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A huge increase in the magnetization of two coordination chains based on tetravalent octacyanidometalates (W and Mo ) is observed on irradiation with 436 nm light, while no such behavior is observed for the Nb analogue. A photomagnetic response based solely on [W (CN) ] is demonstrated for the first time. The observed behavior is attributed to the light-induced excited spin state trapping (LIESST) effect at the octacyanidometalate, and to the resulting magnetic exchange ON/OFF photoswitching between the Mn center and the photoinduced high-spin (S=1) W or Mo centers.

The photoinduced properties of the octacoordinated complex K4MoIV(CN)8⋅2 H2O were studied by theoretical calculations, crystallography, and optical and magnetic measurements. The crystal structure recorded at 10 K after blue light irradiation reveals an heptacoordinated Mo(CN)7 species originating from the light‐induced cleavage of one Mo−CN bond, concomitant with the photoinduced formation of a paramagnetic signal. When this complex is heated to 70 K, it returns to its original diamagnetic ground state, demonstrating full reversibility. The photomagnetic properties show a partial conversion into a triplet state possessing significant magnetic anisotropy, which is in agreement with theoretical studies. Inspired by these results, we isolated the new compound [K(crypt‐222)]3[MoIV(CN)7]⋅3 CH3CN using a photochemical pathway, confirming that photodissociation leads to a stable heptacyanomolybdate(IV) species in solution.

We report a new bimetallic cyanido-bridged trinuclear complex [Cu(enpnen)][Mo(CN)]·6.75HO (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 χ T( 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 Cu-NC-Mo pair and the light-induced excited spin-state trapping (LIESST) effect in Mo center. A numerical model assuming the simultaneous existence of three possible states after irradiation: the MMCT Cu-NC-Mo-CN-Cu state, the LIESST Cu-NC-Mo-CN-Cu state, and the ground-state Cu-NC-Mo-CN-Cu was applied to the data and resulted in Cu-Mo exchange coupling constants J = 11 cm and J = 109 cm 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)] linkages.

Self-assembly of b-diketonate (Htta ¼ thenoyl(trifluoro)acetone) and 4,4 0 -azopyridine (Azo-py) with neodymium(III) ions in the presence of methanol resulted in the formation of mononuclear complex [Nd III (TTA) 3 (MeOH) 2 ]$0.5Azo-py (A) in which two asymmetric units are linked by Azo-py through hydrogen bonding via methanol. A reveals near-infrared emission (NIR) centred at about 895 and 1056 nm, in the 10-370 K temperature range, originating from the two emissive transitions on Nd(III) from 4 F 3/2 to 4 I 9/2 and 4 I 11/2 levels, respectively. Furthermore, the NIR luminescence intensity of A at room temperature augments two times upon thermal elimination of one coordinated methanol molecule. The thermally activated A exhibits single centre ratiometric thermometer behaviour in a wide temperature range from 10 to 300 K. Moreover, fluorescence properties of A were compared to another mononuclear complex [Nd III (TTA) 3 (4-OHpy)(H 2 O)] (B). Assembly A also exhibits field-induced slow magnetic relaxation properties with an energy barrier of DE/k B ¼ 19.7(7) K and an attempt time of relaxation, s 0 ¼ 3.7(8) Â 10 À7 s for fresh sample A, and DE/k B ¼ 27.3 K and s 0 ¼ 8.5(0) Â 10 À8 for assembly A after thermal treatment at 370 K.

Self-assembly of lanthanide­(III) complexes of 2,2′:6′,2″-terpyridine (terpy) with dicyanidoargentate­(I) and dicyanidoaurate­(I) anions in water results in the formation of six isostructural dinuclear systems [LnIII(terpy)­(H2O)­(NO3)2]­[MI(CN)2] (LnIII/MI = Dy/Ag, 1; Dy/Au, 2; Yb/Ag, 3; Yb/Au, 4; Er/Ag, 5; Er/Au, 6). They form three-dimensional supramolecular networks based on dinuclear molecules linked by hydrogen bonds, π–π interactions, and argentophilic (Ag···Ag) or aurophilic (Au···Au) interactions. All of the assemblies show complex solid-state strong UV and weak vis–NIR absorption due to overlapping contributions from 2,2′:6′,2″-terpyridine, dicyanidoargentate­(I), dicyanidoaurate­(I), and lanthanide­(III) ions. Moreover, they exhibit excitation-wavelength-dependent multicolor photoluminescence ranging from bright white to blue via yellow, green, and cyan colors due to variable contributions from the dicyanidometalate and ligand. Assemblies 3–6 show NIR emission originating from YbIII and ErIII metal centers. Furthermore, compounds 1–6 and their magnetically diluted samples are magnetic-field-induced single-molecule magnets with energy barriers of up to 35 K. The effect of noble metal substitution on the magnetic properties of particular lanthanide ions is described. The influence on the thermal anisotropic energy barrier, which relates to the strength of the magnetic anisotropy, depends on the type of lanthanide used. The Ag-to-Au substitution enhances the anisotropy of the prolate YbIII ion and decreases it for the oblate DyIII ion. It also modifies the strength of dipolar interactions affecting the slow magnetic relaxation processes.

The aim of this paper is to show, by systematic studies, the influence of γ-Fe2O3 nanoparticles on the physical parameters of the liquid crystalline matrix, exhibiting a ferroelectric phase in a wide temperature range. The detailed research was carried out by using diffraction (PXRD), microscopic (OM, SEM, FCPM, POM), thermal (DSC), optical (TLI), electric and spectroscopic (FTIR) methods. We show that even the smallest concentration of γ-Fe2O3 nanoparticles largely modifies the parameters of the ferroelectric SmC* phase, such as spontaneous polarization, switching time, tilt angle, rotational viscosity, dispersion anchoring energy coefficient and helix pitch. The admixture also causes a significant reduction in the temperature of phase transitions, broadening the SmA* phase at the expense of the SmC* phase and strong streaking of the texture. We present and explain the non-monotonic modification of these parameters with an increase in the nanoparticle concentration. The influence of oleic acid admixture on these parameters is also widely discussed. We have shown that certain parameters of organic-metal nanocomposites can be controlled by the appropriate amount of metal admixture.

International audienceA unique one-dimensional ribbon [Cu(bapa)]2[Mo(CN)8]·7H2O (1) (bapa = bis(3-aminopropyl)amine), consisting of {[Cu(bapa)]3[Mo(CN)8]2}2− trigonal bipyramids and {[Cu(bapa)]2[Mo(CN)8]2}4− rhombuses linked through [Cu(bapa)]2+, was obtained and its photomagnetic properties were investigated. After irradiation at selected wavelengths (405 and 532 nm) or with white light, a global increase of the magnetic moment was observed. The initial state of the compound can be fully recovered by heating the sample above the temperature of relaxation of 253 K. This work was completed with photoreversibility studies with red and IR light irradiation which confirm a partial light-induced reversibility of the photomagnetic effect in 1. Finally, the photomagnetic phenomenon in 1 is discussed in accordance with two processes: the spin crossover on Mo(IV) centres and the metal-to-metal charge transfer mechanism in the Cu(II)–Mo(IV) pair