Films and monoliths containing the spin crossover complex [Fe(Htrz)(2)(trz)](BF(4)) (trz = 1,2,4-triazole) as nanoparticles have been obtained. The dispersion and consecutive inclusion of the Fe complex in a silica matrix prepared from tetramethoxysilane or tetraethoxysilane afford monoliths or films with a violet colour at room temperature, which turns white above 380 K. This change of colour is reversible. This thermochromic behaviour has been characterized by measuring the magnetic properties together with thermogravimetric studies and Raman spectroscopy, the result of which all demonstrate that both films and monoliths undergo a spin crossover. Microscopy studies confirm the occurrence of the Fe complex as nanoparticles, in both the monoliths and the films. The facile synthesis of these materials as nanoparticles in transparent films should open the possibility of the synthesis of high quality films.

1388-076

The syntheses, structural characterisation, and magnetic and spectroscopic properties of three new polymorphs of the spin-crossover complex [Fe(sal 2 -trien)][Ni(dmit) 2 ] are reported. The results are discussed as a function of their intra-and intermolecular arrangement. Correlation of their crystal structures and magnetic properties suggest that some torsion angles play a significant role in the magnetic properties of this class of compounds. Intermolecular contacts are also of importance, and the nature of the short contacts between molecular species seems to be more crucial than their number in the allowance of spin-crossover.

The salt formed between the large aromatic berberine cation and the long-chain palmitate anion was synthesized and used to prepare aqueous suspensions of particles owing to a solvent-exchange method. Under these conditions, elongated particles were readily obtained. They were studied by transmission microscopy with polarized light, as well as by fluorescence and electron microscopy. They were shown to be probably crystallized nanofibers, which were stable in suspension. Unexpectedly, upon filtration and drying, these fibers evolved to give a reticulated solid. The fluorescence properties of the compound were analyzed in solution, in aqueous suspension and in the powder crystalline state. Interestingly, berberine palmitate is virtually not fluorescent in aqueous solution because of the quenching effect of water, but transition to the solid state was accompanied by a strong increase in fluorescence intensity. This phenomenon was explained by the original molecular arrangement in the solid state. Actually, in the crystal, the anions form a distinct layer, which limits parallel-stacking of the fluorescent cations. Moreover, the berberine cations are protected from the access of water molecules, and so no quenching effect can take place. This example confirms that the newly introduced concept of ion-pair aggregation-induced fluorescence enhancement can be extended to a variety of structures. It also shows the interest of ion pairs for preparing fluorescent nanofibers and reticulated solids using a solvent-exchange method that is particularly easy to implement.

This work reports on the combination between photochromic complexes (Na2[Fe(CN)5(NO)]·2H2O and K2[RuCl5(NO)]) with spin‐crossover compounds derived from FeIII complexes {[Fe(qsal)2]+ and [Fe(salEen)2]+; Hqsal = N‐(8‐quinolyl)salicylaldimine; HsalEen = N‐[(2‐ethylamino)ethyl]salicylaldimine}. These associations have resulted in the synthesis of new materials that contain a spin‐crossover unit and a photochromic unit, as evidenced by their X‐ray structure. Spectroscopic, magnetic and photomagnetic properties of these complexes were studied, with or without light irradiation, to evaluate the possible influence of the photochromic group on the spin transition. [Fe(qsal)2]2[Fe(CN)5(NO)]·solvent, [Fe(salEen)2]2[Fe(CN)5(NO)] and [Fe(qsal)2]2[Ru(CN)5(NO)]·2.5H2O all exhibit a spin transition. The light‐induced excited spin‐state trapping (LIESST) effect was detected in the (Fe‐qsal)‐based complexes. [Fe(qsal)2]2[Ru(CN)5(NO)]·2.5H2O also exhibits a reverse‐LIESST effect. Regardless of the complex, no photochromic effect from the nitroprusside units was detected.