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A series of germinal -diethynylethene ( gem -DEE) bridged diferrocenyl compounds, including 1,1-[bis(ferrocenylethynyl)methylene]cyclohexane ( 1 ), 1,1-[bis(ferrocenylethynyl)methylene]tetrahydro-2 H -pyran ( 2 ), and 1,1-[bis(ferrocenylethynyl)methylene]tetrahydro-2 H -thiopyran ( 3 ) were synthesized and characterized. The Fe ⋯ Fe distance between the two ferrocenyl termini reaches up to ∼9 Å for compounds 2 and 3 . The electrochemical measurements demonstrate moderate electronic coupling between the gem -DEE-bridged ferrocenyl (Fc) termini in this cross-conjugated system. UV–vis–NIR spectroscopy studies suggest that the monocation species of these compounds belong to class II mixed-valence systems in Robin–Day classification. DFT calculations further reveal electronic structures of these cross-conjugated diferrocenyl compounds. [ABSTRACT FROM AUTHOR]

Niobium-based anode materials have good prospects for application in lithium-ion batteries (LIBs) due to the advantages of high specific capacity and high safety. However, the low electronic conductivity poses the main obstacle that limits its performance at present. Here, a mixed-valent niobium based phosphate, K 3 Nb 6 P 4 O 26 @C (KNPO@C), was designed and prepared as the anode material for LIBs. The mixed-valent Nb in KNPO provides multi-electron electrochemical reactions and presents an electronic conductivity higher than that of a sole Nb5+-based material. In addition, the three-dimensional (3D) channels in the crystal structure of KNPO facilitate the rapid transport of lithium-ions. KNPO@C anode delivers a high specific capacity of 250 mA h g–1 at 0.1 C and an excellent cycling stability was measured with a capacity retention of 60.7 % after 1000 cycles at 2 C. The charge/discharge mechanism of KNPO@C was systematically investigated by ex-situ XRD and ex-situ XPS. The kinetic information obtained from the cyclic voltammetry (CV) suggests that the pseudocapacitance effect also play an important role in the specific capacity. These results demonstrate the potential of KNPO@C as a practical anode material for high-performance LIBs. • A mixed-valent niobium based phosphate anode material KNPO@C is first studied in lithium ion batteries. • KNPO@C delivers a high specific capacity over 250 mA h g−1. • KNPO@C shows good capacity retention with 60 % after 1000 cycles. • The Li+ storage mechanism is studied by ex-situ XRD and ex-situ XPS. [ABSTRACT FROM AUTHOR]

The electron transfer of mixed valence complexes is regulated by adjusting the electron-donating ability of the auxiliary ligand of the cyanidometal bridge. [Display omitted] Two pairs of cyanidometal-bridged trinuclear complexes trans -[Cp*(modppe)Ru(μ-NC)Ru(L) 4 (μ-CN)Ru(modppe)Cp*][PF 6 ] n (n = 2, 3; L = pyridine (py), 1[ PF 6 ] n ; 4-methoxypyridine (mopy), 2[ PF 6 ] n ; Cp* = 1,2,3,4,5-pentamethylcyclopentadiene) in two distinct states have been synthesized and fully characterized. The investigated results suggest that 1[ PF 6 ] 3 and 2[ PF 6 ] 3 are Class II mixed valence complexes. The IR spectroscopy and UV–vis-NIR spectroscopy analyses showed that with the increase of the electron-donating ability of the auxiliary ligand of the cyanidometal bridge, the degree of delocalization increases and the energy of the metal-to-metal charge transfer (MMCT) of the mixed valence complexes decreases, supported by TDDFT calculations. [ABSTRACT FROM AUTHOR]

Herein we prepared various mixed-valence Pd SACs via photodeposition. The excited electrons from the conduction band of TiO 2 could be captured and reduce the Pd precursors on graphene to generate Pd SACs catalysts with different valence states. These catalysts indicated excellent catalytic activity for the typical Palladium catalyzed Suzuki and Sonogashira C–C coupling. [Display omitted] • Mixed-valence Pd SACs were obtained through photochemical strategy. • Excellent catalytic activity for Suzuki and Sonogashira C–C coupling. • The mechanism of tailoring the Pd0/Pd2+ atomic ratios was investigated. Heterogeneous Pd single-atom catalysts (Pd SACs) have demonstrated high efficiency in C–C coupling reactions, which are considered the cornerstones of organic synthesis. However, the development of 2D materials for the evaluation of the catalytic efficiency of mixed-valence Pd SACs remains a significant challenge. In this study, we prepared various mixed-valence Pd SACs via photodeposition. The electronic structure and dispersion state of the surface Pd species were confirmed. The important role of graphene oxide in the design of atomically dispersed Pd species was further confirmed through comparative experiments with Pd/TiO 2. The mixed-valence Pd SACs exhibited excellent catalytic activity for the typical palladium-catalyzed Suzuki and Sonogashira C–C coupling. Theoretical calculations and EXAFS spectra were used to determine the mechanism for tailoring the Pd0/Pd2+ atomic ratios. These studies initiate a broad portfolio of mixed-valence metal-based single-atom catalysts (SACs). [ABSTRACT FROM AUTHOR]

The polyhedral building blocks of the layered inorganic network in the mixed-valence title compound, (NH4)(VIVO2)(VVO2)(TeO3), are vertex-sharing VVO4 tetrahedra, distorted VIVO6 octahedra and TeO3 pyramids, which are linked by V—O—V and V—O—Te bonds, forming double layers lying parallel to (100). The presumed TeIV lone-pairs of electrons appear to be directed inwards into cavities in the double layers. The charge-balancing ammonium cations lie between the layers and probably interact with them via N—H...O hydrogen bonds.

Salen ligands are ubiquitous in inorganic chemistry with utility in applications ranging from materials to catalysis. Additionally, salen ligands have the potential for redox-activity due to energetically accessible molecular orbitals. This review will focus on elucidation of the electronic structure in oxidized metal–salen complexes. Due to the highly modular synthesis of these ligands, we present a comprehensive examination of structural factors that play a role in determining the overall electronic structure upon one-electron oxidation. Experimental and theoretical techniques used in the study of oxidized metal-salen complexes are presented, as well as the basics for the interpretation of such techniques. While the emphasis of the review is on complexes of the first-row transition metals, we briefly discuss second- and third-row transition metal–salen complexes, as well as salen-type ligand derivatives. [ABSTRACT FROM AUTHOR]

Noble metal halide compounds are an exciting class of materials which display unique crystal chemistry with temperature and pressure. Here we report two new compounds, single-valence formamidinium platinum iodide [(FA) 2 Pt IV I 6 ] and mixed-valence methylammonium gold iodide [(MA) 2 Au I Au III I 6 ]. Structural changes between 300 K and 100 K have been monitored. The compounds crystallize in two different perovskite-related structure classes, with the added complexity of a disordered, “tumbling”, organic cation at 300 K. This tumbling is significantly reduced at 100 K. (FA) 2 Pt IV I 6 undergoes in-phase octahedral tilting similar to related vacancy-ordered perovskite materials. At 100 K, (MA) 2 Au I Au III I 6 undergoes a transition which facilitates stronger Au–I covalent bonding as made evident by a contraction of the unit cell and distances between Au and I atoms in the ab plane. [ABSTRACT FROM AUTHOR]

Two mononuclear rhodium complexes, Rh(I)-1,5-cyclooctadiene and Rh(III)-pentamethylcyclopentadienyl, and a bimetallic Rh(I)-Rh(III) mixed-valence complex were synthesised. The complexes were fully characterised using an array of analytical techniques which included NMR and infrared spectroscopy, single-crystal X-ray diffractometry, elemental analysis, and mass spectrometry. These complexes were evaluated as catalyst precursors in the hydroformylation of olefins. All catalyst precursors were active in the hydroformylation of 1-octene under optimised conditions. The rhodium complexes generally showed chemoselectivity towards the formation of linear aldehydes. The electrochemical behaviour of the rhodium complexes was examined using cyclic voltammetry. [ABSTRACT FROM AUTHOR]

The novel trisbipyridyl iron complex of formula [Fe(Mebpy-CN) 3 ](PF 6 ) 2 ( 1 ) (with Mebpy-CN = 4-methyl-2,2′-bipyridine-4′-carbonitrile) and three novel heteropolynuclear complexes of formulae: [(Mebpy-CN) 2 Fe(Mebpy-CN)Ru(NH 3 ) 5 ](PF 6 ) 4 ( 2 ), [(Mebpy-CN)Fe{(Mebpy-CN)Ru(NH 3 ) 5 } 2 ](PF 6 ) 6 ( 3 ) and [Fe{(Mebpy-CN)Ru(NH 3 ) 5 } 3 ](PF 6 ) 8 ( 4 ), were synthesized and characterized by spectroscopic and electrochemical techniques. When introducing peripheral ruthenium ammines to complex ( 1 ) using Mebpy-CN as a bridging ligand in complexes ( 2 ) to ( 4 ), the molar absorptivities increase in the visible region with increasing nuclearity of the complex. When oxidizing the Ru centers in the heteropolynuclear species, the corresponding three mixed-valent species are obtained, displaying IVCT (intervalence charge transfer) bands at λ max = 850 nm, with molar absorptivities that are also enhanced by increasing the number of pentaammineruthenium moieties. The modulation of the absorption properties of transition metal complexes in the visible and NIR regions is a relevant issue for improving the performance of Dye-Sensitized Solar Cells, since their efficiency can be enlarged with increasing absorption in these regions. [ABSTRACT FROM AUTHOR]

Here we report properties of thiophene-rich, acetylide-type mono-, di- and tri-nuclear ruthenium molecular wires 1 – 4 , which are prepared by rationally designed coupling of vinylidene intermediates. Electrochemical analysis of 1 – 3 reveals fully reversible redox waves, the numbers of which are equal to those of the ruthenium fragments. Spectroelectrochemical analysis of 2 and 3 reveals the clear step-by-step oxidation processes. Analysis of NIR absorption bands reveals that the monocationic species 2 + and 3 + are highly charge-delocalized species, which are further supported by DFT and TD-DFT calculations of their model complexes. [ABSTRACT FROM AUTHOR]

The chemistry of mixed-valence complexes joins that of molecular electronics in the quantum cellular automata (QCA) paradigm, a concept which has been demonstrated to be a possible alternative to the transistor-based technology, in which binary information is encoded in the configuration of charge among redox-active molecular sites. Experimental and theoretical efforts have recently been devoted to molecular mixed-valence organometallic systems containing two and four metal centers as candidates for QCA. Properties of specific examples based on hypothetical organometallic molecules are theoretically analyzed and discussed with the aid of DFT calculations. [ABSTRACT FROM AUTHOR]

The diheme enzyme MauG utilizes H 2 O 2 to perform oxidative posttranslational modification on a protein substrate. A bis -Fe(IV) species of MauG was previously identified as a key intermediate in this reaction. Heterolytic cleavage of the O O bond of H 2 O 2 drives the formation of the bis -Fe(IV) intermediate. In this work, we tested a hypothesis that a glutamate residue, Glu113 in the distal pocket of the pentacoordinate heme of MauG, facilitates heterolytic O O bond cleavage, thereby leading to bis -Fe(IV) formation. This hypothesis was proposed based on sequence alignment and structural comparison with other H 2 O 2 -utilizing hemoenzymes, especially those from the diheme enzyme superfamily that MauG belongs to. Electron paramagnetic resonance (EPR) characterization of the reaction between MauG and H 2 O 2 revealed that mutation of Glu113 inhibited heterolytic O O bond cleavage, in agreement with our hypothesis. This result was further confirmed by the HPLC study in which an analog of H 2 O 2 , cumene hydroperoxide, was used to probe the pattern of O O bond cleavage. Together, our data suggest that Glu113 functions as an acid-base catalyst to assist heterolytic O O bond cleavage during the early stage of the catalytic reaction. This work advances our mechanistic understanding of the H 2 O 2 -activation process during bis -Fe(IV) formation in MauG. [ABSTRACT FROM AUTHOR]

One-electron reduction of a pyrazolate-bridged triangular Fe3(μ3-O) core induces a cascade wherein all three metal centers switch from high-spin Fe3+ to low-spin Fe2.66+. This hypothesis is supported by spectroscopic data (1H-NMR, UV-vis-NIR, infra-red, 57Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters. This is, to the best of our knowledge, the first example of a one-electron redox event causing concerted change in multiple iron centers. [ABSTRACT FROM AUTHOR]

Keywords: cyanides; crystal structure; electron transfer; mixed-valence; remote substituents EN cyanides crystal structure electron transfer mixed-valence remote substituents 1 1 1 04/27/23 20230425 NES 230425 B The Front Cover b shows a new series of trinuclear Fe-Ru-Fe mixed-valence compounds obtained by changing the electron-donating ability of the remote substituents (R) of the ligand on the bridging metal center. Cyanides, crystal structure, electron transfer, mixed-valence, remote substituents Front Cover: Influence of Changing the Remote Substituents on Charge Transfer Properties of Cyanide-Bridged Trinuclear Fe-Ru-Fe Complexes (Eur. J. Inorg. [Extracted from the article]

Three new oxo-centered trinuclear complexes, one of them a mixed-valence complex [Mn3O(C7H4O2Cl)6(Py)3]Py (1) and the others, mixed-metal complexes of [Fe2MnO(C7H4O2Cl)6(Py)3]NO3 (2) and [Fe2CoO(C7H4O2Cl)6(Py)3] (3) were synthesized by the direct reaction between metal nitrates and p-chlorobenzoic acid. These complexes were characterized by elemental analyses (CHN), atomic absorption spectroscopy and spectral (IR, electronic) studies. These are new type of oxo-bridged mixed-metal complexes in which the carboxylate ligand is p-chlorobenzoic acid. The UV spectra of the complexes exhibited a strong band in the region 42,500 cm-1 which is related to the (π → π*) transitions of the pyridine ligand. The IR spectra of these compounds showed two strong stretching vibrations bands, indicating a bridging coordination mode of the carboxylic group of the ligand in the complexes.

Charge transfer, mixed-valence, open-shell acceptor, open-shell donor, radical dimer Keywords: charge transfer; mixed-valence; open-shell acceptor; open-shell donor; radical dimer EN charge transfer mixed-valence open-shell acceptor open-shell donor radical dimer 1 1 1 03/16/23 20230313 NES 230313 B Stable organic radicals b can serve as ideal building blocks for the construction of molecular functional materials due to their unique open-shell structures. In this Concept, both recent experimental progress and design strategies of stable organic radicals participating in charge transfer as open-shell donors, acceptors, and dimers to construct functional materials are discussed. [Extracted from the article]

[Display omitted] • A heteroatom-containing Fe MOF with binuclear mixed-valence cluster was synthesized. • The band structure and charge transfer were favorably regulated via valence mixing. • The iron catalyst performs well in facilitating H 2 generation under visible light. Fe-oxo cluster-based metal–organic frameworks (MOFs) offer a tunable platform for visible-light-driven catalysis, yet the unmatched energy level and the ease of charge recombination strongly hinder their application in photocatalytic H 2 generation. In this work, we report an Fe(II/III) mixed-valence catalyst derived from the transition of an Fe(II) 2 N 2 O 10 cluster-based MOF in water through a solvent displacement pathway. Both electronic band structure and charge transfer dynamics are effectively optimized via heteroatom coordination and valence mixing in the iron clusters. 25 times the visible-light-induced H 2 yield of pristine FeMOF was obtained by Fe(II/III) MOF with platinum as cocatalyst. The Fe MOF catalyst also shows significantly superior performance in comparison with the well-known oxide catalyst α-Fe 2 O 3 and the commonly investigated MOF catalyst NH 2 -UiO-66. This work provides a direction for the structural engineering of Fe-MOFs for photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed-valence cobalt oxides are constructed by inducing air during the cooling procedure. • The ratio of Co2+/Co3+ can be regulated by controlling the temperature of inducing air. • The mixed valence and oxygen vacancies of hollow Co/CoO/Co 3 O 4 /NCS contribute to boosting ORR/OER. • In Zn-air battery and Mg-air battery, Co/CoO/Co 3 O 4 /NCS shows superior capacity performance than Pt/C. As the bifunctional oxygen electrocatalysts, the mixed-valence metal oxide with multiple oxidation state of metal ions usually gives analogous alloy effect. However, the irreversible surface reconstruction of the electrocatalyst during the electrochemical catalysis usually changes the oxidation state of metal ions in the near-face to higher oxidation state especially in the mixed-valence metal oxide. For the modulation equilibrium, we adopt a new approach to prepare the mixed-valence cobalt oxide with the regulatable ratio of Co2+/Co3+ by inducing air at a certain temperature during the cooling procedure. The obtained Co/CoO/Co 3 O 4 /NCS with hollow nanosphere possesses multiple heterointerfaces accompanying rich oxygen vacancies. Together with the contribution of the mixed valence and oxygen vacancies, Co/CoO/Co 3 O 4 /NCS exhibits an exceptional ORR activity with a half-wave potential of 0.844 V and superb OER activity with a low overpotential of 285 mV at 10 mA cm−2. The as-fabricated Zn-air batteries with Co/CoO/Co 3 O 4 /NCS catalyst exhibit a remarkable open-circuit voltage (1.47 V), a competitive power density of 146.5 mW cm−2, and good durability without nearly no performance decay for over 400 h at 5.0 mA cm−2. More attractively, when constructed into Mg-air batteries, Co/CoO/Co 3 O 4 /NCS cathode realizes an excellent stable discharge voltage over 90 h at 20 mA cm−2. [ABSTRACT FROM AUTHOR]

Hydrothermal reaction of racemic 1,2-bis(1,2,4-triazol-4-yl)propane ( rac -btrip) and benzene-1,3,5-tricarboxylic acid (H 3 btc) with copper(II) acetate in an aqueous triethylamine and acetonitrile mixture afforded blue-green cuboctahedral crystals of the MOF inclusion compound 3D-{[Cu(NCCH 3 ) 4 ][Cu 3 (μ 6 -btc) 2 ] 2 (O 2 CCH 3 ) (H 2 O,CH 3 CN) x (btrip) 1.5 } n , 1 . This MOF is isostructural with the prototypical MOF HKUST-1 (Cu 3 (btc) 2 , Cu-btc) and the first HKUST-1 derivative which accommodates a defined guest, namely the cationic tetra(acetonitrile)copper(I) complex [Cu(NCCH 3 ) 4 ] + in the A-type octahedral pores of the 3D HKUST-1 framework. In-situ reduction of Cu(II) to Cu(I) in the course of the hydrothermal synthesis is afforded by the sacrificial btrip ligand which is not incorporated as a linker but as a template molecule into the cuboctahedral B- and C-type pores according to 1 H NMR digestion analysis. N 2 adsorption isotherm analysis for the activated HKUST-1 inclusion compound 1 gave a BET surface area of 576 m 2 /g. [ABSTRACT FROM AUTHOR]

(Ba 1− x La x )(Ti 1− x Tb x )O 3 (0.03 ≤ x ≤ 0.20) (BLTT) and (Ba 1− x La x )(Ti 1− x Tb x )O 3 –0.03 n Tb ( x = 0.03, n = 0, 1, 3, 5, 7) (BL3TT- n T) ceramics were prepared using a mixed oxides method. The structure, microstructure, dielectric properties, valence state, and defect chemistry of BLTT and BL3TT- n T were investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and dielectric temperature and frequency measurements. The solid solution limits of Tb in BLTT and BL3TT- n T were determined by XRD to be x = 0.15 and n = 3, respectively. The incorporation of the extra Tb ions in BLTT enhanced the relative density of the ceramic from 84% to 96%, accompanied by an improvement in dielectric permittivity. The defect chemistry of BLTT is discussed. Tb ions coexist in mixed-valence states, at the Ba-site as Tb 3+ , and at the Ti-site as Tb 3+ /Tb 4+ . The dielectric-peak temperature ( T m ) decreased linearly at a rate of −19 °C/%(La Tb) for BLTT. Due to its higher room-temperature permittivity ( ε ′ = 2450) and lower loss (tan δ = 0.029), BLTT with x = 0.07 can be considered as a promising dielectric for X7U applications. The existence of a small number of metastable Tb 4+ ions at Ti-sites and the predominant presence of La 3+ Tb 3+ complexes at double sites are both responsible for the lower tan δ of BLTT. [ABSTRACT FROM AUTHOR]

The new dinucleating redox-active ligand (LH4), bearing two redox-active NNO-binding pockets linked by a 1,2,3-triazole unit, is synthetically readily accessible. Coordination to two equivalents of PdII resulted in the formation of paramagnetic (S=1/2) dinuclear Pd complexes with a κ²-N,N'-bridging triazole and a single bridging chlorido or azido ligand. A combined spectroscopic, spectroelectrochemical, and computational study confirmed Robin-Day Class II mixed-valence within the redox-active ligand, with little influence of the secondary bridging anionic ligand. Intervalence charge transfer was observed between the two ligand binding pockets. Selective one-electron oxidation allowed for isolation of the corresponding cationic ligand-based diradical species. SQUID (super-conducting quantum interference device) measurements of these compounds revealed weak anti-ferromagnetic spin coupling between the two ligand-centered radicals and an overall singlet ground state in the solid state, which is supported by DFT calculations. The rigid and conjugated dinucleating redox-active ligand framework thus allows for efficient electronic communication between the two binding pockets. [ABSTRACT FROM AUTHOR]

We report the synthesis of a Co(III) complex with the five-coordinate salen-type ligand (N,N′-bis(3,5-di-tert-butyl-2-hydroxybenzyliden)-1,7-diamino-4-methyl-4-azaheptane). This complex is stable in air with a trigonal bipyramidal geometry and we show spectroscopically and computationally that a high-spin triplet ground state is preferred. This spin state is readily modulated by introduction of an exogenous ligand (pyridine, acetonitrile) to yield a six-coordinate complex with low-spin ground state. The five-coordinate complex exhibits solvent- and ligand-dependent electrochemical behavior in solution for the CoII/IIItransition and undergoes a one-electron ligand oxidation to generate a phenoxyl radical species that is relatively stable in the absence of oxygen. We show that this phenoxyl radical species is a Class I mixed-valence compound that can undergo photoinduced inner-sphere charge transfer with the neighboring phenoxide. This process is mediated by the Co(III) center which acts as a bridge. Understanding this behavior will lead to a better understanding of a dicobalt bis-salen analog previously reported by our group as a proton reduction catalyst. [ABSTRACT FROM AUTHOR]

Heterometallic Prussian blue analogues are known to exhibit thermally induced charge transfer, resulting in switching of optical and magnetic properties. However, charge-transfer phase transitions have not been reported for the simplest FeFe cyanide-bridged systems. A mixed-valence FeII/FeIII cyanide-bridged coordination polymer, {[Fe(Tp)(CN)3]2Fe(bpe)⋅5 H2O} n, which demonstrates a thermally induced charge-transfer phase transition, is described. As a result of the charge transfer during this phase transition, the high-spin state of the whole system does not change to a low-spin state. This result is in contrast to FeCo cyanide-bridged systems that exhibit charge-transfer-induced spin transitions. [ABSTRACT FROM AUTHOR]

Red crystals of [TBA] 2 [Pt 5 Cl 20 ] were obtained by reacting [TBA] 2 [PtCl 6 ] with an excess of AlCl 3 at room temperature in CH 2 Cl 2 . The salt [PPN] 2 [Pt 5 Cl 20 ] containing the same anion was prepared by reaction of platinum tetrachloride with a small excess of [PPN]Cl in 1,2-dichloroethane at room temperature. Single crystal X-Ray diffraction studies confirmed that both species contained the mixed-valence [Pt 5 Cl 20 ] 2− anion with two dinuclear platinum (IV) Pt 2 Cl 10 fragments organized around a central square planar platinum (II) in a chair arrangement. [ABSTRACT FROM AUTHOR]

This article reports on some basic and conceptual principles concerning electron transfer (ET) and/or intervalence transfer (IT) phenomena in inorganic mixed-valence systems.

• In the current manuscript, we have reported mixed-valence vanadium (IV/V) and divanadium (V,V) complexes supported by tetradentate ligand. A reasonable good agreement between the J values obtained from experimental data and those obtained from Density Functional Theory (DFT) calculations at the B3LYP level of theory was achieved. • The rationalization of observed magnetic-exchange coupling constants was achieved, based on structural parameters (magnetostructural considerations). Theoretical calculations have been done to rationalized experimental electronic structure of complexes. • Although there are many reports on mixed-valence vanadium (IV,V) systems but this is the first report where we have reported the theoretical justifications for our experimental results of such complexes. • In current manuscript, we have attempted to highlights the importance of ligand design with varied denticity, donor atom type, rigidity/flexibility, bridging capability, and successful use of such ligands to synthesize several noteworthy transition metal complexes. Using deprotonated forms of tetradentate phenol amine ligands 2-((((1-methylbenzimidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol (HL1), dinuclear vanadium(IV,V) complex of composition [(L1) 2 (VIVO)(µ-O)(VVO)](ClO 4) (1) was synthesized and characterized by X–ray crystallography, UV–Vis, EPR and magnetic susceptibility measurements. Direct current (DC) variable-temperature magnetic susceptibility measurements on polycrystalline sample of 1 were carried out in the temperature range 1.8–300 K. Electron paramagnetic resonance and magnetic studies for 1 demonstrated the complete localization of the single 3d electron on one of vanadium ion and very weak antiferromagnetic interaction between the paramagnetic vanadium(IV) ions in the crystal lattice. The cyclic voltammogram observed with 1 , revealed one oxidation process which is tentatively assigned to VIVVV/V 2 V. [(L1) 2 (VVO) 2 (µ-O)](ClO 4) 2 (2. 2.5CH 2 Cl 2) has been synthesized chemically from 1 and were thoroughly characterized by X–ray crystallography, UV–Vis, 51V NMR and IR measurements. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to their high band degeneracy and intrinsic low lattice thermal conductivity, n -type Mg 3 Sb 2 -based thermoelectric materials have drawn a lot of attention in thermoelectric applications in recent years. By using simple and efficient fast induction melting and hot pressing, the n -type Mg 3.5−x Ni x SbBi 0.96 Te 0.04 (x = 0, 0.015, 0.02, 0.03, 0.04, 0.05, and 0.06) samples have been successfully synthesized. The structure of Mg 3.5−x Ni x SbBi 0.96 Te 0.04 samples is examined, as well as their thermoelectric properties. The findings demonstrate that the mixed valence of Ni2+ and Ni3+ that occupied distinct Mg sites occurred as the Ni doping level grew in the Mg 3.5−x Ni x SbBi 0.96 Te 0.04 samples. The trivalent Ni3+ increases carrier concentrations dramatically, while the divalent Ni2+ increases the effective mass. The mixed valence of Ni causes lattice disorder, which enhances phonon scattering and reduces lattice thermal conductivity. As a result, the Mg 3.485 Ni 0.015 SbBi 0.96 Te 0.04 sample has a high ZT value of 1.58 at 743 K and an average ZT value of 1.22 from 323 to 743 K. This work suggests that the mixed valence of cationic dopant effectively improve the thermoelectric performance of n -type Mg 3 Sb 2 -based compounds. [Display omitted] • Mg 3.5−x Ni x SbBi 0.96 Te 0.04 sample with mixed valence of Ni were fabricated by fast induction melting. • The trivalent Ni3+ remarkably increase carrier concentrations and decrease the lattice thermal conductivity. • A high average ZT value of 1.22 from 323 to 743 K was obtained in n-type Mg 3.485 Ni 0.015 SbBi 0.96 Te 0.04 sample. [ABSTRACT FROM AUTHOR]

Four conjugated organic triphenylamine-based mixed-valence chromophores, T1 – T4 , with large two-photon absorption (2PA) across sections were designed, synthesized and fully characterized by IR, MS, EI and NMR spectroscopy. Photophysical properties and mixed-valence characters of them were investigated. It was found that T4 displayed prodigious 2PA response when extending conjugation system and enriching electron density within the molecule. The enriched electron character of T4 makes it to be selectively oxidized with copper salt in solution, forming stable mixed-valence state and then used for colorimetric detection of Cu 2+ ions. A simple device was fabricated using T4 for “naked eye” detection of Cu 2+ . The device can detect Cu 2+ as low as 0.01 μM. [ABSTRACT FROM AUTHOR]

The reduction of CoIIIin the tetraamine-encapsulating ligand complex [CoIII{(μ-ET)(Me2)cyclen}(H2O)2]3+by [FeII(CN)6]4−has been studied kinetico-mechanistically at different pH, temperatures, and pressures. The process agrees with the expected outer-sphere redox mechanism, with the value of the encounter-complex equilibrium constant large enough to allow for kinetic determination of the first-order electron transfer reaction rate constant. The value of the encounter-complex equilibrium constant,Kpre-eq, is not only dependent on the charge of the redox partners, but also on the establishment of an important network of hydrogen bonds. These can also explain the differences obtained in the activation volumes determined for the diaqua andbis-hydroxo complexes. Neither the leaching of CoIInor the presence of [FeIII(CN)6]3−is observed in the final reaction medium, which indicates that a fast sequence involving substitution on the transient CoIIcomplex followed by a fast inner-sphere electron transfer takes place. This sort of mechanism has already been established for encapsulating pentaamine ligand complexes, but this is the first example of such a sequential reaction occurring on a tetradentate ligand complex. Preliminary UV–Vis and electrochemical characterization experiments have been conducted on the final reaction mixtures, suggesting the formation of a stable cyanide-bridged CoIII/FeIImixed-valence complex of the same type reported in the literature for encapsulating {CoIII(N)5} skeletons. The kinetics of formation of a new cyanido-bridged mixed-valence CoIII/FeIIcomplex has been studied at different temperatures and pressures. [ABSTRACT FROM AUTHOR]

A novel octacobalt-containing polyoxoniobate, Na6K12[H2Co8O4(Nb6O19)4]⋅39 H2O, has been prepared by a combination of hydrothermal and diffusion methods. The polyanion [H2Co8O4(Nb6O19)4]18− incorporates a tetrameric assembly of Lindqvist-type [Nb6O19]8− fragments trapping a {CoII4CoIII4} cluster which comprises a central {CoIII4O4} cubane core, surrounded by another four CoII ions linkers. Furthermore, magnetic measurements show that the compound exhibits antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

The Pt-halide complex trans- PtI{C 6 H 4 NAr 2 }(PPh 3 ) 2 (Ar = C 6 H 4 OMe-4, 3 ) was prepared by oxidative addition of N(C 6 H 4 I)Ar 2 ( 2 ) to Pt(PPh 3 ) 4 . Reactions of trans- PtI{C 6 H 4 NAr 2 }(PPh 3 ) 2 ( 3 ) with 1-alkynes under CuI catalysed dehydrohalogenation conditions allows the preparation of a range of platinum ethynyl compounds containing up to four redox-active triarylamine centres. The compounds trans -Pt(C CAr)(C 6 H 4 NAr 2 )(PPh 3 ) 2 ( 4a ), trans -Pt(C CC 6 H 4 NAr 2 )(C 6 H 4 NAr 2 )(PPh 3 ) 2 ( 4b ), { trans -Pt(C 6 H 4 NAr 2 )(PPh 3 ) 2 } 2 (μ-C C-1,4-C 6 H 4 C C) ( 5 ) and N{C 6 H 4 C CPt(C 6 H 4 NAr 2 )(PPh 3 ) 2 } 3 ( 6 ) undergo a single electrochemical event for each chemically distinct type of triarylamine in the molecular backbone. The complete reversibility of the larger systems means that they can be used for charge storage materials capable of releasing up to four electrons. A combination of electrochemical, spectroelectrochemical and quantum chemical analyses reveal weak electronic coupling between the amine moieties in the redox products derived from one-electron oxidation. [ABSTRACT FROM AUTHOR]

Phosphinoalkynes P(C≡CCHMe-4)Ph ( 1) and P(C≡CCHC≡CCHMe-4)Ph ( 2) have been prepared from CuI catalysed reactions of the corresponding 1-alkyne and PClPh. The trimethylamine- N-oxide promoted reaction of PPh, 1 or 2 with [Fe(μ-pdt)(CO)] (pdt = propanedithiolate) affords derivatives [Fe(μ-pdt)(CO){PRPh}] [R=Ph ( 3), C≡CCHMe ( 5), C≡CCHC≡CCHMe ( 6)] or, at elevated temperatures, [Fe(μ-pdt)(CO)(PPh)] ( 4). The cyclic voltammograms of compounds 3 and 4 feature almost fully reversible one-electron oxidation processes and an irreversible reduction, whilst the electrochemical response of the alkynyl phosphine substituted complexes 5 and 6 is irreversible for both oxidation and reduction. IR spectroelectrochemical studies of 4 are consistent with an oxidation processes leading to a delocalized or (Class III) mixed valence [FeFe] core in which the iron centers have an average oxidation state of 1.5. The molecular structures of the alkynyl phosphine substituted clusters 5 and 6 are also reported. [ABSTRACT FROM AUTHOR]

Hydrogen bond scheme shapes the conformation of the cyanido-bridged Fe 2 W 2 rhombus clusters, whereas external stimulation induces the change in intermolecular contacts within the new series of Fe 2 W 2 -based solvated salts and co-crystal salts. [Display omitted] We present the new cyanido-bridged rhombus {[FeII(TPMA)] 2 [WV(CN) 8 ] 2 }2– (Fe 2 W 2) (TPMA = tris(2-pyridylmethyl)amine) cluster as a potential Secondary Building Block (SBB) for construction of polynuclear molecular materials. Fe 2 W 2 is formed easily in self-assembly process between [FeII(TPMA)]Cl 2 and TBA 3 [W(CN) 8 ] in H 2 O/MeOH media, and was co-crystallized in (TBA) 2 {Fe 2 W 2 }⋅2H 2 O (1), and (TBA) 2 {Fe 2 W 2 }⋅ m MeOH⋅ n H 2 O (2) solvated salts, and in (TBA) 2 {Fe 2 W 2 }⋅H 3 PG⋅ m MeOH⋅ n H 2 O (3) (H 3 PG = phloroglucinol, 1,3,5-trihydroxybenzene; co-former) solvated co-crystal salt. Crystals of 1 undergo reversible SCSC transformation 1 ⇄ 1deh upon controlled dehydration and rehydration processes, whereas crystals of 2 reveal anisotropic thermal expansion during heating from 100 K to room temperature. Both processes involve changes of the selected intermolecular distances or local molecular reorientation involving intermolecular cation–anion and anion-anion contacts. [FeII(TPMA)(µ-NC) 2 ] moieties reveal low-spin (LS) state in each case, however, conformation of the Fe 2 W 2 rings varies from the "staggered" in 1 , nearly "eclipsed" in 2 to fully "eclipsed" in 3 , which is attributed to various hydrogen bond CN N⋅⋅⋅H O schemes involving the terminal cyanido ligands in [W(CN) 8 ]3– and co-crystallizing molecules. In particular, the conformation of Fe 2 W 2 in 3 is fully controlled by an unprecedented cyclic double hydrogen bond {Fe 2 W 2 }⋅⋅⋅H 3 PG synthon, H 3 PG forming a bridge over the Fe 2 W 2 rhombus plane through binding the opposite [W(CN) 8 ] corners. This arrangement is co-stabilized by close-to-parallel contacts of H 3 PG with TPMA walls protruding out of the rhombus plane. The Fe 2 W 2 rhombus is stable in MeOH solution and shows notable affinity to H 3 PG in the gas phase, which was confirmed by ESI-MS data. UV–Vis-NIR spectroscopy discloses an optical FeII → WV MMCT transition and mixed-valence FeII//III-WV/IV electronic ground state. [ABSTRACT FROM AUTHOR]

[Display omitted] • An unsymmetrical mixed-valence oxidovanadium(IV/V) binuclear complex was synthesized. • DFT calculations and EPR spectroscopy indicates a localized mixed-valence. • The bromoperoxidase activity using the phenol red was evaluated. The mixed-valence binuclear complex [{VO(acac)(bpy)}(μ–O){VO(bpy)(ox)}]·2H 2 O (1), where acac− = acetylacetonate, bpy = 2,2-bipyridine and ox2− = oxalate, was synthesized under mild conditions and characterized by elemental analysis and infrared (IR), electron paramagnetic resonance (EPR), and electronic (UV/Vis) spectroscopies. According to single-crystal X-ray diffraction data, the two nonequivalent oxidovanadium centers of the {(VO) 2 (μ-O)}3+ core adopt an anti -angular configuration and differ in the O , O -donor ligands. Density functional theory (DFT) at the ωB97X-D/def2TZVP level was used to optimize the molecular structure and describe the electronic structure of 1 in the solid state, indicating a localized mixed-valence system. Continuous-wave EPR analysis at 77 K suggests the predominance of binuclear species in dmf and dmso solutions of 1 and 1:1 mixtures of these solvents with water. This finding is supported by comparing experimental and calculated rotational radius, g-tensor and vanadium hyperfine couplings. In the presence of KBr and H 2 O 2 , complex 1 acts as a pre-catalyst in a solvent-modulated bromination of phenol red to produce bromophenol blue. Kinetic studies in dmf/H 2 O indicate a first-order dependence on vanadium with a reaction rate constant of 703 mol−2 L2 s−1. The better performance of 1 as a pre-catalyst in dmf/H 2 O than in dmso/H 2 O may be due to a higher formation rate for the active oxidoperoxidovanadium(V) species. [ABSTRACT FROM AUTHOR]

Solvothermal reaction of CuCl 2 ·2H 2 O and 2-(4-pyridyl)benzimidazole (PyHBIm) in a acetonitrile-water mixed solvent afforded a mixture of [Cu I 2 Cu II (CN) 2 (PyHBIm) 2 Cl 2 ] n ( 1 ) and [Cu II (PyH 2 BIm) 2 Cl 4 ] ( 2 ). Complex 1 is a mixed-valence 1D ribbon Cu(I,II)-cyanide coordination polymer. One Cu(II) center linearly links two Cu(I) ions via two μ 2 -CN bridges. XPS spectrum and bond valence sum (BVS) analysis have confirmed the mixed-valence characteristics. Cu(II) ion adopts a centrosymmetric square-planar geometry surrounded by two cyanides and two pyridyl groups. Cu(I) ions adopt a trigonal geometry coordinated by cyanide, imidazole group and Cl − anion. The cyanide ligand is in situ generated from the cleavage of acetonitrile solvent, which indicates that acetonitrile is an environmentally friend cyanating agent. The mechanism of acetonitrile in situ cleavage under solvothermal condition is explained. Complex 2 is a centrosymmetric mononuclear Cu(II) compound. Four equivalent Cl − anions lie on the equatorial plane. The protonated PyH 2 BIm + cation as a monodentate ligand coordinates to Cu(II) center via pyridyl terminal. [ABSTRACT FROM AUTHOR]

The novel bridging ligand 3,6-bis(phenylcyanamido)-1,2,4,5-tetrazine (tdpcH2) and its dinuclear complex [{Ru(ttpy)(bpy)}2(μ-tdpc)][PF6]2 were prepared and characterized by elemental analysis and 1H NMR spectroscopy. Cyclic voltammetry and vis-NIR and IR spectroelectrochemistry of [{Ru(ttpy)(bpy)}2(μ-tdpc)]2+ showed that [{Ru(ttpy)(bpy)}2(μ-tdpc)]3+ is a Class II mixed-valence system with metal−metal coupling of 400 cm−1 assuming a transition dipole moment length of 21 Å. DFT calculations of tdpc2− suggested that the stability of the HOMO results in weak metal−metal coupling via the hole-superexchange mechanism. [ABSTRACT FROM AUTHOR]

Mono-(( Z)-2-amino-3-(( E)-ferrocenylideneamino)butenedinitrile) ( 1) and bis-(( E)-2,3-bis-(( E)-ferrocenylideneamino)butenedinitrile) ( 2) substituted Schiff bases obtained by the reaction between ferrocenecarbaldehyde and diaminomaleonitrile were prepared and characterized by 1H and 13C NMR, IR, and UV-vis-NIR spectroscopy methods, elemental analysis, and X-ray crystallography. Density functional theory and time-dependent density functional theory were used to elucidate the electronic structure and the origin of observed excited states in both compounds. Electrochemical techniques were employed to investigate the possibility for the formation of a mixed-valence state of the iron centers in 2+, which are connected by a conjugated π-system. Two reversible oxidation potentials were observed in cyclic voltammetry, and spectroelectrochemical experiments revealed the presence of a low-energy intervalence charge transfer band in 2+, corresponding to class II of the mixed-valence systems. Both complexes were tested for cation-recognition properties using a variety of main group and transition-metal cations. It was shown that complex 1 can be used as a selective optical sensor in recognition of Hg2+ ions. It was also shown by NMR spectroscopy and X-ray crystallography that one of the final reaction products between Hg2+ ions and complex 1 is 2-ferrocenyl-4,5-dicyanoimidazole ( 3). [ABSTRACT FROM AUTHOR]

A dinuclear Ru(II)–Ru(III) complex, [Ru(acac)2(μ2-tropC2)RuCp(dppe)] (2a, acac = acetylacetonato, Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane, HtropC2H = 5-acetylenyltropolone), has been newly synthesized and fully characterized. 2a is composed of two hetero units, [RuIICp(dppe)] and [RuIII(acac)2(trop)], and it showed a broad absorption in the NIR region, indicating the electronic communication between the two hetero units. 2a quantitatively converted to the vinylidene form [2aH](TsO) by the addition of p-toluenesulfonic acid monohydrate (TsOH·H2O) to the chloroform solution of 2a. The weak NIR absorption exhibited by 2a disappeared in [2aH](TsO). [2aH](TsO) re-converted to the acetylide 2a after the addition of triethylamine to the acetonitrile solution of [2aH](TsO). 1H NMR and UV–vis–NIR spectroscopy indicated the mutual interconversion and on/off behavior of the electronic communication between the two hetero units. Moreover, structural interconversion also proceeded in the solid state. 2a swiftly converted to [2aH](TsO) after grinding with solid TsOH·H2O for 5 min. The conversion yield estimated from IR measurements was 70%. [2aH](TsO) re-converted to 2a after re-grinding with AcONa with a conversion yield of 84%. These results indicate the usability of 2a as a molecular switch triggered by protonation/deprotonation both in solution and solid state. [ABSTRACT FROM AUTHOR]

A large-scale production process composed of the novel Forcespinning® technology followed by relatively low-temperature calcination (450°C) was developed in this report for a flexible/bendable energy storage material of heterogeneous vanadium oxide/polyvinylpyrrolidone derivative nanofibers with bark-like topography. It overcomes the low fabrication-efficiency and cost-performance shortcomings of previous techniques, such as tedious synthesis and high carbonization/growth temperature. The mechanical flexibility from moderately cross-linked polymeric backbones and the mixed valence-induced high electronic conductivity (4.48×104 Sm−1) from vanadium oxide concurrently endow these nanohybrid fibers as high performance flexible electrode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Reported is a mixed-valence VIV/VV tetrametallate cluster, which is charge neutral and stable in solution. The complex is characterized by single-crystal X-ray diffraction analysis, IR and UV–VIS–NIR absorption spectroscopy, cyclic voltammetry, room temperature magnetic susceptibility measurements and quantum chemical calculations. [Copyright &y& Elsevier]

Highlights: [•] One mixed-valence CoIIICoII complex derived from a Robson type macrocyclic ligand. [•] Rare example of an active cobalt catalyst for catechol oxidase activity. [•] Single crystal X-ray structure and ESI-MS spectra. [•] Unique examples of hydrogen bonded metal complex⋯solvent aggregates in gas phase (ESI-MS). [•] Drastic change of properties as a result of slight change in ligand periphery. [ABSTRACT FROM AUTHOR]