Search Results (15)

Light-responsive liposomes have been developed for the on-demand release of drugs. However, efficient delivery of chemotherapeutic drugs to tumor for cancer theranostics remains a challenge. Herein, folic acid (FA), an established ligand for targeted drug delivery, was used to decorate light-sensitive porphyrin-phospholipid (PoP) liposomes, which were assessed for FA-targeted chemophototherapy (CPT). PoP liposomes and FA-conjugated PoP liposomes were loaded with Doxorubicin (Dox), and physical properties were characterized. In vitro, FA-PoP liposomes that were incubated with FA receptor-overexpressing human KB cancer cells showed increased uptake compared to non-targeted PoP liposomes. Dox and PoP contributed towards chemophototherapy (CPT) in vitro, and PoP and FA-PoP liposomes induced cell killing. In vivo, mice bearing subcutaneous KB tumors treated with PoP or FA-PoP liposomes loaded with Dox, followed by 665 nm laser treatment, had delayed tumor growth and improved survival. Dox delivery to tumors increased following laser irradiation for both PoP and FA-PoP liposomes. Thus, while Dox-FA-PoP liposomes were effective following systemic administration and local light irradiation in this tumor model, the FA targeting moiety did not appear essential for anti-tumor responses. Full article

Non-heme Fe monooxygenases activate C–H bonds using intermediates with high-spin Fe^IV–oxido centers. To mimic these sites, a new tripodal ligand [pop]³⁻ was prepared that contains three phosphoryl amido groups that are capable of stabilizing metal centers in high oxidation states. The ligand was used to generate [Fe^IVpop(O)]⁻, a new Fe^IV–oxido complex with an S = 2 spin ground state. Spectroscopic measurements, which included low-temperature absorption and electron paramagnetic resonance spectroscopy, supported the assignment of a high-spin Fe^IV center. The complex showed reactivity with benzyl alcohol as the external substrate but not with related compounds (e.g., ethyl benzene and benzyl methyl ether), suggesting the possibility that hydrogen bonding interaction(s) between the substrate and [Fe^IVpop(O)]⁻ was necessary for reactivity. These results exemplify the potential role of the secondary coordination sphere in metal-mediated processes. Full article

Reaction of [Au(tht)₂](ClO₄) (tht = tetrahydrothiophene), [Cu(CH₃CN)₄](ClO₄), 3,6-di-tert-butyl-1,8-diethynyl-9H-carbazole (H₃decz), and bis(2-diphenylphosphinophenyl)ether (POP) in the presence of triethylamine (NEt₃) gave the cluster complex Au₄Cu₂(decz)₂(POP)₂ as yellow crystals. As revealed by X-ray crystallography, the Au₄Cu₂ cluster exhibits scissor-like structure sustained by two decz and two POP ligands and stabilized by Au-Cu and Au-Au interactions. The Au₄Cu₂ cluster shows bright yellow to orange photoluminescence upon irradiation at >300 nm, arising from ³[π (decz)→5d (Au)] ³LMCT (ligand-to-metal charge transfer) and ³[π→π* (decz)] ³IL (intraligand) triplet states as revealed by theoretical and computational studies. When it is mechanically ground, reversible phosphorescence conversion from yellow to red is observed owing to more compact molecular packing and thus stronger intermetallic interaction. Variable-temperature luminescence studies reveal that it displays distinct red-shifts of the emission whether the temperature is elevated or lowered from ambient temperature, suggestive of exceptional thermochromic phosphorescence characteristics. Full article

A class of so-called POP ligands (Xanthos, NiXantphos, DPEphos) are of a great interest to the coordination chemistry due to their wide P-M-P bite angles and ability to show either κ²- or κ³-binding modes. Such κ²–κ³-rearrangement is valuable for catalytic application and internal stabilization of intermediates. To widen the scope of ruthenium-based catalysts for Atom Transfer Radical Polymerization (ATRP) two new approaches to the synthesis of closo-ruthenacarboranes with aforementioned POP ligands were developed and six new 17-e (3,3-(POP)-3-Cl-closo-3,1,2-RuC₂B₉H₁₁; 2, 4, 7) and 18-e (3,3-(POP)-3-NCCH₃-closo-3,1,2-RuC₂B₉H₁₁; 3, 5, 8) clusters were synthesized and characterized by means of NMR or ESR spectroscopy, MALDI mass-spectrometry and single crystal X-ray diffraction studies. The unique 18-e complex of Ru(II) with dioxygen ligand 3,3-(DPEphos)-3-(η²-O₂)-closo-3,1,2-RuC₂B₉H₁₁ (9) was isolated and characterized by X-ray diffraction. It was shown that aforementioned POP ligands coordinate to ruthenium by two phosphorus atoms in a κ²-fashion. The performed electrochemical studies have shown reversible Ru(II)-Ru(III) transition making the complexes suitable for application in catalysis of polymerization. The test experiments on methyl methacrylate (MMA) polymerization indicate the proceeding of the process in according with an ATRP mechanism. Full article

Solid supports functionalized with molecular metal catalysts combine many of the advantages of heterogeneous and homogeneous catalysis. A (NNN)Ru-incorporated porous organic polymer (POP-bp/bbpRuCl₃) exhibited high catalytic efficiency and broad functional group tolerance in the C–C cross-coupling of secondary and primary alcohols to give β-alkylated secondary alcohols. This catalyst demonstrated excellent durability during successive recycling without leaching of Ru which is ascribed to the strong binding of the pincer ligands to the metal ions. Full article

Oligopeptidase B (OpB) is a two-domain, trypsin-like serine peptidase belonging to the S9 prolyloligopeptidase (POP) family. Two domains are linked by a hinge region that participates in the transition of the enzyme between two major states—closed and open—in which domains and residues of the catalytic triad are located close to each other and separated, respectively. In this study, we described, for the first time, a structure of OpB from bacteria obtained for an enzyme from Serratia proteomaculans with a modified hinge region (PSPmod). PSPmod was crystallized in a conformation characterized by a disruption of the catalytic triad together with a domain arrangement intermediate between open and closed states found in crystals of ligand-free and inhibitor-bound POP, respectively. Two additional derivatives of PSPmod were crystallized in the same conformation. Neither wild-type PSP nor its corresponding mutated variants were susceptible to crystallization, indicating that the hinge region modification was key in the crystallization process. The second key factor was suggested to be polyamine spermine since all crystals were grown in its presence. The influences of the hinge region modification and spermine on the conformational state of PSP in solution were evaluated by small-angle X-ray scattering. SAXS showed that, in solution, wild-type PSP adopted the open state, spermine caused the conformational transition to the intermediate state, and spermine-free PSPmod contained molecules in the open and intermediate conformations in dynamic equilibrium. Full article

The preparation and characterization of [Cu(POP)(biq)][PF₆] and [Cu(xantphos)(biq)][PF₆] are reported (biq = 1,1′-biisoquinoline, POP = bis(2-(diphenylphosphanyl)phenyl)ether, and xantphos = (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane). The single crystal structure of [Cu(POP)(biq)][PF₆] 0.5Et₂O was determined and compared to that in three salts of [Cu(POP)(bq)]⁺ in which bq = 2,2′-biquinoline. The P–C–P angle is 114.456(19)^o in [Cu(POP)(biq)]⁺ compared to a range of 118.29(3)–119.60(3)^o [Cu(POP)(bq)]⁺. There is a change from an intra-POP PPh₂-phenyl/(C₆H₄)₂O-arene π-stacking in [Cu(POP)(biq)]⁺ to a π-stacking contact between the POP and bq ligands in [Cu(POP)(bq)]⁺. In solution and at ambient temperatures, the [Cu(POP)(biq)][PF₆]⁺ and [Cu(xantphos)(biq)]⁺ cations undergo several concurrent dynamic processes, as evidenced in their multinuclear NMR spectra. The photophysical and electrochemical behaviors of the heteroleptic copper (I) complexes were investigated, and the effects of changing from bq to biq are described. Short Cu···O distances within the [Cu(POP)(biq)]⁺ and [Cu(xantphos)(biq)]⁺ cations may contribute to their very low photoluminescent quantum yields. Full article

The preparation, characterization and electrochemical and photophysical properties of a series of desymmetrized heteroleptic [Cu(P^P)(N^N)][PF₆] compounds are reported. The complexes incorporate the chelating P^P ligands bis(2-(diphenylphosphanyl)phenyl)ether (POP) and (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) (xantphos), and 6-substituted 2,2′-bipyridine (bpy) derivatives with functional groups attached by –(CH₂)_n– spacers: 6-(2,2′-bipyridin-6-yl)hexanoic acid (1), 6-(5-phenylpentyl)-2,2′-bipyridine (2) and 6-[2-(4-phenyl-1H-1,2,3,triazol-1-yl)ethyl]-2,2′-bipyridine (3). [Cu(POP)(1)][PF₆], [Cu(xantphos)(1)][PF₆], [Cu(POP)(2)][PF₆], [Cu(xantphos)(2)][PF₆], and [Cu(xantphos)(3)][PF₆] have been characterized in solution using multinuclear NMR spectroscopy, and the single crystal structure of [Cu(xantphos)(3)][PF₆]^.0.5Et₂O was determined. The conformation of the 6-[2-(4-phenyl-1H-1,2,3,triazol-1-yl)ethyl]-substituent in the [Cu(xantphos)(3)]⁺ cation is such that the α- and β-CH₂ units reside in the xanthene ‘bowl’ of the xantphos ligand. The 6-substituent desymmetrizes the structure of the [Cu(P^P)(N^N)]⁺ cation and this has consequences for the interpretation of the solution NMR spectra of the five complexes. The NOESY spectra and EXSY cross-peaks provide insight into the dynamic processes operating in the different compounds. For powdered samples, emission maxima are in the range 542–555 nm and photoluminescence quantum yields (PLQYs) lie in the range 13–28%, and a comparison of PLQYs and decay lifetimes with those of [Cu(xantphos)(6-Mebpy)][PF₆] indicate that the introduction of the 6-substituent is not detrimental in terms of the photophysical properties. Full article

The synthesis and structural characterization of 5,6′-dimethyl-2,2′-bipyridine (5,6′-Me₂bpy) are reported, along with the preparations and characterizations of [Cu(POP)(5,6′-Me₂bpy)][PF₆] and [Cu(xantphos)(5,6′-Me₂bpy)][PF₆] (POP = bis(2-(diphenylphosphanyl)phenyl)ether, xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene). Single-crystal X-ray structure determinations of [Cu(POP)(5,6′-Me₂bpy)][PF₆] and [Cu(xantphos)(5,6′-Me₂bpy)][PF₆] confirmed distorted tetrahedral copper(I) coordination environments with the 5-methylpyridine ring of 5,6′-Me₂bpy directed towards the (C₆H₄)₂O unit of POP or the xanthene unit of xantphos. In the xantphos case, this preference may be attributed to C–H…π interactions involving both the 6-CH unit and the 5-methyl substituent in the 5-methylpyridine ring and the arene rings of the xanthene unit. ¹H NMR spectroscopic data indicate that this ligand orientation is also preferred in solution. In solution and the solid state, [Cu(POP)(5,6′-Me₂bpy)][PF₆] and [Cu(xantphos)(5,6′-Me₂bpy)][PF₆] are yellow emitters, and, for powdered samples, photoluminescence quantum yields (PLQYs) are 12 and 11%, respectively, and excited-state lifetimes are 5 and 6 μs, respectively. These values are lower than PLQY and τ values for [Cu(POP)(6,6′-Me₂bpy)][PF₆] and [Cu(xantphos)(6,6′-Me₂bpy)][PF₆], and the investigation points to the 6,6′-dimethyl substitution pattern in the bpy ligand being critical for enhancement of the PLQY. Full article

The syntheses and characterizations of the chelating ligand 6-chloro-6′-methyl-2,2′-bipyridine (6-Cl-6′-Mebpy) and of the copper(I) compounds [Cu(POP)(6-Cl-6′-Mebpy)][PF₆] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆] (POP = bis(2-(diphenylphosphanyl)phenyl)ether and xantphos = 4,5-bis(diphenylphosphanyl)-9,9-dimethyl-9H-xanthene) are described. The single crystal structures of both complexes were determined; the copper(I) ion is in a distorted tetrahedral environment and in [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆], the disorder of the 6-Cl-6′-Mebpy ligand indicates there is no preference of the ‘bowl’-like cavity of the xanthene unit to host either the methyl or chloro-substituent, consistent with comparable steric effects of the two groups. The electrochemical and photophysical properties of [Cu(POP)(6-Cl-6′-Mebpy)][PF₆] and [Cu(xantphos)(6-Cl-6′-Mebpy)][PF₆] were investigated and are compared with those of the related compounds containing 6,6′-dichloro-2,2′-bipyridine or 6,6′-dimethyl-2,2′-bipyridine ligands. Trends in properties of the [Cu(P^P)(N^N)]⁺ complexes were consistent with 6-Cl-6′-Mebpy behaving as a combination of the two parent ligands. 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

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

This manuscript summarizes and analyzes X-ray data of monomeric cis-PtP₂CCl derivatives. These complexes crystallize in the following crystal systems: tetragonal, P4₂/n (3), triclinic, Pī (10), orthorhombic, P2₁2₁2₁ (prevails)(16), and monoclinic, P2₁/c (prevails) (36) examples. There are three sub-groups of the respective complexes: Pt(η¹-PL)₂(η¹-CL)(η¹-Cl); Pt(η²-P₂L)(η¹-CL)(η¹-Cl) and Pt(η¹-PL)(η²-P,CL)(η¹-Cl). The chelating P,P-donor ligands form: four-(POP, PCP), five-(PC₂P), six-(PC₃P, PCNCP), seven-(PC₄P) and even ten-(PCNCNCNCP) membered rings. The chelating P.C-donor ligands create three-(PC), four-(PCC) and five-(PC₂C) membered rings. The mean Pt-L bond distance elongates in the sequence: 2.10 Å (C, trans to P) < 2.222 Å (P, trans to Cl) < 2.312 Å (P, trans to C) < 2.360 Å (Cl, trans to P). There are examples which exist in two isomeric forms, of the distortion isomer type. Full article

The first MMX-type quasi-one-dimensional (Q1D) Pt chain complex (MMX chain) that contains a mono-protonated diamine as countercation, {o-(H₃NC₆H₄NH₂)}₄[Pt₂(pop)₄I]·H₂O (pop = P₂H₂O₅^2–), was synthesized. According to the crystal structural analysis, –NH₂ group was hydrogen-bonded to either lattice H₂O molecule or –NH₃⁺ group in addition to typical hydrogen bond between –NH₃⁺ group and pop ligand. To control the partial deprotonation of the countercation will be an important method for achieving the high-conductive MMX-chain polymer by the hole doping. Full article