Category Archives: European Journal of Inorganic Chemistry

Significant Effect of 2nd Sphere Interactions on the Reductive Activation of O2 by non‐heme Iron(II) Complexes – Application to the Electroassisted Oxidation of Thioanisole

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Significant Effect of 2nd Sphere Interactions on the Reductive Activation of O2 by non-heme Iron(II) Complexes – Application to the Electroassisted Oxidation of Thioanisole

2nd sphere hydrogen bonds within non-heme iron complexes significantly improves the potential of the reductive O2 activation process, by generating stabilizing interactions within the Fe/O2 adduct. O2 can be activated at a much more favorable potential, which we took advantage of to achieve the electroassisted oxidation of thioanisole by O2.


Abstract

New mononuclear non-heme FeII complexes derived from a well-known pentadentate amine/pyridine ligand were synthesized. The new ligand bears an additional OH group on one pyridyl aimed at developing second sphere hydrogen bonds. Two binding modes of the ligand were observed that can be selectively obtained through the choice of the counterion: the OH group develops an intramolecular H-bond with the 6th exogenous ligand in the classical mode, or an intermolecular one with the unbound triflate counterion in the alternative mode. The complexes were studied by cyclic voltammetry in the reductive activation of O2. The addition of an H-bond improves the O2 activation potential with a gain of 90 mV in the classical case and 220 mV in the alternative one. The difference is ascribed to the development of stabilizing H-bonds within the FeIII-peroxo intermediate with the proximal O atom of peroxo (classical mode) or the distal one (alternative mode). Ultimately, the complex in the alternative mode activates O2 at −0.5 V vs SCE (500 mV gain compared to free O2). We took advantage of this significantly reduced energetic cost to carry out and achieve the electroassisted oxidation of thioanisole by O2 at −0.5 V vs SCE.

Successive magnetic transitions and frustrated magnetism in Fe2(HPO3)3 ⋅ 4H2O

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Successive magnetic transitions and frustrated magnetism in Fe2(HPO3)3 ⋅ 4H2O

By combined magnetic susceptibility and specific heat measurements, we find two successive antiferromagnetic (AFM) transitions at ~9 K and ~5 K in Fe2(HPO3)3 ⋅ 4H2O. Through density functional theory (DFT) analysis we have calculated the AFM states. Two AFM configurations, namely AFM I and AFM II, are almost degenerate in energy and their competition leads to the two successive AFM phase transitions at low temperature, reflecting the frustrated magnetism in Fe2(HPO3)3 ⋅ 4H2O.


Abstract

We report the magnetic and optical properties of Fe2(HPO3)3 ⋅ 4H2O. By combined magnetic susceptibility and specific heat measurements, we find two antiferromagnetic (AFM) transitions (T N1=9 K, T N2=5 K) which originate from the AFM exchange interactions mediated by the (HPO3)2− anions. Compared with the non-hydrated compound Fe2(HPO3)3, the magnetic interaction strength and ordering temperature of Fe2(HPO3)3 ⋅ 4H2O are both reduced by a factor of ~2. Through density functional theory (DFT) analysis we find almost degenerate AFM states in Fe2(HPO3)3 ⋅ 4H2O which are close in energy. The competition of these AFM states might lead to the two successive AFM phase transitions at low temperature. The low ordering temperature as well as competing AFM states both imply frustrated magnetism in Fe2(HPO3)3 ⋅ 4H2O, probably originating from the complex competing AFM interactions. The optical properties of Fe2(HPO3)3 ⋅ 4H2O are also investigated by photoluminescence and infrared spectroscopies.

Synthesis and Characterization of Dearomatized Pyridine‐Derived Alkyl‐Amido‐tert‐Butylphosphine Iron(II) Complexes

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Synthesis and Characterization of Dearomatized Pyridine-Derived Alkyl-Amido-tert-Butylphosphine Iron(II) Complexes

Little is known about the reactivities of [PN‘−Fe−CH2R] complexes. Until recently, there was little reason to suspect anything interesting about them. However, recent ROMP precatalysts of the [PN‘−Fe−CH2R] formulation from the Milstein group justify fundamental coordination and reactivity studies and herein detail our own efforts.


Abstract

Neutral three-coordinate iron alkylidenes of the form PN−Fe=CHR have been proposed as viable candidates for alkene metathesis. Indeed, during the final stages of preparing this current study, a separate report disclosed that dearomatized PN−Fe-alkyl complexes are active precatalysts for ring-opening metathesis polymerization (ROMP) of norbornene implicating PN−Fe=CHR species as possible intermediates. In yet another separate report, we prepared Zn analogues of PN−Fe-alkyl complexes and herein provide an account for the synthesis, characterization, and reactivity of some new iron complexes with the same tBu substituted PN platform.

Water Adducts of the Lewis Superacids: Tris(pentafluoroethyl)gallane and ‐indane

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Water Adducts of the Lewis Superacids: Tris(pentafluoroethyl)gallane and -indane

Herein we report on the synthesis of tris(pentafluoroethyl)indane, In(C2F5)3. It is accessible in the form of its dihydrate [In(C2F5)3(OH2)2]. An improved synthesis for the gallium analogue [Ga(C2F5)3(OH2)2] is also reported. Due to their stability and convenient accessibility, the hydrates are ideal starting compounds for the chemistry of tris(pentafluoroethyl)gallium and -indium compounds, for example hydroxogallates and -indates.


Abstract

Lewis superacids (LSA) are defined by a fluoride ion affinity (FIA) that exceeds that of SbF5, and are thus characterized as hard according to the HSAB concept. Soft superacidity was defined for compounds exceeding the hydride ion affinity (HIA) of B(C6F5)3. Herein we report on the synthesis of a Lewis acid being superacidic only on the soft regime: tris(pentafluoroethyl)indane, In(C2F5)3. It is accessible in the form of its dihydrate [In(C2F5)3(OH2)2]. An improved synthesis for the gallium analogue [Ga(C2F5)3(OH2)2] is also reported. Tris(pentafluoroethyl)indane dihydrate, [In(C2F5)3(OH2)2], was fully characterized by IR and NMR spectroscopy, as well as by single crystal X-ray diffraction. Due to their stability and convenient accessibility, the hydrates are ideal starting compounds for the chemistry of tris(pentafluoroethyl)gallium and -indium compounds, for example hydroxogallates and -indates. An attempt to determine its gas-phase structure and that of the gallium analogue by electron diffraction demonstrates that they lose water ligands upon evaporation. The energetics of these processes were predicted by quantum-chemical calculations as was the nature of bonding in the free Lewis acids and their mono- and dihydrates. Furthermore, the synthesis and structural diversity of hydroxido tris(pentafluoroethyl) gallates and one indate are presented.

A Thermoresponsive Lead‐Free Organic‐Inorganic Hybrid Perovskite as a Dielectric Switch

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A Thermoresponsive Lead-Free Organic-Inorganic Hybrid Perovskite as a Dielectric Switch

This manuscript reports two-dimensional lead-free organic-inorganic hybrid perovskite [Cyclobutylammonium]2CuCl4. It demonstrates compelling features, including distinct phase transitions, thermochromic properties, and stable dielectric switching behavior. Its combination of non-toxicity and functional attributes makes it a promising candidate for further exploration and application in the fields of thermoresponsive and dielectric switching materials.


Abstract

Thermochromic perovskites, renowned for their tunable bandgap, high absorption coefficient, and reversible color changes, emerge as promising candidates for applications in smart windows. These advancements not only have the potential to enhance occupant comfort but also contribute significantly to reducing energy consumption in buildings. Here, we present a two-dimensional lead-free organic-inorganic hybrid perovskite [Cyclobutylammonium]2CuCl4 which shows phase transitions from C2/c to P21/c to P21/c space group at 319.5 K and 348.8 K, respectively. Accompanying these transitions is a fascinating, reversible thermochromic behavior that is dependent on the phase structure. This behavior manifests as a vibrant sequence transitioning from yellow to brown and finally to a slightly dark brown. Most importantly, the demonstrated ability to switch stably between high and low dielectric states indicates the enormous potential of this material as a dielectric switch. This non-toxic thermoresponsive perovskite, characterized by its appropriate transition temperatures, reversible phase structure-dependent thermochromism, and stable dielectric switching behavior, is expected to generate significant interest within the fields of thermoresponsive and dielectric switching materials. The integration of these features not only positions this perovskite as a noteworthy subject of scientific inquiry but also opens avenues for practical applications in diverse fields.

Mixed‐Valence Manganese Carboxylate Clusters, {MnIII6MnII4}, {MnIII7MnII5Na}, and {MnIII7MnII5}, Derived from the Combined Use of Di‐2‐pyridyl Ketone with Selected Aliphatic Diols

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Mixed-Valence Manganese Carboxylate Clusters, {MnIII6MnII4}, {MnIII7MnII5Na}, and {MnIII7MnII5}, Derived from the Combined Use of Di-2-pyridyl Ketone with Selected Aliphatic Diols

The combined use of di-2-pyridyl ketone with the aliphatic diols 1,3-propanediol (pdH2) or 1,4-butanediol (1,4-bdH2) in manganese carboxylate chemistry has afforded three new polynuclear clusters with the {MnIII 6MnII 4} and {MnIII 7MnII 5} nuclearities. The compounds feature unique multilayer cores, not previously observed in manganese cluster chemistry, and possess interesting magnetic properties.


Abstract

Three new polynuclear clusters with the formulae [Mn10O4(OH)(OMe){(py)2C(O)2}2{(py)2C(OMe)(O)}4(MeCO2)6](ClO4)2 (1), Na[Mn12O2(OH)3(OMe){(py)2C(O)2}6{(py)2C(OH)(O)}2(MeCO2)2(H2O)10](ClO4)8 (2) and [Mn12O4(OH)2{(py)2C(O)2}6{(py)2C(OMe)(O)}(MeCO2)3(NO3)3(H2O)(DMF)2](NO3)2 (3) were prepared from the combination of di-2-pyridyl ketone, (py)2CO, with the aliphatic diols (1,3-propanediol (pdH2) or 1,4-butanediol (1,4-bdH2)) in Mn carboxylate chemistry. The reported compounds do not include the aliphatic diols employed in this reaction scheme; however, their use is essential for the formation of 1–3. The crystal structures of 1–3 are based on multilayer cores which, to our knowledge, are reported for the first time in Mn cluster chemistry. Direct current (dc) magnetic susceptibility studies showed the presence of dominant antiferromagnetic exchange interactions within 1–3. Alternating current (ac) magnetic susceptibility studies revealed the presence of out-of-phase signals below 3.0 K for 2 and 3 indicating the slow relaxation of the magnetization vector, characteristic of single-molecule magnets; the Ueff value of 2 was found to be 23 K and the preexponential factor τ0 ~7.6×10−9 s.

Phosphate Triester Hydrolysis by Mononuclear Iron(III) Complexes: the Role of Benzimidazole in the Second Coordination Sphere

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Phosphate Triester Hydrolysis by Mononuclear Iron(III) Complexes: the Role of Benzimidazole in the Second Coordination Sphere

This research addresses the scarcity of examples in phosphate triester hydrolysis by introducing three mononuclear iron(III) complexes. Notably, complexes 2 and 3, featuring benzimidazole moieties, demonstrated strategic variations in aliphatic chain lengths, influencing catalytic activity. Structural analyses, including spectrophotometry and DFT modelling, revealed their high-spin nature and distorted octahedral geometries. Catalytic experiments showed a significant (27 times) enhancement in hydrolysis rates for diethyl-2,4-dinitrophenylphosphate, highlighting the potential of these complexes as efficient catalysts for agrochemical degradation.


Abstract

Over the years, phosphate ester hydrolysis catalyzed by coordination compounds has attracted extensive research on developing new bioinspired compounds. However, the literature lacks sufficient examples displaying activity toward phosphate triesters specifically, limiting the understanding of efficient strategies for the hydrolysis of this compound hydrolysis. Herein, we report preparing and characterizing three mononuclear iron(III) complexes (1, 2, and 3) and their hydrolase-like activity. Complexes 2 and 3 have benzimidazole (BIMZ) moieties and were strategically designed to separate the BIMZ moiety from the first coordination sphere, and complex 1 (without BIMZ) was used as a reference. Several techniques provided structural information, including spectrophotometry, spectrometry, electrochemistry, elemental analysis, and 57Fe Mossbauer. Density functional theory (DFT) revealed distorted octahedral geometries due to the presence of the BIMZ groups. These groups also directly affected the protonation equilibria and catalytic activity. The phosphate triester diethyl-2,4-dinitrophenylphosphate (DEDNPP) hydrolysis was enhanced at least 27 times compared to the uncatalyzed reaction, with complexes 2 and 3, thus showing higher catalytic rates (k cat). Moreover, a longer carbon chain led to a higher hydrolysis rate but less interaction with substrate. These findings provide background for further investigations and the development of efficient catalysts for agrochemical degradation.

Spectroscopic Study on the Complexation of trivalent Actinide and Lanthanide ions with TEDGA in Solution

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Spectroscopic Study on the Complexation of trivalent Actinide and Lanthanide ions with TEDGA in Solution

By using NMR spectroscopy, this study provides novel insights into the M(III)-TEDGA interaction in [M(TEDGA)3]3+ complexes (M=Ln, Am). The chemical shift analyses solidify the assumption of almost identical metal-ligand interaction between Am(III)−O and Ln(III)−O.


Abstract

NMR spectroscopy studies on the complexation of La(III), Sm(III), Lu(III), Y(III) and Am(III) with N,N,N′,N′-tetraethyldiglycolamide (TEDGA) have been performed. Initial studies concerning the stoichiometry of the complexes prove the formation of [M(TEDGA)3]3+ in D2O and [M(TEDGA)1-3]3+ in CD3CN. Decreasing the solvent polarity translates to an increase of the complex stability as shown by complementary TRLFS studies with Cm(III). Due to delocalization of the lone electron pair of the amide nitrogen atom, the M(III)−O interaction has been studied indirectly by collecting 13C and 15N NMR data. The observed chemical shifts prove that the interaction of the trivalent ions, An(III) and Ln(III), and TEDGA is almost identical.

From Phenols to Antimicrobial Phenazines: Tyrosinase‐like Catalytic Activity of a Bisguanidine Based Bis(μ‐oxido) Complex

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From Phenols to Antimicrobial Phenazines: Tyrosinase-like Catalytic Activity of a Bisguanidine Based Bis(μ-oxido) Complex

Complex phenolic derivatives like naphthols, quinolinols and indolols are converted via a catalytic oxygenation reaction using a bisguanidine stabilized oxido complex as catalyst. Subsequent condensation with 1,2-phenylendiamine results in phenazines products which function as biological antimicrobial agents against bacteria.


Abstract

The catalytically active center of the enzyme tyrosinase, standing out for its unusual substrate diversity, consists of a side-on μ-η2:η2-peroxido complex ( S P). Several ligand systems stabilizing a S P and able to mimic the catalytic activity of the enzyme towards simple phenolic substrates are known. Only a few catalytically active systems based on the isoelectronic isomer structure of S P, a bis(μ-oxido)dicopper(III) complex (O), were investigated until now. Two years ago, we presented with the TMGbenza a hybrid guanidine based tyrosinase model system stabilizing an O species with an exceptional substrate diversity. Herein we studied the catalytic activity of another O species stabilized by the bisguanidine ligand TMG2tol. The reaction conditions for the catalytic oxygenation were optimized and a broad spectrum of phenolic substrates like naphthol, quinolinols and indolols was tested. Naturally occurring phenazine derivatives like phenazine-1-carboxylamide (PCN) and phenazine-1-carboxylic acid (PCA) show antifungal as well as antibacterial activity, functioning as biological control agents against crop disease like take-all. Hence, the synthesized phenazines were evaluated for their potential antimicrobial activities against representative gram-positive and gram-negative bacteria.

A Water‐Stable Europium Metal‐Organic Framework as a Turn‐Off Fluorescence Sensor for Ascorbic Acid Detection in Human Serum

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A Water-Stable Europium Metal-Organic Framework as a Turn-Off Fluorescence Sensor for Ascorbic Acid Detection in Human Serum

A turn-off fluorescence sensor of Eu-NDBC exhibits a rapid quenching to ascorbic acid, which can accurately monitor ascorbic acid in human serum.


Abstract

Ascorbic acid (AA) is a biomarker of some nervous system diseases, whose detection is of significance in many fields. The hydrothermal reaction of naphthalene-2,6-dicarboxylic acid (H2NDBC) with Eu3+ produced a europium MOF, Eu-NDBC. Eu-NDBC emits the combined emissions from the intraligand charge transfer (ILCT) of NDBC2− ligand and 5D0→7Fj (j=1–4) transfers of Eu(III). The factors of MOF dosage, pH and fluorescence response time are optimized as 0.6 mg, 7.35, and 5 min respectively. The sensitivity test shows a linear fitting equation of I0/I=0.00239 ⋅ CAA+1.03774 (CAA=AA concentration), with its limit of detection calculated as 4.53 μM in a wide linear range of 0–900 μM. The linear fitting of Stern-Volmer equation gives KSV=2.46×103 M−1 and Kq=4.96×106 M−1 S−1, suggesting Eu-NDBC sensing AA is a dynamic fluorescence quenching process. Nine control amino acids can't affect Eu-NDBC sensing AA and the emission intensity stay stable in five fluorescence quenching-recovery cycles. The returned CAA closed to the set CAA and the recoveries around 100 % support the accurate AA detection by Eu-NDBC in human serum. Totally, Eu-NDBC can be regarded as a quantitative turn-off fluorescence sensor to AA with high sensitivity and selectivity, rapid response and durability.