The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)

Old materials with new tricks: multifunctional open-framework materials.

The magnetic properties of many magnetic materials can be controlled by external stimuli. The principal focus here is on the thermal, photochemical, electrochemical, and chemical control of phase transitions that involve changes in magnetization. The molecular compounds described herein range from metal complexes, through pure organic compounds to composite materials. Most of the Review is devoted to the properties of valence-tautomeric compounds, molecular magnets, and spin-crossover complexes, which could find future application in memory devices or optical switches.

Control of magnetic properties through external stimuli.

The behaviour of spin crossover compounds is among the most 
striking and fascinating shown by relatively simple molecular species. This 
review aims to draw attention to the various ways in which spin crossover 
phenomena are manifested in iron(II) complexes, to offer some 
rationalisation for these, and to highlight their possible applications. 
Typical examples have been selected along with more recent ones in order to 
give an overall view of the scope and development of the area. The article 
is structured to provide the basic material for those who wish to enter the 
field of spin crossover.

Spin crossover phenomena in Fe(II) complexes

Molecules to build solids : high tc molecule-based magnets by design and recent revival of cyano complexes chemistry

Metal–organic frameworks (MOFs), also known as coordination polymers, represent an interesting class of crystalline molecular materials that are synthesized by combining metal-connecting points and bridging ligands. The modular nature of and mild conditions for MOF synthesis have permitted the rational structural design of numerous MOFs and the incorporation of various functionalities via constituent building blocks. The resulting designer MOFs have shown promise for applications in a number of areas, including gas storage/separation, nonlinear optics/ferroelectricity, catalysis, energy conversion/storage, chemical sensing, biomedical imaging, and drug delivery. The structure–property relationships of MOFs can also be readily established by taking advantage of the knowledge of their detailed atomic structures, which enables fine-tuning of their functionalities for desired applications. Through the combination of molecular synthesis and crystal engineering, MOFs thus present an unprecedented opportunity fo...

Metal-organic frameworks as a tunable platform for designing functional molecular materials.

Photoinduced magnetization was observed in a Prussian blue analog, K0.2Co1.4- [Fe(CN)6]·6.9H2O. An increase in the critical temperature from 16 to 19 kelvin was observed as a result of red light illumination. Moreover, the magnetization in the ferrimagnetic region below 16 kelvin was substantially increased after illumination and could be restored almost to its original level by thermal treatment. These effects are thought to be caused by an internal photochemical redox reaction. Furthermore, blue light illumination could be used to partly remove the enhancement of the magnetization. Such control over magnetic properties by optical stimuli may have application in magneto-optical devices.

http://science.sciencemag.org/content/sci/272/5262/704.full.pdf

Photoinduced Magnetization of a Cobalt-Iron Cyanide

Reversible photoinduced magnetization was observed in a cobalt iron cyanide thin film. Magnetic properties of the prussian blue analog, K 0.4 Co 1.3 [Fe(CN) 5 ].5H 2 O, can be switched between ferrimagnetic and paramagnetic by visible and near-IR light illumination. The critical temperature after illumination was about 26 K. This material, obtained via an electrochemical route in the form of thin films on an electrode, provides a new system whose magnetic properties can be controlled by both photochemical and electrochemical redox reactions.

Reversible Photoinduced Magnetization

We have succeeded in controlling magnetic properties such as the saturation magnetization, the Weiss temperature and the coercive field using compounds in the series (NiIIxMnII1-x)15[CrIII(CN)6], 

Tuning of Superexchange Couplings in a Molecule-Based Ferroferrimagnet: (NiIIxMnII1-x)1.5[CrIII(CN)6]

Rational design of a magnetic material (nickel nitroprusside) at the molecular level allowed switching of a spin coupling by means of photoinduced metal to ligand charge transfer (MLCT). Before irradiation, spins on Ni2+ are in a disordered state. An illumination at 375 nm induces a MLCT from Fe to NO and forms new spins on Fe and NO. The newly appearing spin on Fe orders the spins on the nearest Ni2+ ions around Fe. In other words, one MLCT aligns five spin sources resulting in the formation of magnetic clusters with S = 5. Furthermore, such a photoinduced spin ordering can be rerandomized by thermal treatment.

Tomokazu Iyoda

Papers

Photoinduced Magnetization of a Cobalt-Iron Cyanide

Reversible Photoinduced Magnetization

Tuning of Superexchange Couplings in a Molecule-Based Ferroferrimagnet: (NiIIxMnII1-x)1.5[CrIII(CN)6]

Molecular-Level Design of a Photoinduced Magnetic Spin Coupling System: Nickel Nitroprusside

A soft-hard-tunable molecule-based magnet via photo-induced spin-flopping transition in a MnTEtOPP-TCNE charge transfer salt