A family of ferric catecholate complexes exhibiting unusual magnetic properties is described.

Here, we report a new photosensitive metal–organic framework (MOF) that was constructed via the modification of UiO-66-NH2 with diarylethene molecules (DAE, 4-(5-Methoxy-1,2-dimethyl-1H-indol-3-yl)-3-(2,5-dimethylthiophen-3-yl)-4-furan-2,5-dione). The material that was obtained was a highly crystalline porous compound. The photoresponse of the modified MOF was observed via UV–Vis and IR spectroscopy. Most of the DAE molecules inside of the UiO-66-pores had an open conformation after synthesis. However, the equilibrium was able to be shifted further toward an open conformation using visible light irradiation with a wavelength of 520 nm. Conversely, UV-light with a wavelength of 450 nm initiated the transformation of the photoresponsive moieties inside of the pores to a closed modification. We have shown that this transformation could be used to stimulate hydrogen adsorption–desorption processes. Specifically, visible light irradiation increased the H2 capacity of modified MOF, while UV-light decreased it. A similar hybrid material with DAE moieties in the UiO-66 scaffold was applied for hydrogen storage for the first time. Additionally, the obtained results are promising for smart H2 storage that is able to be managed via light stimuli.

VT transition from the high-spin Co II to low-spin Co III state was observed for complex (N-cyclo-hexyl-2--di-tert-butyl-catecholato)cobalt in both solid and liquid form. For the first time we demonstrate the low-temperature nanosecond pump-probe XANES experiment revealing the valence tautomeric transition in a solution of Co complex.Reversible transition was induced both under the temperature and laser radiation stimuli.

X-ray absorption spectroscopy (XAS) was used to characterize the structure of the photoactive Co(II) azobenzene complex. Optical absorption spectra show that photoinduced changes occur only in dimethylformamide (DMF) solvent, while in acetonitrile, this complex is photochemically inactive. Co Kedge XAS spectra indicate 6-coordinated species in acetonitrile with a structure similar to one in the crystalline form of the complex. However, in DMF, an activation process occurs related to the decrease of coordination number, bond shortening and absorption edge shift to the higher energies. Quantitative analysis indicates that observed spectral changes are related to the high spin -low spin transition in the Co complex accompanied by the bond dissociation and solvent coordination.

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