Triphenylphosphine Ligands Research Articles

Synthesis and characterisation of group 11 metal complexes with a guanidine-tagged triphenylphosphine and evaluation of the isolated Au(i) complexes in gold-mediated organic reactions

Reactivity of a guanidine-tagged triphenylphosphine ligand towards group 11 metal ions differs for Cu(i)/Ag(i) and Au(i). A stable digold complex, stabilised by aurophilic interactions, converts into an active Au(i) catalyst upon protonation.

Nonlinear Optical Studies of [Pt17(CO)12(PPh3)8]n+ Metal Nanoclusters and Their Enhancement via All-Plastic Photonic Crystal Cavity

Metal nanoclusters of atomic precision have recently emerged as potential candidates for nonlinear optical applications owing to their strong quantum confinement effects. Herein, we report the nonlinear absorptive and refractive properties of platinum-17 (Pt17) metal nanoclusters stabilized by carbon monoxide and triphenyl phosphine ligands. The open aperture z-scan studies in the nanosecond regime reveal a transmittance dip at the focus characteristic of molecule-like behavior and discrete energy levels. The clusters also exhibited a significantly lower optical limiting threshold value and self-defocusing behavior which can be deployed to resist intense optical radiation. We also demonstrate a photonic crystal cavity-assisted enhancement in the absorptive nonlinearity of the synthesized clusters as a result of intense field localization in the defect layer. Our study throws light on the application of these ultrasmall structures in nanophotonic devices.

How mono- and diphosphine ligands alter regioselectivity of the Rh-catalyzed annulative cleavage of bicyclo[1.1.0]butanes

Rh(I)-catalyzed cycloisomerizations of bicyclo[1.1.0]butanes provide a fruitful approach to cyclopropane-fused heterocycles. Products and stereochemical outcome are highly dependent on catalyst. The triphenylphosphine (PPh3) ligand provides pyrrolidines, placing substituents anti to the cyclopropyl group. The 1,2-bis(diphenylphosphino)ethane (dppe) ligand yields azepanes with substituents syn to the cyclopropyl group. In this work, quantum mechanical DFT calculations pinpoint a reversal of regio- and diastereoselectivity, suggesting a concerted (double) C−C bond cleavage and rhodium carbenoid formation, driven by strain-release. The ligand-influenced cleavage step determines the regioselectivity of carbometalation and product formation, and suggests new applications of bicyclobutanes.

Efficient Ullmann and Suzuki-Miyaura cross-coupling reactions catalyzed by heterogeneous Pd-porous carbon beads catalysts in aqueous media

Carbon-carbon coupling reactions are of great interest for a wide range of applications including pharmaceutical compounds and biologically active molecules. Usually, coupling reactions were performed using a homogeneous catalyst and organic solvent. Thus, the use of greener solvents as well as the heterogenization of the classical metal-based catalyst are desirable and still under development. This contribution describes the synthesis of biaryl compounds in water by Ullmann and Suzuki reactions with carbon-supported Pd nanoparticles. As expected, the microwave activation method drastically decrease the reaction time. The utilization of trioctylphosphine (TOP) or triphenylphosphine (TPP) ligands slow down the Pd leaching without cancelling it compared to the unliganded Pd catalyst. Moreover, a treatment with H2O2 appears beneficial with respect to a thermal-oxidative treatment at 1500 °C due to higher hydrophilicity of the resultant carbon support. These results and methodology contribute to a greener future for C–C coupling reactions.

Effect of TiO2 Film Thickness on the Stability of Au9 Clusters with a CrOx Layer.

Radio frequency (RF) magnetron sputtering allows the fabrication of TiO2 films with high purity, reliable control of film thickness, and uniform morphology. In the present study, the change in surface roughness upon heating two different thicknesses of RF sputter-deposited TiO2 films was investigated. As a measure of the process of the change in surface morphology, chemically -synthesised phosphine-protected Au9 clusters covered by a photodeposited CrOx layer were used as a probe. Subsequent to the deposition of the Au9 clusters and the CrOx layer, samples were heated to 200 ℃ to remove the triphenylphosphine ligands from the Au9 cluster. After heating, the thick TiO2 film was found to be mobile, in contrast to the thin TiO2 film. The influence of the mobility of the TiO2 films on the Au9 clusters was investigated with X-ray photoelectron spectroscopy. It was found that the high mobility of the thick TiO2 film after heating leads to a significant agglomeration of the Au9 clusters, even when protected by the CrOx layer. The thin TiO2 film has a much lower mobility when being heated, resulting in only minor agglomeration of the Au9 clusters covered with the CrOx layer.

The palladium-based complexes bearing 1,3-dibenzylbenzimidazolium with morpholine, triphenylphosphine, and pyridine derivate ligands: synthesis, characterization, structure and enzyme inhibitions

The palladium-based complexes bearing N-heterocyclic carbene (NHC) ligand have long attracted attention as active catalysts for many catalytic reactions. Recently, the biological activities of these complexes, which are stable to air and moisture, have also been wondered. With the aim, we report the synthesis of a series of (NHC)Pd(Br2)(L) complexes (NHC: 1,3-dibenzylbenzimidazolium, L: morpholine, triphenylphosphine, pyridine, 3-chloropyridine, and 2-aminopyridine). All complexes were characterized by NMR (1H and 13C), FTIR spectroscopic and elemental analysis techniques. In addition, the single crystal structures of the complex 3, 4, and 6 were determined through single crystal x-ray crystallographic method. Furthermore, the carbonic anhydrase I and II isoenzymes (hCAs) and acetylcholinesterase (AChE) inhibition effects of these palladium-based complexes bearing NHC ligand were investigated. They showed highly potent inhibition effect with Ki values are between 10.06 ± 1.49–68.56 ± 11.53 nM for hCA I isoenzyme, 7.74 ± 0.66 to 49.39 ± 6.50 nM for hCA II isoenzyme and 22.83 ± 3.21 to 64.09 ± 9.05 nM for AChE enzyme.

Methoxyl-substituted phosphine ligand properties and a case study of formation adducts to indium(III) bromide by DFT calculations

Six bulky triphenylphosphine ligands containing substituted methoxyl groups (tris(2,4,6-trimethoxyphenyl)phosphine (TMP), tris(2,6-dimethoxyphenyl)phosphine (TDP), tris(o-methoxyphenyl)phosphine (o-Anis3P), tris(p-methoxyphenyl)phosphine (p-Anis3P), tris(m-methoxyphenyl)phosphine (m-Anis3P) and triphenylphosphine (PPh3)) were studied by DFT (density functional theory) calculations and experimental solution/solid-state 31P NMR spectroscopy. The basicity and binding ability of these substituted ligands, proven by comparison of structural data with DFT-predicted data, are in the order TMP > TDP > o-Anis3P > p-Anis3P > m-Anis3P > PPh3. Molecular structures for InBr3 with bulky ligands (TMP, TDP, o-Anis3P, p-Anis3P, m-Anis3P and PPh3) were calculated using DFT. P-In bond distances generated from these six optimized molecular structures and the calculated intramolecular interaction energies are in agreement with the ligand properties, with strong donation ability for those with the short bond distance; the In-P bond distance from shortest to longest follows a similar trend as predicted by DFT calculations. DFT calculations for these adducts show that methoxyl substitution to triphenylphosphine (PPh3) ligands contributed to its electron donor ability resulting in lower P-In bond distances with relatively large bond interaction energies.

Excited‐State Dynamics of Phosphorescent Trinuclear Re(I) Complexes

AbstractThe excited‐state dynamics of cyanide‐bridged trinuclear carbonyl rhenium(I) complexes with general formula of [Re]p[Re]c[Re]p {[Re]c=[(−NC)ReI(CO)2(phen)(CN−)]; [Re]p=[−ReI(CO)2(L L)(La)], L L= diimine or diphosphine, La=triphenylphosphine or carbonyl ligand} and the monomeric peripheral control complexes have been elucidated through a study with ultrafast transient absorption spectroscopy. The time constants for the energy transfer between the MLCT excited states of the peripheral and central Re(I) chromophores (ca. 0.56–0.78 ps) are typical for other cyanide‐bridged polynuclear transition metal complexes. The emissive excited states and the absorption transient have been characterized by nanosecond transient Raman spectroscopy.

Biotin-Targeted Au(I) Radiosensitizer for Cancer Synergistic Therapy by Intervening with Redox Homeostasis and Inducing Ferroptosis.

The search for highly selective sensitizers with a novel mechanism for tumor targeting therapy is of considerable interest. In this work, we have developed a series of new biotin-targeted Au(I) complexes. Through systematic biological evaluation and comparison, biotinylated Au(I) complex 3a containing a triphenylphosphine ligand was screened, as it realized both prominent efficient inhibition and selective cytotoxicity to cancer cells, and the effect was better than that of popularly used auranofin. Meanwhile, complex 3a, as a potent radiosensitizer, enhances anticancer effects in vitro and in vivo and has sensitization selectivity. From the action mechanism study, we provide evidence that complex 3a could intervene in redox homeostasis through targeted binding and strong suppression of thioredoxin reductase (TrxR) and induce the ferroptosis death process, enabling it to sensitize tumor cells to radiotherapy. Thus, complex 3a has enormous potential as an efficient and specific radiosensitizing agent in cancer therapy.

Carboranethiol-Protected Propeller-Shaped Photoresponsive Silver Nanomolecule

We report the synthesis, structural characterization, and photophysical properties of a propeller-shaped Ag21 nanomolecule with six rotary arms, protected with m-carborane-9-thiol (MCT) and triphenylphosphine (TPP) ligands. Structural analysis reveals that the nanomolecule has an Ag13 central icosahedral core with six directly connected silver atoms and two more silver atoms connected through three Ag-S-Ag bridging motifs. While 12 MCT ligands protect the core through metal-thiolate bonds in a 3-6-3-layered fashion, two TPP ligands solely protect the two bridging silver atoms. Interestingly, the rotational orientation of a silver sulfide staple motif is opposite to the orientation of carborane ligands, resembling the existence of a bidirectional rotational orientation in the nanomolecule. Careful analysis reveals that the orientation of carborane ligands on the cluster's surface resembles an assembly of double rotors. The zero circular dichroism signal indicates its achiral nature in solution. There are multiple absorption peaks in its UV-vis absorption spectrum, characteristic of a quantized electronic structure. The spectrum appears as a fingerprint for the cluster. High-resolution electrospray ionization mass spectrometry proves the structure and composition of the nanocluster in solution, and systematic fragmentation of the molecular ion starts with the loss of surface-bound ligands with increasing collision energy. Its multiple optical absorption features are in good agreement with the theoretically calculated spectrum. The cluster shows a narrow near-IR emission at 814 nm. The Ag21 nanomolecule is thermally stable at ambient conditions up to 100 °C. However, white-light illumination (lamp power = 120-160 W) shows photosensitivity, and this induces structural distortion, as confirmed by changes in the Raman and electronic absorption spectra. Femtosecond and nanosecond transient absorption studies reveal an exceptionally stable excited state having a lifetime of 3.26 ± 0.02 μs for the carriers, spread over a broad wavelength region of 520-650 nm. The formation of core-centered long-lived carriers in the excited state is responsible for the observed light-activated structural distortion.

Highly regioselective tandem hydroformylation of substituted styrene using Iminophosphine rhodium complex immobilized on carbon

With an exponential increase in fossil fuel consumption and an increasing demand for carbon-based materials, it draws the attention of researchers to seek alternative carbon sources. Herein, we report the sustainable route for the synthesis of ionic carbon from bio-derived sugarcane-waste (Bagasse) and further anchoring with iminophosphine rhodium complex (Rh@BCNP) and utilized for tandem hydroformylation reaction. The SEM analysis confirms the formation of spherical shape morphology of carbon with sizes ranging from 30-150 nm. The successful functionalization of the iminophosphine rhodium complex on the carbon surface was determined by XPS, TEM, FE-SEM, 31P NMR, 13C CP-MAS-NMR, and FTIR analysis. Furthermore, ICP-OES analysis confirms the presence of 0.307 mmoles/g of Rh and 0.484 mmoles/g of P on the carbon surface. Rh@BCNP catalyst is the best combination of triphenylphosphine ligand, imine, and rhodium metal, resulting in hybrid material with some acidic properties of carbon that favour the selectivity towards linear products. Rh@BCNP showed remarkable catalytic performance under moderate reaction conditions (80 °C, 40 bar (CO + H2)) in 5 h. This sharp divergence from other methods leading to linear amines and acetals results in a novel atom economic approach to synthesize pharmaceuticals and industrial products. The Rh@BCNP catalyst gave recyclability up to five cycles.

A Highly Fluorescent σ‐Bonded Platinum(II) Diketopyrrolopyrrole Complex

AbstractA σ‐bonded platinum(II) diketopyrrolopyrrole (Pt‐DPP) complex was synthesized from a reaction of p‐pinacolatoborylphenyl‐substituted DPP with dichloro(1,5‐cyclooctadiene)platinum(II), followed by a ligand exchange reaction with triphenylphosphine. The Pt‐DPP complex is highly fluorescent not only in solution but also in the solid state. From the comparison of the emission properties with those of N‐benzyl‐DPPs bearing phenyl and p‐bromophenyl substituents, the intense emission of the Pt‐DPP complex is ascribed to the DPP‐centered fluorescence. In the solid state, aggregation‐caused quenching is mitigated by the well‐segregated molecular packing due to the bulky triphenylphosphine ligands. The facile synthesis and unique fluorescence properties of the Pt‐DPP complex are beneficial for creating DPP‐based functional chromophores.

Atomic-precision Pt6 nanoclusters for enhanced hydrogen electro-oxidation

The discord between the insufficient abundance and the excellent electrocatalytic activity of Pt urgently requires its atomic-level engineering for minimal Pt dosage yet maximized electrocatalytic performance. Here we report the design of ultrasmall triphenylphosphine-stabilized Pt6 nanoclusters for electrocatalytic hydrogen oxidation reaction in alkaline solution. Benefiting from the self-optimized ligand effect and atomic-precision structure, the nanocluster electrocatalyst demonstrates a high mass activity, a high stability, and outperforms both Pt single atoms and Pt nanoparticle analogues, uncovering an unexpected size optimization principle for designing Pt electrocatalysts. Moreover, the nanocluster electrocatalyst delivers a high CO-tolerant ability that conventional Pt/C catalyst lacks. Theoretical calculations confirm that the enhanced electrocatalytic performance is attributable to the bifold effects of the triphenylphosphine ligand, which can not only tune the formation of atomically precise platinum nanoclusters, but also shift the d-band center of Pt atoms for favorable adsorption kinetics of *H, *OH, and CO.

The Palladium-Based Complexes Bearing 1,3-Dibenzylbenzimidazolium with Morpholine, Triphenylphosphine, and Pyridine Derivate Ligands: Synthesis, Characterization, Structure and Biological Activity

The Palladium-Based Complexes Bearing 1,3-Dibenzylbenzimidazolium with Morpholine, Triphenylphosphine, and Pyridine Derivate Ligands: Synthesis, Characterization, Structure and Biological Activity

The Palladium-Based Complexes Bearing 1,3-Dibenzylbenzimidazolium with Morpholine, Triphenylphosphine, and Pyridine Derivate Ligands: Synthesis, Characterization, Structure Elucidation and Biological Activities

The Palladium-Based Complexes Bearing 1,3-Dibenzylbenzimidazolium with Morpholine, Triphenylphosphine, and Pyridine Derivate Ligands: Synthesis, Characterization, Structure Elucidation and Biological Activities

Synthesis and catalytic application of new [{IrCl(cod)}2(μ2-diNHC)] and [{Ir(cod)(sulfonated phosphine)}2(μ2-diNHC)] complexes

Four new dinuclear iridium(I) complexes were synthesized from the di(N-heterocyclic carbene) ligand precursors 1,1′-methylene-bis(3-benzyl-imidazolium)dichloride and 1,1′-methylene-bis(3-(2,4,6-trimethylbenzyl)imidazolium)dichloride. The complexes were fully characterized by spectroscopic methods, HR-MS (ESI) spectrometry, furthermore, the structure of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Complexes 3a and 3b which have sulfonated triphenylphosphine ligands, were successfully used under mild conditions as catalysts in reduction reaction of ketones via hydrogen transfer from aqueous 2-propanol, and for hydrogenation of alkynes in aqueous-organic biphasic systems.

Chiral amine ligands at rhenium(V) pentahydride complexes allow for characterization of an energetically accessible and reversible steric inversion of diastereotopic phosphorus atoms

Three new rhenium(V) pentahydride complexes stabilized by a pair of triphenylphosphine ligands and a chiral amine ligand were prepared. Dynamic 31P-{1H} NMR spectroscopy of the chiral complexes demonstrates an unusual steric inversion for the diastereotopic pair of phosphorus atoms in each chiral complex. One chiral ReH5(PPh3)2(amine) complex is supported by an aromatic amine ligand and demonstrates unambiguously that such ligands participate in a steric inversion dynamic process rather than a simple rotation about the Re-N bond. The activation parameters and rate constants for the steric inversion can be determined directly or indirectly for non-hydride atom dynamic processes in two of the three chiral complexes from simulations of dynamic NMR spectra. Characterization of the steric inversion step by atoms other than hydride ligands allows for a means to test whether any hydride ligand exchange processes are manifestations of the steric inversion process. Under the experimental conditions in this report, a pairwise exchange of hydride ligands that reside in pseudododecahedral A sites appears to be a separate manifestation of the steric inversion dynamic process. A change in the nominal coordination number seems likely to cause the steric inversion that is reported.

The Utilization of Para‐Substituted Triphenylphosphine Derivatives to Synthesize Highly Emissive Cyclometalated Platinum(II) Complexes

AbstractHerein, the synthesis and characterization of a series of heteroleptic cycloplatinated(II) complexes [Pt(p‐MeC6H4)(dfppy)(L)], dfppy=2‐(2,4‐difluorophenyl)pyridinate), with different para‐substituted triphenylphosphine ligands (L) are reported. The complexes exhibit greenish‐blue phosphorescence under UV light at room temperature in their solid states. Their emissions appear as structured bands which indicates that the emissions mainly originate from the electronic transitions in the dfppy ligand with small contribution of metal to ligand and/or ligand to ligand charge transfers. The phosphine ligands do not have a considerable impact on the shape and wavelength of the emissions. However, the electron density of the phosphine ligands affects the emission strengths significantly. To rationalize the experimental photophysical data, density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations were employed for all the complexes.

Structure, UV spectroscopic and electrochemical properties of 2-methyl-8-quinolinolato rhodium (I) complexes, containing carbonyl, triphenylphosphine or triphenylphosphite ligands

The known Rh(2-Me-8-Oxq)(CO)2 complex (1) was prepared through treatment of dicarbonyl(acetylacetonate)rhodium (I) with 2-methyl-8-hydroxyquinoline for the first time. The reactions of 1 with triphenylphosphine and triphenylphosphite result in complexes Rh(2-Me-8-Oxq)(PPh3)(CO) (2) and Rh(2-Me-8-Oxq)[P(OPh)3](CO) (3) that were characterized by IR and NMR spectroscopy. The structures of complexes 2 and 3 were determined by single-crystal X-ray diffraction analysis. The complexes show the 2-methyl-8-quinolinolato ligand in the expected coordination mode with a slightly disordered square planar geometry at the rhodium center. In the crystal, molecules of Rh(2-Ме-8-Oxq)(CO)(PPh3) (2) form centrosymmetric dimers due to π-stacking interactions. No intermolecular contacts are observed in the crystal of 3. The UV spectroscopic and electrochemical properties of complexes 1–3 were studied. Their electronic spectra in CH3CN show three quinoline-centered absorptions. The electrochemical study revealed that the oxidation of the complexes 1–3 is two-electron and leads to the formation of dication Rh (III) species while their reduction gives radical anions, which undergoes rapid decomposition.

Modulation of catalytic and biomolecular binding properties of ruthenium(II)-arene complexes with the variation of coligands for selective toxicity against cancerous cells

Four ruthenium(II)-arene complexes, viz. [Ru(p-cym)(2-ampy)Cl]PF61, [Ru(benzene)(2-ampy)Cl]SO3CF32, [Ru(p-cym)(2-ampy)PPh3](PF6)23 and [Ru(benzene)(2-ampy)PPh3](SO3CF3)24 [2-ampy = 2-aminomethyl pyridine] have been synthesized and characterized. Different analytical techniques have been utilized to characterize 1–4 and a DFT study was used to optimize the geometries and calculate the energies of the frontier molecular orbitals. An MTT assay revealed the potency of complexes 1–4 against MCF-7 (breast cancer) and Hela (cervical cancer) cell lines. The presence of the triphenyl phosphine ligand in complexes 3 and 4 makes the complexes more cytotoxic with respect to their chloro-analogues. The complexes are found to be specifically cytotoxic against cancerous cell lines only, as they were inactive against the normal HEK 293 cell line. An absorption and fluorescence titration study of complexes 1–4 showed significant interactions with DNA and proteins. Interestingly, all the complexes show potent catalytic activity for the hydrogen transfer of NADH and converted NADH to NAD+, which helps to induce the accumulation of intracellular reactive oxygen species (ROS) in MCF-7 cells. To analyze the morphological changes in the cells, the Hoechst staining method was applied to capture images of apoptotic cells through confocal microscopy.