Cationic Complexes Research Articles

Asymmetric Hydrogenation of Tetrapyridine‐Type N‐Heteroarenes Using Phosphine‐Free Ruthenium Diamine Catalysts†

Comprehensive SummaryChiral ruthenium‐catalyzed enantioselective hydrogenation of tetrapyridine‐type N‐heteroarenes was firstly developed. The partial reduction of adjacent tetraheteroaromatic substrates proceeded smoothly in the presence of phosphine‐free chiral cationic ruthenium diamine complexes, affording unprecedented high reactivity, enantioselecitivity and diastereoselectivity (up to 93% yield, >99% ee and 92 : 8 dr). The potential application of chiral tetradentate pyridine‐amine products as chiral ligands has been demonstrated in the Cu‐catalyzed asymmetric Friedel–Crafts alkylation reaction between indoles and nitroalkenes.

Cyclopentadienyl and indenyl ruthenium(II) complexes containing diazafluorenone derivative ligands: Syntheses, characterization, antibacterial and cytotoxicity studies

We have successfully synthesized a series of eight versatile, half-sandwich ruthenium(II) cationic complexes [(Cp/Ind)Ru(к2(N∩N)L)(PPh3)]PF6 (1–8), where L represents a 4,5-diazafluorenone derivative ligand. These complexes were isolated as their hexafluorophosphate salts and subjected to thorough characterization using various spectroscopic techniques such as FT-IR, NMR, UV and Mass. Furthermore, single-crystal X-ray diffraction studies determined the molecular structures of representative complexes 1, 7, and 8. We screened the synthesized complexes and ligands in vitro to assess their potential antibacterial activity against three bacterial strains: the Gram-positive Staphylococcus aureus, the Gram-negative Escherichia coli and Klebsiella pneumoniae. Remarkably, all the compounds exhibited potent antibacterial activity against the tested organisms. In addition, we conducted a cell viability assessment to evaluate the cytotoxicity of the free ligands. The results indicated that the ligands did not demonstrate statistically significant cytotoxicity. However, it is noteworthy that complex 1 displayed more pronounced cytotoxic effects on the DL cell line, followed by complexes 3, 5, and 7.

Synthesis of gold(I) diaminocarbene complexes by the addition of amines across coordinated isocyanoferrocene

Gold(I) acyclic diaminocarbene complexes of the [AuCl{C(NHFc)(NR2)}] type (Fc = ferrocenyl) were conveniently synthesized by a one-pot procedure. In this method, 1 equiv. of isocyanoferrocene (FcNC) and an excess of primary or secondary amines R2NH (dimethylamine, morpholine, methylamine, cyclohexylamine, and p-toluidine) are sequentially added to [AuCl(SMe2)] as a gold source in dichloromethane. The stepwise synthesis, in which [AuCl(FcNC)] is the isolated intermediate, worked equally well but generated lower overall yields due to compound loss during the two purification steps. The approach was further extended to synthesize the corresponding cationic biscarbene complexes [Au{C(NHFc)(NR2)}2]Cl simply by using 2 equiv. of FcNC during the “first” reaction step. The compounds form conformational isomers in solution that differ by the orientation of substituents at the carbene units. Based on DFT calculations, these isomers exhibit similar energies (energy difference ≤ 5 kcal mol–1). The crystal structures revealed symmetrical carbene units and the dominant role of the N-H⋅⋅⋅Cl interactions in the crystal assemblies in all cases, which also control the tendency for a particular conformation in the solid state.

The Synthesis, Characterization, and Fluxional Behavior of a Hydridorhodatetraborane.

The octahydridotriborate anion plays a crucial role in the field of polyhedral boron chemistry, facilitating the synthesis of higher boranes and the preparation of diverse transition metal complexes. Among the stable forms of this anion, CsB3H8 (or (n-C4H9)4N)[B3H8] have been identified. These salts serve as valuable precursors for the synthesis of metallaboranes, wherein the triborate anion acts as a ligand coordinating to the metal center. In this study, we have successfully synthesized a novel rhodatetraborane dihydride, [Rh(η2-B3H8)(H)2(PPh3)2] (1), which represents a Rh(III) complex featuring a bidentate chelate ligand fasormed by B3H8-. Extensive characterization of this rhodatetraborane complex has been performed using NMR spectroscopy in solution and X-ray diffraction analysis in the solid state. Notably, the complex exhibits intriguing fluxional behavior, which has been investigated using NMR techniques. Moreover, we have explored the reactivity of complex 1 towards pyridine (py) and dimethylphenylphosphine (PMe2Ph). Our findings highlight the labile nature of this four-vertex rhodatetraborane as it undergoes disassembly upon attack from the corresponding Lewis base, resulting in the formation of borane adducts, LBH3, where L = py, PMe2Ph. Furthermore, in these reactions, we report the characterization of new cationic hydride complexes, such as [Rh(H)2(PPh3)2 (py)]+ (2) and [Rh(H)2(PMe2Ph)4]+. Notably, the latter complex has been characterized as the octahydridotriborate salt [Rh(H)2(PMe2Ph)4][B3H8] (3), which extends the scope of rhodatetraborane derivatives.

Homoleptic Transition Metal Carbonyl Cations: Synthetic Approaches, Characterization and Follow-Up Chemistry.

ConspectusCarbon monoxide, CO, is one of the most important ligands in organometallic chemistry. It is an excellent π-acceptor and a moderate σ-donor. Therefore, most of the known transition metal carbonyls (TMCs) exhibit a zerovalent or even negative metal oxidation state (OS) of up to -4. However, given the right conditions, the carbonyl ligand also forms homoleptic cationic complexes with one or more transition metal atoms, the transition metal carbonyl cations (TMCCs), known with an OS of up to +3. Despite their long-standing history upon discovery of the first [M(CO)6]+ examples (M = Mn, Tc, Re) by E. O. Fischer in 1962 as well as their very fundamental nature, it took until the 1990s for the scope to be widened by Aubke, Strauss and Willner. Yet, many potential TMCC entries known from gas-phase mass spectrometry work remained unknown on preparative grounds. This is due to their high reactivity, which puts scientists to new challenges and encourages the development of suitable solvents, anions and oxidants, to cope with the demands of these fundamental salts─later referred to as pseudo-gas-phase conditions and innocent deelectronators and solvents.Hence, the utilization of extremely weakly coordinating perfluorinated alkoxyaluminates [Al(ORF)4]- and [F{Al(ORF)3}2]- (ORF = -OC(CF3)3) in combination with the polar but non- or weakly coordinating innocent solvents 1,2-difluorobenzene (oDFB) and 1,2,3,4-tetrafluorobenzene (TFB) yielded the first TMCC salts containing heptacoordinate [M(CO)7]+ (M = Nb, Ta) as well as paramagnetic [M(CO)6]+· (M = Cr, Mo, W) or [Ni(CO)4]+·. However, the use of typical inorganic oxidants Ag+, [NO]+ and Ag+/0.5 I2 regularly led to unwanted side reactions. For example, the Lewis acidic silver(I) cations form Lewis pairs with various Lewis basic TMCs yielding partly clustered [Agx{TMC}y]x+ complex salts, while nitrosonium cations may substitute for carbonyl ligands, forming [M(CO)x-1(NO)]+ complexes. The synergistic oxidizing reagent Ag+/0.5 X2 can add halonium ions X+ to the TMCs (X = Cl, Br, I). This prevented the synthesis of univalent group 8 TMCC salts. Yet, the application of radical cation salts of perfluorinated arenes as innocent deelectronators finally yielded salts of [Fe(CO)5]+· and [M3(CO)14]2+ (M = Ru, Os).TMCC salts are excellent starting materials, and the reaction of [Co(CO)5]+ and [Ni(CO)4]+· with benzene led to the previously unknown bis(benzene) sandwich complexes [Co(benzene)2]+ and [Ni(benzene)2]+·. Under the right conditions, even the very weakly bound oDFB-complex salts with [M(oDFB)2]+ (M = Co, Ni) cations form, useful as naked metal(I) synthons and for small-molecule activation.

Sulfonato Complex Formation Rather than Sulfonate Binding in the Extraction of Base Metals with 2,2′-Biimidazole: Extraction and Complexation Studies

The application of a bidentate aromatic N,N’-donor ligand, 2,2′-biimidazole (BIIMH2), as an extractant in the form of 1-octyl-2,2′-biimidazole (OBIIMH) and related derivatives in the solvent extraction of base metal ions (Mg2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) from an acidic sulfonate medium using dinonylnaphthalene disulfonic acid (DNNDSA) as a synergist was investigated. OBIIMH with DNNDSA as a co-extractant showed a lack of selectivity for base metals ions (Mg2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) despite its similarity with a related bidentate aromatic ligand, 2,2′-pyridylimidazole, which showed preference for Ni(II) ions. The nickel(II) specificity, through stereochemical “tailor-making”, was not achieved as expected and the extracted species were isolated to study the underlying chemistry. The homemade metal sulfonate salts, M(RSO3)2·6H2O (R = Toluene and M2+ = Co2+, Ni2+, Cu2+ and Zn2+), were used as precursors of the metal complexes of BIIMH2 using toluene-4-sulfonic acid as the representative sulfonate. Spectroscopic analysis and single-crystal X-ray analysis supported the formation of similar neutral distorted octahedral sulfonato complexes through the bis coordination of BIIMH2 and two sulfonate ions rather than the formation of cationic complex species with anion coordination of sulfonates. We attributed the observation of similar complex species and the similar stability constants of the bis-complexes in solution as the cause for the lack of pH-metric separation of the later 3d metal ions.

Cu(II)-acylhydrazone complex, a potent and selective antitumor agent against human osteosarcoma: Mechanism of action studies over in vitro and in vivo models

Osteosarcoma (OS) is a frequent bone cancer, affecting largely children and young adults. Cisplatin (CDDP) has been efficacious in the treatment of different cancer such us OS but the development of chemoresistance and important side effects leading to therapeutic failure. Novel therapies including copper compounds have shown to be potentially effective as anticancer drugs and one alternative to usually employed platinum compounds.The goal of this work is the evaluation of the in vitro and in vivo antitumoral activity and dilucidate the molecular target of a Cu(II) cationic complex containing a tridentate hydrazone ligand, CuHL for short, H2L=N'-'-(2-hydroxy-3-methoxybenzylidene)thiophene-2-carbohydrazide, against human OS MG-63 cells.Anticancer activity on MG-63 cell line was evaluated in OS monolayer and spheroids. CuHL significantly impaired cell viability in both models (IC50 2D: 2.1 ± 0.3 μM; 3D: 9.1 ± 1.0 μM) (p < 0.001). Additional cell studies demonstrated the copper compound inhibits cell proliferation and conveys cells to apoptosis, determined by flow cytometry. CuHL showed a great genotoxicity, evaluated by comet assay. Proteomic analysis by Orbitrap Mass Spectometry identified 27 differentially expressed proteins: 17 proteins were found overexpressed and 10 underexpressed in MG-63 cells after the CuHL treatment. The response to unfolded protein was the most affected biological process.In addition, in vivo antitumor effects of the compound were evaluated on human OS tumors xenografted in nude mice. CuHL treatment, at a dose of 2 mg/kg i.p., given three times/week for one month, significantly inhibited the progression of OS xenografts and was associated to a reduction in mitotic index and to an increment of tumor necrosis (p < 0.01). Administration of standard-of-care cytotoxic agent CDDP, following the same treatment schedule as CuHL, failed to impair OS growth and progression.

Three heteroleptic copper(I) complexes with [Cu(P˄P)N2]+ structure and their fluorescence sensing for VOCs

The design and research of luminescent and volatile organic compound (VOC) fluorescent sensing materials are of great significance and challenge. We report herein the ligand substitution reaction and VOC sensing of new heteroleptic [Cu(P˄P)N2]+ type copper(I) complexes. Firstly, three new complexes 1–3 were designed by utilizing a chelate diphosphine ligand 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene (Xantphos) and synthesized by the substitution reaction of different N‐containing ligands of 4‐PBO (1), 3‐PBO (2), and 4,4′‐Bipy (3) (4‐PBO = 2‐(4′‐pyridyl)‐benzoxazole, 3‐PBO = 2‐(3′‐pyridyl)‐benzoxazole, 4,4′‐Bipy = 4,4′‐bipyridine), respectively. Three complexes were characterized by elemental analysis, spectroscopic analysis (IR, UV–Vis), single‐crystal X‐ray diffraction (SCXRD), and photoluminescence study. The SCXRD study revealed that complexes 1 and 2 both exhibit a molecular structure with tetrahedral copper(I) complex cation and hexafluorophosphate anion, while complex 3 differs in that its cation is a binuclear copper(I) structure bridged by 4,4′‐bipyridine. Three complexes 1–3 present supramolecular ribbon, supramolecular dimer, and supramolecular framework structure, respectively. Some differences of their UV–Vis absorption spectra were explained by TD‐DFT calculation and wavefunction analysis. It is found that 1 has an abnormal luminescence blue shift, and a luminescence mechanism through the high‐energy T2 excited state is proposed by TD‐DFT calculation. Based on 3, a fluorescent test strip was developed, and its fast and selective fluorescent sensing of pyridine vapor through quenching mechanism was successfully realized. The fluorescent quenching mechanism of the material was also studied, and it was proposed that the quenching should be attributed to the photoinduced electron transfer (PET) mechanism.

Towards Incorporation in Larger Architectures: A Polymeric Halogen Bond‐Based Iridium Sensor

AbstractThis study reports the synthesis and characterization of a "click‐able" iridium(III) complex as halogen bond‐based anion sensor. The functionalization is exemplarily demonstrated by the attachment of poly(ethylene glycol) azide via a "copper‐click"‐reaction. Subsequently, the polymeric XB donor complex is characterized in depth with 1H NMR spectroscopy, size exclusion chromatography, and MALDI‐ToF‐MS. Moreover, the anion binding capabilities are demonstrated with emission titrations revealing strong anion complexation. These findings emphasize the great potential of this approach to tune the complex's properties or include other functions such as cation complexation sites to exploit cooperative effects by using polymeric substituents on the iridium complex.

Synthesis, characterization and structural study of two imidazole oxime ligand and their ZnII mononuclear coordination compounds

This paper presents a combined experimental and computational study of two new mononuclear Zinc(II) coordination compounds. The {Zn(MICO)2Cl2} (I) and{Zn(MIPMO)2Cl2} (II) complexes have been synthesized and characterized by NMR, UV, FTIR and single crystal X-ray diffraction techniques. The single crystal X-ray analyses reveal that the centrosymmetric ZnII cation in both complexes {Zn(MICO)2Cl2} (I) and {Zn(MIPMO)2Cl2} (II) is tetrahedrally coordinated by two chelating imidazole oxime ligands and by two chlorine atoms in a distorted tetrahedral geometry. The intremolecular interactions were found to play an important role in determining the most favorable structure of the free ligands, therefore controlling the final coordination mode. The cohesion of the structure and stability are ensured by intermolecular OH···O, OH···N, OH···Cl and CH···O hydrogen bonds. Hirshfeld surface analysis was performed to study the nature of intermolecular interactions within the crystal structure via 3D and 2D fingerprint surfaces and to demonstrate H-bonding with close contacts in crystal via dnorm surface. The stability of the prepared ZnII complexes has been evaluated through the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), and energy gap. The molecular geometries and electronic transitions of the two complexes and their ligands in the ground state have been calculated using the mPW1PW91 basis at the TZVP level of theory.

A Comparison of Di- and Trinuclear Platinum Complexes Interacting with Glycosaminoglycans for Targeted Chemotherapy.

Heparan sulfate proteoglycans (HSPGs) and their associated proteins aid in tumor progression through modulation of biological events such as cell invasion, angiogenesis, metastasis, and immunological responses. Metalloshielding of the anionic heparan sulfate (HS) chains by cationic polynuclear platinum complexes (PPCs) prevents the HS from interacting with HS-associated proteins and thus diminishes the critical functions of HSPG. Studies herein exploring the PPC-HS interactions demonstrated that a series of PPCs varying in charge, nuclearity, distance between Pt centers, and hydrogen-bonding ability influence HS affinity. We report that the polyamine-linked complexes have high HS affinity and display excellent in vivo activity against breast cancer metastases and those arising in the bone and liver compared to carboplatin. Overall, the PPC-HS niche offers an attractive approach for targeting HSPG-expressing tumor cells.

Bismut in der Dynamisch Kovalenten Chemie: Makrocyclen und Siebenkernige Komplexkationen mit Ungewöhnlichen Strukturen

AbstractDynamisch kovalente Chemie (DCvC) ist ein wertvolles und breit eingesetztes Werkzeug in der modernen Synthesechemie, das auf dem reversiblen Knüpfen und Brechen kovalenter Bindungen basiert. Eine der inhärenten Stärken dieses Ansatzes ist das Potential, in einfachen Syntheseprotokollen reversibel neue Strukturmotive generieren zu können, die mit anderen Methoden nur schwer oder gar nicht zugänglich sind und eine Vielzahl von Bindungsbrüchen und ‐knüpfungen erfordern. Bislang sind diese fundamentalen synthesechemischen und konzeptionellen Herausforderungen in der DCvC verstärkt mit leichteren p‐Block‐Elementen angegangen worden, obwohl schwerere p‐Block‐Elemente angesichts geringer Bindungsdissoziationsenergien ideal geeignet für den Einsatz in der DCvC erscheinen. Wir zeigen hier, dass eine zweikernige metallorganische Bismutverbindung, bestehend aus zwei Thioxanthen‐verbrückten BiMe2‐Einheiten, bereitwillig selektive und reversible Bi−C Bindungsbrüche vollzieht, wenn sie externen Stimuli ausgesetzt wird. Das Ausnutzen von DCvC in der metallorganischen Chemie schwerer p‐block‐Elemente gewährt Zugang zu präzedenzlosen Makrocyclen und oligonuklearen Komplexen mit Fass‐ähnlicher Struktur.

Bismuth in Dynamic Covalent Chemistry: Access to a Bowl-Type Macrocycle and a Barrel-Type Heptanuclear Complex Cation.

Dynamic covalent chemistry (DCvC) is a powerful and widely applied tool in modern synthetic chemistry, which is based on the reversible cleavage and formation of covalent bonds. One of the inherent strengths of this approach is the perspective to reversibly generate novel structural motifs in an operationally simple approach, which are difficult or impossible to access with more traditional methods and require multiple bond cleaving and bond forming steps. To date, these fundamentally important synthetic and conceptual challenges in the context of DCvC have predominantly been tackled by exploiting compounds of lighter p-block elements, albeit heavier p-block elements show low bond dissociation energies and appear to be ideally suited for this approach. Here we show that a dinuclear organometallic bismuth compound, containing BiMe2 groups that are connected by a thioxanthene linker, readily undergoes selective and reversible cleavage of its Bi-C bonds upon exposure to external stimuli. The exploitation of DCvC in the field of organometallic heavy p-block chemistry grants access to unprecedented macrocyclic and barrel-type oligonuclear compounds.

EPR Sensing of a Cation Species by Aza-Crown Ethers Incorporating a Persistent Nitroxidic Radical Unit.

New nitroxides based on aza-crown ethers were prepared and employed as selective sensors for the detection of inorganic and organic cations by EPR analysis of the corresponding host-guest complexes. The nitroxide unit behaves as a sensitive probe for a number of alkali and alkaline earth metal cations affording EPR spectra differing in the value of nitrogen hyperfine constants and in the appearance of splitted signals due to the non-zero nuclear spin of some metal cation upon complexation. Owing to the remarkable EPR spectral differences between the host and the corresponding cation complex the new macrocycles are likely to act as multitasking tools to recognize several cationic species. EPR behaviour of the larger nitroxide azacrown 1⋅ when acting as a wheel in a radical synthetic bistable [2]rotaxane containing both secondary dialkylammonium and 1,2-bis(pyridinium) molecular stations, was also investigated. Reversible movements of the macrocycle between the two recognition sites in the rotaxane were promptly revealed by EPR, which shows significant changes either in nitrogen coupling constant values (aN ) or in the spectral shape in the two rotaxane co-conformations.

Tweaking the conjugation effects on a pair of new triazene compounds by targeted deprotonation: a spectroscopic and theoretical overview.

Triazene compounds (-NNN(H)-) exhibit versatility in biological, physical, and chemical applications. In their anionic form (-NNN-)(-), they can act as coordinating sites for metals, forming metallic complexes. In this study, two new isomeric triazene compounds with meta- and para-substituents in their neutral and anionic forms were investigated. A combination of detailed experimental spectroscopic characterization and computational chemistry analyses were employed. The new compounds, 1-(2-benzamide)-3-(3-nitrophenyl) triazene (m-TZN) and 1-(2-benzamide)-3-(4-nitrophenyl) triazene (p-TZN), were compared to 1,3-diphenyltriazene (dph-TZN) to understand the effects of functionalization and targeted triazene deprotonation. The anionic forms are stable, and our investigation suggests that these new compounds are suitable tridentate ligands that can act as chelating agents for metallic cations in stable complexes, similar to those found in vitamin B12. The absorption, vibrational, and electronic properties of the newly synthesized triazene compounds were extensively characterized using FT-IR/FT-Raman and UV-Vis spectroscopy. Their distinct molecular properties, intramolecular hydrogen bond effects, stability, and electronic transitions were investigated using the ORCA software. These analyses involved DFT and TD-DFT calculations at the ωB97X-D3/Def2-TZVP level of theory with THF CPCM implicit solvation to determine the molecular topology and electronic structure. The advanced STEOM-DLPNO-CCSD method for excited states was employed, enabling an in-depth analysis of ground and excited-state chemistry, accounting for precise electronic correlation and solvation effects. Explicit THF solvation was tested on the full TD-DFT ωB97X-D3/Def2-TZVP level and using ONIOM on the STEOM calculation. Reactivity was studied using Fukui functions, and action as chelating agents was investigated using GFN-xTB2 and DFT.

Elusive Active Intermediates and Reaction Mechanisms of ortho-/ipso-Hydroxylation of Benzoic Acid by Hydrogen Peroxide Mediated by Bioinspired Iron(II) Catalysts.

Aromatic hydroxylation of benzoic acids (BzOH) to salicylates and phenolates is fundamentally interesting in industrial chemistry. However, key mechanistic uncertainties and dichotomies remain after decades of effort. Herein, the elusive mechanism of the competitive ortho-/ipso-hydroxylation of BzOH by H2O2 mediated by a nonheme iron(II) catalyst was comprehensively investigated using density functional theory calculations. Results revealed that the long-postulated FeV(O)(anti-BzO) oxidant is an FeIV(O)(anti-BzO•) species 2 (anti- and syn- are defined by the orientation of the carboxyl oxygen of BzO to the oxo), which rules out the noted two-oxidant mechanism proposed previously. We propose a new mechanism in which, following the formation of an FeV(O)(syn-BzO) species (3) and its electromer FeIV(O)(syn-BzO•) (3'), 3/3' either converts to salicylate and phenolate via intramolecular self-hydroxylation (route A) or acts as an oxidant to oxygenate another BzOH to generate the same products (route B). In route A, the rotation of the BzO group along the C-O bond forms 2, in which the BzO group is orientated by π-π stacking interactions. An electrophilic ipso-addition forms a phenolate by concomitant decarboxylation or an ortho-attack forms a cationic complex, which readily undergoes an NIH shift and a BzOH-assisted proton shift to form a salicylate. In route B, 3 oxidizes an additional BzOH molecule directed by hydrogen bonding and π-π stacking interactions. In both routes, selectivity is determined by the chemical property of the BzO ring. These mechanistic findings provide a clear mechanistic scenario and enrich the knowledge of hydroxylation of aromatic acids.

Three Iodoargentate-Based Hybrids Decorated by Metal Complexes: Structures, Optical/Photoelectric Properties and Theoretical Studies.

So far, the development of new iodoargentate-based hybrids, especially those compounds with metal complex cations, and the understanding of their structure-activity relationships have been of vital importance but full of challenges. Herein, using the in-situ-generated metal complex cations as structural directing agents, three new iodoargentate-based hybrids, namely, [Co(phen)3]Ag2PbI6 (phen = 1,10-phenanthroline; 1), [Ni(5,5-dmpy)3]Ag7I9·CH3CN (5,5-dmpy = 5,5-dimethyl-2,2-bipyridine; 2) and [Co(5,5-dmpy)3]Ag5I8 (3), have been solvothermally prepared and then structurally characterized. Compound 1 represents one new heterometallic Ag-Pb-I compound characteristic of the chain-like [Ag2PbI6]n2n- anions. Compound 2 features the straight one-dimensional (1D) [Ag7I9]n2n- anionic moieties, while compound 3 contains infrequent two types of curved [Ag5I8]n3n- anions. Optical properties reveal that the title compounds exhibit interesting semiconductor behaviors with the band gaps of 1.59-2.78 eV, which endow them with good photoelectric switching performances under the alternate light irradiations. We also present their Hirshfeld surface analyses, and the theoretical studies (band structures, density of states (DOS) and partial density of states (PDOS)).

Electronic Structure of the Complete Series of Gas-Phase Manganese Acetylacetonates by X-ray Absorption Spectroscopy.

Metal centers in transition metal-ligand complexes occur in a variety of oxidation states causing their redox activity and therefore making them relevant for applications in physics and chemistry. The electronic state of these complexes can be studied by X-ray absorption spectroscopy, which is, however, due to the complex spectral signature not always straightforward. Here, we study the electronic structure of gas-phase cationic manganese acetylacetonate complexes Mn(acac)1-3+ using X-ray absorption spectroscopy at the metal center and ligand constituents. The spectra are well reproduced by multiconfigurational wave function theory, time-dependent density functional theory as well as parameterized crystal field and charge transfer multiplet simulations. This enables us to get detailed insights into the electronic structure of ground-state Mn(acac)1-3+ and extract empirical parameters such as crystal field strength and exchange coupling from X-ray excitation at both the metal and ligand sites. By comparison to X-ray absorption spectra of neutral, solvated Mn(acac)2,3 complexes, we also show that the effect of coordination on the L3 excitation energy, routinely used to identify oxidation states, can contribute about 40-50% to the observed shift, which for the current study is 1.9 eV per oxidation state.

Cover Feature: Highly Electrophilic Mononuclear Cationic Aluminium Alkoxide Complexes: Syntheses, Reactivity and Catalytic Applications (Chem. Eur. J. 55/2023)

Cover Feature: Highly Electrophilic Mononuclear Cationic Aluminium Alkoxide Complexes: Syntheses, Reactivity and Catalytic Applications (Chem. Eur. J. 55/2023)

Neutral and Cationic Molybdenum Imido Alkylidene Cyclic Alkyl Amino Carbene (CAAC) Complexes for Olefin Metathesis.

The first neutral and cationic Mo imido alkylidene cyclic alkyl amino carbene (CAAC) complexes of the general formulae [Mo(N-Ar)(CHCMe2Ph)(X)2(CAAC)] and [Mo(N-Ar)(CHCMe2Ph)(X)(CAAC)][B(ArF)4] (X = Br, Cl, OTf, OC6F5; CAAC = 1-(2,6-iPr2-C6H3)-3,3,5,5-tetramethyltetrahydropyrrol-2-ylidene) have been synthesized from molybdenum imido bishalide alkylidene DME precursors. Different combinations of the imido and "X" ligands have been employed to understand synthetic peculiarities. Selected complexes have been characterized by single crystal X-ray analysis. Due to the pronounced σ-donor/π-acceptor characteristics of CAACs, the corresponding neutral and cationic molybdenum imido alkylidene CAAC complexes do not require the presence of stabilizing donor ligands such as nitriles. Calculations on the PBE0-D3BJ/def2-TZVP level for PBE0-D3BJ/def2-SVP optimized geometries revealed partial charges at molybdenum similar to the corresponding molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes with a slightly higher polarization of the molybdenum alkylidene bond in the CAAC complexes. All cationic complexes have been tested in olefin metathesis reactions and showed improved activity compared to the analogous NHC complexes for hydrocarbon-based substrates, allowing for turnover numbers (TONs) up to 9500 even at room temperature. Some Mo imido alkylidene CAAC complexes are tolerant towards functional groups like thioethers and sulfonamides.