Spin Crossover in Hofmann Clathrates

LCC

 

 

 

Spin Crossover in Hofmann Clathrates
A very comprehensive review published in Coordination Chemistry Reviews

Hofmann-type clathrates constitute one of the most versatile families of coordination frameworks displaying spin-crossover (SCO) behaviour, offering unparalleled opportunities for tuning bistability from bulk materials to nanoparticles and thin films. Over the past two decades, significant advances in synthetic methodologies have been achieved, particularly through the use of tetra- and di-cyanometallate building blocks ([MII(CN)4]2 –, [MI(CN)2]) combined with mono- or bidentate bridging organic ligands. These strategies have enabled the construction of structurally diverse FeII-based frameworks exhibiting cooperative and often abrupt spin transitions. This review highlights recent progress in bulk synthesis, structural engineering, and property modulation in Hofmann-type SCO complexes. It emphasizes how dimensionality, ligand design, and metal-metal connectivity govern transition temperatures, hysteresis, and multistep behavior. In this bulk regime, particular attention is devoted to the interplay between spin transition and electron transfer in mixed-valence or redox-active clathrates, which emerges as a powerful handle to encode and expand multifunctional responses. A considerable research effort has also focused on downsizing these materials into nanoparticles while maintaining, or even enhancing, cooperativity. This approach unlocks new prospects for solution processability, surface functionalization, and device integration.Parallel advances in host-guest chemistry demonstrate that these flexible frameworks can encapsulate neutral or charged species, leading to pronounced modulation of SCO behavior, guest-triggered phase transitions, and stimuli-responsive properties. Particular attention is devoted to 2D and 3D host-guest systems and to the emergence of “active” guest molecules capable of mechanical, electronic, or photonic coupling with the SCO matrix. Moreover, advances in the fabrication of thin films, micro-structured architectures, and nanostructured surfaces are increasingly positioning Hofmann-type clathrates at the forefront of applications in molecular electronics, memory devices, spintronics, sensing, and photo-switching. Yet, despite their remarkable functional potential, their practical implementation in devices remains limited. This is likely owing to their intrinsic fragility and the challenges associated with their manipulation, processing, and integration into innovative device architectures. Additional efforts are therefore required, particularly in the development of advanced nanotechnologies, to ultimately translate these materials into genuine societal applications. This review provides a comprehensive account of the field, underscoring key structure-property relationships across multiple length scales. It also outlines current challenges and opportunities for developing high-performance, multifunctional SCO Hofmann frameworks for emerging technologies.

Figure (a) Stacking of three consecutive layers showing the CH3Bz molecules in the channels of {FeII(L17)2[AgI(CN)2]2}·CH3Bz. (b) Thermal dependence of the χMT product for {FeII(L17)2[AgI(CN)2]2}·XBz (adapted from Turo-Cortés et al, J. Mater. Chem. C 2022, 10 (29),).


Reference

Spin crossover in Hofmann clathrates: From bulk materials to nanoparticles and thin films,
Saioa Cobo, Carlos Bartual-Murgui, Lionel Salmon, M. Carmen Muñoz, Gábor Molnár, José Antonio Real, Azzedine Bousseksou,
Coordination Chemistry Reviews, Volume 561, 2026, 217917, ISSN 0010-8545,
https://doi.org/10.1016/j.ccr.2026.217917
(https://www.sciencedirect.com/science/article/pii/S001085452600353X)

Contacts

Azzedine Bousseksou  Azzedine.Bousseksou@lcc-toulouse.fr

For press enquiries:
Evelyne Prévots  evelyne.prevots@lcc-toulouse.fr

LCC CNRS

Laboratoire de chimie de coordination du CNRS

205 route de Narbonne, BP 44099
31077 Toulouse cedex 4
France

+ 33 5 61 33 31 00

Laboratoire de Chimie de Coordination
Privacy Policy

To improve your browsing experience. Cookies provide information on how the site is used: statistics such as the number of visitors, the average length of visits or the number of pages viewed. On the other hand, disabling cookies may prevent you from using certain features, such as sharing content via social networks.
By clicking "Accept", you agree to the use of cookies from this site and to our privacy policy.

You can adjust all your cookie settings by navigating the tabs on the left.