| Content Provider |
World Health Organization (WHO)-Global Index Medicus |
| Author |
Biswas, Sourav Gupta, Tulika Singh, Saurabh Kumar Pissas, Michael Das, Sourav Chandrasekhar, Vadapalli Rajaraman, Gopalan |
| Description |
Author Affiliation: Biswas S ( Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India.); Das S ( Department Of Chemistry, Institute of Infrastructure Technology Research and Management, Near Khokhara Circle, Maninagar East, Ahmedabad, 380026, India.); Gupta T ( Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.); Singh SK ( Department of Molecular Theory and Spectroscopy, Max-Planck Institute for Chemical Energy Conversion, Stiftstr 34-36, 45470, Mülheim an der Ruhr, Germany.); Pissas M ( Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, NCSR Demokritos, 15310 Ag. Paraskevi, Attiki, Greece.); Rajaraman G ( Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.); Chandrasekhar V ( Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India.) |
| Abstract |
A family of five isostructural butterfly complexes with a tetranuclear $[Ln_{4}]$ core of the general formula $[Ln_{4}(LH)_{2}(μ_{2}-η^{1}η^{1}Piv)(η^{2}-Piv)(μ_{3}-OH)_{2}]⋅x H_{2}O⋅y MeOH⋅z CHCl_{3}$ (1: $Ln=Dy^{III},$ x=2, y=2, z=0; 2: $Ln=Tb^{III},$ x=0, y=0, z=6; 3: $Ln=Er^{III},$ x=2, y=2, z=0; 4: $Ln=Ho^{III},$ x=2, y=2, z=0; 5: $Ln=Yb^{III},$ x=2, y=2, z=0; $LH_{4}=6-\{[bis(2-hydroxyethyl)amino]methyl\}-N′-(2-hydroxy-3-methoxybenzylidene)picolinohydrazide;$ PivH=pivalic acid) was isolated and characterized both structurally and magnetically. Complexes 1–5 were probed by direct and alternating current (dc and ac) magnetic susceptibility measurements and, except for 1, they did not display single-molecule magnetism (SMM) behavior. The ac magnetic susceptibility measurements show frequency-dependent out-of-phase signals with one relaxation process for complex 1 and the estimated effective energy barrier for the relaxation process was found to be 49 K. We have carried out extensive ab initio (CASSCF+RASSI-SO+SINGLE_ANISO+POLY_ANISO) calculations on all the five complexes to gain deeper insights into the nature of magnetic anisotropy and the presence and absence of slow relaxation in these complexes. Our calculations yield three different exchange coupling for these $Ln_{4}$ complexes and all the extracted J values are found to be weakly ferro/antiferromagentic in nature $(J_{1}=+2.35,$ $J_{2}=−0.58,$ and $J_{3}=−0.29 cm^{−1}$ for 1; $J_{1}=+0.45,$ $J_{2}=−0.68,$ and $J_{3}=−0.29 cm^{−1}$ for 2; $J_{1}=+0.03,$ $J_{2}=−0.98,$ and $J_{3}=−0.19 cm^{−1}$ for 3; $J_{1}=+4.15,$ $J_{2}=−0.23,$ and $J_{3}=−0.54 cm^{−1}$ for 4 and $J_{1}=+0.15,$ $J_{2}=−0.28,$ and $J_{3}=−1.18 cm^{−1}$ for 5). Our calculations reveal the presence of very large mixed toroidal moment in complex 1 and this is essentially due to the specific exchange topology present in this cluster. Our calculations also suggest presence of single-molecule toroics (SMTs) in complex 2. For complexes 3–5 on the other hand, the transverse anisotropy was computed to be large, leading to the absence of slow relaxation of magnetization. As the magnetic field produced by SMTs decays faster than the normal spin moments, the concept of SMTs can be exploited to build qubits in which less interference and dense packing are possible. Our systematic study on these series of $Ln_{4}$ complexes suggest how the ligand design can help to bring forth such SMT characteristics in lanthanide complexes. |
| ISSN |
09476539 |
| e-ISSN |
15213765 |
| Journal |
Chemistry - A European Journal |
| Issue Number |
51 |
| Volume Number |
22 |
| Language |
English |
| Publisher |
Wiley-VCH;ChemPubSoc Europe |
| Publisher Date |
2016-12-19 |
| Publisher Place |
Germany |
| Access Restriction |
Open |
| Subject Keyword |
Chemistry |
| Content Type |
Text |
| Resource Type |
Article |
| Subject |
Organic Chemistry Catalysis |
