Single‐molecule magnets (SMMs) are at the forefront of new technological advances in quantum information processing and spintronics. Despite the recent impressive breakthroughs in extending the magnetic blocking temperatures beyond liquid‐nitrogen temperatures, significant challenges await in terms of integrating and addressing such compounds in devices. With this ultimate goal in mind, the design of multifunctional SMMs not only allows to imbue molecules of interest with specific properties that would allow for in situ monitoring of the SMM operation in real time, but can also provide critical insights into our understanding of the magnetic behaviour. In this Review, we highlight how magnetism and luminescence can be harmoniously combined within single molecules to achieve these objectives. The key design principles to attain the simultaneous combination of photoluminescence and slow relaxation of the magnetization are discussed, along with an outlook on how such molecules could be beneficial for emerging next‐generation spintronics devices.

The effect of electron-withdrawing ligands on the energy barriers of Single-Molecule Magnets (SMMs) is investigated. By introducing highly electron-withdrawing atoms on targeted ligands, the energy barrier was significantly enhanced. The structural and magnetic properties of five novel SMMs based on a dinuclear {Dy2} phenoxo-bridged motif are explored and compared with a previously studied {Dy2} SMM (1). All complexes share the formula [Dy2(valdien)2(L)2]·solvent, where H2valdien = N1,N3-bis(3-methoxysalicylidene) diethylenetriamine, the terminal ligand L = NO3(-) (1), CH3COO(-) (2), ClCH2COO(-) (3), Cl2CHCOO(-) (4), CH3COCHCOCH3(-) (5), CF3COCHCOCF3(-) (6), and solvent = 0.5 MeOH (4), 2 CH2Cl2 (5). Systematic increase of the barrier was observed for all complexes with the most drastic increase seen in 6 when the acac ligand of 5 was fluorinated resulting in a 7-fold enhancement of the anisotropic barrier. Ab initio calculations reveal more axial g tensors as well as higher energy first excited Kramers doublets in 4 and 6 leading to higher energy barriers for those complexes.

A combined experimental and theoretical approach reveals the intricacies related to an YbIII complex, which functions dually as a SMM and a luminescent thermometer.

Lanthanide‐complex‐based luminescence thermometry and single‐molecule magnetism are two effervescent fields of research, owing to the great promise they hold from an application standpoint. The high thermal sensitivity achievable, their contactless nature, along with sub‐micrometric spatial resolution make these luminescent thermometers appealing for accurate temperature probing in miniaturised electronics. To that end, single‐molecule magnets (SMMs) are expected to revolutionise the field of spintronics, thanks to the improvements made in terms of their working temperature—now surpassing that of liquid nitrogen—and manipulation of their spin state. Hence, the combination of such opto‐magnetic properties in a single molecule is desirable in the aim of overcoming, among others, addressability issues. Yet, improvements must be made through design strategies for the realisation of the aforementioned goal. Moving forward from these considerations, we present a thorough investigation of the effect that changes in the ligand scaffold of a family of terbium complexes have on their performance as luminescent thermometers and SMMs. In particular, an increased number of electron‐withdrawing groups yields modifications of the metal coordination environment and a lowering of the triplet state of the ligands. These effects are tightly intertwined, thus, resulting in concomitant variations of the SMM and the luminescence thermometry behaviour of the complexes. Supported by ab initio calculations, we can rationally interpret the observed trends and provide solid foundations for the development of opto‐magnetic lanthanide complexes.

The dynamic uptake behaviour of a gaseous guest has been observed crystallographically, yielding a unique and ever-changing set of host–guest interactions that will drive the improvement of high-capacity iodine capture materials.