Search Results (12)

The reaction of bis(pentafluorophenyl)mercury with the ligands bis(diphenylphosphano) methane P,P’-dioxide ({Ph₂P(O)}₂CH₂) (1), bis{2-(N,N,N’N’-tetraethyldiaminophosphano) imidazol-1-yl} methane P,P’-dioxide ({2-PO(NEt₂)₂C₃N₂H₂}₂CH₂) (2) and bis (2-diphenylphosphanophenyl) ether P,P’-dioxide ({2-PPh₂(O)C₆H₄}₂O) (3) afforded crystalline σ-donor complexes [{Hg(C₆F₅)₂}₂{Ph₂P(O)}₂CH₂] (1Hg), [Hg(C₆F₅)₂{2-PO(NEt₂)₂C₃N₂H₂}₂CH₂]_n (2Hg) and [Hg(C₆F₅)₂{2-PPh₂(O)C₆H₄}₂O] (3Hg), respectively. The molecular structures of 1Hg, 2Hg and 3Hg show considerable differences. In complex 1Hg, a single bridging bidentate ligand connects two three-coordinate T-shape mercury atoms with a near linear C-Hg-C atom array. Complex 2Hg is a one-dimensional coordination polymer in which adjacent four-coordinate mercury atoms with a linear C-Hg-C atom array are linked by bridging bidentate O,O’- ligands, whilst in complex 3Hg a T-shape three-coordinate mercury atom is ligated by (3) in a monodentate fashion. The Hg-O bond lengths of complexes 1Hg, 2Hg and 3Hg differ substantially (range 2.5373(14)-2.966(3) Å) owing to structural and bonding differences. Full article

Bis(pyrazol-1-yl)acetic acid (HC(pz)₂COOH) and bis(3,5-dimethyl-pyrazol-1-yl)acetic acid (HC(pz^Me2)₂COOH) were converted into the methyl ester derivatives 1 (L^OMe) and 2 (L^2OMe), respectively, and were used for the preparation of silver(I) complexes 3–5. The Ag(I) complexes were prepared by the reaction of AgNO₃ and 1,3,5-triaza-7-phosphaadamantane (PTA) or triphenylphosphine (PPh₃) with L^OMe and L^2OMe in methanol solution. All Ag(I) complexes showed a significant in vitro antitumor activity, proving to be more effective than the reference drug cisplatin in the in-house human cancer cell line panel containing examples of different solid tumors. Compounds were particularly effective against the highly aggressive and intrinsically resistant human small-cell lung carcinoma (SCLC) cells, either in 2D and 3D cancer cell models. Mechanistic studies revealed their ability to accumulate into cancer cells and to selectively target Thioredoxin (TrxR), thus leading to redox homeostasis unbalance and ultimately inducing cancer cell death through apoptosis. Full article

Deprotonation of a bis(amino)phosphane H₂L = PhP(HNBtd)₂ bearing a heterocyclic Btd = 2,1,3-benzothiadiazol-4-yl substituents at nitrogen atoms by silylamides LiNTms₂ and Y(NTms₂)₃ (Tms = trimethylsilylamide) results in lithium and yttrium complexes with the deprotonated HL^– and L^2– forms as κ²-N and κ⁴-N chelating ligands. A binuclear complex [LiHL]₂ was crystallized from Et₂O, and was shown to reversibly dissociate in thf (tetrahydrofuran) with the NH_(soln)–PH_(crystal) tautomeric shift; the compound [Li₂L] was spectroscopically characterized. Yttrium readily forms stable bis-ligand complexes [YL₂]^– and [YL(HL)]. In the latter, the H atom in HL resides on phosphorus; the coordination sphere remains accessible to another ligands, and it was crystallized as [{YL(HL)}₂(µ-dioxane)] species (YN₈O coordination). In the former complex, the coordination sphere was saturated (YN₈) by closer bound ligands; it was crystallized as a salt with [Li(thf)₄]⁺. The monoligand complex could not be cleanly obtained in a 1:1 reaction of H₂L and Y(NTms₂)₃, and was only crystallographically characterized as a dimer [YL(NTms)₂]₂. Partial oxidation of the central P atom with the formation of phosphine-oxide ligands PhP(O)(NBtd)^2– was observed. They co-crystallize in the same position as non-oxidized ligands in [YL₂]^– and [YL(NTms₂)]₂ species and participate in bonding between two units in the latter. TD-DFT calculations reveal that main transitions in the visible region of electronic spectra correspond to the charge transfer bands mostly associated with the orbitals located on Btd fragments. Full article

Treatment of bis(iminophosphorane)phosphane ligands 2a–2e with Li₂PdCl₄ gave a set of novel diphosphane-derived complexes bearing two metallacycle rings, each one enclosing a P=N double bond: the unprecedented bis(iminophosphorane)phosphane-[C,N,S] palladacycles. In the case of the ligand derived from bis(diphenylphosphino)methane, 2a, both the single and the double palladacycle complexes were obtained. Reaction of 3a with bis(diphenylphosphino)ethane did not yield the expected product with the diphosphane bonded to both palladium atoms, but rather the novel coordination compound 5. The crystal structures of 3c and 5 are described. Full article

In the present article, copper(I) complexes of bis(pyrazol-1-yl) carboxylic acid (LH), bis(3,5-dimethylpyrazol-1-yl) carboxylic acid (L²H), and bis(pyrazol-1-yl) acetates conjugated with an N-methyl-d-aspartate (NMDA) receptor antagonist (L^NMDA or L^2NMDA) and phosphane ligands (triphenylphosphine or 1,3,5-triaza-7-phosphaadamantane) were synthesized. The selection of an NMDA antagonist for the coupling with LH and L²H was suggested by the observation that NMDA receptors are expressed and play a role in different types of cancer models. All the new complexes showed a significant antitumor activity on a panel of human tumor cell lines of different histology, with cisplatin-sensitive, cisplatin-resistant, or multi-drug-resistant phenotype. Their half maximal inhibitory concentration (IC₅₀) values were in the low- and sub-micromolar range and, in general, significantly lower than that of cisplatin. Interestingly, the fact that all the complexes proved to be significantly more active than cisplatin even in three-dimensional (3D) spheroids of H157 and BxPC3 cancer cells increased the relevance of the in vitro results. Finally, morphological analysis revealed that the most representative complex 8 induced a massive swelling of the endoplasmic reticulum (ER) membrane, which is a clear sign of ER stress. Full article

We describe the synthesis and characterization of [Cu(POP)(1)][PF₆], [Cu(POP)(2)][PF₆], [Cu(xantphos)(1)][PF₆], and [Cu(xantphos)(2)][PF₆] in which ligands 1 and 2 are 2-(pyridin-2-yl)quinoline and 2-(6-methylpyridin-2-yl)quinoline, respectively. With 2,2'-bipyridine (bpy) as a benchmark, we assess the impact of the extended π-system on structural and solid-state photophysical properties. The single crystal structures of [Cu(POP)(2)][PF₆], [Cu(xantphos)(1)][PF₆], and [Cu(xantphos)(2)][PF₆] were determined and confirmed a distorted tetrahedral copper(I) coordination environment in each [Cu(P^P)(N^N)]⁺ cation. The xanthene unit in [Cu(xantphos)(1)][PF₆] and [Cu(xantphos)(2)][PF₆] hosts the quinoline unit of 1, and the 6-methylpyridine group of 2. ¹H NMR spectroscopic data indicate that these different ligand orientations are also observed in acetone solution. In their crystal structures, the [Cu(POP)(2)]⁺, [Cu(xantphos)(1)]⁺, and [Cu(xantphos)(2)]⁺ cations exhibit different edge-to-face and face-to-face π-interactions, but in all cases, the copper(I) centre is effectively protected by a ligand sheath. In [Cu(POP)(2)][PF₆], pairs of cations engage in an efficient face-to-face π-stacking embrace, and we suggest that this may contribute to this compound having the highest photoluminescence quantum yield (PLQY = 21%) of the series. With reference to data from the Cambridge Structural Database, we compare packing effects and PLQY data for the complexes incorporating 2-(pyridin-2-yl)quinoline and 2-(6-methylpyridin-2-yl)quinoline, with those of the benchmark bpy-containing compounds. We also assess the effect that Cu⋯O distances in the {Cu(POP)} and {Cu(xantphos)} domains of [Cu(P^P)(N^N)][X] compounds have on solid-state PLQY values. Full article

A series of [Cu(POP)(N^N][PF₆] and [Cu(xantphos)(N^N][PF₆] compounds has been prepared and characterized in which POP = bis[2-(diphenylphosphanyl)phenyl]ether (IUPAC PIN oxydi(2,1-phenylene)bis(diphenylphosphane), xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene (IUPAC PIN (9,9-dimethyl-9H-xanthene- 4,5-diyl)bis(diphenylphosphane)) and the N^N ligands are 4-(4-bromophenyl)-6,6′-dimethyl-2,2′- bipyridine (1), 5,5′-bis(3-methoxyphenyl)-6-methyl-2,2′-bipyridine (2), and 6-benzyl-2,2′-bipyridine (3). The single crystal structures of [Cu(xantphos)(1)][PF₆]·CH₂Cl₂, [Cu(xantphos)(2)][PF₆]·CH₂Cl₂ and [Cu(POP)(3)][PF₆]·0.5H₂O were determined by X-ray diffraction. Each complex contains a copper(I) ion in a distorted tetrahedral environment with chelating N^N and P^P ligands. In the [Cu(xantphos)(1)]⁺ and [Cu(xantphos)(2)]⁺ cations, there are face-to-face π-stackings of bpy and PPh₂ phenyl rings (i.e., between the ligands); in addition in [Cu(xantphos)(2)][PF₆]·CH₂Cl₂, inter-cation π-embraces lead to the formation of infinite chains as a primary packing motif. In [Cu(POP)(3)][PF₆]·0.5H₂O, centrosymmetric pairs of [Cu(POP)(3)]⁺ cations engage in C–H…π (phenyl to bpy) and offset face-to-face (bpy…bpy) contacts. The electrochemical and photophysical properties of the compounds containing ligands 1 and 2 are reported. They are green or yellow emitters in the solid-state (λ_em in the range 535–577 nm) with values for the photoluminescence quantum yield (PLQY) in the range 19%–41%. Full article

Heteroleptic [Cu(BIPHEP)(N^N)][PF₆] complexes (BIPHEP = 1,1′-biphenyl-2,2′-diylbis(diphenylphosphane)), in which N^N is 2,2′-bipyridine (bpy), 6-methyl-2,2′-bipyridine (6-Mebpy), 6-ethyl-2,2′-bipyridine (6-Etbpy), or 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me₂bpy), have been synthesized and characterized using multinuclear NMR spectroscopies and electrospray ionization mass spectrometry. The single crystal structures of [Cu(BIPHEP)(bpy)][PF₆]∙CH₂Cl₂, [Cu(BIPHEP)(5,5′-Me₂bpy)][PF₆]∙CH₂Cl₂, [Cu(BIPHEP)(6-Mebpy)][PF₆]∙Et₂O∙0.5H₂O and [Cu(BIPHEP)(6-Etbpy)][PF₆] confirm distorted tetrahedral {Cu(P^P)(N^N)} coordination environments. Each compound shows a quasi-reversible Cu⁺/Cu²⁺ process. In deaerated solution, the compounds are weak emitters. Powdered samples are yellow emitters (λ_em^max in the range 558–583 nm) and [Cu(BIPHEP)(5,5′-Me₂bpy)][PF₆] exhibits the highest photoluminescence quantum yield (PLQY = 14%). On cooling to 77 K (frozen 2-methyloxolane), the emission maxima are red-shifted and the excited state lifetimes increase from τ_1/2 < 8 μs, to τ_1/2 values of up to 53 μs, consistent with the compounds with N^N = 6-Mebpy, 6-Etbpy and 5,5′-Me₂bpy exhibiting thermally activated delayed fluorescence (TADF). Full article

Blue light-initiated alcoholic reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) using bis (acyl) phosphane oxide (BAPO) as the photo-initiator is developed to prepare diblock copolymer nano-objects. High monomer conversion (95%) was achieved within 2 h of blue light irradiation in an isopropanol/water mixture. Effects of solvent, light intensity, and reaction temperature on the polymerization kinetics were evaluated. Finally, the effect of reaction temperature on the morphologies of diblock copolymer nano-objects was investigated and two morphological phase diagrams were constructed at 25 and 70 °C. Transmission electron microscopy (TEM) measurement confirmed that increasing the reaction temperature promoted the evolution of higher order morphology. We believe this study will provide more mechanistic insights into alcoholic RAFT dispersion polymerization for the creation of diblock copolymer nano-objects with well-defined structures. Full article

A class of gold(I) phosphane complexes have been identified as inhibitors of dihydrofolate reductase (DHFR) from E. coli, an enzyme that catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF), using NADPH as a coenzyme. In this work, to comprehend the nature of the interaction at the basis of these inhibitory effects, the binding properties of bis- and tris-phosphane gold(I) chloride compounds in regards to DHFR have been studied by emission spectroscopy and spectrophotometric assays. The lack of cysteine and seleno-cysteine residues in the enzyme active site, the most favorable sites of attack of Au(I) moieties, makes this work noteworthy. The interaction with the gold compounds results into the quenching of the DHFR tryptophan’s emissions and in an enhancement of their intrinsic emission intensities. Moreover, a modulating action of NADPH is highlighted by means of an increase of the gold compound affinity toward the enzyme; in fact, the dissociation constants calculated for the interactions between DHFR and each gold compound in the presence of saturating NADPH were lower than the ones observed for the apo-enzyme. The fluorimetric data afforded to K_d values ranged from 2.22 ± 0.25 µM for (PPh₃)₂AuCl in the presence of NADPH to 21.4 ± 3.85 µM for ⁴L₃AuTf in the absence of NADPH. By elucidating the energetic aspects of the binding events, we have attempted to dissect the role played by the gold phosphane/protein interactions in the inhibitory activity, resulting in an exothermic enthalpy change and a positive entropic contribution (ΔH° = −5.04 ± 0.08 kcal/mol and ΔS° = 7.34 ± 0.005 cal/mol·K). Full article

A simple, highly efficient synthesis of a series of novel chiral non-racemic rigid tetracyclic phosphorus ligands, applicable in important chemical asymmetric transformations, was performed. In a tandem cross-coupling/C-H bond activation reaction, a well-recognised and readily available ligand (R,R)-NORPHOS was used as the starting material. The palladium complexes of new ligands were obtained and characterised on the example of a crystalline dichloropalladium complex of [(1R,2R,9S,10S,11R,12R)-4-phenyltetracyclo[8.2.1.0^2,9.0^3,8]trideca-3,5,7-triene-11,12-diyl]bis(diphenylphosphane). A notably high activity and stereoselectivity of the palladium catalysts based on the new ligands were confirmed in a model asymmetric allylic substitution reaction. Herein, we discuss the geometry of the palladium complexes formed and its impact on the efficiency of the catalysts. A comparison of their geometric features with other bis(phosphane) ligand complexes found in the Cambridge Structural Database and built density functional theory (DFT) commutated models is also presented and rationalised. Full article

We report the synthesis and characterization of [Cu(P^P)(N^S)][PF₆] complexes with P^P = bis(2-(diphenylphosphino)phenyl) ether (POP) or 4,5-bis(diphenylphosphino)-9,9- dimethylxanthene (xantphos) and N^S = 2-(iso-propylthio)pyridine (iPrSpy) or 2-(tert-butylthio)pyridine (tBuSpy). The single crystal structures of [Cu(POP)(iPrSPy)][PF₆] and [Cu(POP)(tBuSPy)][PF₆] have been determined and confirm a distorted tetrahedral copper(I) centre and chelating P^P and N^S ligands in each complex. Variable temperature (VT) ¹H and ³¹P{¹H} NMR spectroscopy reveals dynamic behavior with motion of the POP backbone in [Cu(POP)(iPrSPy)][PF₆] and [Cu(POP)(tBuSPy)][PF₆] frozen out at 238 K. VT NMR spectroscopic data including EXSY peaks in the ROESY spectrum of [Cu(xantphos)(tBuSPy)][PF₆] at 198 K reveal that two conformers exist in an approximate ratio of 5:1. Replacing bpy by the N^S ligands shifts the Cu⁺/Cu²⁺ oxidation to a higher potential. The copper(I) compounds are weak emitters in the solid state with PLQY values of <2%. These values are similar to those for [Cu(POP)(bpy)][PF₆] and [Cu(xantphos)(bpy)][PF₆] in the solid state. Full article