Lord of the Dance Dynamic hydrogen‐bonding interactions and spin‐transition behavior play a key role in stabilizing intermediate phases in a multi‐step spin transition. In their Communication on page ...595 ff., M. Nihei, H. Oshio, et al. present a hydrogen‐bonding donor–acceptor system, comprising a spin transition‐active square complex Co2Fe2 and aromatic hydrogen‐bond‐donor molecules, which exhibits a three‐step spin transition in response to temperature.
A series of thermoplastic polyester elastomer (TPEE) derivatives based on recycled polyethylene terephthalate (r-PET) and poly(tetramethylene glycol) together with differing amounts (n%, n = 0, 1, 3, ...and 5) of 1,6-hexanediamine (HDA) were prepared. Blending of the copolymer with a rod-like liquid crystal (4-cyano-3-fluorophenyl 4-ethylbenzoate (4CFE)), named TPEEn%-4CFE, was studied. Among them, the TPEE3%-4CFE mixture featured optimal blending, with liquid crystals well-connected with the HDA moieties in the TPEE framework through hydrogen-bonding interaction, according to X-ray and Fourier-transform infrared spectroscopy analyses. A packing diagram is proposed to illustrate the unique performance of TPEE3%-4CFE, attributed to the enhancement of π–π interactions. The polarized mesophase and morphology indicated favorable dispersion of liquid crystals in the TPEE matrix in TPEE3%-4CFE, which was applied successfully in electrochemical sensing for ascorbic acid for the first time. The TPEE3%-4CFE-modified carbon paste electrode sensor is a rapid-response sensor with high sensitivity of approximately 11.30 μA mM−1, a wide linear dynamic range of 0.181.26 μM, and a limit of detection of 0.4 mM–1.6 mM.
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•TPEE3%-4CFE is a rapid-response sensor with good sensitivity of ∼11.30 μA mM−1.•TPEE3%-4CFE has wide linear dynamic range of ∼0.181.26 μM.•The limit of detection (LOD) of TPEE3%-4CFE was found to be from 0.4 mM to 1.6 mM.
In this work, a close correlation between variations of critical temperature (Tc) and the hole concentration of (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1-x(Fe3O4)x systems was studied. The ...(Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1-x(Fe3O4)x samples were fabricated using the solid-state reaction method, where x ranged from 0 to 0.2. The Tc values of the samples deduced from magnetization versus temperature measurement gradually decreased with increasing the Fe3O4 content (x). To investigate a possible reason for the observed decrease in the values of Tc in the samples, the valence state of copper (V) and the hole concentration (p) in all samples were examined by analyzing the Cu K-edge and Cu L2,3-edge X-ray absorption near edge structure (XANES) spectra. The values of V and p monotonously decreased with the increase in Fe3O4 doping content (x) and agreed with the behavior of Tc. The existence of Fe3+ was confirmed by analyzing Fe L2,3-edge XANES. Hence, Fe3+ ions possibly entered the lattice structure of the samples and filled the holes in CuO2 planes. The degradation of superconductivity in Fe3O4 doped samples was then explained.
Nanograins of Mg-containing amorphous calcium carbonate were prepared in an l-α-lecithin solution from which spherulitic crystallites of high-Mg calcite were subsequently formed. The structures of ...the spherulites of high-Mg calcite were carefully characterized using powder X-ray diffraction, electron microscopy, and solid-state NMR spectroscopy. While the initial growth of Mg-calcite spherulites occurs through the particle attachment pathway, the process of ion-by-ion addition appears to be the predominant mechanism of formation near the end stage of the crystal growth. Consequently, the outer region of the Mg-calcite spherulites displays a higher crystallinity than the inner region, which is a direct consequence of the interplay between multiple pathways.
The synthesis, characterization and transformation of the thermally unstable {Fe(NO)2}9 dinitrosyl iron complex (DNIC) (OMe)2Fe(NO)2- (2) were investigated. The {Fe(NO)2}9 DNIC 2 characterized by ...single-crystal X-ray diffraction is exclusively stabilized by the weak intermolecular Fe(OMe)2(K+) interactions (O(3)K(1) and O(4)K(1) distances of 2.818(3) and 2.810(3) Å, respectively). The binding affinity of chalcogenolate-containing ligands toward the {Fe(NO)2}9 motif follows the series SEt- > SPh- > OPh- > OMe-, which is dictated by the synergistic cooperation of the electron-donating order (SEt- > SPh- > OPh-) and the soft-hard order (from soft to hard, SEt- ∼ SPh- > OPh- > OMe-). In comparison with the XAS Fe K-edge pre-edge energy of {Fe(NO)2}9 (RS)2Fe(NO)2- (R = Ph (4), Et (5)) and (PhO)2Fe(NO)2- (6) DNICs falling within the reported range of 7113.4-7113.9 eV, the distinctive pre-edge energy of 7114.2 eV exhibited by complex 2 suggests that the electronic structure of {Fe(NO)2}9 DNIC 2 may be qualitatively described as a {FeIII(NO-)2}9 electronic structure induced by the dominant ionic character of Fe-OMe bonds, instead of the resonance hybrids of {FeII(NO-)(˙NO)}9 and {FeIII(NO-)2}9 electronic structures induced by the dominant metal-ligand covalency of {Fe(NO)2}9 DNICs 4-6. As shown in TD-DFT computation, the increased population of NO ligands in MO 125β (45.1% NO) attenuating the OMe-induced polarization imposed on the Fe center through the delocalized covalent nature of Fe-NO bonds supports the lower/synergistic NO/OMe → Fe charge transfer energy (1216 nm) observed in the solid-state UV-vis spectrum of complex 2 compared to those (1140 nm) of complexes 4-6.
t-{Fe(abpt)2N(CN)22} abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole is an intriguing spin-crossover system that crystallizes in two polymorphs. Polymorph A is paramagnetic; its crystal structure ...consists of a single molecule located at the center of inversion symmetry. Polymorph B, on the other hand, exhibits a rather complicated two-step-like spin transition; its crystal structure consists of two symmetry-independent molecules. The crystal structure of polymorph B has been derived in the different spin states: above the high-temperature step (300 K), between the two steps (90 K), below the incomplete low-temperature step (50 K), in the light-induced metastable state (15 K), in the thermally quenched metastable state (15 K), and after relaxation from the quenched state (15 K). The correlation between the structure and magnetic properties is precisely established, allowing the complicated magnetic behavior of polymorph B to be well understood. A unique order−disorder phase transition, resulting in a modulation of the metastable state structures, is detected for the first time on such spin-transition compounds. The modulation of the structure originates from a particular ordering of the dicyanamide ligand at one of the two Fe sites.
A small peptide mimetic molecule can form diverse nanostructures such as nano-vesicles, nano-tubes and nano-ribbons/fibrils by self-assembly, in response to various physical and chemical stimulations.
A combination of N/S/Fe K-edge X-ray absorption spectroscopy (XAS), X-ray diffraction data, and density functional theory (DFT) calculations provides an efficient way to unambiguously delineate the ...electronic structures and bonding characters of Fe–S, N–O, and Fe–N bonds among the direduced-form Roussin’s red ester (RRE) Fe2(μ-SPh)2(NO)42–(1) with {Fe(NO)2}10-{Fe(NO)2}10 core, the reduced-form RRE Fe2(μ-SPh)2(NO)4−(3) with {Fe(NO)2}9-{Fe(NO)2}10 core, and RRE Fe2(μ-SPh)2(NO)4 (4) with {Fe(NO)2}9-{Fe(NO)2}9 core. The major contributions of highest occupied molecular orbital (HOMO) 113α/β in complex 1 is related to the antibonding character between Fe(d) and Fe(d), Fe(d), and S atoms, and bonding character between Fe(d) and NO(π*). The effective nuclear charge ( Z eff) of Fe site can be increased by removing electrons from HOMO to shorten the distances of Fe···Fe and Fe–S from 1 to 3 to 4 or, in contrast, to increase the Fe–N bond lengths from 1 to 3 to 4. The higher IR νNO stretching frequencies (1761, 1720 cm–1 (4), 1680, 1665 cm–1 (3), and 1646, 1611, 1603 cm–1 (1)) associated with the higher transition energy of N1s →σ*(NO) (412.6 eV (4), 412.3 eV (3), and 412.2 eV (1)) and the higher Z eff of Fe derived from the transition energy of Fe1s → Fe3d (7113.8 eV (4), 7113.5 eV (3), and 7113.3 eV (1)) indicate that the N–O bond distances of these complexes are in the order of 1 > 3 > 4. The N/S/Fe K-edge XAS spectra as well as DFT computations reveal the reduction of complex 4 yielding complex 3 occurs at Fe, S, and NO; in contrast, reduction mainly occurs at Fe site from complex 3 to complex 1.
In addition to probing the formation of dinitrosyl iron complexes (DNICs) by the characteristic Fe K-edge pre-edge absorption energy ranging from 7113.4 to 7113.8 eV, the distinct S K-edge pre-edge ...absorption energy and pattern can serve as an efficient tool to unambiguously characterize and discriminate mononuclear DNICs and dinuclear DNICs containing bridged-thiolate and bridged-sulfide ligands. The higher Fe–S bond covalency modulated by the stronger electron-donating thiolates promotes the Fe → NO π-electron back-donation to strengthen the Fe–NO bond and weaken the NO-release ability of the mononuclear DNICs, which is supported by the Raman ν(Fe–NO) stretching frequency. The Fe–S bond covalency of DNICs further rationalizes the binding preference of the {Fe(NO)2} motif toward thiolates following the trend of SEt− > SPh− > SC7H4SN−. The relative d-manifold energy derived from S K-edge XAS as well as the Fe K-edge pre-edge energy reveals that the electronic structure of the {Fe(NO)2}9 core of the mononuclear DNICs (NO)2Fe(SR)2− is best described as {FeIII(NO–)2}9 compared to {FeIII(NO–)2}9–{FeIII(NO–)2}9 for the dinuclear DNICs Fe2(μ-SEt)(μ-S)(NO)4− and Fe2(μ-S)2(NO)42–.
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