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Dey S, Rajaraman G. Attaining record-high magnetic exchange, magnetic anisotropy and blocking barriers in dilanthanofullerenes. Chem Sci 2021; 12:14207-14216. [PMID: 34760206 PMCID: PMC8565386 DOI: 10.1039/d1sc03925c] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 10/06/2021] [Indexed: 11/29/2022] Open
Abstract
While the blocking barrier (U eff) and blocking temperature (T B) for "Dysprocenium" SIMs have been increased beyond liquid N2 temperature, device fabrication of these molecules remains a challenge as low-coordinate Ln3+ complexes are very unstable. Encapsulating the lanthanide ion inside a cage such as a fullerene (called endohedral metallofullerene or EMF) opens up a new avenue leading to several Ln@EMF SMMs. The ab initio CASSCF calculations play a pivotal role in identifying target metal ions and suitable cages in this area. Encouraged by our earlier prediction on Ln2@C79N, which was verified by experiments, here we have undertaken a search to enhance the exchange coupling in this class of molecules beyond the highest reported value. Using DFT and ab initio calculations, we have studied a series of Gd2@C2n (30 ≤ 2n ≤ 80), where an antiferromagnetic J Gd⋯Gd of -43 cm-1 was found for a stable Gd2@C38-D 3h cage. This extremely large and exceptionally rare 4f⋯4f interaction results from a direct overlap of 4f orbitals due to the confinement effect. In larger cages such as Gd2@C60 and Gd2@C80, the formation of two centre-one-electron (2c-1e-) Gd-Gd bonds is perceived. This results in a radical formation in the fullerene cage leading to its instability. To avoid this, we have studied heterofullerenes where one of the carbon atoms is replaced by a nitrogen atom. Specifically, we have studied Ln2@C59N and Ln2@C79N, where strong delocalisation of the electron yields a mixed valence-like behaviour. This suggests a double-exchange (B) is operational, and CASSCF calculations yield a B value of 434.8 cm-1 and resultant J Gd-rad of 869.5 cm-1 for the Gd2@C59N complex. These parameters are found to be two times larger than the world-record J reported for Gd2@C79N. Further ab initio calculations reveal an unprecedented U cal of 1183 and 1501 cm-1 for Dy2@C59N and Tb2@C59N, respectively. Thus, this study offers strong exchange coupling as criteria for new generation SMMs as the existing idea of enhancing the blocking barrier via crystal field modulation has reached its saturation point.
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Affiliation(s)
- Sourav Dey
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
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Shen W, Hu S, Lu X. Endohedral Metallofullerenes: New Structures and Unseen Phenomena. Chemistry 2020; 26:5748-5757. [PMID: 31886563 DOI: 10.1002/chem.201905306] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 12/27/2019] [Indexed: 02/06/2023]
Abstract
Endohedral metallofullerenes (EMFs), namely fullerenes with metallic species encapsulated inside, represent an ideal platform to investigate metal-metal or metal-carbon interactions at the sub-nanometer scale by means of single-crystal X-ray diffraction (XRD) crystallography. Herein, recent progress in the identification of new structures and unprecedented properties are discussed according to the categories of monometallofullerenes, dimetallofullerenes, carbide clusterfullerenes, and nitride clusterfullerenes. In particular, the dimerization and the cage-isomer dependent oxidation state of the inner metal atom are summarized in terms of pristine monometallofullerenes. Metal-metal bonds involving lanthanide-lanthanides or actinide-actinides are discussed based on both experimental and theoretical studies. The cluster-cage matching and/or mutual selections, as well as the rarely seen M=C double bonds, are discovered in M2 C2 @C2n , U2 C@C80 , M2 TiC@C80 , and Ti3 C3 @C80 . Subsequently, the geometries of different M3 N clusters in various cages are discussed, revealing size-matching between the internal M3 N cluster and the outer cage induced by the planarity of the cluster. Finally, an outlook regarding the future developments of the molecular structures and applications of EMFs is presented.
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Affiliation(s)
- Wangqiang Shen
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, China
| | - Shuaifeng Hu
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, China
| | - Xing Lu
- State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, China
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Yu B, Shen W, Yang L, Liu Y, Pan C, Cong H, Jin P, Lu X. Regioselective Synthesis, Crystallographic Characterization, and Electrochemical Properties of Pyrazole‐ and Pyrrole‐Ring‐Fused Derivatives of Y
2
@
C
3
v
(8)‐C
82. Chemistry 2020; 26:2464-2469. [DOI: 10.1002/chem.201905076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 12/05/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Bing Yu
- Lab for New Fiber Materials and Modern TextileGrowing Base for State Key LaboratoryCollege of Chemical and Environmental EngineeringQingdao University Qingdao 266071 P. R. China
| | - Wangqiang Shen
- State Key Laboratory of Materials Processing and Die & Mould TechnologySchool of Materials Science and EngineeringHuazhong University of Science and Technology 1037 Luoyu Road Wuhan 430074 P. R. China
| | - Le Yang
- School of Materials Science and EngineeringHebei University of Technology Tianjin 300130 P. R. China
| | - Yangchun Liu
- Lab for New Fiber Materials and Modern TextileGrowing Base for State Key LaboratoryCollege of Chemical and Environmental EngineeringQingdao University Qingdao 266071 P. R. China
| | - Changwang Pan
- State Key Laboratory of Materials Processing and Die & Mould TechnologySchool of Materials Science and EngineeringHuazhong University of Science and Technology 1037 Luoyu Road Wuhan 430074 P. R. China
| | - Hailin Cong
- Lab for New Fiber Materials and Modern TextileGrowing Base for State Key LaboratoryCollege of Chemical and Environmental EngineeringQingdao University Qingdao 266071 P. R. China
| | - Peng Jin
- School of Materials Science and EngineeringHebei University of Technology Tianjin 300130 P. R. China
| | - Xing Lu
- State Key Laboratory of Materials Processing and Die & Mould TechnologySchool of Materials Science and EngineeringHuazhong University of Science and Technology 1037 Luoyu Road Wuhan 430074 P. R. China
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Singh MK, Shukla P, Khatua M, Rajaraman G. A Design Criteria to Achieve Giant Ising-Type Anisotropy in Co II -Encapsulated Metallofullerenes. Chemistry 2019; 26:464-477. [PMID: 31506987 DOI: 10.1002/chem.201903618] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 09/05/2019] [Indexed: 11/10/2022]
Abstract
Discovery of permanent magnetisation in molecules just like in hard magnets decades ago led to the proposal of utilising these molecules for information storage devices and also as Q-bits in quantum computing. A significant breakthrough with a blocking temperature as high as 80 K has been recently reported for lanthanocene complexes. While enhancing the blocking temperature further remains one of the primary challenges, obtaining molecules that are suitable for the fabrication of the devices sets the bar very high in this area. Encouraged by the fact that our earlier predictions of potential single-molecule magnets (SMMs) in lanthanide-containing endohedral fullerenes have been verified, here we set out to undertake a comprehensive study on CoII -ion-encapsulated fullerene as potential SMMs. To study this class of molecules, we have utilised an array of theoretical methods ranging from density functional to ab initio CASSCF/NEVPT2 methods for obtaining reliable estimate of zero-field splitting parameters D and E. Additionally, we have also employed, for the first time a combination of molecular dynamics based on DFT methods coupled with CASSCF/NEVPT2 methods to seek the role of conformational isomers in the relaxation of magnetisation. Particularly, we have studied, Co@C28 , Co@C38 and Co@C48 cages and their isomers as potential target molecules that could yield substantial magnetic anisotropy. Our calculations categorically reveal a very large Ising anisotropy in this class of molecules, with Co@C48 cages predicted to yield D values as high as -127 cm-1 . Our calculations on the smaller cages reveal the free movement of CoII ion inside the cage, leading to the likely scenario of faster relaxation of magnetisation. However, larger fullerene cages were found to solve this issue. Further models with incorporating units such as {CoOZn}, {CoScZnN} inside larger fullerenes yield axial zero-field splitting values as high as -200 cm-1 with negligible E/D values. As these units represent a strong axiality coupled with a viable way to obtain air-stable low-coordinate CoII complexes, this opens up a new paradigm in the search of SMMs in this class of molecules.
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Affiliation(s)
- Mukesh Kumar Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Pratima Shukla
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Munmun Khatua
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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Hu S, Shen W, Yang L, Duan G, Jin P, Xie Y, Akasaka T, Lu X. Crystallographic and Theoretical Investigations of Er 2 @C 2 n (2 n=82, 84, 86): Indication of Distance-Dependent Metal-Metal Bonding Nature. Chemistry 2019; 25:11538-11544. [PMID: 31290169 DOI: 10.1002/chem.201902321] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Indexed: 02/03/2023]
Abstract
Successful isolation and characterization of a series of Er-based dimetallofullerenes present valuable insights into the realm of metal-metal bonding. These species are crystallographically identified as Er2 @Cs (6)-C82 , Er2 @C3v (8)-C82 , Er2 @C1 (12)-C84 , and Er2 @C2v (9)-C86 , in which the structure of the C1 (12)-C84 cage is unambiguously characterized for the first time by single-crystal X-ray diffraction. Interestingly, natural bond orbital analysis demonstrates that the two Er atoms in Er2 @Cs (6)-C82 , Er2 @C3v (8)-C82 , and Er2 @C2v (9)-C86 form a two-electron-two-center Er-Er bond. However, for Er2 @C1 (12)-C84 , with the longest Er⋅⋅⋅Er distance, a one-electron-two-center Er-Er bond may exist. Thus, the difference in the Er⋅⋅⋅Er separation indicates distinct metal bonding natures, suggesting a distance-dependent bonding behavior for the internal dimetallic cluster. Additionally, electrochemical studies suggest that Er2 @C82-86 are good electron donors instead of electron acceptors. Hence, this finding initiates a connection between metal-metal bonding chemistry and fullerene chemistry.
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Affiliation(s)
- Shuaifeng Hu
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
| | - Wangqiang Shen
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
| | - Le Yang
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, P. R. China
| | - Guangxiong Duan
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
| | - Peng Jin
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, 300130, P. R. China
| | - Yunpeng Xie
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
| | - Takeshi Akasaka
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
| | - Xing Lu
- State Key Laboratory of Materials Processing and Die &, Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074, P. R. China
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