Cationic Transition Metal Complexes Research Articles

1D Lead Bromide Hybrids Directed by Complex Cations: Syntheses, Structures, Optical and Photocatalytic Properties.

This study presents the synthesis, structural characterization, and evaluation of the photocatalytic performance of two novel one-dimensional (1D) lead(II) bromide hybrids, [Co(2,2'-bpy)3][Pb2Br6CH3OH] (1) and [Fe(2,2'-bpy)3][Pb2Br6] (2), synthesized via solvothermal reactions. These compounds incorporate transition metal complex cations as structural directors, contributing to the unique photophysical and photocatalytic properties of the resulting materials. Single-crystal X-ray diffraction analysis reveals that both compounds crystallize in monoclinic space groups with distinct 1D lead bromide chain configurations influenced by the nature of the complex cations. Optical property assessments show band gaps of 3.04 eV and 2.02 eV for compounds 1 and 2, respectively, indicating their potential for visible light absorption. Photocurrent measurements indicate a significantly higher electron-hole separation efficiency in compound 2, correlated with its narrower band gap. Additionally, photocatalytic evaluations demonstrate that while both compounds degrade organic dyes effectively, compound 2 also exhibits notable hydrogen evolution activity under visible light, a property not observed in 1. These findings highlight the role of metal complex cations in tuning the electronic and structural properties of lead(II) bromide hybrids, enhancing their applicability in photocatalytic and optoelectronic devices.

Fluoride Abstraction Induced by Tris(pentafluoroethyl)difluorophosphorane: A Convenient Way to Synthesize Cationic N-Heterocyclic Carbene- and Cyclic (Alkyl)(amino)carbene-Ligated Copper Alkyne and Arene Complexes.

We herein report the convenient synthesis of different N-heterocyclic carbene (NHC)- and cyclic (alkyl)(amino)carbene (cAAC)-ligated copper cations using the weakly coordinating tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C2F5)3PF3]-). The reaction of the fluorido complexes [(carbene)CuF] (carbene = NHC, cAACMe) 2a-2f and the tris(pentafluoroethyl)difluorophosphorane (C2F5)3PF2 in the presence of alkynes or arenes led to fluoride transfer from Cu to the phosphorane with formation of the cationic transition metal complexes [(carbene)Cu(L)]+ and the weakly coordinating counteranion [(C2F5)3PF3]- (FAP). Using this method, the complexes [(IDipp)Cu(L)]+FAP- (IDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolin-2-ylidene; L = PhC≡CPh, 4d; PhC≡CMe, 5d), [(cAACMe)Cu(L)]+FAP- (cAACMe = 1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene; L = PhC≡CPh, 4f; PhC≡CMe, 5f), [(SIDipp)Cu(C6Me6)]+FAP- (6e), (SIDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolidine-2-ylidene), and [(cAACMe)Cu(C6Me6)]+FAP- (6f) have been synthesized and characterized. The complexes [(IDipp)Cu(C6Me6)]+FAP- (6d) and [(cAACMe)Cu(C6Me6)]+FAP- (6f) have been used as catalysts for the copper(I)-catalyzed cycloaddition of benzyl azide to terminal alkynes.

Binding Properties of Small Electrophilic Anions [B6 X5 ]- and [B10 X9 ]- (X=Cl, Br, I): Activation of Small Molecules Based on π-Backbonding.

Superelectrophilic anions constitute a special class of molecular anions that show strong binding of weak nucleophiles despite their negative charge. In this study, the binding characteristics of smaller gaseous electrophilic anions of the types [B6 X5 ]- and [B10 X9 ]- (with X=Cl, Br, I) were computationally and experimentally investigated and compared to those of the larger analogues [B12 X11 ]- . The positive charge of vacant boron increases from [B6 X5 ]- via [B10 X9 ]- to [B12 X11 ]- , as evidenced by increasing attachment enthalpies towards typical σ-donor molecules (noble gases, H2 O). However, this behavior is reversed for σ-donor-π-acceptor molecules. [B6 Cl5 ]- binds most strongly to N2 and CO, even more strongly than to H2 O. Energy decomposition analysis confirms that the orbital interaction is responsible for this opposite trend. The extended transition state natural orbitals for chemical valence method shows that the π-backdonation order is [B6 X5 ]- >[B10 X9 ]- >[B12 X11 ]- . This predicted order explains the experimentally observed red shifts of the CO and N2 stretching fundamentals compared to those of the unbound molecules, as measured by infrared photodissociation spectroscopy. The strongest red shift is observed for [B6 Cl5 N2 ]- : 222 cm-1 . Therefore, strong activation of unreactive σ-donor-π-acceptor molecules (commonly observed for cationic transition metal complexes) is achieved with metal-free molecular anions.

Syntheses, crystal structure and properties of two chalcogenidoantimonates Mn(en)3Sb2S4 and Co(en)3Sb2Se4

Two chalcogenidoantimonates Mn(en)3Sb2S4 (1) and Co(en)3Sb2Se4 (2) have been synthesized in solvothermal conditions. 1 and 2 are consist of transition metal complex cations and [Sb2Q4]2- (Q = S, Se) anions. They have band gaps of 2.20 eV and 2.25 eV, respectively, indicating that they can be used as semiconductor materials. The photocurrent responses of 1 and 2 were also investigated. Photocatalytic experiments showed that both 1 and 2 could degrade methylene blue (MB) upon visible light irradiation, reaching 47 % for 1 and 30 % for 2, indicating that both compounds are good photocatalytic materials. Therefore, they present a promising potential for the photoelectric research chalcogenides.

Enantioselective transition-metal catalysis via an anion-binding approach.

Asymmetric transition-metal catalysis represents a powerful strategy for accessing enantiomerically enriched molecules1-3. The classical strategy for inducing enantioselectivity with transition-metal catalysts relies on direct complexation of chiral ligands to produce a sterically constrained reactive metal site that allows formation of the major product enantiomer while effectively inhibiting the pathway to the minor enantiomer through steric repulsion4. The chiral-ligand strategy has proven applicable to a wide variety of highly enantioselective transition-metal-catalysed reactions, but important scenarios exist that impose limits to its successful adaptation. Here, we report a new approach for inducing enantioselectivity in transition-metal-catalysed reactions that relies on neutral hydrogen-bond donors (HBDs)5,6 that bind anions of cationic transition-metal complexes to achieve enantiocontrol and rate enhancement through ion pairing together with other non-covalent interactions7-9. A cooperative anion-binding effect of a chiral bis-thiourea HBD is demonstrated to lead to high enantioselectivity (up to 99% enantiomeric excess) in intramolecular ruthenium-catalysed propargylic substitution reactions10. Experimental and computational mechanistic studies show the attractive interactions between electron-deficient arene components of the HBD and the metal complex that underlie enantioinduction and the acceleration effect.

Syntheses, crystal structure, and photoelectric properties of two Zn-based chalcogenidoantimonates Zn-Sb-Q (Q = S, Se).

Metal chalcogenides are a special class of semiconducting materials characterized by their rich structures and compositions, making them a promising option for a broad range of applications in the field of inorganic chemistry. However, the path forward is not without its challenges, notably in the realms of interface management and enhancing carrier concentration. To address these issues, we solvothermally synthesized two novel chalcogenidoantimonates [Zn(tren)]2Sb2Se5 (1) [tren = tris (2-aminoethyl) amine] and [Zn(tepa)H]2Sb2S6 (2) (tepa = tetraethylenepentamine) utilizing transition metal Zn by band gap optimization strategy in the visible region. Both compounds exhibited distinct zero-dimensional cluster structures, with transition metal complex cations acting as structure-directing agents. A comprehensive analysis of the electronic structure, band gap, and photocurrent response of these crystals was undertaken, revealing significantly enhanced photocatalytic properties compared to preceding studies. This research underscores the potential of antimony chalcogenides in the realm of photoelectric properties and promotes the applications of chalcogenides.

Orthogonal Arylation of a Diene‐Sulfonamide Using Cationic Transition Metal Catalysts

AbstractThe regioselectivity of two mechanistically distinct alkenylation reactions catalyzed by in situ‐formed cationic transition metal complexes was studied using N‐allyl‐N‐phenylethenesulfonamide as a model compound. Orthogonal selectivity was observed for the Ru‐catalyzed C−H‐activating alkenylation with acetanilides, which occurs preferentially at the electron deficient double bond, and for a Pd‐catalyzed Heck‐type coupling with arene diazonium salts, which occurs preferentially at the more electron rich double bond of the N‐allyl substituent.

Heterometallic Pb–Ag Iodides from 1‐D Chains to 2‐D Layers Induced by Transition Metal Complex Cations: Syntheses, Crystal Structures, and Photocatalytic Properties

Novel heterometallic Pb‐Ag iodides [TM(en)3]PbAgI5 [TM = Mn (1), Fe (2), Zn (3)], [Ni(en)2]PbAg2I6 (4) (en = ethylenediamine), and [Ni(dien)(MeCN)3]Pb3Ag2I10·MeCN (5) (dien = diethylenetriamine) were prepared using TM(II) (TM = Mn, Fe, Zn, Ni) complex cations as structure directing agents under different conditions. In compounds 1–3, one AgI4 tetrahedron and one PbI6 octahedron are connected via edge‐sharing into the ternary heterometallic 1‐D polymeric anion [PbAgI5]n2n–. In 4, two AgI4 tetrahedra share a common edge to form the bimeric Ag2I6 unit. The Ag2I6 unit connected one PbI6 octahedron via iodine atoms to form a 2‐D [PbAg2I6]n2n– layer. In 5, two AgI4 tetrahedra and three PbI6 octahedra are interlinked by sharing common edges to generate a 2‐D [Pb3Ag2I10]n2n– waved layer. Compounds 1–5 exhibit band gaps at 2.67, 2.61, 2.79, 2.76 and 2.42 eV, respectively. Photocatalytic experiments show that compounds 1, 3 and 5 perform catalytic activities in photodegradation of MB in water at room temperature. Compound 5 displays higher catalytic activity than 1 and 3 in the photodegradation of MB. The ·O2– radical is the main reactive species in the photodegradation of MB over compound 3, while all ·O2–, ·OH and h+ reactive species play an important role in the photocatalytic reaction using compound 5 as the catalyst.

Anticancer and Antibacterial Activity of Transition Metal Complexes

AbstractDeaths caused by cancer and bacterial infection necessitate the development of new and potential compounds with desired properties that could circumvent the problem of chemo resistant cancer and bacteria. The present review focuses on potent transition metal complexes with tunable activity against cancer cells and multidrug‐resistant bacteria. Mechanistically, transition metal complexes induce cell accumulation in the G2 phase, as well as DNA breakage and endoplasmic reticulum stress that inhibit the growth of cancerous cells. Parallelly, redox‐active, cationic transition metal complexes induce oxidative stress on bacteria and disrupt the microbial cell membrane. The MIC of some transition metal complexes were in the low micromolar range while some of the transition metal complexes show higher antibacterial activity compared to those of clinically used antibiotics. Here the potential and future of this class of metallodrugs, either as anticancer or antimicrobial agents, is discussed.

Construction of π-Surface-Metalated Pillar[5]arenes which Bind Anions via Anion-π Interactions.

By simple ligand exchange of the cationic transition-metal complexes [(Cp*)M(acetone)3 ](OTf)2 (Cp*=pentamethylcyclopentadienyl and M=Ir or Rh) with pillar[5]arene, mono- and polynuclear pillar[5]arenes, a new class of metalated host molecules, is prepared. Single-crystal X-ray analysis shows that the charged transition-metal cations are directly bound to the outer π-surface of aromatic rings of pillar[5]arene. One of the triflate anions is deeply embedded within the cavity of the trinuclear pillar[5]arenes, which is different to the host-guest behavior of most pillar[5]arenes. DFT calculation of the electrostatic potential revealed that the metalated pillar[5]arenes featured an electron-deficient cavity due to the presence of the electron-withdrawing transition metals, thus allowing encapsulation of electron-rich guests mainly driven by anion-π interactions.

ChemInform Abstract: Recent Advances in Crystalline Hydrated Borates with Non‐metal or Transition‐metal Complex Cations

AbstractReview: 116 refs.

Mn(dien)2]2[SbSe4Cu(μ2-Se4)]: A heterometallic polyselenide containing a chelating μ2-Se4

Presented here are the synthesis and crystal structure of a heterometallic copper-antimony polyselenide, namely, [Mn(dien)2]2[SbSe4Cu(μ2-Se4)] (1) (dien=diethylenetriamine). Single-crystal X-ray diffraction analysis revealed that compound 1 belongs to the noncentrosymmetric space group P212121 and its structure features a discrete anionic [SbSe4Cu(μ2-Se4)]4− cluster with two transition metal complex cations of [Mn(dien)2]2+. The unusual [SbSe4Cu(μ2-Se4)]4− cluster is constructed by a {SbSe4} tetrahedron corner-sharing a Se atom with a planar trigonal {CuSe3} in which the other two Se atoms are from a chelating (Se4) ligand forming a five-membered {Cu(Se4)} ring. The optical absorption edge of 1 was estimated to be 1.39eV, and its thermal stability was investigated via thermogravimetric analysis.

Asymmetric Hydrogenation of Quinoline Derivatives Catalyzed by Cationic Transition Metal Complexes of Chiral Diamine Ligands: Scope, Mechanism and Catalyst Recycling.

This personal account is focused on the asymmetric hydrogenation of quinolines and their analogues recently developed by using phosphorus-free chiral cationic ruthenium(II)/η6 -arene-N-monosulfonylated diamine complexes. In our initial study, the chiral Ru-diamine complexes were found to be highly effective catalysts for the asymmetric hydrogenation of difficult quinoline substrates in room temperature ionic liquids (RTILs) with unprecedentedly excellent enantioselectivity. Our further systematic study revealed that a wide range of quinoline derivatives could be efficiently hydrogenated in alcoholic solvents, or under solvent-free and concentrated conditions with good to excellent stereoselectivity. Complexes of iridium analogues could also efficiently catalyze the asymmetric hydrogenation of quinolines in undegassed solvent. Asymmetric tandem reduction of various 2-(aroylmethyl)quinolines was achieved in high yield with excellent enantioselectivity and good diastereoselectivity. More challenging substrates, alkyl- and aryl-substituted 1,5- and 1,8-naphthyridine derivatives were successfully hydrogenated with these chiral ruthenium catalysts to give 1,2,3,4-tetrahydronaphthyridines with good to excellent enantioselectivity. Unlike the asymmetric hydrogenation of ketones, quinoline is reduced via a stepwise H+ /H- transfer process outside the coordination sphere rather than a concerted mechanism. The enantioselectivity originates from the CH/π attraction between the η6 -arene ligand in the Ru-complex and the fused phenyl ring of dihydroquinoline via a 10-membered ring transition state with the participation of TfO- anion. In addition, the Ru-catalyzed asymmetric hydrogenation of quinolines could be carried out in some environmentally benign reaction media, such as undegassed water, RTILs and oligo(ethylene glycol)s (OEGs). In the latter two cases, unique chemoselectivity and/or reactivity were observed. Catalyst recycling could also be realized by using [BMIM]PF6 and OEGs as solvents, as well as via magnetic nanoparticles. Applications of this catalytic protocol were also exemplified by the employments of the reduced products for the syntheses of some important natural alkaloids, pharmaceutical intermediates, as well as chiral diamine ligands.

Polyborate anions templated by cationic transition-metal complexes: [Co(diNOsar)]2[B3O3(OH)4]Cl5.4.75 H2O

GRAPHICAL ABSTRACT

Syntheses, Crystal Structures, and Photocatalytic Properties of Polymeric Iodoargentates [TM(2,2‐bipy)3]Ag3I5 (TM = Mn, Fe, Co, Ni, Zn)

AbstractFive isostructural polymeric iodoargentates incorporating similar transition metal complex cations as structure‐directing agents, – namely, [TM(2,2‐bipy)3]Ag3I5 [TM = Mn (1), Fe (2), Co (3), Ni (4), Zn (5)] – have been solvothermally synthesized and structurally characterized. The title compounds contain saturated [TM(2,2‐bipy)3]2+ cations and one‐dimensional (1D) [Ag3I5]2– anionic chains formed by trans‐interconnection of [Ag3I5] semicubes through Ag–I bonds. The optical absorption spectra indicate that compounds 1–5 are semiconductors with estimated band gaps of 2.28, 1.87, 1.95, 2.01, and 2.61 eV, respectively, which are mainly ascribed, on the basis of density functional theory (DFT) calculations, to charge transitions between the [Ag3I5]2– anionic chains and organic cationic units. We evaluated the photocatalytic efficiencies of compounds 1, 2, 4, and 5 with regard to the decomposition of crystal violet (CV) under visible irradiation, and the four compounds showed excellent photodegradation abilities in comparison with N‐doped P25, with an order of 1 > 2 > 4 > 5 > P25. The luminescent properties and thermal stabilities of the title compounds were also studied.

ChemInform Abstract: Recent Advances in Solid‐State White Light‐Emitting Electrochemical Cells

AbstractReview: 73 refs.

Comparing Effects of Different Transition Metal Complexes under Osmotic Stress in the B-To-Z DNA Transition

The equilibrium transition from B-DNA to Z-DNA is driven by salt cations and by neutral osmolytes. Transition metal complex cations, such as cobalthexammine and cobalttrisethylenediamine, stabilize the Z-DNA form of poly[d(G-C)] through electrostatic interactions with the DNA backbone and site-specific hydrogen bonds. These complexes can be used to measure the position of the B-Z equilibrium in the presence of osmolytes. Previous studies in our lab and Donald Rau's lab (1) have shown that applying an osmotic stress in osmolyte solutions decreases the concentrations of complex required to form the more sparsely hydrated Z-DNA. We have found that the cobalttrisethylenediamine complex is less effective than the cobalthexammine complex in driving the transition, possibly because the three bidentate ligands in the former result in a lower conformational entropy than the six monodentate ligands in the latter. On the other hand, the binding of cobalttrisethylenediamine to Z-DNA appears to be more strongly subject to competition by hydrating water molecules, as indicated by greater sensitivity to osmotic stress (2). For example, a sucrose concentration of 4.07 osmolal decreased the transition midpoint concentration of the trisethylenediamine complex by 2.5-fold, while the midpoint concentration of the hexammine complex was decreased by only about one-third. Similar trends were also observed with monohydroxylic osmolytes such as methanol and dihydroxylic compounds such as propylene glycol. Future studies will compare the (+) and (-) enantiomers of cobalttrisethylenediamine, in an attempt to explore stereospecific aspects of their binding to DNA. Supported by Towson University Undergraduate Research Grants (to M. Cisse, A. Diedrich and D. Rey-Ardila) and by the Towson University Department of Chemistry.1. Preisler et al (1995) Biochemistry 34, 14400-144072. Ashman et al (2011) Biophysical Society meeting poster presentation

New Benchmark Set of Transition-Metal Coordination Reactions for the Assessment of Density Functionals.

We present the WCCR10 data set of 10 ligand dissociation energies of large cationic transition metal complexes for the assessment of approximate exchange-correlation functionals. We analyze nine popular functionals, namely BP86, BP86-D3, B3LYP, B3LYP-D3, B97-D-D2, PBE, TPSS, PBE0, and TPSSh by mutual comparison and by comparison to experimental gas-phase data measured with well-known precision. The comparison of all calculated data reveals a large, system-dependent scattering of results with nonnegligible consequences for computational chemistry studies on transition metal compounds. Considering further the comparison with experimental results, the nonempirical functionals PBE and TPSS turn out to be among the best functionals for our reference data set. The deviation can be lowered further by including Hartree-Fock exchange. Accordingly, PBE0 and TPSSh are the two most accurate functionals for our test set, but also these functionals exhibit deviations from experimental results by up to 50 kJ mol(-1) for individual reactions. As an important result, we found no functional to be reliable for all reactions. Furthermore, for some of the ligand dissociation energies studied in this work, invoking semiempirical dispersion corrections yields results which increase the deviation from experimental results. This deviation increases further if structure optimization including such dispersion corrections is performed, although the contrary should be the case, pointing to the need to develop the currently available dispersion corrections further. Finally, we compare our results to other benchmark studies and highlight that the performance assessed for different density functionals depends significantly on the reference molecule set chosen.

Recent Advances in Solid‐State White Light‐Emitting Electrochemical Cells

AbstractCompared to organic light‐emitting diodes, solid‐state light‐emitting electrochemical cells (LECs) exhibit advantages of simple device structures, low operation voltages, and compatibility with air‐stable metal electrodes. Since the first demonstration of white LECs in 1997, the cells have been studied extensively, due to their potential applications in solid‐state lighting. This article reviews the development of white LECs based on conjugated polymers and cationic transition metal complexes. Important achievements of each work on white LECs are highlighted. Finally, the outlook for future development of white LECs is discussed.

Novel thioarsenates {[Mn(2,2′-bipy)2(SCN)][Mn(2,2′-bipy)](AsVS4)}2and {[Mn(2,2′-bipy)2(SCN)]2[AsIII2(S2)2S2]}: introducing an anionic second ligand to modify MnIIcomplex cations of 2,2′-bipyridine

Two novel manganese thioarsenates, {[Mn(2,2'-bipy)2(SCN)][Mn(2,2'-bipy)](As(V)S4)}2 (1, 2,2'-bipy = 2,2'-bipyridine) and {[Mn(2,2'-bipy)2(SCN)]2[As(III)2(S2)2S2]} (2), containing thiocyanate-modified Mn-2,2'-bipy complex cations were synthesized. They feature two terminal [Mn(2,2'-bipy)2(SCN)](+) complex cations bridged by a polyanion {[Mn(2,2'-bipy)]2(As(V)S4)2}(2-) for 1 and a cyclic thioarsenate anion (As(III)2S6)(2-) for 2. In 2, the [As(III)2(S2)2S2](2-) anion can be described as two (As(III)S3)(3-) trigonal-pyramids interlinked through S-S bonds. The method to obtain new metal complex cations shown here, introducing an anionic second ligand to modify the number of coordination sites and the charges of the metal complex cations simultaneously, is different from the traditional methods, varying either the TM center or the organic ligand or employing mixed neutral organic ligands, and may open up a new route for preparing novel chalcogenidometalates. Compounds 1 and 2 exhibit wide optical gaps of 2.20 and 2.67 eV, respectively, and photoluminescence with the emission maxima occurring around 440 nm. Magnetic measurements show the presence of antiferromagnetic interactions between Mn(II) centers in the two compounds.