Abstracts
Luminescent materials for imaging, sensors and theranostics
Bifunctional lanthanoid-based molecular materials: exploring opto-magnetic properties of a mononuclear Yb complexJulio Corredoira-vázquez1, Paula Oreiro-martínez2, Ana M. G. Deibe2, Luís D. Carlos3, Matilde Fondo2
1Departamento de Química Inorgánica, Facultade de Química, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain. Phantom-g, CICECO – Aveiro Institute of Materials, Department of Physics, University of Aveiro, 3810-193 – Aveiro, Portugal., 2Departamento de Química Inorgánica, Facultade de Química, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain., 3Phantom-g, CICECO – Aveiro Institute of Materials, Department of Physics, University of Aveiro, 3810-193 – Aveiro, Portugal.
E-mail: julio.corredoira.vazquez@usc.es
Multifunctional molecular materials are a type of compounds that mix various physical or chemical properties in one molecule. Among the various multifunctional systems, much attention has been given to the design of magnetic molecular materials with additional capabilities. This interest changed the direction of the field of molecular magnetism with the discovery of the first single ion magnet (SIM) in 2003, the terbium bis-phthalocyanine complex [Tb(Pc)2], which demonstrated that mononuclear lanthanoid complexes can show slow relaxation of magnetisation. In addition, complexes based on trivalent lanthanoid ions exhibit specific luminescence covering a broad spectrum, from the visible to the near-infrared, with outstanding features such as narrow emission, long lifetimes and high luminescence. Despite these useful properties, the number of these compounds studied spectroscopically remains small. Hence, the first study reporting the coexistence of slow relaxation of magnetisation and luminescence based on lanthanoids was published in 2009.The first study linking relaxation dynamics and light emission was published in 2012, while an inductive effect between magnetic fields and luminescence was demonstrated in 2016. Consequently, interest in bifunctional molecular materials that combine luminescence with magnetic properties has grown. Lanthanoid-based magneto-luminescent complexes are promising for a variety of applications, such as molecular spintronics devices, single molecule detection and quantum readout. Among the lanthanoid ions, Dy3+ is commonly used to design luminescent single-molecule magnets (SMMs) due to its unique properties. Yb3+ is also investigated, but few examples of mononuclear Yb SIMs have been spectroscopically analysed. In addition, the temperature dependence of luminescent properties in Yb-based materials remains underexplored, despite their potential for optical temperature sensors. Considering these data and our ongoing research on lanthanoid coordination chemistry, we have examined the opto-magnetic properties of a mononuclear Yb complex with a planar pentadentate ligand (H2L), detailed in this study.The mononuclear complex [Yb(L)Br(EtOH)] (1) was isolated and structurally characterised. The opto-magnetic properties of 1 were investigated, showing that this complex is a bifunctional compound. Consequently, 1 reveals two coexisting functionalities: single-molecule magnetic behaviour induced by an external field (Hdc=1000 Oe), and temperature-dependent (11-361 K) Yb3+ centred NIR luminescence. The magnetic relaxation in this complex is of the Orbach-Raman-QTM type with a barrier to magnetisation reversal of 55.82 K (38.80 cm-1).
Keywords: Multifunctional molecular materials, Lanthanoids, Single-ion magnets, Luminescent Thermometer
Acknowledgments: This article is based upon work from COST Action CA22131. J.C.V. thanks Xunta de Galicia for his postdoctoral fellowship. P.O.-M. thanks the Fundación Segundo Gil Dávila for her PhD grant.