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121.
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基于席夫碱分隔配体H2vanophen(1,2-苯二胺缩邻香草醛),通过引入不同的阴离子,构筑了3个Cu-Tb基金属配合物[Cu2(vanophen)2TbCl2(MeOH)2]Cl·3MeOH(1)、[Cu2(vanophen)2TbCl2(MeOH)2](TCNQ)1.5·2MeOH(2)和[Cu2(vanophen)2Tb2(N3)6]·2MeOH(3)(TCNQ=7,7,8,8-四氰基对苯二醌二甲烷),并详细研究了它们的结构和磁性。除了抗衡阴离子外,配合物1和2具有非常相似的[CuTbCu]三核结构;其中Cu(Ⅱ)离子处于席夫碱配体中的[N2O2]配位口袋中,而Tb(Ⅲ)离子则和配体中的[O4]配位口袋中的全部或部分O原子配位。对应于一个三核基元,配合物1中的抗衡阴离子为一个Cl-离子,而配合物2中的抗衡阴离子是一个TCNQ-0.5阴离子及半个TCNQ-阴离子。配合物3是由end-end及end-on叠氮桥联2个[CuTb]单元形成的四核[CuTb]2配合物。磁性研究表明,三核配合物1和2均为场致的单分子磁体而配合物3为零场单分子磁体,其中配合物1和3的能垒分别为(11.1±0.3) cm-1和(20.2±0.3) cm-1。相比于配合物1,配合物2具有更低的能垒,这可能源于其中的阴离子自由基和三核[CuTbCu]基元之间的弱的磁相互作用。 相似文献
123.
Raul Berrocal-Martin Dr. Carlos Sanchez-Cano Dr. Cookson K. C. Chiu Dr. Russell J. Needham Prof. Peter J. Sadler Dr. Steven W. Magennis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4980-4987
The metallation of nucleic acids is key to wide-ranging applications, from anticancer medicine to nanomaterials, yet there is a lack of understanding of the molecular-level effects of metallation. Here, we apply single-molecule fluorescence methods to study the reaction of an organo-osmium anticancer complex and DNA. Individual metallated DNA hairpins are characterised using Förster resonance energy transfer (FRET). Although ensemble measurements suggest a simple two-state system, single-molecule experiments reveal an underlying heterogeneity in the oligonucleotide dynamics, attributable to different degrees of metallation of the GC-rich hairpin stem. Metallated hairpins display fast two-state transitions with a two-fold increase in the opening rate to ≈2 s−1, relative to the unmodified hairpin, and relatively static conformations with long-lived open (and closed) states of 5 to ≥50 s. These studies show that a single-molecule approach can provide new insight into metallation-induced changes in DNA structure and dynamics. 相似文献
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125.
Dr. Djamila Guettas Dr. Frédéric Gendron Dr. Guglielmo Fernandez Garcia Dr. François Riobé Dr. Thierry Roisnel Dr. Olivier Maury Dr. Guillaume Pilet Prof. Olivier Cador Dr. Boris Le Guennic 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4389-4395
A textbook dysprosium dinuclear complex based on acetylacetone ligands, [Dy2(acac)4(μ2-acac)2(H2O)2], has been synthesized and fully characterized. This simple dimeric lanthanide complex shows well-resolved solid-state luminescence and behaves as a single-molecule magnet under zero DC field. A seminal crystal-field approach is used to marry both magnetism and luminescence in the frame of an energetic picture. 相似文献
126.
Hagen Kaemmerer Dr. Valeriu Mereacre Dr. Ayuk M. Ako Dr. Samir Mameri Dr. Christopher E. Anson Dr. Rodolphe Clérac Prof. Annie K. Powell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(61):15096-15102
In an assisted self-assembly approach starting from the [Mn6O2(piv)10(4-Me-py)2(pivH)2] cluster a family of Mn−Ln compounds (Ln=Pr−Yb) was synthesised. The reaction of [Mn6O2(piv)10(4-Me-py)2(pivH)2] ( 1 ) with N-methyldiethanolamine (mdeaH2) and Ln(NO3)3 ⋅ 6H2O in MeCN generally yields two main structure types: for Ln=Tb−Yb a previously reported Mn5Ln4 motif is obtained, whereas for Ln=Pr−Eu a series of Mn7Ln3 clusters is obtained. Within this series the GdIII analogue represents a special case because it shows both structural types as well as a third Mn2Ln2 inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn7Ln3 analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=NdIII( 2 ), SmIII( 3 ) and GdIII ( 5 ) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K. 相似文献
127.
Dr. Joana T. Coutinho Dr. Mauro Perfetti Dr. José J. Baldoví Dr. Maria A. Antunes Philipp P. Hallmen Heiko Bamberger Dr. Iris Crassee Dr. Milan Orlita Prof. Manuel Almeida Prof. Joris van Slageren Dr. Laura C. J. Pereira 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1758-1766
Early actinide ions have large spin-orbit couplings and crystal field interactions, leading to large anisotropies. The success in using actinides as single-molecule magnets has so far been modest, underlining the need for rational strategies. Indeed, the electronic structure of actinide single-molecule magnets and its relation to their magnetic properties remains largely unexplored. A uranium(III) single-molecule magnet, [UIII{SiMe2NPh}3-tacn)(OPPh3)] (tacn=1,4,7-triazacyclononane), has been investigated by means of a combination of magnetic, spectroscopic and theoretical methods to elucidate the origin of its static and dynamic magnetic properties. 相似文献
128.
Alejandro V. Funes Dr. Luca Carrella Prof. Dr. Eva Rentschler Prof. Dr. Pablo Alborés 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(40):14308-14318
We have prepared and structurally characterized a new member of the butterfly‐like {CoIII2DyIII2} single‐molecule magnets (SMMs) through further CoIII decoration, with the formula [CoIII4DyIII2(OH)2(teaH)2(tea)2(Piv)6] (teaH3=triethanolamine; Piv=trimethylacetate or pivalate). Direct current (DC) susceptibility and magnetization measurements were performed allowing the extraction of possible crystal‐field parameters. A simple electrostatic modeling shows reasonable agreement with experimental data. Alternating current (AC) susceptibility measurements under a zero DC field and under small applied fields were performed at different frequencies (i.e., 10–1500 Hz) and at low temperatures (i.e., 2–10 K). Multiple magnetization relaxation pathways are observed. Comparison with previously reported {CoIII2DyIII2} complex measurements allows an overall discussion about the origin of the dynamic behavior and its relationship with crystal‐field split ground multiplet sublevels. 相似文献
129.
Fine Tuning of the Anisotropy Barrier by Ligand Substitution Observed in Linear {Dy2Ni2} Clusters 下载免费PDF全文
Dr. Yan Li Qiu Shang Dr. Yi‐Quan Zhang Prof. Dr. En‐Cui Yang Prof. Dr. Xiao‐Jun Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18840-18849
Three new heterometallic single‐molecule magnets (SMMs), [Dy2Ni2(bipy)2(RC6H4COO)10] [bipy=2,2′‐bipyridine, R=H ( 1 ), CH3 ( 2 ), and NO2 ( 3 )], are synthesized solvothermally with different 3‐substituted benzoate ligands (RC6H4COO?), and are characterized both structurally and magnetically. Structural analyses reveal that the three entities are structurally analogous, exhibiting an approximately linear {Dy2Ni2} core bridged by ten carboxylate moieties from the RC6H4COO? ligands. A noncoordinating substituent group attached on the phenyl ring results in minor geometry distortions of 1 – 3 , but causes a significant decrease in the Mulliken atomic charge on the axially shortest O donor through inductive and/or conjugative effects. Weak intramolecular ferromagnetic (for DyIII???DyIII) and antiferromagnetic (for DyIII???NiII) interactions with slightly different coupling strengths are observed in 1 – 3 at low temperatures, and the effective anisotropy barriers to block the magnetization reversal are 39.9, 25.9, and 2.8 cm?1, respectively, under zero direct‐current field. Ab initio calculations reveal that ligand substitution by the noncoordinating electron‐withdrawing/electron‐donating group can give rise to good modulation of the energy gap between the two lowest Kramers doublets, as well as the orientation of the local easy axis of the DyIII ion magnetization. The directions of the local easy axis of the DyIII ion can further influence the dipole spin–spin interaction and the molecular anisotropy of the entire molecule, which, together with the energy separation between the ground and first excited ground states, become the significant factors determining the effective anisotropy barrier heights of 1 – 3 . These important results demonstrate that the charge distributions of the ligand‐field environments play essential roles in SMM performance, which should be considered seriously and utilized efficiently during the rational design of new, more feasible and practical SMMs. 相似文献
130.