Search

A series of trimetallic cyanidometal‐bridged compounds [MenCp(dppe)FeII‐(μ‐NC)‐RuII(MeOpy)4‐(μ‐CN)‐FeII(dppe)CpMen] ‐ [PF6]2 (N[PF6]2, n=0, N =1; n=1, N=2; n=3, N=3; Cp=cyclopentadiene, dppe=1,2‐bis(diphenylphosphino)ethane, MeOpy=4‐methoxypyridine) and their one‐ and two‐electron oxidized compounds N3+ and N4+ were synthesized and characterized. Meanwhile, a series of corresponding linear cyanido‐bridged pentanuclear compounds [MenCp(dppe)FeIII‐(μ‐NC)‐RuII(MeOpy)4‐(μ‐NC)‐AgI‐(μ‐CN)‐RuII(MeOpy)4‐(μ‐CN)‐FeIII(dppe)CpMen][BF4]5 (M[BF4]5, n=0, M=4; n=1, M=5; n=3, M=6) were also obtained and well characterized. The investigations suggest that in the trinuclear system there exists remote interaction between the two Fe centers, but no significant interactions exist across the central silver unit between the metals on the two sides of the silver center in the pentanuclear system. In both the trinuclear N4+ and the pentanuclear M5+ complexes, there exists the neighboring RuII→FeIII MM′CT transitions, and the MM'CT energy in the corresponding trinuclear system is higher than those in the pentanuclear system in which no remote metal‐metal interaction occurs. Meanwhile, as the substituted methyl groups on the cyclopentadiene increases, the redox potential of the ruthenium in the trinuclear N4+ series increases, but that in the pentanuclear M5+ complexes decreases. [ABSTRACT FROM AUTHOR]

Crystal structures of a series of organic–inorganic hybrid gold iodide perovskites, formulated as A2[AuII2][AuIIII4] [A=methylammonium (MA) (1) and formamidinium (FA) (2)], A′2[I3]1−x[AuII2]x[AuIIII4] [A′=imidazolium (IMD) (3), guanidinium (GUA) (4), dimethylammonium (DMA) (5), pyridinium (PY) (6), and piperizinium (PIP) (7)], systematically changed depending on the cation size. In addition, triiodide (I3−) ions were partly incorporated into the AuI2− sites of 3–7, whereas they were not incorporated into those of 1 and 2. Such a difference comes from the size of the organic cation. Optical absorption spectra showed characteristic intervalence charge‐transfer bands from AuI to AuIII species, and the optical band gap increased as the size of the cation became larger. [ABSTRACT FROM AUTHOR]

Class II mixed‐valence bimetallic complexes {[Cp′(PP)M]C≡C−C≡N[M′(PP)′Cp′]}2+ (M, M′=Ru, Fe; PP=dppe, (PPh3)2; Cp′=Cp*, Cp) exist as conformational ensembles in fluid solution, with a population of structures ranging from cis‐ to trans‐like geometries. Each conformer gives rise to its own series of low‐energy intervalence charge‐transfer (IVCT) and local d–d transitions, which overlap in the NIR region, giving complex band envelopes in the NIR absorption spectrum, which prevent any meaningful attempt at analysis of the band shape. However, DFT and time‐dependent (TD)DFT calculations with dispersion‐corrected global‐hybrid (BLYP35‐D3) or local hybrid (lh‐SsirPW92‐D3) functionals on a small number of optimised structures chosen to sample the ground state potential energy hypersurfaces of each of these complexes has proven sufficient to explain the major features of the electronic spectra. Although modest in terms of computational expense, this approach provides a more accurate description of the underlying molecular electronic structure than would be possible through analysis of the IVCT band by using the static point‐charge model of Marcus–Hush theory and derivatives, or TDDFT calculations from a single (global) minimum energy geometry. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate, based on experimental and theoretical evidence, that the isolated [2(CH3CN)2]2+ complex prepared in CH3CN and containing a mixed‐valent {Cu2II,IS} core evolves towards a new [2(CH3CN)3]2+ species upon solvation in CH3CN. Unlike its type III structural analogue [2(H2O)(OTf)]+ active toward N2O reduction, this new type I compound is inactive. This outcome opens new perspectives for a rational for N2O activation using bio‐inspired Cu/S complexes, especially on the role of the valence localization/delocalization and the Cu−Cu bond on the reactivity. [ABSTRACT FROM AUTHOR]

The compounds [Fe(CO)3(dRpf)] n+, n=0, 1, 2 and dRpf=1,1′-bis(dicyclohexylphosphino)ferrocene ([ 1] n +) or 1,1′-bis(diisopropylphosphino)ferrocene ([ 2] n +), were obtained as two-step reversible redox systems by photolytic and redox reactions. The iron-iron distance decreases from about 4 Å to about 3 Å on oxidation, which takes place primarily at the tricarbonyliron moiety. Whereas ferrocene oxidation is calculated to occur only in excited states, the near infrared absorptions of the mixed-valent monocations are due to an unprecedented 'inverse' inter-valence charge transfer from the electron-rich iron(II) in the ferrocene backbone to the electron-deficient tricarbonyliron(I). Protonation of complex 1 results in the formation of the structurally characterized hydride [ 1H]BF4, which reacts with acetone to form the dication, 12+, and isopropanol. While the hydride [ 2H]BF4 was found to be unstable, protonation of 2 in acetone resulted in the clean formation of 22+, formally a hydrogen transfer. [ABSTRACT FROM AUTHOR]

Cooperative performance of mixed-valent Eu2+/Eu3+ in single-compound phosphors offers significant advantages in color rendering and luminescence efficiency, but their synthesis is challenging because of Eu2+ oxidation. Using the tunable nature of the metal-ion nodes in metal-organic frameworks (MOFs), we present an in situ reduction and crystallization route for preparing MOFs and doping Eu2+/Eu3+ with a controlled ratio. These materials exhibit rich photoluminescence, including intrinsic- and sensitized-emissions of Eu2+ and Eu3+, and long-lived luminescence from charge transfer. Color rendering can be easily achieved by fine-tuning the valence states of Eu. A linear relation between temperature and the intensity ratio of Eu2+/Eu3+ emissions provides outstanding properties for applications as self-calibrated luminescent thermometers with a wide working temperature range. Further incorporation of Tb3+ into the MOFs results in white light, utilizing all Eu2+,Tb3+, and Eu3+ emissions in a single crystalline lattice. [ABSTRACT FROM AUTHOR]

Crystals of mixed-valent Au complexes have been grown from solutions of cyclohexanecarbonitrile and a stoichiometric amount of gold(I) and gold(III) chloride. The purely obtained compound was characterized as bis(cyclohexanecarbonitrile)gold(I) tetrachloridoaurate(III). The crystal packing of the mixed valent Au(I/III) compound demonstrates a columnar arrangement of the gold(I) and gold(III) atoms. The new structure displays the shortest unsupported gold(I)-gold(III) interactions with the sub-van der Waals distance of 324-325 pm, which is assumed as an aurophilic bonding interaction. [ABSTRACT FROM AUTHOR]

Ring opening of thiophenes containing an azo function in 2-position and subsequent dimerization through CC coupling were observed on reaction with [Ru(acac)2(CH3CN)2] (acac=acetylacetonate) to produce two 1,3,5-hexatriene-linked redox-active azothiocarbonyl chelate systems. Interaction of the non-innocent chelate ligands and of the metals at a nanoscale distance of 1.45 nm via the conjugated hexatriene bridge was studied by magnetic and electron spectroscopic measurements in conjunction with DFT calculations, revealing four-center magnetic interactions of this unique setting and weak intervalence coupling after reduction. [ABSTRACT FROM AUTHOR]

Herein we evaluate the influence of an electric field on the coupling of two delocalized electrons in the mixed-valence polyoxometalate (POM) [GeV14O40]8− (in short V14) by using both a t-J model Hamiltonian and DFT calculations. In absence of an electric field the compound is paramagnetic, because the two electrons are localized on different parts of the POM. When an electric field is applied, an abrupt change of the magnetic coupling between the two delocalized electrons can be induced. Indeed, the field forces the two electrons to localize on nearest-neighbors metal centers, leading to a very strong antiferromagnetic coupling. Both theoretical approaches have led to similar results, emphasizing that the sharp spin transition induced by the electric field in the V14 system is a robust phenomenon, intramolecular in nature, and barely influenced by small changes on the external structure. [ABSTRACT FROM AUTHOR]