Search

Two‐coordinate Au(I) complexes with a donor‐metal‐acceptor (D‐M‐A) structure have shown rich luminescent properties. However, charge‐neutral dinuclear donor‐metal‐acceptor type Au(I) complexes featuring aurophilic interactions have been seldom explored. Herein, we describe the structures and photoluminescence properties of two dinuclear Au(I) complexes, namely DiAu‐Ph and DiAu‐Me. Single crystal X‐ray structural analysis of DiAu‐Ph reveals a short intramolecular Au‐Au distance of 3.224 Å. In dilute solution and doped films, excitation wavelength dependent multiple phosphorescence phenomena were observed for these dinuclear complexes. Theoretical calculations reveal that the aurophilic interaction causes increased contribution of the Au d orbital to the highest occupied molecular orbitals. Thus, the gap between singlet and triplet excited states (ΔEST) is enlarged, which disables the thermally activated delayed fluorescence (TADF). Moreover, the large energy separation (0.45–0.52 eV) and the different orbital configurations between the various excited states result in an inefficient internal conversion, accounting for their multiple phosphorescence properties. [ABSTRACT FROM AUTHOR]

Hydrogen bonds involving the oxygen atoms of intermediates that result from copper‐mediated O2 activation play a key role for controlling the reactivity of Cux/O2 active sites in metalloenzymes and synthetic model complexes. However, structural insight into H‐bonding in such transient species as well as thermodynamic information about proton transfer to or from the O2‐derived ligands is scarce. Here we present a detailed study of the reversible interconversion of a μ1,2‐peroxodicopper(II) complex ([1]+) and its μ1,1‐hydroperoxo congener ([2]+) via (de)protonation, including the isolation and structural characterization of several H‐bond donor (HBD) adducts of [1]+ and the determination of binding constants. For one of these adducts a temperature‐dependent μ1,2‐peroxo/μ1,1‐hydroperoxo equilibrium associated with reversible H+‐translocation is observed, its thermodynamics investigated experimentally and computationally, and effects of H‐bonding on spectroscopic parameters of the CuII2(μ1,2‐O2) species are revealed. DFT calculations allowed to fully map and correlate the trajectories of H+‐transfer and μ1,2‐peroxo→μ1,1‐peroxo rearrangement. These findings enhance our understanding of two key intermediates in bioinspired Cu2/O2 chemistry. [ABSTRACT FROM AUTHOR]

A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons. [ABSTRACT FROM AUTHOR]

The reaction of the dianionic species [Fe2(CO)6(μ-PPh)2]2− with tBuN(CH2Cl)2 gives the di-iron carbonyl aza-diphosphido-bridged complex [Fe2(CO)6(µ-{P(Ph)CH2}2NtBu)] (1). Attempts to prepare 1 by click-chemistry by reacting [Fe2(CO)6(μ-PHPh)2] with CH2O and tBuNH2 afforded a bis-phosphido compound [Fe2(CO)6(µ-P(Ph)CH2NHtBu)2] (2) which exists as two, syn and anti, isolable isomers depending on the relative orientation of the groups carried by the phosphorus atoms. In the presence of HBF4.Et2O, in dichloromethane, 1 leads to the stabilized ammonium species [Fe2(CO)6(µ-{P(Ph)CH2}2NHtBu)](BF4) (3). The derivatives 1–3 were characterized by IR and 1H, 31P-{1H} NMR spectroscopies. Their structures in a solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics. [ABSTRACT FROM AUTHOR]

There is a dearth of experiments on the synthesis of binuclear bridging complexes in current experimental textbooks, and limited knowledge exists regarding secondary amine synthesis and Cu(II) oxidation. In this study, drawing from the foundational reactions in organic chemistry theory, two routes were devised to synthesize the target secondary amine ligand. Route 1 is predicated on nucleophilic substitution reactions, while Route 2 involves nucleophilic addition condensation and reduction. Leveraging the principles of coordination chemistry and the conjugated drive effect in organic chemistry, Cu(II), with its weak oxidizing properties, oxidized secondary amines into conjugated aromatic imines (Schiff base) structures. Concurrently, the coordination of Schiff base and the bridging coordination of chloride ions were harnessed to form stable chlorine-bridged binuclear Cu(I) complexes. To suit the experimental teaching conditions in tertiary institutions, a straightforward operational set-up was designed to visually illustrate the identification of copper ion valence states in Cu(I) complexes. The experimental principles herein encompass not only fundamental chemical reaction knowledge but also embody the latest scientific research findings. With mild reaction conditions, intuitive experimental observations, good reproducibility, and high yields, this experiment effectively enhances students' comprehensive experimental operation skills and cultivates their abilities in organic synthesis and coordination chemistry. [ABSTRACT FROM AUTHOR]

Two new paddlewheel-type dirhodium (Rh2) complex isomers, formulated as trans-2,2- and 3,1-forms of [Rh2(bhp)4] (bhp = 6-bromo-2-hydroxypyridinate), were obtained by the reaction of 6-bromo-2-hydroxypyridine with [Rh2(O2CCH3)4(H2O)2] and characterized by NMR, ESI-MS, and elemental analyses. Single crystal X-ray diffraction analyses clarified that the crystal structure of trans-2,2-form takes a conventional paddlewheel-type dimer structure with no axial coordination ligands, i.e., trans-2,2-[Rh2(bhp)4], whereas that of the 3,1-form changed significantly depending on the kinds of solvent used for crystallization processes; dimer-of-dimers-type tetrarhodium complex, i.e., 3,1-[Rh2(bhp)4]2, and a conventional paddlewheel-type dimer complex with an axial DMF ligand, i.e., 3,1-[Rh2(bhp)4(DMF)], were observed. The 3,1-form showed unique absorption changes that were not observed in the trans-2,2-form; the trans-2,2-form showed an absorption band at approximately 780 nm both in the solid state and in solution (CH2Cl2 and DMF), whereas the 3,1-form showed a similar absorption band at 783 nm in CH2Cl2 solution, but their corresponding bands were blue-shifted in solid state (655 nm) and in DMF solution (608 nm). The molecular structures and the origin of their unique absorption properties of these Rh2 complexes were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT). [ABSTRACT FROM AUTHOR]

Abstract A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons.

In this study, new complexes are produced by bonding of transition metal dinuclear chlorides (CoCl2.6H2O, MnCl2.4H2O, and FeCl2.6H2O) with a polychelated ligand called 9-Phenyl-2,3,7-trihydroxy-6-fluorone, represented by (L), in a 1:2 (metal: ligand) ratio. Applying the appropriate chemical and physical methods, such as melting points, molar electrical conductivity, magnetic sensitivity, FT-IR, UV-Visible, and mass spectrometric studies, the produced complexes were characterized. All complexes are non-electrolytic, according to analyzes of molar electrical conductivity. All complexes have an octahedral structure, according to studies of magnetic sensitivity and Uv-Visible spectra. The mass spectrometry measurements showed the presence of the molar mass bands of the complex and the appearance of other bands resulting from the fragmentation of the complexes. For the metallic complexes spectra, FT-IR revealed a shift in the shape and intensity of the complexes bands at lower frequencies. The bonding of the metal to the oxygen atom can be observed by this shift in the bond stretch of the ligands. The size of the coordination between the ligand and the ions of the metallic elements is the cause. The measurement of the complexes' melting point is high, which suggests that the resultant complexes are quite stable.

The reaction of the dianionic species [Fe2(CO)6(μ-PPh)2]2− with tBuN(CH2Cl)2 gives the di-iron carbonyl aza-diphosphido-bridged complex [Fe2(CO)6(µ-{P(Ph)CH2}2NtBu)] (1). Attempts to prepare 1 by click-chemistry by reacting [Fe2(CO)6(μ-PHPh)2] with CH2O and tBuNH2 afforded a bis-phosphido compound [Fe2(CO)6(µ-P(Ph)CH2NHtBu)2] (2) which exists as two, syn and anti, isolable isomers depending on the relative orientation of the groups carried by the phosphorus atoms. In the presence of HBF4.Et2O, in dichloromethane, 1 leads to the stabilized ammonium species [Fe2(CO)6(µ-{P(Ph)CH2}2NHtBu)](BF4) (3). The derivatives 1–3 were characterized by IR and 1H, 31P-{1H} NMR spectroscopies. Their structures in a solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics.

Copyright of Journal of University of Anbar for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rare-earth metal sesquioxides (RE2O3) are stable compounds that require high activation energies in solid-state reactions or strong acids for dissolution in aqueous media. Alternatively, dissolution and downstream chemistry of RE2O3 have been achieved with ionic liquids (ILs), but typically with additional water. In contrast, the anhydrous IL 1-butyl-3-methylimidazolium acetate [BMIm][OAc] dissolves RE2O3 for RE = La–Ho and forms homoleptic dinuclear metal complexes that crystallize as [BMIm]2[RE2(OAc)8] salts. Chloride ions promote the dissolution without being included in the compounds. Since the lattice energy of RE2O3 increases with decreasing size of the RE3+ cation, Ho2O3 dissolves very slowly, while the sesquioxides with even smaller cations appear to be inert under the applied conditions. The Sm and Eu complex salts show blue and red photoluminescence and Van Vleck paramagnetism. The proton source for the dissolution is the imidazolium cation. Abstraction of the acidic proton at the C2-atom yields an N-heterocyclic carbene (imidazole-2-ylidene). The IL can be regenerated by subsequent reaction with acetic acid. In the overall process, RE2O3 is dissolved by anhydrous acetic acid, a reaction that does not proceed directly.

[Display omitted] An unusual neutral dinuclear palladium(II) complex with two head-to-head orientated μ- P , S -bridging ligands was obtained by the reaction of Pd(MeCN) 2 Cl 2 with (1 R ,5 R)-3-(4-phenylthiobutoxy)-2,4-diphenyl-2,4-diaza-3-phospha-bicyclo[3.4.0]nonane. The dimeric structure of the complex in the solid state and in solution was thoroughly confirmed using appropriate analytical techniques: single crystal X-ray diffraction analysis, HRMS, FTIR and NMR spectroscopy. [ABSTRACT FROM AUTHOR]

The di-iron carbonyl dithiolene bridged complex [Fe2(CO)6(µ-S2C2(CO2Me)2)] (1) reacts with 1 equivalent of phosphane PR3 (R = Ph, OMe) to give, as major products, monosubstituted derivatives [Fe2(CO)5L(µ-S2C2(CO2Me)2)] (L = PPh3 (2), P(OMe)3 (3)). In the presence of an excess (3–4 equiv.) of P(OMe)3, the cleavage of 1 arises partly and a mixture of the mononuclear species [Fe(CO)(P(OMe)3)2(κ2-S2C2(CO2Me)2)] (4) and 3 is obtained. The compounds 2–4 were analyzed by IR and 1H, 31P-{1H} NMR spectroscopies. Their structures in solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics. [ABSTRACT FROM AUTHOR]

Heterometallic FeCo dinuclear complexes on the basis of the redox-active 1,10-phenanthroline-5,6-dione with ancillary bis(pyrazolyl)borate anions and tetradentate N-donor ligands (N,N′-dialkyl-2,11-diaza[3.3]-(2,6)pyridinophane and tris(2-pyridilmethyl)amine derivatives) were studied by the DFT UTPSSh/6–311 + + G(d,p) method in a view to possible spin-crossover (SCO) or valence tautomeric (VT) interconversions. The electronic structures (namely, spin and oxidation states of the electronically labile centers) and magnetic properties of the considered compounds were found to be determined by the position of the outer-sphere PF6– counterion and the type of N-donor base. The most energetically preferred isomers contain a counterion near the cobalt ion. The presence of PF6– next to the iron center stabilizes the ferric state of this metal and the dianionic form of the 1,10-phenanthroline-5,6-dione linker ligand. The variation of the structural peculiarities allowed us revealing the dinuclear complexes prone to exhibit the SCO and VT processes, which makes them promising building blocks of magnetic materials. [ABSTRACT FROM AUTHOR]

A synthetic strategy to access asymmetric dinuclear bis(ansa-metallocene) pre-catalysts is described. As a key step, the Pd-catalyzed Suzuki cross-coupling of 9,9-bis(trimethylsilyl)-fluoren-2-yl-boronic acid with a substituted 2-bromo-9H-fluorene generates an asymmetric 2,2′-bifluorene platform, which can be individually functionalized at the two differentiated 9-positions. Herein, as a first demonstration of this strategy, we report the asymmetric dinuclear bis(ansa-zirconocene) complex 2,2′-[{Me2C(Flu)(Cp)}ZrCl2][{Me2C(7-tBuFlu)(Cp)}ZrCl2], which has been characterized with NMR spectroscopy and high-resolution mass spectrometry. The performance of this bimetallic pre-catalyst when combined with MAO has been evaluated in ethylene, propylene, and ethylene/1-hexene (co-)polymerization. This pre-catalyst is revealed to be less productive than the mononuclear reference pre-catalyst {Me2C(2,7-tBuFlu)(Cp)}ZrCl2, likely because of higher steric hindrance induced by the linkage at the difluorenyl platform. The resulting (co-)polymers featured only slight differences in terms of molecular weights, tacticity, and comonomer incorporation. No bimodal molecular weight distribution was achieved at any produced polymer; this might have originated from the close similarity of the connected Cp/Flu moieties or a rapid chain-transfer phenomenon between the different active sites which were quite close to each other. [ABSTRACT FROM AUTHOR]

Two differently substituted pyrazole ligands have been investigated with regard to the topology of their Pt complexes: upon deprotonation, two mononuclear 1:2 PtII-pyrazole complexes—one of the sterically unhindered 4-Me-pzH and one of the bulky 3,5-tBu-pzH (pzH = pyrazole)—yield the corresponding 1:2 PtII-pyrazolato species; the former a triangular, trinuclear metallacycle (1), and the latter a dinuclear, half-lantern species (2) formed via the unprecedented cyclometallation of a butyl group. Stoichiometric oxidation of the colorless PtII2 complex produces the deep-blue, metal–metal bonded PtIII2 analog (3) with a rarely encountered unsymmetrical coordination across the Pt-Pt bond. All three complexes have been characterized by single crystal X-ray structure determination, 1H-NMR, IR, and UV-vis-NIR spectroscopic methods. The XPS spectra of the PtII2 and PtIII2 species are also reported. Density functional theory calculations were carried out to investigate the electronic structure, spectroscopic properties, and chemical bonding of the new complexes. The calculated natural population analysis charges and Wiberg bonding indices indicate a weak σ-interaction in the case of 2 and a formal Pt-Pt single bond in 3.

Rare-earth metal sesquioxides (RE2O3) are stable compounds that require high activation energies in solid-state reactions or strong acids for dissolution in aqueous media. Alternatively, dissolution and downstream chemistry of RE2O3 have been achieved with ionic liquids (ILs), but typically with additional water. In contrast, the anhydrous IL 1-butyl-3-methylimidazolium acetate [BMIm][OAc] dissolves RE2O3 for RE = La–Ho and forms homoleptic dinuclear metal complexes that crystallize as [BMIm]2[RE2(OAc)8] salts. Chloride ions promote the dissolution without being included in the compounds. Since the lattice energy of RE2O3 increases with decreasing size of the RE3+ cation, Ho2O3 dissolves very slowly, while the sesquioxides with even smaller cations appear to be inert under the applied conditions. The Sm and Eu complex salts show blue and red photoluminescence and Van Vleck paramagnetism. The proton source for the dissolution is the imidazolium cation. Abstraction of the acidic proton at the C2-atom yields an N-heterocyclic carbene (imidazole-2-ylidene). The IL can be regenerated by subsequent reaction with acetic acid. In the overall process, RE2O3 is dissolved by anhydrous acetic acid, a reaction that does not proceed directly. [ABSTRACT FROM AUTHOR]

The di-iron carbonyl dithiolene bridged complex [Fe2(CO)6(µ-S2C2(CO2Me)2)] (1) reacts with 1 equivalent of phosphane PR3 (R = Ph, OMe) to give, as major products, monosubstituted derivatives [Fe2(CO)5L(µ-S2C2(CO2Me)2)] (L = PPh3 (2), P(OMe)3 (3)). In the presence of an excess (3–4 equiv.) of P(OMe)3, the cleavage of 1 arises partly and a mixture of the mononuclear species [Fe(CO)(P(OMe)3)2(κ2-S2C2(CO2Me)2)] (4) and 3 is obtained. The compounds 2–4 were analyzed by IR and 1H, 31P-{1H} NMR spectroscopies. Their structures in solid state were determined by X-ray diffraction analyses, which accord with their spectroscopic characteristics.

Two new paddlewheel-type dirhodium (Rh2) complex isomers, formulated as trans-2,2- and 3,1-forms of [Rh2(bhp)4] (bhp = 6-bromo-2-hydroxypyridinate), were obtained by the reaction of 6-bromo-2-hydroxypyridine with [Rh2(O2CCH3)4(H2O)2] and characterized by NMR, ESI-MS, and elemental analyses. Single crystal X-ray diffraction analyses clarified that the crystal structure of trans-2,2-form takes a conventional paddlewheel-type dimer structure with no axial coordination ligands, i.e., trans-2,2-[Rh2(bhp)4], whereas that of the 3,1-form changed significantly depending on the kinds of solvent used for crystallization processes; dimer-of-dimers-type tetrarhodium complex, i.e., 3,1-[Rh2(bhp)4]2, and a conventional paddlewheel-type dimer complex with an axial DMF ligand, i.e., 3,1-[Rh2(bhp)4(DMF)], were observed. The 3,1-form showed unique absorption changes that were not observed in the trans-2,2-form; the trans-2,2-form showed an absorption band at approximately 780 nm both in the solid state and in solution (CH2Cl2 and DMF), whereas the 3,1-form showed a similar absorption band at 783 nm in CH2Cl2 solution, but their corresponding bands were blue-shifted in solid state (655 nm) and in DMF solution (608 nm). The molecular structures and the origin of their unique absorption properties of these Rh2 complexes were investigated using density functional theory (DFT) and time-dependent DFT (TDDFT).

Multinuclear complexes of heavy metals, such as tungsten, have demonstrated considerable potential as candidates for advanced radiocontrast agents. Of particular interest is the development of stable non-ionic compounds with high metal content and reasonably low osmolality in solution. Accordingly, we have synthesized a series of neutral W(V) complexes that contain the W2O2(µ-O)2 core and amino acids or disubstituted EDTA derivatives as ligands. The compounds were prepared from the oxalatotungstate(V) complex via a convenient procedure utilizing microwave heating. Their detailed characterization was accomplished by electrospray ionization high-resolution mass spectrometry (ESI-HRMS), 1H and 13C NMR spectroscopy, elemental analysis, and X-ray crystallography. Further experiments to evaluate the utility of the complexes as radiocontrast media were precluded by their poor aqueous solubility. [ABSTRACT FROM AUTHOR]

Two differently substituted pyrazole ligands have been investigated with regard to the topology of their Pt complexes: upon deprotonation, two mononuclear 1:2 PtII-pyrazole complexes—one of the sterically unhindered 4-Me-pzH and one of the bulky 3,5-tBu-pzH (pzH = pyrazole)—yield the corresponding 1:2 PtII-pyrazolato species; the former a triangular, trinuclear metallacycle (1), and the latter a dinuclear, half-lantern species (2) formed via the unprecedented cyclometallation of a butyl group. Stoichiometric oxidation of the colorless PtII2 complex produces the deep-blue, metal–metal bonded PtIII2 analog (3) with a rarely encountered unsymmetrical coordination across the Pt-Pt bond. All three complexes have been characterized by single crystal X-ray structure determination, 1H-NMR, IR, and UV-vis-NIR spectroscopic methods. The XPS spectra of the PtII2 and PtIII2 species are also reported. Density functional theory calculations were carried out to investigate the electronic structure, spectroscopic properties, and chemical bonding of the new complexes. The calculated natural population analysis charges and Wiberg bonding indices indicate a weak σ-interaction in the case of 2 and a formal Pt-Pt single bond in 3. [ABSTRACT FROM AUTHOR]

Conjugated polymers are widely used in energy conversion and sensor applications, but their synthesis relies on imprecise step‐growth or narrow‐scope chain‐growth methods, typically based on transition metal (TM)‐catalyzed cross‐coupling. Here we report that a dinickel complex with a redox‐active naphthyridine diimine ligand accesses new chain‐growth mechanistic manifolds for both donor and acceptor conjugated polymers, represented by poly(3‐hexylthiophene), poly(2,3‐bis(2‐ethylhexyl)thienopyrazine), and poly(2‐(2‐octyldodecyl)benzotriazole). For the latter, our method is particularly effective: we achieve high degrees of polymerization (DP) (>100) with moderate dispersities (Đ) of ≈1.4. Mechanistic analysis supports a radical/radical anion chain‐growth mechanism with organometallic intermediates instead of TM‐catalyzed cross‐couplings. Hence, our work develops new mechanisms for conjugated polymer synthesis and furnishes insights about the elementary reactivity of dinuclear complexes. [ABSTRACT FROM AUTHOR]

Low‐nuclearity copper hydrides are rare and few well‐defined dicopper hydrides have been reported. Herein, we describe the first example of a structurally characterized anionic dicopper hydride complex. This complex does not display typical reactivity associated with low‐nuclearity copper hydrides, such as alcoholysis or insertion reactions. Instead, its stoichiometric and catalytic reactivity is akin to that of copper hydride clusters. The distinct reactivity is ascribed to the robust dinuclear core that is bound tightly within the dinucleating ligand scaffold. [ABSTRACT FROM AUTHOR]

Two heteroleptic homo-dinuclear complexes of Dy(III) and Sm(III) with pyrazine (pyz) as spacer ligand [Ln(TFPB) 3 (μ-pyz)Ln(TFPB) 3 ], along with their mononuclear analogue [Ln(TFPB) 3 (pyz) 2 ] were synthesized and characterized. Diketone TFPB (4,4,4-trifluoro-1-phenyl-1,3-butanedione) was incorporated as main ligand. NMR analysis depicted single peak for pyz protons for dinuclear complexes and two for mononuclear ones, which confirmed the bridging nature of pyz in former complexes. UV spectra revealed two absorption bands despite of the different metal ion and nuclearity of complex, suggesting the absorption of UV-radiation by coordinated moieties inspite of the metal ion involved. The emission spectra exhibited significant intensity of yellow and orange-red peaks for Dy(III) and Sm(III) complexes, respectively, indicating effective sensitization of metal center. The enhanced emission intensity observed in dinuclear Sm-complexes, compared to their mononuclear counterparts, indicates a synergistic effect of the two metal ions on the overall emission properties, rather than a mere additive effect that would be expected from two independent mononuclear units. The photoluminescent properties of synthesized complexes were examined and discussed, suggesting potential applications in display devices. The Correlated Color Temperature (CCT) of these complexes falls within a range suitable for warm light sources and the highest branching ratio observed for 4G 5/2 → 6H 9/2 (for Sm3+ ion) and 4F 9/2 → 6H 13/2 (for Dy3+ ion) transitions suggests potential application in laser amplification. The alignment between band gap measurements obtained from UV and CV analyses highlight the possibility of employing these complexes in semiconductor technologies. • Analyzed solid state luminescence in Sm(III) and Dy(III)-complexes with pyrazine and TFPB ligands. • Explored dual role of pyrazine: Bridging and monodentate behaviours. • Enhanced luminescence intensity in dinuclear Sm-complexes: Evidence for participation of both metal ions in radiative relaxation. • Single 1H NMR signal: Validating bridging role of pyrazine in SmD and DyD. [ABSTRACT FROM AUTHOR]

The trivalent rare‐earth metal hydrido and imido complexes are of versatile reactivity, and many such complexes have been synthesized. However, no example of a rare‐earth metal complex bearing both hydrido‐ and imido‐ligands has been reported. Herein, we report the first rare‐earth metal complex bearing both hydrido‐ and imido‐ligands, namely a hydrido‐ and imido‐bridged dinuclear ytterbium(III) complex. The complex was synthesized via an unprecedented redox reaction of divalent rare‐earth metal hydrido complex with azido compound. DFT calculation indicated that the N2 release from azido compound in the presence of ytterbium(II) is a kinetically facile process because of the cooperative effects of the two metal centers. The reactivity of the hydrido‐ and imido‐bridged dinuclear ytterbium(III) complex was also explored, which showed the redox, addition and σ‐bond metathesis reactivities. [ABSTRACT FROM AUTHOR]

The high natural abundance of aluminium makes the respective fluorophores attractive for various optical applications, but photoluminescence quantum yields above 0.7 have yet not been reported for solutions of aluminium complexes. In this contribution, a dinuclear aluminium(III) complex featuring enhanced photoluminescence properties is described. Its facile one‐pot synthesis originates from a readily available precursor and trimethyl aluminium. In solution, the complex exhibits an unprecedented photoluminescence quantum yield near unity (Φabsolute 1.0±0.1) and an excited‐state lifetime of 2.3 ns. In the solid state, J‐aggregation and aggregation‐caused quenching are noted, but still quantum yields of 0.6 are observed. Embedding the complex in electrospun non‐woven fabrics yields a highly fluorescent fleece possessing a quantum yield of 0.9±0.04. [ABSTRACT FROM AUTHOR]

The title compound was made by the reaction of the CpCo-complex of 2,3,7,8-tetrakis(trimethylsilyl) linear [3]phenylene, in which the metal coordinates one of the cyclobutadiene rings, with CpCo(C2 H4)2. Because of its relative stability, a syn -dicobalt-bound configuration is indicated rather than its anti alternative. [ABSTRACT FROM AUTHOR]

Multinuclear complexes of heavy metals, such as tungsten, have demonstrated considerable potential as candidates for advanced radiocontrast agents. Of particular interest is the development of stable non-ionic compounds with high metal content and reasonably low osmolality in solution. Accordingly, we have synthesized a series of neutral W(V) complexes that contain the W2O2(µ-O)2 core and amino acids or disubstituted EDTA derivatives as ligands. The compounds were prepared from the oxalatotungstate(V) complex via a convenient procedure utilizing microwave heating. Their detailed characterization was accomplished by electrospray ionization high-resolution mass spectrometry (ESI-HRMS), 1H and 13C NMR spectroscopy, elemental analysis, and X-ray crystallography. Further experiments to evaluate the utility of the complexes as radiocontrast media were precluded by their poor aqueous solubility.

The ring‐opening polymerization (ROP) of lactones is mainly catalyzed by tin(II) octanoate Sn(Oct)2, due to its efficiency and easy handling despite the toxic issues of tin. Herein, two novel dinuclear bis(β‐diketiminate) complexes with flexible alkylene bridging groups (1,2‐ethylene and 1,3‐propylene) and biocompatible zinc centers are introduced. The complexes are obtained by deprotonation of the protio‐ligands with Zn(HMDS)2 and fully characterized. Afterwards the complexes are studied regarding their catalytic activity towards the ROP of caprolactones. Briefly, ε‐caprolactone (CL), ε‐phenyl‐ε‐caprolactone (phCL) and ε‐methyl‐ε‐caprolactone (meCL) with and without benzyl alcohol (BnOH) as initiator in toluene are homopolymerized and compared to the known dinuclear 1,4‐phenylene bridged bis(β‐diketiminate) zinc catalyst and the mononuclear counterpart. Thereby, the catalysts are classified upon their efficiency by in situ IR measurements, selectivity, and polymerization control by size exclusion chromatography (SEC) of samples, which are terminated at 60% conversion. The novel zinc catalysts prevent Sn(Oct)2 typical molar mass broadening, show slower reaction rates than 1,4‐phenylene bridged bis(β‐diketiminate) and improve control compared to the mononuclear relative. However, a drastic loss of polymerization control resulting in high molar masses and polydispersities occurrs in the absence of BnOH. Furthermore, these complexes allow the ROP of phCL but are inactive for meCL. [ABSTRACT FROM AUTHOR]

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

Using a pyrazolate‐bridged dinucleating ligand that provides two proximate pincer‐type PNN binding sites ("two‐in‐one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end‐on μ1,2‐bridging N2; in THF 4 is labile and undergoes temperature‐dependent N2/triflate ligand exchange. These pyrazolate‐based systems combine the potential of exhibiting both metal–metal and metal–ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3)3 (using KC8 and Me3SiCl), yielding up to 240 equiv N(SiMe3)3 per catalyst. [ABSTRACT FROM AUTHOR]

Three new BPTA‐bridged binuclear copper(I) complexes bearing three different diphosphine ligands, namely, [(CuI)2(Xantphos)2(BPTA)](BF4)2 (Cu1), [(CuI)2(Dppp)2(BPTA)](BF4)2 (Cu2), and [(CuI)2(Binap)2(BPTA)](BF4)2 (Cu3), have been synthesized and characterized. The X‐ray structure analyses of complex Cu3 show that the central copper(I) ion adopts a distorted tetrahedral geometry. Complexes Cu1 and Cu2 exhibit greenish‐yellow emission with excited‐state lifetime (13μs and 27μs) and photoluminescence quantum yields (6.86 % and 0.62 %) at room temperature in the solid state. Emission decay measurement and theoretical calculation suggest that the transition nature of their emission could be assigned to 3MLCT/3LC excited states. More interesting, complexes Cu1‐Cu3 are weakly emissive in solution but become strongly luminescent in solid state, so it has the aggregation induced emission (AIE) behavior. [ABSTRACT FROM AUTHOR]

A new crystal structure for complex [Cu2Cl2(bipy)2(μ-Cl)(μ-CH3O)] was obtained. X-ray diffraction data showed dinuclear complexes with metal-ions seated on two symmetrically related pentacoordinated environment, in which, a trigonal bipyramidal (TBPY-5) coordination polyhedra was observed. While chloride was detected as monodentate and as a bridging-ligand, the diimine unit and a bridging oxygen from methoxide occupied the remaining positions. The crystal structure accounted for dinuclear complexes interacting to each other via H-bonds involving C–H groups of bipy and monodentate chloride anions of an adjacent molecule. Theoretical studies were conducted by DFT methods employing B3LYP in combination with 6-31G(d). Larger basis sets (6-311G(d) and cc-pVDZ) were taken into account to assess the performance of B3LYP/6-31G(d) in dealing with equilibrium geometry and population analysis. This standard methodology showed to be a reasonable performer to reproduce geometric parameters keeping the computational cost very low. A new crystal structure for complex [Cu2Cl2(bipy)2(μ-Cl)(μ-CH3O)] was obtained, for which, DFT calculations were conducted for the further understanding of geometric and electronic properties. [ABSTRACT FROM AUTHOR]

The dinickel(II) dihydride complex (1K) of a pyrazolate‐based compartmental ligand with β‐diketiminato (nacnac) chelate arms (L−), providing two pincer‐type {N3} binding pockets, has been reported to readily eliminate H2 and to serve as a masked dinickel(I) species. Discrete dinickel(I) complexes (2Na, 2K) of L− are now synthesized via a direct reduction route. They feature two adjacent T‐shaped metalloradicals that are antiferromagnetically coupled, giving an S=0 ground state. The two singly occupied local dx2-y2 type magnetic orbitals are oriented into the bimetallic cleft, enabling metal–metal cooperative 2 e− substrate reductions as shown by the rapid reaction with H2 or O2. X‐ray crystallography reveals distinctly different positions of the K+ in 1K and 2K, suggesting a stabilizing interaction of K+ with the dihydride unit in 1K. H2 release from 1K is triggered by peripheral γ‐C protonation at the nacnac subunits, which DFT calculations show lowers the barrier for reductive H2 elimination from the bimetallic cleft. [ABSTRACT FROM AUTHOR]

Using a new bis(tridentate) compartmental pyrazolate‐centered ligand HL, the bis(pyrazolato)‐bridged diiron complex [L2FeII2][OTf]2 (1) and its singly oxidized mixed‐valent congener [L2FeIIFeIII][OTf]3 (2) have been synthesized and structurally characterized. While 1 features two HS‐FeII ions coordinated to two cis‐axial pyridine moieties in a highly distorted octahedral environment, the metal ions in 2 are coordinated by the ligand strand in a trans‐axial configuration. Very different Fe–N bond lengths and distinctly different coordination polyhedra are associated with pronounced valence localization in the case of 2. The electronic structures and magnetic properties of 1 and 2 have been further investigated by Mössbauer spectroscopy and variable temperature magnetic susceptibility measurements. In the case of 1, weak antiferromagnetic coupling is observed between the two HS‐FeII ions (J = –0.6 cm–1), while the HS‐FeII and LS‐FeIII ions in 2 are ferromagnetically coupled (J = +5.2 cm–1) to give an ST = 5/2 ground state with significant zero‐field splitting (DFe(II) = 2.3 cm–1). The findings are rationalized with the help of DFT computations. [ABSTRACT FROM AUTHOR]

The development of efficient water oxidation catalysts (WOCs) is of key importance in order to drive sustainable reductive processes aimed at producing renewable fuels. Herein, two novel dinuclear complexes, [(Cp*Ir) 2 (μ- κ 3-O,N,O-H 4 -EDTMP)] (Ir-H 4 -EDTMP , H 4 -EDTMP4− = ethylenediamine tetra(methylene phosphonate)) and [(Cp*Ir) 2 (μ- κ 3-O,N,O-EDTA)] (Ir-EDTA , EDTA4− = ethylenediaminetetraacetate), were synthesized and completely characterized in solution, by multinuclear and multidimensional NMR spectroscopy, and in the solid state, by single crystal X-Ray diffraction. They were supported onto rutile TiO 2 nanocrystals obtaining Ir-H 4 -EDTMP@TiO 2 and Ir-EDTA@TiO 2 hybrid materials. Both molecular complexes and hybrid materials were found to be efficient catalysts for WO driven by NaIO 4 , providing almost quantitative yields, and TON values only limited by the amount of NaIO 4 used. As for the molecular catalysts, Ir-H 4 -EDTMP (TOF up to 184 min−1) exhibited much higher activity than Ir-EDTA (TOF up to 19 min−1), likely owing to the higher propensity of the former to generate a coordination vacancy through the dissociation of a Ir–OP bond (2.123 Å, significantly longer than Ir–OC, 2.0913 Å), which is a necessary step to activate these saturated complexes. Ir-H 4 -EDTMP@TiO 2 (up to 33 min−1) and Ir-EDTA@TiO 2 (up to 41 min−1) hybrid materials showed similar activity that was only marginally reduced in the second and third catalytic runs carried out after having separated the supernatant, which did not show any sign of activity, instead. The observed TOF values for hybrid materials are higher than those reported for analogous systems deriving from heterogenized mononuclear complexes. This suggests that supporting dinuclear molecular precursors could be a successful strategy to obtain efficient heterogenized water oxidation catalysts. [ABSTRACT FROM AUTHOR]

Dinuclear metallodrugs offer much potential in the development of novel anticancer chemotherapeutics as a result of the distinct interactions possible with bio‐macromolecular targets and the unique biological activity that can result. Herein, we describe the development of isostructural homo‐dinuclear OsII–OsII and hetero‐dinuclear OsII–RuII organometallic complexes formed from linking the arene ligands of [M(η6‐arene)(C2O4)(PTA)] units (M=Os/Ru; PTA=1,3,5‐triaza‐7‐phosphaadamantane). Using these complexes together with the known RuII–RuII analogue, a chromatin‐modifying agent, we probed the impact of varying the metal ions on the structure, reactivity and biological activity of these complexes. The complexes were structurally characterised by X‐ray diffraction experiments, their stability and reactivity were examined by using 1H and 31P NMR spectroscopy, and their biological activity was assessed, alongside that of mononuclear analogues, through MTT assays and cell‐cycle analysis (HT‐29 cell line). The results revealed high antiproliferative activity in each case, with cell‐cycle profiles of the dinuclear complexes found to be similar to that for untreated cells, and similar but distinct profiles for the mononuclear complexes. These results indicate these complexes impact on cell viability predominantly through a non‐DNA‐damaging mechanism of action. The new OsII–OsII and OsII–RuII complexes reported here are further examples of a family of compounds operating via mechanisms of action atypical of the majority of metallodrugs, and which have potential as tools in chromatin research. [ABSTRACT FROM AUTHOR]

We have investigated the reactivities of a series of dinuclear iridium(II,II) and rhodium(II,II) 1,3‐butadiene‐1,4‐diyl complexes derived from two types of alkyne‐containing ligands. Newly developed ligand 2 afforded 2nd generation diiridium complexes that have higher reactivity toward halide substitution and acetylide formation. The significant differences in reactivity, influenced by the 1,3‐butadiene‐1,4‐diyl ligand backbone of these complexes, have been systematically investigated by synthetic studies as well as X‐ray crystallographic and spectroscopic analyses. [ABSTRACT FROM AUTHOR]

We recently reported the syntheses, crystal structures, and protonation reactions of dinitrogen divanadium complexes bearing triamidoamine ligands, ([{V(LR)}2(µ‐N2)] (R = iBu (1), EtBu (2), and iPr2Bn (3)). In this study, we have additionally synthesized two novel dinitrogen‐divanadium complexes with similar derivatives (R = Bn (4) and MeBn (5)), which are characterized spectroscopically and structurally. The X‐ray structures have both revealed a divanadium complex with a bridging N2 ligand. The protonation reactions of the µ‐N2 ligands for 4 and 5 in the presence of M+[C10H8]– (M+ = Na+, K+) and proton source (HOTf or [LutH](OTf)) have given ammonia. Particularly, the NH3 yield from the reaction of 5 with K+[C10H8]– and [LutH](OTf) has been 341 %. Furthermore, mixed valence Na+ adduct of 1, [Na{V(LiBu)}2(µ‐N2)] (6), which is prepared by the reaction of 1 with sodium metal, has been prepared and its crystal structure has also been determined. Compound 6 is electrochemically and spectroscopically characterized, which is also evaluated by DFT calculation method. [ABSTRACT FROM AUTHOR]

Polytopic ligands have become ubiquitous in coordination chemistry because they grant access to a variety of mono‐ and polynuclear complexes of transition metals as well as rare‐earth and main‐group elements. Nitrogen‐based ditopic ligands, in which two monoanionic N,N‐binding sites are framed within one molecule, are of particular importance and are therefore the primary focus of this review. In detail, bis(amidine)s, bis(guanidine)s, bis(β‐diimine)s, bis(aminotroponimine)s, bis(pyrrolimine)s, and miscellaneous bis(N,N‐chelating) ligands are reviewed. In addition to the general synthetic protocols, the application of these ligands is discussed along with their coordination chemistry, the multifarious binding modes, and the ability of these ligands to bridge two (or more) metal(loids). [ABSTRACT FROM AUTHOR]

A bis(chalcone) molecule (H 2 L) was synthesized via Aldol's condensation from terephthalaldehyde and 2′-hydroxyacetophenone and it was used as bridging ligand for the preparation of five dinuclear copper(II) complexes of the composition [Cu(N N)(μ–L)Cu(N N)](NO 3) 2 ⋅ n H 2 O (n = 0–2) (1 – 5), where N N stands for a bidentate N-donor ligand such as phen (1,10-phenanthroline, 1), bpy (2,2′-bipyridine, 2), mebpy (5,5′-dimethyl-2,2′-dipyridine, 3), bphen (bathophenanthroline, 4) and nphen (5-nitro-1,10-phenanthroline, 5). The compounds were characterized by different suitable techniques to confirm their purity, composition, and structure. Moreover, the products were evaluated for their in vitro cytotoxicity on a panel of human cancer cell lines: ovarian (A2780), ovarian resistant to cisplatin (A2780R), prostate (PC3), osteosarcoma (HOS), breast (MCF7) and lung (A549), and normal fibroblasts (MRC-5), showing significant cytotoxicity in most cases, with IC 50 ≈ 0.35–7.8 μM. Additionally, the time-dependent cytotoxicity and cellular uptake of copper, together with flow cytometric studies concerning cell-cycle arrest, induction of cell death and autophagy and induction of intracellular ROS/superoxide production in A2780 cells, were also performed. The results of biological testing on A2780 cells pointed out a possible mechanism of action characterized by the G2/M cell cycle arrest and induction of apoptosis by triggering the intrinsic signalling pathway associated with the damage of mitochondrial structure and depletion of mitochondrial membrane potential. Dinuclear Cu(II) complexes bearing a bridging bis(chalcone) ligand revealed high in vitro cytotoxicity, initiated A2780 cell arrest at G2/M phase and efficiently triggered intrinsic pathway of apoptosis. [Display omitted] • Dinuclear Cu(II) complexes with a bridging bis(chalcone) ligand were prepared. • In vitro cytotoxicity against six human cancer cell lines was evaluated. • The complexes revealed good selectivity of normal cells over the cancer ones. • Cellular effects were studied using flow-cytometry in ovarian A2780 cells. • Mechanism of apoptosis has been suggested to initiate A2780 cell arrest at G2/M phase. [ABSTRACT FROM AUTHOR]

A series of coordination compounds of redox‐active 1,10‐phenanthroline‐5,6‐diimine with CoII bis‐diketonates and FeII dihydrobis(pyrazolyl)borates has been computationally designed by means of density functional theory (DFT UB3LYP*/6‐311++G(d,p)) calculations of their electronic structure, energy characteristics, and magnetic properties. Four types of complexes differing by the nature and position of the terminal metal‐centered fragments have been considered. The performed systematic calculations have revealed the systems capable of undergoing thermally initiated spin‐state switching rearrangements, including those governed by the synchronized mechanisms of spin crossover and valence tautomerism. The predicted magnetic characteristics allow one to consider the dinuclear cobalt complexes and heterometallic Co/Fe compounds with 1,10‐phenanthroline‐5,6‐diimine as building blocks for molecular and quantum electronics devices. © 2019 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A sound synthetic procedure for the preparation of trans‐[PtBr(µ‐Br)(PPh3)]2 is described. The species was fully characterized and used to obtain [PtBr2(PPh3)(L)] complexes (L = DMSO, p‐toluidine, pyridine) by a bridge‐splitting reaction. All products were fully characterized by NMR spectroscopy, together with cis‐[PtBr2(PPh3)(NCCH3)], obtained as an intermediate in the synthesis of the dinuclear precursor. Cis‐[PtBr2(PPh3)(NCCH3)] was also studied by X‐ray diffraction. [ABSTRACT FROM AUTHOR]