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1.
Yin‐Shan Meng Jin Xiong Mu‐Wen Yang Yu‐Sen Qiao Zhi‐Qiang Zhong Hao‐Ling Sun Jun‐Bo Han Tao Liu Bing‐Wu Wang Song Gao 《Angewandte Chemie (International ed. in English)》2020,59(31):13037-13043
We investigate a family of dinuclear dysprosium metallocene single‐molecule magnets (SMMs) bridged by methyl and halogen groups [Cp′2Dy(μ‐X)]2 (Cp′=cyclopentadienyltrimethylsilane anion; 1 : X=CH3?; 2 : X=Cl?; 3 : X=Br?; 4 : X=I?). For the first time, the magnetic easy axes of dysprosium metallocene SMMs are experimentally determined, confirming that the orientation of them are perpendicular to the equatorial plane which is made up of dysprosium and bridging atoms. The orientation of the magnetic easy axis for 1 deviates from the normal direction (by 10.3°) due to the stronger equatorial interactions between DyIII and methyl groups. Moreover, its magnetic axes show a temperature‐dependent shifting, which is caused by the competition between exchange interactions and Zeeman interactions. Studies of fluorescence and specific heat as well as ab initio calculations reveal the significant influences of the bridging ligands on their low‐lying exchange‐based energy levels and, consequently, low‐temperature magnetic properties. 相似文献
2.
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
3.
Jun‐Liang Liu Wei‐Quan Lin Yan‐Cong Chen Silvia Gómez‐Coca Daniel Aravena Prof. Dr. Eliseo Ruiz Ji‐Dong Leng Prof. Dr. Ming‐Liang Tong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(51):17567-17577
A series of heterometallic [LnIIIxCuIIy] complexes, [Gd2Cu2]n ( 1 ), [Gd4Cu8] ( 2 ), [Ln9Cu8] (Ln=Gd, 3?Gd ; Ln=Dy, 3?Dy ), were successfully synthesized by a one‐pot route at room temperature with three kinds of in situ carbonyl‐related reactions: Cannizzaro reaction, aldol reaction, and oxidation. This strategy led to dysprosium analogues that behaved as single‐molecule magnets (SMMs) and gadolinium analogues that showed significant magnetocaloric effect (MCE). In this study a numerical DFT approach is proposed by using pseudopotentials to calculate the exchange coupling constants in three polynuclear [GdxCuy] complexes; with these values exact diagonalization or quantum Monte Carlo simulations have been performed to calculate the variation of the magnetic entropy involved in the MCE. For the [Dy9Cu8] complexes, local magnetic properties of the DyIII centers have been determined by using the CASSCF+RASSI method. 相似文献
4.
Dr. Fabio Carniato Dr. Lorenzo Tei Prof. Maurizio Cossi Prof. Leonardo Marchese Prof. Mauro Botta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(35):10727-10734
Functionalised MCM‐41 mesoporous silica nanoparticles were used as carriers of GdIII complexes for the development of nanosized magnetic resonance imaging contrast agents. Three GdIII complexes based on the 1,4,7,10‐tetraazacyclododecane scaffold (DOTA; monoamide‐, DOTA‐ and DO3A‐like complexes) with distinct structural and magnetic properties were anchored on the silica nanoparticles functionalised with NH2 groups. The interaction between GdIII chelates and surface functional groups markedly influenced the relaxometric properties of the hybrid materials, and were deeply modified passing from ionic ? NH3+ to neutral amides. A complete study of the structural, textural and surface properties together with a full 1H relaxometric characterisation of these hybrid materials before and after surface modification was carried out. Particularly for the anionic complex 2 attached to MCM‐41, an impressive increase in relaxivity (r1p) was observed (from 20.3 to 37.8 mM ?1 s?1, 86.2 % enhancement at 20 MHz and 310 K), mainly due to a threefold faster water exchange rate after acetylation of the surface ? NH3+ ions. This high r1p value, coupled with the large molar amount of grafted 2 onto the silica nanoparticles gives rise to a value of relaxivity per particle of 29 500 mM ?1 s?1, which possibly allows it to be used in molecular imaging procedures. Smaller changes were observed for the hybrid materials based on neutral 1 and 3 complexes. In fact, whereas 1 shows a weak interaction with the surface and acetylation induced only some decrease of the local rotation, complex 3 appears to be involved in a strong interaction with surface silanols. This results in the displacement of a coordinated water molecule and in a decrease of the accessibility of the solvent to the metal centre, which is unaffected by the modification of ammonium ions to neutral amides. 相似文献
5.
Lena Scherthan Sebastian F. M. Schmidt Hendrik Auerbach Tim Hochdrffer Juliusz A. Wolny Wenli Bi Jiyong Zhao Michael Y. Hu Tom Toellner E. Ercan Alp Dennis E. Brown Christopher E. Anson Annie K. Powell Volker Schünemann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3482-3487
Time‐domain synchrotron Mössbauer spectroscopy (SMS) based on the Mössbauer effect of 161Dy has been used to investigate the magnetic properties of a DyIII‐based single‐molecule magnet (SMM). The magnetic hyperfine field of [Dy(Cy3PO)2(H2O)5]Br3?2 (Cy3PO)?2 H2O?2 EtOH is with B0=582.3(5) T significantly larger than that of the free‐ion DyIII with a 6H15/2 ground state. This difference is attributed to the influence of the coordinating ligands on the Fermi contact interaction between the s and 4f electrons of the DyIII ion. This study demonstrates that 161Dy SMS is an effective local probe of the influence of the coordinating ligands on the magnetic structure of Dy‐containing compounds. 相似文献
6.
Preparation of Highly Efficient MRI Contrast Agents through Complexation of Cationic GdIII‐Containing Metallosurfactant with Biocompatible Polyelectrolytes
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Yingying Chen Qin Zhu Xinghui Cui Weijun Tang Heng Yang Prof. Yuan Yuan Prof. Aiguo Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12477-12482
Novel contrast agents were developed through assembling of GdIII‐containing metallosurfactant (MS) with biocompatible polyelectrolytes sodium hyaluronate (HA), heparinsodium (HS) and dextran sulfate sodium (DSS). The formed polyelectrolyte–surfactant complexes showed different structural patterns as the charge ratio increased, including spherical aggregates, rod‐like aggregates and network patterns in monovalent HA system, while spherical structures emerged in multivalent HS and DSS systems. Energy dispersive spectroscopy analysis and scanning electron microscopy mapping showed the presence of GdIII in these complexes. Inductively coupled plasma atomic emission spectrometry was further used to quantify the contents of GdIII in the assemblies. T1 magnetic resonance imaging showed that these GdIII‐loaded complexes exhibited relaxivity of up to 63.81 mM ?1 s?1, much higher than that of Ominiscan (4.64 mM ?1 s?1). The cytotoxicity test in vitro demonstrated the excellent biocompatibility of these complexes, which is essential for clinical application. 相似文献
7.
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
8.
Six‐Coordinate Lanthanide Complexes: Slow Relaxation of Magnetization in the Dysprosium(III) Complex
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Dr. Bo Na Xue‐Jing Zhang Prof. Dr. Wei Shi Prof. Dr. Yi‐Quan Zhang Prof. Dr. Bing‐Wu Wang Chen Gao Prof. Dr. Song Gao Prof. Dr. Peng Cheng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15975-15980
A series of six‐coordinate lanthanide complexes {(H3O)[Ln(NA)2]?H2O}n (H2NA=5‐hydroxynicotinic acid; Ln=GdIII ( 1?Gd ); TbIII ( 2?Tb ); DyIII ( 3?Dy ); HoIII ( 4?Ho )) have been synthesized from aqueous solution and fully characterized. Slow relaxation of the magnetization was observed in 3?Dy . To suppress the quantum tunneling of the magnetization, 3?Dy diluted by diamagnetic YIII ions was also synthesized and magnetically studied. Interesting butterfly‐like hysteresis loops and an enhanced energy barrier for the slow relaxation of magnetization were observed in diluted 3?Dy . The energy barrier (Δτ) and pre‐exponential factor (τ0) of the diluted 3?Dy are 75 K and 4.21×10?5 s, respectively. This work illustrates a successful way to obtain low‐coordination‐number lanthanide complexes by a framework approach to show single‐ion‐magnet‐like behavior. 相似文献
9.
White Light Emissive DyIII Single‐Molecule Magnets Sensitized by Diamagnetic [CoIII(CN)6]3− Linkers
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Dr. Szymon Chorazy Dr. Michał Rams Dr. Koji Nakabayashi Prof. Dr. Barbara Sieklucka Prof. Dr. Shin‐ichi Ohkoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7371-7375
The self‐assembly of DyIII–3‐hydroxypyridine (3‐OHpy) complexes with hexacyanidocobaltate(III) anions in water produces cyanido‐bridged {[DyIII(3‐OHpy)2(H2O)4] [CoIII(CN)6]}?H2O ( 1 ) chains. They reveal a single‐molecule magnet (SMM) behavior with a large zero direct current (dc) field energy barrier, ΔE=266(12) cm?1 (≈385 K), originating from the single‐ion property of eight‐coordinated DyIII of an elongated dodecahedral geometry, which are embedded with diamagnetic [CoIII(CN)6]3? ions into zig‐zag coordination chains. The SMM character is enhanced by the external dc magnetic field, which results in the ΔE of 320(23) cm?1 (≈460 K) at Hdc=1 kOe, and the opening of a butterfly hysteresis loop below 6 K. Complex 1 exhibits white DyIII‐based emission realized by energy transfer from CoIII and 3‐OHpy to DyIII. Low temperature emission spectra were correlated with SMM property giving the estimation of the zero field ΔE. 1 is a unique example of bifunctional magneto‐luminescent material combining white emission and slow magnetic relaxation with a large energy barrier, both controlled by rich structural and electronic interplay between DyIII, 3‐OHpy, and [CoIII(CN)6]3?. 相似文献
10.
Large Hexadecametallic {MnIII–LnIII} Wheels: Synthesis,Structural, Magnetic,and Theoretical Characterization
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Kuduva R. Vignesh Dr. Stuart K. Langley Dr. Boujemaa Moubaraki Prof. Keith S. Murray Prof. Gopalan Rajaraman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16364-16369
The synthesis, gas sorption studies, magnetic properties, and theoretical studies of new molecular wheels of core type {MnIII8LnIII8} (Ln=Dy, Ho, Er, Y and Yb), using the ligand mdeaH2, in the presence of ortho‐toluic or benzoic acid are reported. From the seven wheels studied the {Mn8Dy8} and {Mn8Y8} analogues exhibit SMM behavior as determined from ac susceptibility experiments in a zero static magnetic field. From DFT calculations a S=16 ground state was determined for the {Mn8Y8} complex due to weak ferromagnetic MnIII–MnIII interactions. Ab initio CASSCF+RASSI‐SO calculations on the {Mn8Dy8} wheel estimated the MnIII–DyIII exchange interaction as ?0.1 cm?1. This weak exchange along with unfavorable single‐ion anisotropy of DyIII/MnIII ions, however, led to the observation of SMM behavior with fast magnetic relaxation. The orientation of the g‐anisotropy of the DyIII ions is found to be perpendicular to the plane of the wheel and this suggests the possibility of toroidal magnetic moments in the cluster. The {Mn8Ln8} clusters reported here are the largest heterometallic MnIIILnIII wheels and the largest {3d–4f} wheels to exhibit SMM behavior reported to date. 相似文献
11.
Ju‐Wen Zhang Yi Man Yu‐Ning Ren Wen‐Hua Liu Bin‐Qiu Liu Yan‐Ping Dong 《无机化学与普通化学杂志》2019,645(6-7):580-587
The syntheses and crystal structures of eight lanthanide complexes with formula [Ln(2,5‐DCB)x(phen)y] are reported, which are characterized via single‐crystal, powder X‐ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis, photoluminescence measurement, and DC/AC magnetic measurement. These eight complexes are isostructural, and possess a discrete dinuclear structure. The adjacent dinuclear molecules are linked by the hydrogen bonding interactions into a one‐dimensional (1D) supramolecular chain. The neighboring 1D chains are further extended into a two‐dimensional (2D) supramolecular layer by the π–π stacking interactions. The photoluminescent properties of complexes 1 (NdIII), 2 (SmIII), 3 (EuIII), 5 (TbIII), 6 (DyIII), and 8 (YbIII) were investigated. Magnetic investigations also reveal the presence of ferromagnetic interactions in complexes 4 (GdIII), 6 (DyIII), and 7 (ErIII). Additionally, complex 6 (DyIII) demonstrates field‐induced slow magnetic relaxation behavior. 相似文献
12.
Angelos B. Canaj Sourav Dey Emma Regincs Martí Claire Wilson Gopalan Rajaraman Mark Murrie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14284-14289
Following a novel synthetic strategy where the strong uniaxial ligand field generated by the Ph3SiO? (Ph3SiO?=anion of triphenylsilanol) and the 2,4‐di‐tBu‐PhO? (2,4‐di‐tBu‐PhO?=anion of 2,4‐di‐tertbutylphenol) ligands combined with the weak equatorial field of the ligand LN6 , leads to [DyIII(LN6)(2,4‐di‐tBu‐PhO)2](PF6) ( 1 ), [DyIII(LN6)(Ph3SiO)2](PF6) ( 2 ) and [DyIII(LN6)(Ph3SiO)2](BPh4) ( 3 ) hexagonal bipyramidal dysprosium(III) single‐molecule magnets (SMMs) with high anisotropy barriers of Ueff=973 K for 1 , Ueff=1080 K for 2 and Ueff=1124 K for 3 under zero applied dc field. Ab initio calculations predict that the dominant magnetization reversal barrier of these complexes expands up to the 3rd Kramers doublet, thus revealing for the first time the exceptional uniaxial magnetic anisotropy that even the six equatorial donor atoms fail to negate, opening up the possibility to other higher‐order symmetry SMMs. 相似文献
13.
Dr. Loïck Moriggi Dr. Mohammad A. Yaseen Prof. Lothar Helm Prof. Peter Caravan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3675-3686
The objective of this work was the synthesis of serum albumin targeted, GdIII‐based magnetic resonance imaging (MRI) contrast agents exhibiting a strong pH‐dependent relaxivity. Two new complexes ( Gd‐glu and Gd‐bbu ) were synthesized based on the DO3A macrocycle modified with three carboxyalkyl substituents α to the three ring nitrogen atoms, and a biphenylsulfonamide arm. The sulfonamide nitrogen coordinates the Gd in a pH‐dependent fashion, resulting in a decrease in the hydration state, q, as pH is increased and a resultant decrease in relaxivity (r1). In the absence of human serum albumin (HSA), r1 increases from 2.0 to 6.0 mM ?1 s?1 for Gd‐glu and from 2.4 to 9.0 mM ?1 s?1 for Gd‐bbu from pH 5 to 8.5 at 37 °C, 0.47 T, respectively. These complexes (0.2 mM ) are bound (>98.9 %) to HSA (0.69 mM ) over the pH range 5–8.5. Binding to albumin increases the rotational correlation time and results in higher relaxivity. The r1 increased 120 % (pH 5) and 550 % (pH 8.5) for Gd‐glu and 42 % (pH 5) and 260 % (pH 8.5) for Gd‐bbu . The increases in r1 at pH 5 were unexpectedly low for a putative slow tumbling q=2 complex. The Gd‐bbu system was investigated further. At pH 5, it binds in a stepwise fashion to HSA with dissociation constants Kd1=0.65, Kd2=18, Kd3=1360 μM . The relaxivity at each binding site was constant. Luminescence lifetime titration experiments with the EuIII analogue revealed that the inner‐sphere water ligands are displaced when the complex binds to HSA resulting in lower than expected r1 at pH 5. Variable pH and temperature nuclear magnetic relaxation dispersion (NMRD) studies showed that the increased r1 of the albumin‐bound q=0 complexes is due to the presence of a nearby water molecule with a long residency time (1–2 ns). The distance between this water molecule and the Gd ion changes with pH resulting in albumin‐bound pH‐dependent relaxivity. 相似文献
14.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(34):10237-10241
Assembly of the triangular, organic radical‐bridged complexes Cp*6Ln3(μ3‐HAN) (Cp*=pentamethylcyclopentadienyl; Ln=Gd, Tb, Dy; HAN=hexaazatrinaphthylene) proceeds through the reaction of Cp*2Ln(BPh4) with HAN under strongly reducing conditions. Significantly, magnetic susceptibility measurements of these complexes support effective magnetic coupling of all three LnIII centers through the HAN3−. radical ligand. Thorough investigation of the DyIII congener through both ac susceptibility and dc magnetic relaxation measurements reveals slow relaxation of the magnetization, with an effective thermal relaxation barrier of Ueff=51 cm−1. Magnetic coupling in the DyIII complex enables a large remnant magnetization at temperatures up to 3.0 K in the magnetic hysteresis measurements and hysteresis loops that are open at zero‐field up to 3.5 K. 相似文献
15.
Silvio Aime Eliana Gianolio Davide Corpillo Camilla Cavallotti Giovanni Palmisano Massimo Sisti GiovanniB. Giovenzana Roberto Pagliarin 《Helvetica chimica acta》2003,86(3):615-632
The three novel pyridine‐containing 12‐membered macrocyclic ligands 1 – 3 were synthesized. The coordinating arms are represented by three acetate moieties in 1 and 3 and by one acetate and two phosphonate moieties in 2 . In all three ligands, the acetate arm in the distal position is substituted, with a benzyl group in 1 and 2 and with an arylmethyl moiety in 3 . The relaxivities r1p (20 MHz, 25°) of GdIII complexes are: GD?1 , r1p=8.3 mM ?1 s?1; GD?2 , r1p8.1 mM ?1 s?1; Gd?3 , r1p10.5 mM ?1 s?1. 1H‐NMRD and 17O‐NMR T2 data show that Gd?1 and Gd?3 contain two H2O molecules in the inner sphere, whereas the presence of two phosphonate arms allows the coordination of only one H2O molecule in Gd?2 . Interestingly, the exchange lifetime of coordinated H2O in the three complexes is similar in spite of the difference in the coordination number of the GdIII ion (i.e., 9 in Gd?1 and Gd?3 , and 8 in Gd?2 ). 1H‐Relaxometric measurements at different pH and in the presence of lactate and oxalate were carried out to get some insight into the formation of ternary complexes from Gd?1 and Gd?3 . Finally, it was found that binding to human‐serum albumin (HSA) of Gd?1 and Gd?2 , though weak, yields limited relaxivity enhancements, likely as a consequence of effects on the hydration sphere caused by donor atoms on the surface of the protein. 相似文献
16.
Exchange coupling and magnetic anisotropy in a family of bipyrimidyl radical‐bridged dilanthanide complexes: Density functional theory and ab initio calculations
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The origin of the magnetic anisotropy energy barriers in a series of bpym? (bpym = 2,2′‐bipyrimidine) radical‐bridged dilanthanide complexes [(Cp*2Ln)2(μ‐bpym)]+ [Cp* = pentamethylcyclopentadienyl; Ln = GdIII ( 1 ), TbIII ( 2 ), DyIII ( 3 ), HoIII ( 4 ), ErIII ( 5 )] has been explored using density functional theory (DFT) and ab initio methods. DFT calculations show that the exchange coupling between the two lanthanide ions for each complex is very weak, but the antiferromagnetic Ln‐bpym? couplings are strong. Ab initio calculations show that the effective energy barrier of 2 or 3 mainly comes from the contribution of a single TbIII or DyIII fragment, which is only about one third of a single Ln energy barrier. For 4 or 5 , however, both of the two HoIII or ErIII fragments contribute to the total energy barrier. Thus, it is insufficient to only increase the magnetic anisotropy energy barrier of a single Ln ion, while enhancing the Ln‐bpym? couplings is also very important. © 2014 Wiley Periodicals, Inc. 相似文献
17.
Dr. Xin-Da Huang Xiu-Fang Ma Prof. Dr. Li-Min Zheng 《Angewandte Chemie (International ed. in English)》2023,62(15):e202300088
Photo-responsive lanthanide-based single-molecule magnets (SMM) hold great promise for future switching and memory devices. Herein, we report a dysprosium phosphonate [DyIII(SCN)2(NO3)(depma)2(4-hpy)2] ( 1Dy ), which features a supramolecular framework containing layers of hydrogen-bonding network and pillars of π–π interacted anthracene units. The photocycloaddition reaction of anthracene pairs led to a rapid and reversible single-crystal-to-single-crystal (SC–SC) structural transition to form the 1D coordination polymer [DyIII(SCN)2(NO3)(depma2)(4-hpy)2]n ( 2Dy ), accompanied by photoswitchable SMM properties with the reduction of effective energy barrier by half and the narrowing of the butterfly-like hysteresis loop. The diluted sample showed a photo-induced switch of the blocking temperature (TB) from 3.8 K for 1Dy@Y to 2.6 K for 2Dy@Y . This work may inspire the construction of lanthanide-based molecular materials with targeted photo-responsive magnetic properties. 相似文献
18.
Role of Magnetic Exchange Interactions in the Magnetization Relaxation of {3d–4f} Single‐Molecule Magnets: A Theoretical Perspective
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Dr. Saurabh Kumar Singh Mohammad Faizan Beg Prof. Dr. Gopalan Rajaraman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):672-680
Combined density functional and ab initio calculations are performed on two isomorphous tetranuclear {Ni3IIILnIII} star‐type complexes [Ln=Gd ( 1 ), Dy ( 2 )] to shed light on the mechanism of magnetic exchange in 1 and the origin of the slow magnetization relaxation in complex 2 . DFT calculations correctly reproduce the sign and magnitude of the J values compared to the experiments for complex 1 . Acute ?Ni?O?Gd bond angles present in 1 instigate a significant interaction between the 4fxyz orbital of the GdIII ion and 3d orbital of the NiII ions, leading to rare and strong antiferromagnetic Ni???Gd interactions. Calculations reveal the presence of a strong next‐nearest‐neighbour Ni???Ni antiferromagnetic interaction in complex 1 leading to spin frustration behavior. CASSCF+RASSI‐SO calculations performed on complex 2 suggest that the octahedral environment around the DyIII ion is neither strong enough to stabilize the mJ |±15/2〉 as the ground state nor able to achieve a large ground‐state–first‐excited‐state gap. The ground‐state Kramers doublet for the DyIII ion is found to be the mJ |±13/2〉 state with a significant transverse anisotropy, leading to very strong quantum tunneling of magnetization (QTM). Using the POLY_ANISO program, we have extracted the JNiDy interaction as ?1.45 cm?1. The strong Ni???Dy and next‐nearest‐neighbour Ni???Ni interactions are found to quench the QTM to a certain extent, resulting in zero‐field SMM behavior for complex 2 . The absence of any ac signals at zero field for the structurally similar [Dy(AlMe4)3] highlights the importance of both the Ni???Dy and the Ni???Ni interactions in the magnetization relaxation of complex 2 . To the best of our knowledge, this is the first time that the roles of both the Ni???Dy and Ni???Ni interactions in magnetization relaxation of a {3d–4f} molecular magnet have been established. 相似文献
19.
《中国化学快报》2023,34(8):108055
The combination of cyclopentadiene, β-diketonate and tripyrazoylborate ligands with dysprosium ion afforded five mononuclear compounds: [(Cp)2Dy(Tp*)] (1Dy), [(Cp)Dy(Tp*)Cl(THF)] (2Dy), [(Cp)Dy(Tp)Cl(THF)] (3Dy), [(DBM)Dy(Tp)Cl(THF)] (4Dy), [{(Tp)Dy(DBM)2(H2O)}·THF] (5Dy) (Cp = cyclopentadiene; Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; Tp = hydrotris(1-pyrazolyl)borate; DBM = dibenzoylmethanoate). Magnetic study revealed that 1Dy and 3Dy exhibited typical butterfly-type hysteresis. AC susceptibility study combined with ab initio calculations indicated that the magnetic relaxation behaviors of 1Dy–4Dy were governed by the Orbach and Raman processes under applied DC field. Moreover, 3Dy showed two-step magnetic relaxation, which was attributed to the static disordering of the coordinated THF molecule. Magnetic anisotropy analysis indicated that it was the relative strength of the interactions between DyIII and surrounding ligands that determined the orientation of the magnetic easy axis. 相似文献
20.
Dr. F. Pointillart T. Guizouarn B. Lefeuvre Dr. S. Golhen Dr. O. Cador Dr. L. Ouahab 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):16929-16934
The rational synthesis of the 2‐{1‐methylpyridine‐N‐oxide‐4,5‐[4,5‐bis(propylthio)tetrathiafulvalenyl]‐1H‐benzimidazol‐2‐yl}pyridine ligand ( L ) is described. It led to the tetranuclear complex [Dy4(tta)12( L )2] ( Dy‐Dy2‐Dy ) after coordination reaction with the precursor Dy(tta)3?2 H2O (tta?=2‐thenoyltrifluoroacetonate). The X‐ray structure of Dy‐Dy2‐Dy can be described as two terminal mononuclear units bridged by a central antiferromagnetically coupled dinuclear complex. The terminal N2O6 and central O8 environments are described as distorted square antiprisms. The ac magnetism measurements revealed a strong out‐of‐phase signal of the magnetic susceptibility with two distinct sets of data. The high‐ and low‐frequency components were attributed to the two terminal mononuclear single‐molecule magnets (SMMs) and the central dinuclear SMM, respectively. A magnetic hysteresis loop was detected at very low temperature. From both structural and magnetic points of view, the tetranuclear SMM Dy‐Dy2‐Dy is a self‐assembly of two known mononuclear SMMs bridged by a known dinuclear SMM. 相似文献