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61.
The recently proposed systems of various anions (A) confined inside C60 , A− @ C60 , which in turn behave as large and stable anions, (A @ C60)− , can find potential applications in various fields. On the other hand, it has earlier been shown that from the dihalogens (X2 ) encapsulated C60 , X2 @ C60 , only F2 @ C60 can be introduced as a system in which the cage acts as a cation C60+ and interacts with an endohedral anion, F2− , forming the F2− @ C60+ as a single-molecule crystal compound. In this work, two density functional theory energy decomposition analysis (EDA) schemes, where in one of them the noninteracting kinetic, electrostatic, and exchange-correlation energies come into play while another scheme, called as EDA-SBL, includes the steric, electrostatic, and quantum effects as essential ingredients (S. Liu, J. Chem. Phys. 2007 , 126, 244103), are utilized to find out what energetic components govern the unique characteristics of the (A @ C60)− and X2 @ C60 confinements. It is shown that the noninteracting kinetic energy and steric energies have important contributions to the total interaction energies for the considered systems. However, there are other confinements for which the electrostatic and exchange-correlation contributions play also imperative roles. Furthermore, we find reasonable correlations between interaction energies and their components as well as the energetic components themselves, leading to an alternative EDA scheme including the noninteracting kinetic, steric, and electrostatic energies for investigations on other endohedral fullerenes. Extending our analyses to large size confinements, Cl− @ Cn with n up to 90 as illustrative examples, the quantitative cooperativity concept is also explored, where the positive and negative cooperativity profiles unveil a specific size of the anionic confinements to form the most stable large anion. 相似文献
62.
Dr. Mei Ding Dr. Anne K. Hickey Dr. Maren Pink Prof. Joshua Telser Prof. David L. Tierney Martin Amoza Mathieu Rouzières Tarik J. Ozumerzifon Wesley A. Hoffert Prof. Matthew P. Shores Prof. Eliseo Ruiz Dr. Rodolphe Clérac Prof. Jeremy M. Smith 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(45):10625-10632
The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(η5-C5R5)2]+ (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(η5-C5Me5)2]BArF are revealed. Multireference quantum mechanical calculations show a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible for the SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(η5-C5Bn5)2]BF4 and [Fe(η5-C5Bn5)2]PF6, also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems. 相似文献
63.
Viktoria Wedler Dustin Quinones Prof. Dr. Heiko Peisert Prof. Dr. Erik Schäffer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(64):e202202036
Single-molecule assays often require functionalized surfaces. One approach for microtubule assays renders surfaces hydrophobic and uses amphiphilic blocking agents. However, the optimal hydrophobicity is unclear, protocols take long, produce toxic waste, and are susceptible to failure. Our method uses plasma activation with hydrocarbons for hexamethyldisilazane (HMDS) silanization in the gas phase. We measured the surface hydrophobicity, its effect on how well microtubule filaments were bound to the surface, and the number of nonspecific interactions with kinesin motor proteins. Additionally, we tested and discuss the use of different silanes and activation methods. We found that even weakly hydrophobic surfaces were optimal. Our environmentally friendly method significanty reduced the overall preparation effort and resulted in reproducible, high-quality surfaces with low variability. We expect the method to be applicable to a wide range of other single-molecule assays. 相似文献
64.
Shelby E. Stavretis Duncan H. Moseley Fan Fei Hui-Hui Cui Dr. Yongqiang Cheng Dr. Andrey A. Podlesnyak Dr. Xiaoping Wang Dr. Luke L. Daemen Dr. Christina M. Hoffmann Dr. Mykhaylo Ozerov Zhengguang Lu Prof. Komalavalli Thirunavukkuarasu Dr. Dmitry Smirnov Tieyan Chang Dr. Yu-Sheng Chen Dr. Anibal J. Ramirez-Cuesta Prof. Xue-Tai Chen Prof. Zi-Ling Xue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15846-15857
Large separations between ground and excited magnetic states in single-molecule magnets (SMMs) are desirable to reduce the likelihood of spin reversal in the molecules. Spin-phonon coupling is a process leading to magnetic relaxation. Both the reversal and coupling, making SMMs lose magnetic moments, are undesirable. However, direct determination of large magnetic states separations (>45 cm−1) is challenging, and few detailed investigations of the spin-phonon coupling have been conducted. The magnetic separation in [Co(12-crown-4)2](I3)2(12-crown-4) ( 1 ) is determined and its spin-phonon coupling is probed by inelastic neutron scattering (INS) and far-IR spectroscopy. INS, using oriented single crystals, shows a magnetic transition at 49.4(1.0) cm−1. Far-IR reveals that the magnetic transition and nearby phonons are coupled, a rarely observed phenomenon, with spin-phonon coupling constants of 1.7–2.5 cm−1. The current work spectroscopically determines the ground–excited magnetic states separation in an SMM and quantifies its spin-phonon coupling, shedding light on the process causing magnetic relaxation. 相似文献
65.
Frontispiece: Lanthanide Tetrazolate Complexes Combining Single‐Molecule Magnet and Luminescence Properties: The Effect of the Replacement of Tetrazolate N3 by β‐Diketonate Ligands on the Anisotropy Energy Barrier 下载免费PDF全文
66.
67.
This paper investigates the single-molecule magnets of pure and Cr/Fe-doped Mn12-Ac. The components of the mixed crystals are identified by AC susceptibility technique. The ground-state spin and anisotropy parameters of doped Mn12-Ac are obtained: (i) MnllCr-Ac (S=19/2, D=0.62K, B=0.0009K, A=63K), and (ii) Mn11Fe-Ac (S=21/2, D=0.39 K, B=0.001 K, △=55 K). The single-ion origin of the magnetic anisotropy is discussed. 相似文献
68.
Dr. Toshiharu Ishizaki Hideaki Karasaki Dr. Yuto Kage Misaki Kamioka Yitong Wang Dr. Shigeki Mori Prof. Dr. Naoto Ishikawa Prof. Dr. Takamitsu Fukuda Prof. Dr. Hiroyuki Furuta Prof. Dr. Soji Shimizu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(49):12686-12692
A novel pyrrolopyrrole azadipyrrin ( Janus-PPAD ) with Janus duality was synthesized by a Schiff base–forming reaction of diketopyrrolopyrrole. The orthogonal interactions of the hydrogen-bonding ketopyrrole and metal-coordinating azadipyrrin moieties in Janus-PPAD enabled the metal ions to be arranged at regular intervals: zinc(II) and cobalt(II) coordination provided metal-coordinated Janus-PPAD dimers, which can subsequently form hydrogen-bonded one-dimensional arrays both in solution and in the solid state. The supramolecular assembly of the zinc(II) complex in solution was investigated by 1H NMR spectroscopy based on the isodesmic model, in which a binding constant for the elongation of assemblies is constant. Owing to the tetrahedral coordination, in the solid state, the cobalt(II) complex exhibited a slow magnetic relaxation due to the negative D value of −27.1 cm−1 with an effective relaxation energy barrier Ueff of 38.0 cm−1. The effect of magnetic dilution on the relaxation behavior is discussed. The relaxation mechanism at low temperature was analyzed by considering spin lattice interactions and quantum tunneling effects. The easy-axis magnetic anisotropy was confirmed, and the relevant wave functions were obtained by ab initio CASSCF calculations. 相似文献
69.
70.
Dr. Jan-Philipp Venne Dr. Bastian Feldscher Dr. Stephan Walleck Anja Stammler Dr. Hartmut Bögge Prof. Dr. Jürgen Schnack Prof. Dr. Thorsten Glaser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4992-5004
The anisotropy barrier of polynuclear single-molecule magnets is expected to be higher with less tunneling the better stabilized the spin ground state is so that less MS mixing in the ground state and with excited spin states occur. We have realized this experimentally in two structurally related heptanuclear SMMs: the triplesalen-based [MnIII 6 CrIII]3+ and the triplesalalen-based *[MnIII 6 CrIII]3+ . The ligand system triplesalen was developed to enforce ferromagnetic interactions by the spin-polarization mechanism. However, we found weak antiferromagnetic couplings, that we assigned to an inefficient spin-polarization by a heteroradialene formation. To prevent this heteroradialene formation, the triplesalalen ligand H6talalen was designed. Here, we present the building block [(talalen )MnIII3]3+ and its application for the assembly of [{(talalen )MnIII3}2{CrIII(CN)6}]3+ (= *[MnIII 6 CrIII]3+ ). Both the trinuclear and heptanuclear complexes are SMMs. The comparison to the related triplesalen complex [(feld )MnIII3]3+ proves the absence of heteroradialene character and the enforcement of ferromagnetic MnIII-MnIII interactions in the (talalen )6− complexes. This results in an increase of the barrier for spin reversal Ueff from 25 K in the triplesalen-based [MnIII 6 CrIII]3+ SMMs to 37 K in the triplesalalen-based *[MnIII 6 CrIII]3+ SMM proving the success of our concept. Based on this study, the next step in the rational improvement of our SMMs is discussed. 相似文献