Electronic structure of metallocenes

Removal enhancement of persistent basic fuchsin dye from wastewater using an eco-friendly, cost-effective Fenton process with sodium percarbonate and waste iron catalyst

In this comprehensive investigation, we evaluate the efficacy of the Fenton process in degrading basic fuchsin (BF), a resistant dye. Our primary focus is on the utilization of readily available, environmentally benign, and cost-effective reagents for the degradation process. Furthermore, we delve into various operational parameters, including the quantity of sodium percarbonate (SPC), pH levels, and the dimensions of waste iron bars, to optimize the treatment efficiency. In the course of our research, we employed an initial SPC concentration of 0.5 mM, a pH level of 3, a waste iron bar measuring 3.5 cm in length and 0.4 cm in diameter, and a processing time of 10 min. Our findings reveal the successful elimination of the BF dye, even when subjected to treatment with diverse salts and surfactants under elevated temperatures and acidic conditions (pH below 3). This underscores the robustness of the Fenton process in purifying wastewater contaminated with dye compounds. The outcomes of our study not only demonstrate the efficiency of the Fenton process but highlight its adaptability to address dye contamination challenges across various industries. Critically, this research pioneers the application of waste iron bars as a source of iron in the Fenton reaction, introducing a novel, sustainable approach that enhances the environmental and economic viability of the process. This innovative use of recycled materials as catalysts represents a significant advancement in sustainable chemical engineering practices.

Electronic Structure and Photophysics of Low Spin d5 Metallocenes

The electronic structure and photophysics of two low spin metallocenes, decamethylmanganocene (MnCp*2) and decamethylrhenocene (ReCp*2), were investigated to probe their promise as photoredox reagents. Computational studies support the assignment of 2E2 ground state configurations and low energy ligand-to-metal charge transfer transitions for both complexes. Weak emission is observed at room temperature for ReCp*2 with τ = 1.8 ns in pentane, whereas MnCp*2 is not emissive. Calculation of the excited state reduction potentials for both metallocenes reveal their potential potency as excited state reductants (E°'([MnCp*2]+/0*) = -3.38 V and E°'([ReCp*2]+/0*) = -2.61 V vs Fc+/0). Comparatively, both complexes exhibit mild potentials for photo-oxidative processes (E°'([MnCp*2]0*/-) = -0.18 V and E°'([ReCp*2]0*/-) = -0.20 V vs Fc+/0). These results showcase the rich electronic structure of low spin d5 metallocenes and their promise as excited state reductants.

The rigidity and chelation effect of ligands on the hydrogen evolution reaction catalyzed by Ni(II) complexes

With increasing interest in nickel-based electrocatalysts, three heteroleptic Ni(II) dithiolate complexes with the general formula [Ni(II)L(L')2] (1-3), L = 2-(methylene-1,1'-dithiolato)-5,5'-dimethylcyclohexane-1,3-dione and L' = triphenylphosphine (1), 1,1'-bis(diphenylphosphino)ferrocene (DPPF) (2), and 1,2-bis(diphenylphosphino)ethane (DPPE) (3), have been synthesized and characterized by various spectroscopic techniques (UV-vis, IR, 1H, and 31P{1H} NMR) as well as the electrochemical method. The molecular structure of complex 2 has also been determined by single-crystal X-ray crystallography. The crystal structure of complex 2 reveals a distorted square planar geometry around the nickel metal ion with a NiP2S2 core. The cyclic voltammograms reveal a small difference in the redox properties of complexes (ΔE° = 130 mV) while the difference in the catalytic half-wave potential becomes substantial (ΔEcat/2 = 670 mV) in the presence of 15 mM CF3COOH. The common S^S-dithiolate ligand provides stability, while the rigidity effect of other ligands (DPPE (3) > DPPF (2) > PPh3 (1)) regulates the formation of the transition state, resulting in the NiIII-H intermediate in the order of 1 > 2 > 3. The foot-of-the-wave analysis supports the widely accepted ECEC mechanism for Ni-based complexes with the first protonation step as a rate-determining step. The electrocatalytic proton reduction activity follows in the order of complex 1 > 2 > 3. The comparatively lower overpotential and higher turnover frequency of complex 1 are attributed to the flexibility of the PPh3 ligand, which favours the easy formation of a transition state.

Electromigration Forces on Atoms on Graphene Nanoribbons: The Role of Adsorbate-Surface Bonding

The synthesis of the two-dimensional (2D) material graphene and nanostructures derived from graphene has opened up an interdisciplinary field at the intersection of chemistry, physics, and materials science. In this field, it is an open question whether intuition derived from molecular or extended solid-state systems governs the physical properties of these materials. In this work, we study the electromigration force on atoms on 2D armchair graphene nanoribbons in an electric field using ab initio simulation techniques. Our findings show that the forces are related to the induced charges in the adsorbate-surface bonds rather than only to the induced atomic charges, and the left and right effective bond order can be used to predict the force direction. Focusing in particular on 3d transition metal atoms, we show how a simple model of a metal atom on benzene can explain the forces in an inorganic chemistry picture. This study demonstrates that atom migration on 2D surfaces in electric fields is governed by a picture that is different from the commonly used electrostatic description of a charged particle in an electric field as the underlying bonding and molecular orbital structure become relevant for the definition of electromigration forces. Accordingly extended models including the ligand field of the atoms might provide a better understanding of adsorbate diffusion on surfaces under nonequilibrium conditions.

C-Term Faraday Rotation in Low Symmetry tert-Butyl Substituted Polyferroceniums

Molecular thin films are currently being investigated as candidate materials to replace conventional atomistic inorganic crystal-based Faraday rotators. High symmetry paramagnetic species have been reported to exhibit large Verdet constants via magnetic field splitting of degenerate ground states. However, lower symmetry open-shell species have not been extensively studied. Herein, we report the Faraday rotation of two poly di-tert-butylferroceniums with diphenylsilane and vinylene linkers. Thin films of oxidized poly[(1,1'-di-tert-butylferrocenyl)diphenylsilane] [poly(tBu2fc-SiPh2)] displayed a 30% increase in maximum Verdet constant relative to the previously reported decamethylferrocenium/PMMA composite, with Verdet constants of -4.52 × 104 deg T-1 m-1 at 730 nm and 4.46 × 104 deg T-1 m-1 at 580 nm. When a sp2-type linker was used, as with the oxidized poly(1,1'-di-tert-butyl-ferrocenylene)vinylene [poly(tBu2fc-C═C)], negligible Faraday rotation was observed. Hence, Faraday rotation can be maintained when molecular symmetry is broken, however orbital symmetry breaking in optical transitions of interest leads to a significant loss in magneto-optical activity.

Persilylation of ferrocene: the ultimate discipline in sterically overcrowded metal complexes

We report the preparation and structural characterization of the first persilylated metallocene via the metalation of decabromoferrocene. Although Grignard conditions turned out to be insufficient due to the steric and electronic effects of silyl groups causing a decreased nucleophilicity of the metalated intermediates, stepwise lithium-halogen exchange yields complex mixtures of polysilylated compounds FeC₁₀DMS_nH_10-n (n = 10, 9, 8) including the targeted decasilylated ferrocene. These mixtures were successfully separated allowing a systematic study of silylation effects on ferrocene by XRD, CV, NMR and UV/vis spectroscopy supported by DFT calculations. The findings were used to develop a high-yielding and simple preparation method to generate a tenfold substituted overcrowded ferrocene, FeC₁₀DMS₈Me₂.

Influence of Rare-Earth Ion Radius on Metal-Metal Charge Transfer in Trinuclear Mixed-Valent Complexes

We report the synthesis and characterization of a highly conjugated bisferrocenyl pyrrolediimine ligand, Fc₂PyrDIH (1), and its trinuclear complexes with rare earth ions─(Fc₂PyrDI)M(N(TMS)₂)₂ (2-M, M = Sc, Y, Lu, La). Crystal structures, nuclear magnetic resonance (NMR) spectra, and ultraviolet/visible/near-infrared (UV/vis-NIR) data are presented. The latter are in good agreement with DFT calculations, illuminating the impact of the rare earth ionic radius on NIR charge transfer excitations. For [2-Sc]⁺, the charge transfer is at 11,500 cm^-1, while for [2-Y]⁺, only a d-d transition at 8000 cm^-1 is observed. Lu has an ionic radius in between Sc and Y, and the [2-Lu]⁺ complex exhibits both transitions. From time-dependent density functional theory (TDDFT) analysis, we assign the 11,500 cm^-1 transition as a mixture of metal-to-ligand charge transfer (MLCT) and metal-to-metal charge transfer (MMCT), rather than pure metal-to-metal CT because it has significant ligand character. Typically, the ferrocenes moieties have high rotational freedom in bis-ferrocenyl mixed valent complexes. However, in the present (Fc₂PyrDI)M(N(TMS)₂)₂ complexes, ligand-ligand repulsions lock the rotational freedom so that rare-earth ionic radius-dependent geometric differences increasingly influence orbital overlap as the ionic radius falls. The Marcus-Hush coupling constant H_AB trends as [2-Sc]⁺ > [2-Lu]⁺ > [2-Y]⁺.

Exploring the Emergent Redox Chemistry of Pd(II) Nodes with Pendant Ferrocenes: From Precursors, through Building Blocks, to Self-Assemblies

Energy-relevant small molecule activations and related processes are often multi-electron in nature. Ferrocene is iconic for its well-behaved one-electron chemistry, and it is often used to impart redox activity to self-assembled architectures. When multiple ferrocenes are present as pendant groups in a single structure, they often behave as isolated sites with no separation of their redox events. Herein, we study a suite of molecules culminating in a self-assembled palladium(II) truncated tetrahedron (TT) with six pendant ferrocene moieties using the iron(III/II) couple to inform about the electronic structure and, in some cases, subsequent reactivity. Notably, although known ferrocene-containing metallacycles and cages show simple reversible redox chemistry, this TT undergoes a complex multi-step electrochemical mechanism upon oxidation. The electrochemical behavior was observed by voltammetric and spectroelectrochemical techniques and suggests that the initial Fc-centered oxidation is coupled to a subsequent change in species solubility and deposition of a film onto the working electrode, which is followed by a second separable electrochemical oxidation event. The complicated electrochemical behavior of this self-assembly reveals emergent properties resulting from organizing multiple ferrocene subunits into a discrete structure. We anticipate that such structures may provide the basis for multiple charge separation events to drive important processes related to energy capture, storage, and use, especially as the electronic communication between sites is further tuned.

Enhancement of photovoltaic performance in ferrocenyl π-extended multi donor–π–acceptor (D–D′–π–A) dyes using chenodeoxycholic acid as a dye co-adsorbent for dye sensitized solar cells†

A new set of multi-donor [ferrocene (D) and methoxyphenyl (D′)] conjugated D–D′–π–A based dyes [Fc–(OCH₃–Ph)C <svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata> Created by potrace 1.16, written by Peter Selinger 2001-2019 </metadata><g transform="translate(1.000000,15.000000) scale(0.017500,-0.017500)" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg> CH–CHCN–R{RCOOH (1) and C₆H₄–COOH (2)}] were synthesized as sensitizers for dye-sensitized solar cell (DSSC) applications. These dyes were characterized with the aid of analytical and spectroscopic techniques such as FT-IR, HR-Mass, and ¹H and ¹³C NMR. The thermal stability of the dyes 1 and 2 were investigated using thermogravimetric analysis (TGA) and was found to be stable around 180 °C for dye 1 and 240 °C for dye 2. The electronic absorption spectra for sensitizers display major bands between 400 and 585 nm that could be ascribed to an intramolecular charge transfer (ICT) between the electron donor and acceptor to create an efficient charge separation. The redox behaviour of the dyes was determined by cyclic voltammetry, which revealed the one-electron transfer from the ferrocene to ferrocenium ion (Fe²⁺ ⇌ Fe³⁺), and potential was utilized to determine the band gap of the dyes (2.16 eV for 1 and 2.12 eV for 2). Further, the carboxylic anchor dyes 1 and 2 have been utilized as photosensitizers in TiO₂-based DSSCs with and without co-adsorbance of chenodeoxycholic acid (CDCA), and the photovoltaic performances were studied. The obtained photovoltaic parameters of dye 2 are open-circuit voltage (V_oc) = 0.428 V, short-circuit current density (J_sc) = 0.086 mA cm⁻², the fill factor (FF) = 0.432 and the energy efficiencies (η) = 0.015%, the overall power conversion efficiencies were found to be increased in the presence of CDCA as a co-adsorbent. The photosensitizers with the addition of CDCA show higher efficiencies compared to those in the absence of CDCA, which can prevent the formation of aggregation and increased electron injection of the dyes. Among the dyes, the 4-(cyanomethyl) benzoic acid (2) anchor showed higher photovoltaic performance compared with the cyanoacrylic acid (1) anchor due to the introduction of additional π-linkers and acceptor unit, which enables the lowering of the energy barrier and charge recombination process. In addition, the experimentally observed HOMO and LUMO values were in good agreement with the theoretical calculation by the DFT-B3LYP/6-31+G**/LanL2TZf level of theory.

Enhanced DSSC efficiencies were attained in the presence of chenodeoxycholic acid (CDCA) as a co-adsorbent in multi-donor ferrocenyl dyes.

A free boratriptycene-type Lewis superacid

An exceptionally strong ferrocene-containing, cationic boratriptycene-type Lewis acid is stabilized by a weak Fe⋯B through-space interaction.

From ferrocene to 1,2,3,4,5-pentafluoroferrocene: halogen effect on the properties of metallocene

The sequentially fluorinated ferrocenes (1-, 1,2-di, 1,2,3-tri, 1,2,3,4-tetra and 1,2,3,4,5-pentafluoroferrocene) have been synthesized from ferrocene. Rather than a 'perfluoro' effect, experimental and computational analysis of the complete series robustly demonstrates a linear additive effect of fluorine on the electrochemical and spectroscopic properties of ferrocene.

Two-photon absorption properties of multipolar triarylamino/tosylamido 1,1,4,4-tetracyanobutadienes

The synthesis and characterization of four new tetracyanobutadiene (TCBD) derivatives (1, 3c and 4b-c) incorporating tosylamido and 4-triphenylamino moieties are reported. Along with those of five closely related or differently branched TCBDs derivatives (2, 3a-b, 4c and 5), their linear and (third-order) nonlinear optical properties were investigated by electronic absorption spectroscopy and Z-scan measurements. Among these compounds, the tri-branched compounds 3c and 5 are the most active two-photon absorbers, with effective cross-sections of 275 and 350 GM at 900 nm, respectively. These properties are briefly discussed with the help of DFT calculations, focussing on structural and electronic factors, and contextualized with results obtained previously for related compounds.

Fusing pyrene and ferrocene into a chiral, redox-active triangle

A macrocycle that integrates three ferrocene-pyrene dyads in a triangular C2-symmetric arrangement is synthesised as a racemate in a simple one-pot approach. Crystal structural analysis reveals two enantiomeric conformers that pack alternatingly via π-π stacking and interconvert dynamically in solution. Electrochemical investigations indicate weak electrostatic interactions between Fc groups upon oxidation to a mixed valence triangle.

Synthetic, spectroscopic, structural, and electrochemical investigations of ferricenium derivatives with weakly coordinating anions: ion pairing, substituent, and solvent effects

A facile and effective strategy for the preparation of a series of ferricenium complexes bearing either electron-donating or electron-withdrawing substituents with weakly coordinating anions such as [B(C6F5)4]- or SbF6- is reported. These systems were thoroughly investigated for their ground state electronic structures in both solution and solid states using infrared (IR) and nuclear magnetic resonance (NMR) spectroscopies as well as single crystal X-ray crystallography and electrochemical measurements. The X-ray structures of the six electron-deficient ferricenium derivatives are of particular interest as only a handful (∼5) of such derivatives have been structurally characterized to date. Comparison of the structural data for both neutral and oxidized derivatives reveals that the nature of the substituents on the cyclopentadienyl (Cp) ligands displays a more significant impact on the metal-ligand separations (FeCt) in the oxidized species than in their neutral analogs. Our 1H-NMR measurements corroborate that in the neutral ferrocene derivatives, electron-donating ring substitutions lead to a greater shielding of the ring protons while electron-withdrawing groups via induction deshield the nearby ring protons. However, the data for the paramagnetic ferricenium derivatives reveals that this substitutional behavior is more complex and fundamentally reversed, which is further supported by our structural studies. We ascribe this reversal of behavior in the ferricenium derivatives to the δ back-donation from the iron atom into the Cp rings which can lead to the overall shielding of the ring protons. Interestingly, our NMR results for the electron-deficient ferricenium derivatives in solution also indicate a direct correlation between the solvent dielectric constant and the energy barrier for rotation around the metal-ligand bond in these systems, whereas such a correlation is absent or not significant in the case of the electron-rich ferricenium species or the corresponding neutral ferrocene analogs. In this work, we also present the electrochemical behavior of the corresponding ferricenium/ferrocene redox couples including potential values (E1/2), peak-to-peak separation (ΔE1/2), and diffusion coefficients (D) of the redox active species in order to provide a concise outline of these data in one place. Our electrochemical studies involved three different solvents and two supporting electrolytes. Notably, our findings point to the significant effect of ion-pairing in lowering the energy necessary for reduction of the ferricenium ion and E1/2 in lower-polarity media. This has significant implications in applications of the ferrocene or ferricenium derivatives as redox agents in low-polarity solvents where an accurate determination of redox potential is critical.

C-Term Faraday Rotation in Metallocene Containing Thin Films

The Faraday effect is a magneto-optical (MO) phenomenon that causes the plane of linearly polarized light to rotate when passing through a medium subjected to a parallel magnetic field. Informed by the established quantum mechanical model developed by Buckingham and Stephens, we sought to identify molecules that would exhibit large MO responses. Magnetic circular dichroism studies of ferrocenium in the 1970s revealed its potential as an MO material; however, it has not been evaluated in the context of Faraday rotation and thin-film optical applications. Herein, we report near-infrared (NIR) Faraday rotation in thin films of decamethylferrocenium/poly(methyl methacrylate) composites with maximum Verdet constants of -3.45 × 10⁴ deg T^-1 m^-1 at 810 nm (absorbance = 0.09) and -1.44 × 10⁴ deg T^-1 m^-1 at 870 nm (absorbance = 0.01). These polymer-metallocene thin films deliver larger Verdet constants than commercially used NIR inorganic Faraday rotators and are facile and inexpensive to produce. The temperature dependence and distinct lineshape of the MO responses observed in decamethylferrocenium radical cations, decamethylmanganocene, and chromocene are in accordance with the quantum mechanical model. The observation of a strong C-term Faraday rotation in solid-state organometallic materials provides the groundwork for the development of high-performance metallocene-based Faraday rotators.

1,1'-Bis(diphenylphosphino)ferrocene Platinum(II) Complexes as a Route to Functionalized Multiporphyrin Systems

In this study, the cationic complex [PtMe(Me₂SO)(dppf)]CF₃SO₃ (PtFc) (dppf = 1,1′-bis(diphenylphosphino)ferrocene) was exploited as a precursor to functionalize the multi-chromophoric system hexakis(pyridyl-porphyrinato)benzene (1). The final adduct [PtFc]₁₈-1, containing eighteen platinum(II) organometallic [PtMe(dppf)] fragments, was prepared and characterized through UV/Vis absorption, ³¹P{¹H}-NMR spectroscopy, and fluorescence emission. UV/vis and fluorescence titrations confirmed the coordination between the platinum(II) center and all the pyridyl moieties of the peripheral substituent groups of the porphyrin. The drop casting of diluted dichloromethane solution of [PtFc]₁₈-1 onto a glass surface afford micrometer-sized emissive porphyrin rings.

Ferrocene decorated unusual mercury(ii) dithiocarbamate coordination polymers: crystallographic and computational studies

Three new ferrocene decorated 1D coordination polymers of Hg(ii) dithiocarbamates were synthesized and the nature of their weak interactions was addressed using computational techniques.

Spin-state energetics of metallocenes: How do best wave function and density functional theory results compare with the experimental data?

We benchmark the accuracy of quantum-chemical methods, including wave function theory methods [coupled cluster theory at the CCSD(T) level, multiconfigurational perturbation-theory (CASPT2, NEVPT2) and internally contracted multireference configuration interaction (MRCI)] and 30 density functional theory (DFT) approximations, in reproducing the spin-state splittings of metallocenes. The reference values of the electronic energy differences are derived from the experimental spin-crossover enthalpy for manganocene and the spectral data of singlet-triplet transitions for ruthenocene, ferrocene, and cobaltocenium. For ferrocene and cobaltocenium we revise the previous experimental interpretations regarding the lowest triplet energy; our argument is based on the comparison with the lowest singlet excitation energy and herein reported, carefully determined absorption spectrum of ferrocene. When deriving vertical energies from the experimental band maxima, we go beyond the routine vertical energy approximation by introducing vibronic corrections based on simulated vibrational envelopes. The benchmarking result confirms the high accuracy of the CCSD(T) method (in particular, for UCCSD(T) based on Hartree-Fock orbitals we find for our dataset: maximum error 0.12 eV, weighted mean absolute error 0.07 eV, weighted mean signed error 0.01 eV). The high accuracy of the single-reference method is corroborated by the analysis of a multiconfigurational character of the complete active space wave function for the triplet state of ferrocene. On the DFT side, our results confirm the non-universality problem with approximate functionals. The present study is an important step toward establishing an extensive and representative benchmark set of experiment-derived spin-state energetics for transition metal complexes.

The core of the matter - arene substitution determines the coordination and catalytic behaviour of tris(1-phosphanyl-1'-ferrocenylene)arene gold(I) complexes

Changing the aromatic core of C3-symmetric tris(ferrocenyl)arene-based tris-phosphanes has profound effects on their coordination behaviour towards gold(i). Depending on the arene (s-triazine, benzene, or trifluorobenzene), four different coordination modes can be distinguished and their preference has been rationalised using computational methods. The corresponding 1 : 1 ligand-to-metal complexes, studied by variable-temperature NMR spectroscopy, revealed fluctional behaviour in solution. Given the presence of up to three or six ferrocenylene spacers per complex, their electrochemistry was investigated. The redox-responsive nature of the complexes can be advantageously exploited in the catalytic ring-closing isomerisation of N-(2-propyn-1-yl)benzamide, where the benzene-based 2 : 3 ligand-to-metal complex has been shown to display multiple activity states depending on the degree of (reversible) oxidation in a preliminary trial.

Ferro-self-assembly: magnetic and electrochemical adaptation of a multiresponsive zwitterionic metalloamphiphile showing a shape-hysteresis effect

Metallosurfactants are molecular compounds which combine the unique features of amphiphiles, like their capability of self-organization, with the peculiar properties of metal complexes like magnetism and a rich redox chemistry. Considering the high relevance of surfactants in industry and science, amphiphiles that change their properties on applying an external trigger are highly desirable. A special feature of the surfactant reported here, 1-(Z)-heptenyl-1′-dimethylammonium-methyl-(3-sulfopropyl)ferrocene (6), is that the redox-active ferrocene constituent is in a gemini-position. Oxidation to 6⁺ induces a drastic change of the surfactant's properties accompanied by the emergence of paramagnetism. The effects of an external magnetic field on vesicles formed by 6⁺ and the associated dynamics were monitored in situ using a custom-made optical birefringence and dual dynamic light scattering setup. This allowed us to observe the optical anisotropy as well as the anisotropy of the diffusion coefficient and revealed the field-induced formation of oriented string-of-pearls-like aggregates and their delayed disappearance after the field is switched off.

The self-organization properties of a stimuli responsive amphiphile can be altered by subjecting the paramagnetic oxidized form to a magnetic field of 0.8 T and monitored in real time by coupling optical birefringence with dynamic light scattering.

Triple the fun: tris(ferrocenyl)arene-based gold(i) complexes for redox-switchable catalysis

The modular syntheses of C₃-symmetric tris(ferrocenyl)arene-based tris-phosphanes and their homotrinuclear gold(i) complexes are reported. Choosing the arene core allows fine-tuning of the exact oxidation potentials and thus tailoring of the electrochemical response. The tris[chloridogold(i)] complexes were investigated in the catalytic ring-closing isomerisation of N-(2-propyn-1-yl)benzamide, showing cooperative behaviour vs. a mononuclear chloridogold(i) complex. Adding one, two, or three equivalents of 1,1′-diacetylferrocenium[tetrakis(perfluoro-tert-butoxy)aluminate] as an oxidant during the catalytic reaction (in situ) resulted in a distinct, stepwise influence on the resulting catalytic rates. Isolation of the oxidised species is possible, and using them as (pre-)catalysts (ex situ oxidation) confirmed the activity trend. Proving the intactness of the P–Au–Cl motif during oxidation, the tri-oxidised benzene-based complex has been structurally characterised.

Trinuclear gold(i) complexes of C₃-symmetric tris(ferrocenyl)arene-based tris-phosphanes with four accessible oxidation states catalyse the ring-closing isomerisation of N-(2-propyn-1-yl)benzamide with different rates depending on their redox state.

Tricoordinate Coinage Metal Complexes with a Redox-Active Tris-(Ferrocenyl)triazine Backbone Feature Triazine-Metal Interactions

2,4,6-Tris(1-diphenylphosphanyl-1'-ferrocenylene)-1,3,5-triazine (1) coordinates all three coinage metal(I) ions in a 1:1 tridentate coordination mode. The C3 -symmetric coordination in both solid state and solution is stabilised by an uncommon cation-π interaction between the triazine core and the metal cation. Intramolecular dynamic behaviour was observed by variable-temperature NMR spectroscopy. The borane adduct of 1, 1BH3 , displays four accessible oxidation states, suggesting complexes of 1 to be intriguing candidates for redox-switchable catalysis. Complexes 1Cu, 1Ag, and 1Au display a more complicated electrochemical behaviour, and the electrochemical mechanism was studied by temperature-resolved UV/Vis spectroelectrochemistry and chemical oxidation.

[Cp*RuPb11]3− and [Cu@Cp*RuPb11]2−: centered and non-centered transition-metal substituted zintl icosahedra

Cluster anions [Cp*RuPb₁₁]³⁻ (1) and [Cu@Cp*RuPb₁₁]²⁻ (2) represent the first vertex-substituted zintl icosahedra and 1 is the first non-centered zintl icosahedron isolated in the condensed phase.

Observation of three different linker conformers in a scandium ferrocenedicarboxylate coordination polymer

In the coordination polymer CAU-50 based on 1,1′-ferrocenedicarboxylate and scandium, three different conformers of the same linker molecule are observed.

Ferrocenes with a Persulfurated Cyclopentadienyl Ring: Synthesis, Structural Studies, and Optoelectronic Properties

Persulfurated arenes are a fascinating class of functional molecules with a wide range of potential applications. Ferrocenes are also a multifaceted class of aromatic compounds that can easily be finetuned for an enormous variety of desired properties. A combination of both substance classes might yield an even wider field of applications. Herein, we describe the synthesis of two ferrocenes with one persulfurated cyclopentadienyl ring [C₅ (SR)₅ ], with R=Me or Ph, together with their crystal structures, optical, and electrochemical properties. Both crystal structures show significant intramolecular sulfur-iron interactions as well as weak intermolecular sulfur- contacts. Cyclovoltammetry of the [C₅ (SPh)₅ ] compound shows a high oxidation potential of 651 mV vs. FcH/FcH⁺ .

A review on Fenton process for organic wastewater treatment based on optimization perspective

Water pollution caused by organic wastewater has become a serious concern worldwide. Fenton oxidation process is one of the most effective and suitable methods for the abatement of organic pollutants. However, the process has three obvious shortcomings: the narrow working pH range, the high costs and risks associated with handling, transportation and storage of reagents (H₂O₂ and catalyst), the significant iron sludge related second pollution. In order to overcome these shortcomings, various optimized Fenton processes have been widely studied. Therefore, a summary of the study status of Fenton optimization processes is necessary to develop a novel and high efficiency organic wastewater treatment method. Based on the optimization perspective, taking shortcomings of Fenton process as a breakthrough, the fundamentals, advantages and disadvantages of single Fenton optimization processes (heterogeneous Fenton, photo-Fenton and electro-Fenton) for organic wastewater treatment were reviewed and the corresponding reaction mechanism diagrams were drawn in this paper. Then, the feasibility and application of the coupled Fenton optimization processes (photoelectro-Fenton, heterogeneous electro-Fenton, heterogeneous photoelectro-Fenton, three-dimensional electro-Fenton) for organic wastewater treatment were discussed in depth. Additionally, the effect of some important operation parameters (pH and catalyst, H₂O₂, organic pollutants concentration) on the degradation efficiency of organic pollutants was studied to provide guidance for the optimization of operation parameters. Finally, the possible future research directions for optimized Fenton processes were given. The review aims to assist researchers and engineers to gain fundamental understandings and critical view of Fenton process and its optimization processes, and hopefully with the knowledge it could bring new opportunities for the optimization and future development of Fenton process.

Polar Metallocenes

Crystalline polar metallocenes are potentially useful active materials as piezoelectrics, ferroelectrics, and multiferroics. Within density functional theory (DFT), we computed structural properties, energy differences for various phases, molecular configurations, and magnetic states, computed polarizations for different polar crystal structures, and computed dipole moments for the constituent molecules with a Wannier function analysis. Of the systems studied, Mn₂(C₉H₉N)₂ is the most promising as a multiferroic material, since the ground state is both polar and ferromagnetic. We found that the predicted crystalline polarizations are 30–40% higher than the values that would be obtained from the dipole moments of the isolated constituent molecules, due to the local effects of the self-consistent internal electric field, indicating high polarizabilities.

A porous and redox active ferrocenedicarboxylic acid based aluminium MOF with a MIL-53 architecture

A new redox active MOF Al-MIL-53-FcDC based on 1,1′-ferrocenedicarboxylate exhibits reversible electrochemical activity and permanent porosity.

Ferrocenylethenyl-substituted oxadiazoles with phenolic and nitro anchors as sensitizers in dye sensitized solar cells

Ferrocenylethenyl-substituted oxadiazoles with phenolic and nitro anchors were synthesized and used as sensitizers in dye sensitized solar cells (DSSCs).

Phosphine Oxidation with Water and Ferrocenium(III) Cation Induced by Visible-Light Irradiation

Stoichiometric oxidation of phosphines with water and ferrocenium(III) cation as the oxygen atom source and the oxidizing reagent, respectively, was achieved in acetonitrile under visible-light irradiation by using 2,6-lutidine as the proton acceptor. The reaction required light irradiation, under which fluorescence was observed for the acetonitrile solution of the ferrocenium(III) cation.