Diana Visinescu

Square-like cyano-bridged {Ln ₂ ^III Fe ₂ ^III } field induced SMMs and magnetic coolers operating just above the helium liquefaction temperature have been reported.

Rare K/Mo-based hybrid structures were obtained through a new approach, employing the K ₄ [Mo ^IV (CN) ₈ ] precursor, their capacitive behavior being investigated through cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) tests.

The newly reported cyanido-bridged {Fe^IIM^II} coordination polymers, with rare ladder-like topologies, show gradual HS-to-LS SCO on cooling due to the flexible N6 surrounding of Fe^II metal ions from one pincer and three CN^- ligands (M = Pd, Pt).

Two new families of zinc/cobalt/aluminum-based pigments, with a unique composition, were obtained through the polyol method. The hydrolysis process of a mixture of Co(CH₃COO)₂, Zn(acac)₂ and Al(acac)₃ (acac⁻ = acetylacetonate ion) in 1,4-butanediol afforded dark blue gels (wPZn_xCo_1−xAl), in the presence of a supplementary amount of water, and light green powders (PZn_xCo_1−xAl), respectively, for the water-free procedure (x = 0, 0.2, 0.4). The calcination of the precursors yielded dark green (wZn_xCo_1−xAl) and blue (Zn_xCo_1−xAl) products. XRD measurements and Rietveld refinement indicate the co-existence of three spinel phases, in different proportions: Zn_xCo_1−xAl₂O₄, Co₃O₄ and the defect spinel, γ-Al_2.67O₄. The Raman scattering and XPS spectra are in agreement with the compositions of the samples. The morphology of wZn_xCo_1−xAl consists of large and irregular spherical particle aggregates (ca. 5–100 mm). Smaller agglomerates (ca. 1–5 mm) with a unique silkworm cocoon-like hierarchical morphology composed of cobalt aluminate cores covered with flake-like alumina shells are formed for Zn_xCo_1−xAl. TEM and HR-TEM analyses revealed the formation of crystalline, polyhedral particles of 7–43 nm sizes for wZn_xCo_1−xAl, while for Zn_xCo_1−xAl, a duplex-type morphology, with small (7–13 nm) and larger (30–40 nm) particles, was found. BET assessment showed that both series of oxides are mesoporous materials, with different pore structures, with the water-free samples exhibiting the largest surface areas due, most likely, to the high percent of aluminum oxide. A chemical mechanism is proposed to highlight the role of the water amount and the nature of the starting compounds in the hydrolysis reaction products and, further, in the morpho-structural features and composition of the resulting spinel oxides. The CIE L*a*b* and C* colorimetric parameters indicate that the pigments are bright, with a moderate degree of luminosity, presenting an outstanding high blueness.

A new mixed-valence one-dimensional coordination polymer of formula {[Co^II(MeOH)₂][(μ-NC)₂Co^III(dmphen)(CN)₂]₂}_n·2nH₂O (1) was obtained by reacting the Ph₄P[Co^II(dmphen)(CN)₃] metalloligand (dmphen = 2,9-dimethyl-1,10-phenanthroline and Ph₄P⁺ = tetraphenylphosphonium ion) with cobalt(II) acetate tetrahydrate. The structural analysis shows the formation of a neutral 4,2-ribbon-like chain of vertex-sharing cyanido-bridged {Co^III₂Co^II₂} squares in which the metalloligand underwent an oxidation process and a reorganization to form {Co^III(dmphen)(CN)₄}⁻ linkers that coordinate to the [Co^II(MeOH)₂]²⁺ units through single cyanido ligands. Both cobalt(II) and Co(III) cations are six-coordinated in distorted octahedral environments. The shortest intrachain distance between the paramagnetic cobalt(II) ions is 7.36 Å, a value which is shorter than the shortest interchain one (10.36 Å). Variable-temperature (1.9–300 K) static (dc) magnetic measurements for 1 indicate the occurrence of magnetically isolated high-spin cobalt(II) ions with a D value of +67.0 cm⁻¹. Dynamic alternating current (ac) magnetic measurements between 2.0–13 K reveal that 1 exhibits slow magnetic relaxation under non-zero applied dc fields, being thus a new example of field-induced SIM with easy-plane magnetic anisotropy. Theoretical calculations by CASSCF/NEVPT2 on 1 support the results from magnetometry. The relaxation of the magnetization occurs in the ground state under external dc fields through a two-phonon Raman process and one intra-Kramers mechanism.

The use of two triazine-derived pincer ligands led to the obtaining of a heterometallic compound and of an unexpected 3D coordination polymer (CP). Therefore, by reacting 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) with Zn(NO₃)₂ and K[Ag(CN)₂], the cyanido-bridged [Ag(CN)(m-CN)]₂[Zn(tptz)(H₂O)] (1) trinuclear complex was formed. Compound 1 crystallizes in the orthorhombic polar space group Aea2 and the crystal packing involves argentophilic interactions. When 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine (TPymT) was used as a ligand, along with the same precursors as for 1, a 3D CP was assembled, [Ag₆(CN)₆(TPymT)₂] (2). The formation of 2 was favored, most likely, by the dicyanoargentate(I) ion dissociation and its interesting topology is due to the bridging cyanide ligands and argentophilic interactions. The fluorescence of both compounds was studied and compared to the emission features of their ligands. For the two coordination compounds, ligand-centered fluorescence data are discussed.

The aim of this study is the preparation of nanostructured copper(II) oxide-based materials (CuONPs) through a facile additive-free polyol procedure that consists of the hydrolysis of copper(II) acetate in 1,4-butane diol and its application in hydrogen peroxide sensing. The nonenzymatic electrochemical sensor for hydrogen peroxide determination was constructed by drop casting the CuONP sensing material on top of a glassy carbon electrode (GCE) modified by a layer of poly(3,4-ethylenedioxythiophene) conducting polymer (PEDOT). The PEDOT layer was prepared on GCE using the sinusoidal voltage method. The XRD pattern of the CuONPs reveals the formation of the monoclinic tenorite phase, CuO, with average crystallite sizes of 8.7 nm, while the estimated band gap from UV–vis spectroscopy is of 1.2 eV. The SEM, STEM, and BET analyses show the formation of quasi-prismatic microaggregates of nanoparticles, with dimensions ranging from 1 µm up to ca. 200 µm, with a mesoporous structure. The developed electrochemical sensor exhibited a linear response toward H₂O₂ in the concentration range from 0.04 to 10 mM, with a low detection limit of 8.5 μM of H₂O₂. Furthermore, the obtained sensor possessed an excellent anti-interference capability in H₂O₂ determination in the presence of interfering compounds such as KNO₃ and KNO₂.

Three {Co ^II ( ^R bik) ₂ } single-ion magnets (SIMs) based on the ^Me bik ligand [ ^Me bik = bis(1-methylimidazol-2-yl)ketone] and one mixed-valence {CoIII2Co ^II } _n chain of Co ^II SIMs connected by diamagnetic {CoIII2(μ-2,5-dpp)(CN) ₈ } spacers are discussed.