Photoswitchable stable charge-distributed states in a new cobalt complex exhibiting photo-induced valence tautomerism.

We report the synthesis and magnetic and photomagnetic behaviour of a novel valence tautomeric cobalt complex, [Co(3,5-dbbq)2(µ-bpym)] (1) (3,5-dbbq = 3,5-di-tert-butyl-1,2-benzoquinone and µ-bpym = 2,2'-bipyrimidine). The synthesis is performed by reacting Co2(CO)8 and µ-bpym in the presence of the ligand 3,5-dbbq in a mixed solvent under inert atmosphere. The magnetic behavior clearly shows the presence of electron transfer from the catecholate ligand to the cobalt center, producing valence tautomers of [Co(II)(SQ)2] with a transition temperature (T1/2) of 215 K. Photomagnetic studies, performed via both SQUID magnetometry and X-band electron paramagnetic resonance, show the clear presence of photoinduced valence tautomerism, at temperatures considerably higher than previous systems. A metastable charge distribution is observed, strengthening previous investigations on the character of mixed valence ligands. Entropy-driven valence tautomeric interconversion is observed, and drives the transition to the most stable charge distribution. The complex has the ability to coordinate and can be used as a photoswitchable building block, with the photomagnetic characterisation evidencing a metastable state lifetime of the photo-induced valence tautomeric process of ca. 2.9 × 10(4) s below 20 K. The observed yields are higher than ones in similar systems, showing that tiny changes in the molecular structures may have a huge impact.

Dynamic control of magnetic nanowires by light-induced domain-wall kickoffs.

Controlling the speed at which systems evolve is a challenge shared by all disciplines, and otherwise unrelated areas use common theoretical frameworks towards this goal. A particularly widespread model is Glauber dynamics, which describes the time evolution of the Ising model and can be applied to any binary system. Here we show, using molecular nanowires under irradiation, that Glauber dynamics can be controlled by a novel domain-wall kickoff mechanism. In contrast to known processes, the kickoff has unambiguous fingerprints, slowing down the spin-flip attempt rate by several orders of magnitude, and following a scaling law. The required irradiance is very low, a substantial improvement over present methods of magneto-optical switching. These results provide a new way to control and study stochastic dynamic processes. Being general for Glauber dynamics, they can be extended to different kinds of magnetic nanowires and to numerous fields, ranging from social evolution to neural networks and chemical reactivity.

Sub-terahertz frequency-domain spectroscopy reveals single-grain mobility and scatter influence of large-area graphene.

The response of individual domains in wafer-sized chemical vapor deposition graphene is measured by contactless sub-terahertz interferometry, observing the intrinsic optical conductance and reaching very high mobility values. It is shown that charged scatterers limit the mobility, validating previous theoretical predictions, and sub-terahertz quality assessment is demonstrated, as necessary for large-scale applications in touchscreens, as well as wearable and optoelectronic devices.

Interweaving spins with their environment: novel inorganic nanohybrids with controllable magnetic properties.

We discuss current developments in the synthesis and characterization of magnetic nanohybrids made of molecular magnets and nanostructured materials. We first review several novel approaches that have recently been attempted to combine magnetic coordination complexes with differently-obtained inorganic systems. Special focus is placed on how the altered environment can affect the magnetic properties of single molecules, providing new routes to multifunctional devices based on hybrid magnetic nanosystems. We then show how this approach is opening new outlooks towards the control of nanomagnets using external stimuli (e.g. photons, electrons, etc.) and for the creation of ultra-sensitive devices. Eventually we provide a unified vision of the area, with a personal perspective on the main goals currently at stake and of possible future developments.