Modifications of EHPDB physical properties through doping with Fe2O3Fe_2O_3 nanoparticles (part II)

The aim of our study was to analyze the influence of various concentrations of γ-Fe(2)O(3) nanoparticles on the physical properties of the liquid crystalline ferroelectric SmC* phase, as well as to check the effect of introducing nanoparticles in the LC matrix on their properties in the prepared five nanocomposites. UV-vis spectroscopy showed that the admixture reduced the absorption of nanocomposites in the UV range, additional absorption bands appeared, and all nanocomposites were transparent in the range of 500–850 nm. The molecular dynamics in particular phases of the nanocomposites were investigated by the dielectric spectroscopy method, and it was found that nanoparticles caused a significant increase in the dielectric constant at low frequencies, a strong modification of the dielectric processes in the SmC* phase, and the emergence of new relaxation processes for the highest dopant concentrations. SQUID magnetometry allowed us to determine the magnetic nature of the nanoparticles used, and to show that the blocked state of nanoparticles was preserved in nanocomposites (hysteresis loops were also registered in the ferroelectric SmC* phase). The dependence of the coercive field on the admixture concentration and the widening of the hysteresis loop in nanocomposites in relation to pure nanoparticles were also found. In turn, the FT-MIR spectroscopy method was used to check the influence of the impurity concentration on the formation/disappearance or modification of the absorption bands, and the modification of both the FWHM and the maximum positions for the four selected vibrations in the MIR range, as well as the discontinuous behavior of these parameters at the phase transitions, were found

Structural and magnetic studies of novel 1-D cyanido-bridged [CuII(Me2en)] [CuII(Me2en)2] [MoIV(CN)8).6H2O chain

Background: The design, synthesis and physicochemical characterization of new switchable magnetic materials is among the most important tasks in the search of multifunctional compounds. Along these lines, intense efforts are focused on the investigation of cyanido–bridged coordination polymers: Prussian Blue Analogs and bimetallic coordination networks constructed of octacyanidometallates. Within this family, the CuII–[Mo(CN)8]4- assemblies have been extensively studied for their photomagnetic properties. The main aim of this work was the design, synthesis, as well as structural, spectroscopic and magnetic characterization of novel molecular material based on copper(II) complex with aliphatic bidentate polyamine and octacyanidometallate( IV) which shows a high number of cyanido bridges. The consequent objective was the study of potential photomagnetic properties of this new material. Methods: A newly synthesized compound [CuII(Me2en)][CuII(Me2en)2][MoIV(CN)8]·6H2O (1), Me2en = N,N– dimethylethylenediamine, was investigated structurally using single crystal X-ray diffraction, spectroscopically by studying IR and UV/Vis spectra, and photo- and magnetically characterized by studying its magnetic response in the dark and under irradiation in a variety of magnetic fields and temperatures. Results: Incorporation of N,N–dimethylethylenediamine (Me2en) into the CuII–[MoIV(CN)8]4- system leads to the construction of a novel coordination polymer [CuII(Me2en)][CuII(Me2en)2][MoIV(CN)8]·6H2O (1). The assembly reveals the unique structure consisting of 1–D chains constructed of {[Cu(Me2en)][Mo(CN)8]}n 2n- ladders with {[Cu(Me2en)2]2n+ pendant arms connected through cyanido–bridges to the Mo(IV) centers. Structural parameters of 1 were compared with other Cu(II)–Mo(IV) compounds with bidentate aliphatic polyamine ligands. Magnetic studies of 1 indicate paramagnetic behavior with weak antiferromagnetic interactions at low temperature. Photomagnetic studies with the application of 405, 473, 532 and 650 nm light sources and white light show no detectable photomagnetic effect. Conclusion: Novel 1–D ladder with pendant arms [CuII(Me2en)][CuII(Me2en)2][MoIV(CN)8]·6H2O (1) coordination polymer reveals unprecedented topological pattern and shows one of the highest complexities among 1–D octacyanidometallate– based chains. The local environments of metal centers were compared with other Cu(II)–Mo(IV) assemblies containing bidentate chelating polyamine ligands. In accordance with this analysis, two types of copper(II) moieties were distinguished among this kind of assemblies. Moreover, the analysis of [Mo(CN)8]4- for systems with various dimensionalities shows the same geometry and structural parameters of the moieties, differing in the number of bridging cyanides. Despite similar structural, spectroscopic and magnetic properties of 1 in comparison with other copper(II) complexes with aliphatic polyamines and octacyanidomolybdate(IV) revealing photomagnetic effect, no light induced increase of magnetization was observed. This leads to the observation that a large number of Cu(II)–NC–Mo(IV) linkages does not guarantee the presence of photomagnetic behavior

Irradiation temperature dependence of the photomagnetic mechanisms in a cyanido-bridged CuII2MoIV trinuclear molecule

We report a new bimetallic cyanido-bridged trinuclear complex [CuII(enpnen)]2[MoIV(CN)8]·6.75H2O (1) (enpnen = N,N′-bis(2-aminoethyl)-1,3-propanediamine) that shows reversible photomagnetic effect. The photo-induced increase of magnetization is characterized by the irradiation temperature-dependent shapes of the χMT(T) plots and different magnetization values at low temperature in high magnetic field, suggesting multiple photoexcited states. The photomagnetic effect in 1 is explained through two possible processes simultaneously: the light-induced metal-to-metal charge transfer (MMCT) in the CuII–NC–MoIV pair and the light-induced excited spin-state trapping (LIESST) effect in MoIV center. A numerical model assuming the simultaneous existence of three possible states after irradiation: the MMCT CuI–NC–MoV–CN–CuII state, the LIESST CuII–NC–MoIVHS–CN–CuII state, and the ground-state CuII–NC–MoIVLS–CN–CuII was applied to the data and resulted in Cu–Mo exchange coupling constants J1MMCT = 11 cm–1 and J2LIESST = 109 cm–1 for the MMCT and LIESST mechanisms induced states, respectively. Fractions of respective states after irradiations at different temperatures were also calculated, shedding light on the influence of irradiation temperature on the photomagnetic mechanism. The proposed model can provide the interpretative framework for testing and refinement of the mechanism of photomagnetic effect in other coordination networks with cyanido-bridged Cu–[Mo(CN)8]4– linkages