Heterometallic, Hybrid, Heavy Main-Group Iodometallates Containing Lanthanide Complexes: Template Synthesis, Structures, Thermal, Optical, Luminescent and Magnetic Properties

MATERIAUX+SMR:SDAUsing [Ln(L)8]3+ [Ln = Tb, Y; L = dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF)] cations as templating reagents, the syntheses and crystal structures of the following new metal organicinorganic hybrid complexes based on either discrete clusters or 1D chains of an iodoplumbate or-bismuthate moiety are reported: [Tb(DMSO)8]2[(DMSO)2Pb5I16] (1), [Tb(DMF)(8)][Pb3I9](1)(infinity)center dot DMF (2) and [Ln(DMF)8][Bi2I9] [Ln = Y (3), Tb (4)]. These derivatives were characterized by thermogravimetric analysis (TGA), diffuse-reflectance spectroscopy, luminescence spectroscopy and magnetic studies. TGA studies show that the thermal stability of these complexes decreases in the order 2 > 3 similar to 4 > 1. An optical band-gap in the range 1.902.15 eV in the diffuse-reflectance spectra of 14 indicate their potential use as semiconductors, 3 and 4 being the most promising because of their low band gap values. Compared to the precursors [Tb(DMSO)8]I3 and [Tb(DMF)8]I3, the high energy transitions in the excitation spectra of 1, 2 and 4 are quenched by a process that is best attributed to the autoionization of the carriers in the material. The temperature dependence of the magnetic susceptibilities of 1, 2 and 4 was reproduced well by a CurieWeiss plot at 2-300 K

Photoselective MLCT to d-d pathways for light-induced excited spin state trapping

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The disentangling of hysteretic spin transition, polymorphism and metastability in bistable thin films formed by sublimation of bis(scorpionate) Fe( II ) molecules

International audienceWe investigate the sizeB dependent bistability of a Fe II [HB(3,5B (Me)2Pz)3]2 spinB transition compound in the form of thin films, the thickness of which varies from 130 to 8500 nm. From combined structural, magnetic and optical measurements, we demonstrate that the materials prepared by sublimation consist in crystalline grains of the triclinic phase exhibiting the firstB order spin transition coexisting with those of a new highB spin metastable tetragonal polymorph in a quite large proportion (ca. 42%). Accordingly, we show that the asB sublimed thinB film of a 130 nm thickness retains a remarkable 17 K width hysteresis (T1/2 = 152 K) while the spin transition becomes quantitative by the thermal annealing of the metastable phase at 373 K. Consistently with the calorimetric data, the structural analysis based on singleB crystal xB ray diffraction measurements provides evidences for a thermal hysteresis resulting from successive crystallographic phase transitions, which account for the asymmetric shape of hysteresis and the variation of cooperativity observed in the magnetic and optical data and that, whatever the material dimension