Combined Experimental and Ab Initio Methods for Rationalization of Magneto-Luminescent Properties of YbIII Nanomagnets Embedded in Cyanido/Thiocyanidometallate-Based Crystals.

Jakub J Zakrzewski,Shin-Ichi Ohkoshi,Mikolaj Zychowicz,Robert Jankowski,Kunal Kumar,Maciej Wyczesany,Barbara Sieklucka,Szymon Chorazy

doi:10.1021/acs.jpclett.1c02942

Abstract

The ab initio calculations were correlated with magnetic and emission characteristics to understand the modulation of properties of NIR-emissive [YbIII(2,2′-bipyridine-1,1′-dioxide)4]3+ single-molecule magnets by cyanido/thiocyanidometallate counterions, [AgI(CN)2]− (1), [AuI(SCN)2]− (2), [CdII(CN)4]2–/[CdII2(CN)7]3– (3), and [MIII(CN)6]3– [MIII = Co (4), Ir (5), Fe (6), Cr (7)]. Theoretical studies indicate easy-axis-type ground doublets for all YbIII centers. They differ in the magnetic axiality; however, transversal g-tensor components are always large enough to explain the lack of zero-dc-field relaxation. The excited doublets lie more than 120 cm–1 above the ground one for all YbIII centers. It was confirmed by high-resolution emission spectra reproduced from the ab initio calculations that give reliable insight into energies and oscillator strengths of optical transitions. These findings indicate the dominance of Raman relaxation with the power n varying from 2.93(4) to 6.9(2) in the 4–3–5–1–2 series. This trend partially follows the magnetic axiality, being deeper correlated with the phonon modes schemes of (thio)cyanido matrices.

Highlights

Lanthanide luminescent systems are promising for display devices, light-emitting diodes, optical communication, thermometry, sensing, and bioimaging.4−8 Their unique electronic properties related to spin−orbit coupling and crystal-field effects results in strong magnetic anisotropy leading to the slow relaxation of magnetization
The Orbach process, quantum tunneling of magnetization (QTM), and Raman relaxation operate without the external field, while a direct process is recognized for fieldinduced single-molecule magnets (SMMs)
Lanthanide SMMs were lately applied in optical thermometry,28,29 while their emission spectra are usually used to perform magneto-optical correlations

Summary

Corresponding Author

Zakrzewski − Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland; orcid.org/00000001-9511-5270 Kunal Kumar − Department of Chemistry, School of Science, The University of Tokyo, Tokyo 113-0033, Japan; orcid.org/0000-0002-2626-0615 Mikolaj Zychowicz − Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland Robert Jankowski − Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland Maciej Wyczesany − Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland Barbara Sieklucka − Faculty of Chemistry, Jagiellonian University, 30-387 Krakow, Poland; orcid.org/00000003-3211-5008 Shin-ichi Ohkoshi − Department of Chemistry, School of Science, The University of Tokyo, Tokyo 113-0033, Japan; orcid.org/0000-0001-9359-5928.

■ ACKNOWLEDGMENTS

Findings

■ REFERENCES