{1}$ . In all complexes the lanthanide ions are nine‐coordinate by two nitrogen atoms from the 2,2′‐bipy ligand and seven oxygen atoms from one chelating L ligands and four bridging L ligands, forming distorted tricapped trigonal prismatic arrangements. The lanthanide(III) ions are intramolecularly bridged by eight carboxylate oxygen atoms forming dimeric complexes with Ln ··· Ln distances of 3.92747(15), 3.9664(6), and 3.9415(4) Å for complexes 1 – 3 , respectively. The luminescent properties in the solid state of HL ligand and EuIII complex are also discussed. 相似文献
8.
Trinuclear [CoIII2–LnIII] (Ln=Tb,Dy) Single‐Ion Magnets with Mixed 6‐Chloro‐2‐Hydroxypyridine and Schiff Base Ligands
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Prof. Dr. Cai‐Ming Liu Prof. Dr. De‐Qing Zhang Prof. Dr. Xiang Hao Prof. Dao‐Ben Zhu 《化学:亚洲杂志》2014,9(7):1847-1853
The Schiff base ligand N1,N3‐bis(3‐methoxysalicylidene)diethylenetriamine (H2valdien) and the co‐ligand 6‐chloro‐2‐hydroxypyridine (Hchp) were used to construct two 3d–4f heterometallic single‐ion magnets [Co2Dy(valdien)2(OCH3)2(chp)2] ? ClO4 ? 5 H2O ( 1 ) and [Co2Tb(valdien)2(OCH3)2(chp)2] ? ClO4 ? 2 H2O ? CH3OH ( 2 ). The two trinuclear [CoIII2LnIII] complexes behave as a mononuclear LnIII magnetic system because of the presence of two diamagnetic cobalt(III) ions. Complex 1 has a molecular symmetry center, and it crystallizes in the C2/c space group, whereas complex 2 shows a lower molecular symmetry and crystallizes in the P21/c space group. Magnetic investigations indicated that both complexes are field‐induced single‐ion magnets, and the CoIII2–DyIII complex possesses a larger energy barrier [74.1(4.2) K] than the CoIII2–TbIII complex [32.3(2.6) K]. 相似文献
9.
Two C3‐Symmetric Dy3III Complexes with Triple Di‐μ‐methoxo‐μ‐phenoxo Bridges,Magnetic Ground State,and Single‐Molecule Magnetic Behavior
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Dr. Mikko M. Hänninen Prof. Dr. Antonio J. Mota Dr. Daniel Aravena Prof. Dr. Eliseo Ruiz Prof. Dr. Reijo Sillanpää Dr. Agustín Camón Dr. Marco Evangelisti Prof. Dr. Enrique Colacio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8410-8420
Two series of isostructural C3‐symmetric Ln3 complexes Ln3 ? [BPh4] and Ln3 ? 0.33[Ln(NO3)6] (in which LnIII=Gd and Dy) have been prepared from an amino‐bis(phenol) ligand. X‐ray studies reveal that LnIII ions are connected by one μ2‐phenoxo and two μ3‐methoxo bridges, thus leading to a hexagonal bipyramidal Ln3O5 bridging core in which LnIII ions exhibit a biaugmented trigonal‐prismatic geometry. Magnetic susceptibility studies and ab initio complete active space self‐consistent field (CASSCF) calculations indicate that the magnetic coupling between the DyIII ions, which possess a high axial anisotropy in the ground state, is very weakly antiferromagnetic and mainly dipolar in nature. To reduce the electronic repulsion from the coordinating oxygen atom with the shortest Dy?O distance, the local magnetic moments are oriented almost perpendicular to the Dy3 plane, thus leading to a paramagnetic ground state. CASSCF plus restricted active space state interaction (RASSI) calculations also show that the ground and first excited state of the DyIII ions are separated by approximately 150 and 177 cm?1, for Dy3 ? [BPh4] and Dy3 ? 0.33[Dy(NO3)6], respectively. As expected for these large energy gaps, Dy3 ? [BPh4] and Dy3 ? 0.33[Dy(NO3)6] exhibit, under zero direct‐current (dc) field, thermally activated slow relaxation of the magnetization, which overlap with a quantum tunneling relaxation process. Under an applied Hdc field of 1000 Oe, Dy3 ? [BPh4] exhibits two thermally activated processes with Ueff values of 34.7 and 19.5 cm?1, whereas Dy3 ? 0.33[Dy(NO3)6] shows only one activated process with Ueff=19.5 cm?1. 相似文献
10.
Xiao‐Qing Zhao Yi‐Yan Wang Dong‐Xu Bao Fen‐Hang Zhang Wei Wu Fu‐Sen Xu Qiu‐Hong Zhang Yun‐Chun Li 《应用有机金属化学》2019,33(11)
Six novel decanuclear clusters with formula of {[Fe8Ln2(O)4(OH)4(EtO)2(dhbp)4(dhbpH)2(piv)6]·4EtOH} (Ln = Y ( 1 ), Gd ( 2 ), Tb ( 3 ), Dy ( 4 ), Ho ( 5 ), Er ( 6 ), dhbpH2 = 6,6′‐dihydroxyl‐2,2′‐bipyridine, Hpiv = pivalic acid, EtOH = ethanol) have been synthesized and characterized. Single‐crystal and powder X‐ray diffraction analyses reveal that complexes 1 – 6 are isostructural and show a sandwich‐like FeIII8LnIII2 structure, in which the [Ln2] unit is sandwiched by two planar [Fe4] units. Magnetic properties of complexes 1 – 6 have been investigated and display dominant antiferromagnetic interactions, thereinto, complexes 4 and 6 display weak ferromagnetic behaviors associated with LnIII ions, while others are antiferromagnetic‐like features. Furthermore, complex 4 (FeIII8DyIII2) shows temperature/frequency‐dependent ac signals with an energy barrier of 4.1 K, indicating that complex 4 should be a single‐molecule magnet (SMM) 相似文献
11.
Amir Zaïm Dr. Homayoun Nozary Dr. Laure Guénée Dr. Céline Besnard Dr. Jean‐François Lemonnier Prof. Dr. Stéphane Petoud Prof. Dr. Claude Piguet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7155-7168
Herein, we discuss how, why, and when cascade complexation reactions produce stable, mononuclear, luminescent ternary complexes, by considering the binding of hexafluoroacetylacetonate anions (hfac?) and neutral, semi‐rigid, tridentate 2,6‐bis(benzimidazol‐2‐yl)pyridine ligands ( Lk ) to trivalent lanthanide atoms (LnIII). The solid‐state structures of [Ln( Lk )(hfac)3] (Ln=La, Eu, Lu) showed that [Ln(hfac)3] behaved as a neutral six‐coordinate lanthanide carrier with remarkable properties: 1) the strong cohesion between the trivalent cation and the didentate hfac anions prevented salt dissociation; 2) the electron‐withdrawing trifluoromethyl substituents limited charge‐neutralization and favored cascade complexation with Lk ; 3) nine‐coordination was preserved for [Ln( Lk )(hfac)3] for the complete lanthanide series, whilst a counterintuitive trend showed that the complexes formed with the smaller lanthanide elements were destabilized. Thermodynamic and NMR spectroscopic studies in solution confirmed that these characteristics were retained for solvated molecules, but the operation of concerted anion/ligand transfers with the larger cations induced subtle structural variations. Combined with the strong red photoluminescence of [Eu( Lk )(hfac)3], the ternary system LnIII/hfac?/ Lk is a promising candidate for the planned metal‐loading of preformed multi‐tridentate polymers. 相似文献
12.
Redox‐Driven Symmetry Change for Terbium(III) Bis(porphyrinato) Double‐Decker Complexes by the Azimuthal Rotation of the Porphyrin Macrocycles
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Dr. Ken‐ichi Yamashita Takayo Yamanaka Naoya Sakata Prof. Dr. Takuji Ogawa 《化学:亚洲杂志》2018,13(13):1692-1698
Molecular structures for three oxidation forms (anion, radical, and cation) of terbium(III) bis(porphyrinato) double‐decker complexes have been systematically studied. We found that the redox state controls the azimuthal rotation angle (φ) between the two porphyrin macrocycles. For [TbIII(tpp)2]n (tpp: tetraphenylporphyrinato, n=?1, 0, and +1), φ decreases at each stage of the oxidation process. The decrease in φ is due to the higher steric repulsion between the phenyl rings on the porphyrin macrocycle and the β hydrogen atoms on the other porphyrin macrocycle, which results from the shorter interfacial distance between the two porphyrin macrocycles. Conversely, φ=45° for both [TbIII(oep)2]?1 and [TbIII(oep)2]0 (oep: octaethylporphyrinato), but φ=36° for [TbIII(oep)2]+1. Theoretical calculations suggest that the smaller azimuthal rotation angle of the cation form is due to the electronic interaction in the doubly oxidized ligand system. 相似文献
13.
Ligand π‐Radical Interaction with f‐Shell Unpaired Electrons in Phthalocyaninato–Lanthanoid Single‐Molecule Magnets: A Solution NMR Spectroscopic and DFT Study
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Marko Damjanović Takaumi Morita Prof. Keiichi Katoh Prof. Masahiro Yamashita Prof. Markus Enders 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14421-14432
The phthalocyaninato double‐decker complexes [M(obPc)2]0 (M= YIII, TbIII, DyIII; obPc=2,3,9,10,16,17,23,24‐octabutoxyphthalocyaninato), along with their reduced ([M(obPc)2]?[P(Ph)4]+; M=TbIII, DyIII) and oxidized ([M(obPc)2]+[SbCl6]? (M=YIII, TbIII) counterparts were studied with 1H, 13C and 2D NMR. From the NMR data of the neutral (i.e., with one unpaired electron in the ligands) and anionic TbIII complexes, along with the use of dispersion corrected DFT methods, it was possible to separate the metal‐centered and ligand‐centered contributions to the hyperfine NMR shift. These contributions to the 1H and 13C hyperfine NMR shifts were further analyzed in terms of pseudocontact and Fermi contact shifts. Furthermore, from a combination of NMR data and DFT calculations, we have determined the spin multiplicity of the neutral complexes [M(obPc)2]0 (M=TbIII and DyIII) at room temperature. From the NMR data of the cationic TbIII complex, for which actually no experimental structure determination is available, we have analyzed the structural changes induced by oxidation from its neutral/anionic species and shown that the interligand distance decreases upon oxidation. The fast electron exchange process between the neutral and anionic TbIII double‐decker complexes was also studied. 相似文献
14.
Enhancement of TbIII–CuII Single‐Molecule Magnet Performance through Structural Modification
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María José Heras Ojea Dr. Victoria A. Milway Dr. Gunasekaran Velmurugan Dr. Lynne H. Thomas Dr. Simon J. Coles Dr. Claire Wilson Dr. Wolfgang Wernsdorfer Prof. Gopalan Rajaraman Dr. Mark Murrie 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12839-12848
We report a series of 3d–4f complexes {Ln2Cu3(H3L)2Xn} (X=OAc?, Ln=Gd, Tb or X=NO3?, Ln=Gd, Tb, Dy, Ho, Er) using the 2,2′‐(propane‐1,3‐diyldiimino)bis[2‐(hydroxylmethyl)propane‐1,3‐diol] (H6L) pro‐ligand. All complexes, except that in which Ln=Gd, show slow magnetic relaxation in zero applied dc field. A remarkable improvement of the energy barrier to reorientation of the magnetisation in the {Tb2Cu3(H3L)2Xn} complexes is seen by changing the auxiliary ligands (X=OAc? for NO3?). This leads to the largest reported relaxation barrier in zero applied dc field for a Tb/Cu‐based single‐molecule magnet. Ab initio CASSCF calculations performed on mononuclear TbIII models are employed to understand the increase in energy barrier and the calculations suggest that the difference stems from a change in the TbIII coordination environment (C4v versus Cs). 相似文献
15.
Sandeep Nadella Dr. Paulraj M. Selvakumar Dr. Eringathodi Suresh Dr. Palani S. Subramanian Prof. Dr. Markus Albrecht Dr. Michael Giese Dr. Roland Fröhlich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(52):16784-16792
Phenanthroline‐based hexadentate ligands L1 and L2 bearing two achiral semicarbazone or two chiral imine moieties as well as the respective mononuclear complexes incorporating various lanthanide ions, such as LaIII, EuIII, TbIII, LuIII, and YIII metal ions, were synthesized, and the crystal structures of [ML1Cl3] (M=LaIII, EuIII, TbIII, LuIII, or YIII) complexes were determined. Solvent or water molecules act as coligands for the rare‐earth metals in addition to halide anions. The big LnIII ion exhibits a coordination number (CN) of 10, whereas the corresponding EuIII, TbIII, LuIII, and YIII centers with smaller ionic radii show CN=9. Complexes of L2, namely [ML2Cl3] (M=EuIII, TbIII, LuIII, or YIII) ions could also be prepared. Only the complex of EuIII showed red luminescence, whereas all the others were nonluminescent. The emission properties of the Eu derivative can be applied as a photophysical signal for sensing various anions. The addition of phosphate anions leads to a unique change in the luminescence behavior. As a case study, the quenching behavior of adenosine‐5′‐triphosphate (ATP) was investigated at physiological pH value in an aqueous solvent. A specificity of the sensor for ATP relative to adenosine‐5′‐diphosphate (ADP) and adenosine‐5′‐monophosphate (AMP) was found. 31P NMR spectroscopic studies revealed the formation of a [EuL2(ATP)] coordination species. 相似文献
16.
Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties
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Dr. Maria‐Gabriela Alexandru Dr. Diana Visinescu Prof. Marius Andruh Dr. Nadia Marino Dr. Donatella Armentano Dr. Joan Cano Prof. Francesc Lloret Prof. Miguel Julve 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(14):5429-5446
The use of the [FeIII(AA)(CN)4]? complex anion as metalloligand towards the preformed [CuII(valpn)LnIII]3+ or [NiII(valpn)LnIII]3+ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H2valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[CuII(valpn)LnIII(H2O)3(μ‐NC)2FeIII(phen)(CN)2 {(μ‐NC)FeIII(phen)(CN)3}]NO3 ? 7 H2O}n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [CuII(valpn)LaIII(OH2)3(O2NO)(μ‐NC)FeIII(phen)(CN)3] ? NO3 ? H2O ? CH3CN ( 4 ) were obtained with the [CuII(valpn)LnIII]3+ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[NiII(valpn)LnIII(ONO2)2(H2O)(μ‐NC)3FeIII(bipy)(CN)] ? 2 H2O ? 2 CH3CN}n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [NiII(valpn)LnIII]3+ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [CuII(valpn)LaIII(OH2)3(O2NO)(μ‐NC)FeIII(phen)(CN)3]+, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {FeIII(bipy)(CN)4} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {NiII(valpn)LnIII} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the CuII?LnIII ( 1 – 3 ) and NiII?LnIII ( 5 – 7 ) units, as well as through the single cyanide bridge between the FeIII and either NiII ( 5 – 7 ) or CuII ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τo) and energy barrier (Ea) through the Arrhenius equation being 2.0×10?12 s and 29.1 cm?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (NiII–DyIII) and single cyanide (FeIII–NiII) pathways are masked by the depopulation of the Stark levels of the DyIII ion, this feature most likely accounting for the continuous decrease of χM T upon cooling observed for this last compound. 相似文献
17.
The Building Block [FeIII(pzphen)(CN)4]– and its Lanthanide Complexes: Synthesis,Crystal Structure,and Magnetic Properties
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Jian‐Qing Tao Wen‐Wen Ju Zhou Zhou Li‐Yong Jia Ning‐Ning Chen Yun‐Shan Xue Jun Wang Xing‐Cai Huang 《无机化学与普通化学杂志》2016,642(24):1466-1471
The cyanide building block [FeIII(pzphen)(CN)4]– and its four lanthanide complexes [{FeIII(pzphen)(CN)4}2LnIII(H2O)5(DMF)3] · (NO3) · 2(H2O) · (CH3CN) [Ln = Nd ( 1 ), Sm ( 2 ), DMF = dimethyl formamide] and [{FeIII(pzphen)(CN)4}2LnIII(NO3)(H2O)2(DMF)2](CH3CN) [Ln = Gd ( 3 ), Dy ( 4 )] were synthesized and structurally characterized by single‐crystal X‐ray diffraction. Compounds 1 and 2 are ionic salts with two [FeIII(pzphen)(CN)4]– cations and one LnIII ion, but compounds 3 and 4 are cyano‐bridged FeIII‐LnIII heterometallic 3d‐4f complexes exhibiting a trinuclear structure in the same conditions. Magnetic studies show that compound 3 is antiferromagnetic between the central FeIII and GdIII atoms. Furthermore, the trinuclear cyano‐bridged FeIII2DyIII compound 4 displays no single‐molecular magnets (SMMs) behavior by the alternating current magnetic susceptibility measurements. 相似文献
18.
Rational Electrostatic Design of Easy‐Axis Magnetic Anisotropy in a ZnII–DyIII–ZnII Single‐Molecule Magnet with a High Energy Barrier
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Itziar Oyarzabal Prof. Dr. José Ruiz Prof. Dr. José Manuel Seco Dr. Marco Evangelisti Dr. Agustín Camón Prof. Dr. Eliseo Ruiz Dr. Daniel Aravena Prof. Dr. Enrique Colacio 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14262-14269
Two novel trinuclear complexes [ZnCl(μ‐L)Ln(μ‐L)ClZn][ZnCl3(CH3OH)]?3 CH3OH (LnIII=Dy ( 1 ) and Er ( 2 )) have been prepared from the compartmental ligand N,N′‐dimethyl‐N,N′‐bis(2‐hydroxy‐3‐formyl‐5‐bromo‐benzyl)ethylenediamine (H2L). X‐ray studies reveal that LnIII ions are coordinated by two [ZnCl(L)]? units through the phenoxo and aldehyde groups, giving rise to a LnO8 coordination sphere with square‐antiprism geometry and strong easy‐axis anisotropy of the ground state. Ab initio CASSCF+RASSI calculations carried out on 1 confirm that the ground state is an almost pure MJ=±15/2 Kramers doublet with a marked axial anisotropy, the magnetic moment is roughly collinear with the shortest Dy?O distances. This orientation of the local magnetic moment of the DyIII ion in 1 is adopted to reduce the electronic repulsion between the oblate electron shape of the MJ=±15/2 Kramers doublet and the phenoxo‐oxygen donor atoms involved in the shortest Dy?O bonds. CASSCF+RASSI calculations also show that the ground and first excited states of the DyIII ion are separated by 129 cm?1. As expected for this large energy gap, compound 1 exhibits, in a zero direct‐current field, thermally activated slow relaxation of the magnetization with a large Ueff=140 K. The isostructural Zn–Er–Zn species does not present significant SMM behavior as expected for the prolate electron‐density distribution of the ErIII ion leading to an easy‐plane anisotropy of the ground doublet state. 相似文献
19.
《化学:亚洲杂志》2017,12(5):507-514
Five hexanuclear lanthanide clusters of composition [Ln6(μ4‐O)2(HCOO)2L4(HL′)2(dmf)2] [Ln=Dy ( 1 ), Er ( 2 ), Ho ( 3 ), Tb ( 4 ), Gd ( 5 ); H2L=2‐{[2‐(hydroxymethyl)phenylimino]methyl}‐6‐methoxyphenol; H3L′=3‐{[2‐(hydroxymethyl)phenylimino]methyl}benzene‐1,2‐diol; H3L′ was derived in situ from the H2L ligand] were prepared under solvothermal conditions. The [Ln6] cores of 1 – 5 possess an unprecedented motif, namely, two tetrahedron Ln4 units sharing an edge and two vertices. The six LnIII ions of 1 – 5 are connected through two μ4‐O anions. Magnetic susceptibility studies reveal that complex 1 exhibits frequency dependence of the alternating current susceptibility typical of single‐molecule magnets. Complex 1 possesses a relatively large energy barrier of 85 K among all of the reported Dy6 single‐molecule magnets. 相似文献
20.
Amit Das Dipl.‐Chem. Thomas Michael Scherer Prasenjit Mondal Dr. Shaikh M. Mobin Prof. Dr. Wolfgang Kaim Prof. Dr. Goutam Kumar Lahiri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(45):14434-14443
New compounds [Ru(pap)2(L)](ClO4), [Ru(pap)(L)2], and [Ru(acac)2(L)] (pap=2‐phenylazopyridine, L?=9‐oxidophenalenone, acac?=2,4‐pentanedionate) have been prepared and studied regarding their electron‐transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)2(L)](ClO4) and [Ru(acac)2(L)] were characterized by crystal‐structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the RuIII/II couple, which was in agreement with the very different characteristics of the strongly π‐accepting pap ligand and the σ‐donating acac? ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L? into L. could be deduced from the near‐IR absorption of [RuIII(pap)(L.)(L?)]2+. Other intense long‐wavelength transitions, including LMCT (L?→RuIII) and LL/CT (pap.?→L?) processes, were confirmed by TD‐DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L‐radical‐involving forms, that is, [RuIII(pap0)2(L?)]2+?[RuII(pap0)2(L.)]2+ and [RuIII(pap0)(L?)2]+?[RuII(pap0)(L?)(L?)]+. Calculations of electrogenerated complex [RuII(pap.?)(pap0)(L?)] displayed considerable negative spin density (?0.188) at the bridging metal. 相似文献