Suzuki–Miyaura reaction catalyzed by graphene oxide supported palladium nanoparticles

Pd supported on polyamine modified graphene oxide (GO-NH₂-Pd^2 +) was fabricated for the first time. The prepared catalyst was characterized by transmission electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy and infrared spectroscopy. The catalytic activity of the prepared catalyst was investigated by employing Suzuki–Miyaura coupling reaction as a model reaction. A series of biphenyl compounds were synthesized through the Suzuki–Miyaura reaction using GO-NH₂-Pd^2 + as catalyst. The yields of the products were in the range from 71% to 95%. The catalyst can be readily recovered and reused at least 10 consecutive cycles without significant loss its catalytic activity.     

Palladium(II) thiosemicarbazone-catalyzed Suzuki–Miyaura cross-coupling reactions of aryl halides

A new air- and moisture-stable palladium(II) complex bearing pyridoxal thiosemicarbazone ligand has been synthesized. The synthesized complex was characterized by analytical and spectral methods. The molecular structure of the complex was confirmed by X-ray diffraction method. The palladium(II) complex was used as potential catalyst for Suzuki–Miyaura coupling reaction of several aryl halides under optimized conditions.     

An efficient and recyclable thermoregulated phosphine–palladium catalyst for the carbonylative Suzuki coupling of aryl halides with arylboronic acids in water

An efficient protocol has been developed for the carbonylative Suzuki coupling of aryl halides using the thermoregulated phosphine–palladium as a reusable catalyst in pure water. This protocol was applied to a wide variety of hindered and functionalized aryl iodides and bromides with arylboronic acids, to afford the desired biaryl ketones in good to high yields. The palladium catalyst was easily recovered in the aqueous phase and reused up to eight cycles without a significant decrease in its activity.     

Brønsted acidic ionic liquid as an efficient and recyclable promoter for hydroesterification of olefins catalyzed by a triphenylphosphine–palladium complex

Several Brønsted acidic ionic liquids (BAILs) with different acidic scales were synthesized and employed as acid promoters for the hydroesterification of olefins catalyzed by a triphenylphosphine–palladium complex. The results showed that catalysts with BAIL promoters resulted in moderate to high conversions to the ester product with excellent selectivity, depending on the acidity of BAIL used. The reaction conversion reached a plateau when the catalyst was promoted using BAIL with a Hammett acidity function less than or equal to − 0.11. This catalyst system could be reused several times for the hydroesterification of 1-hexene without a considerable decrease in the catalytic performance.     

Synthesis of poly(triarylamine)s by C–N coupling catalyzed by (N-heterocyclic carbene)-palladium complexes

The use of (N-heterocyclic carbene)-palladium complexes as precatalysts for the synthesis of poly(triarylamine)s by C–N coupling is reported. Effective control of the molecular weight distribution by in situ end-capping during the polymerization was found to be important for application of these polymers as the charge transporting layers of OFETs.     

Suzuki–Miyaura cross-coupling reactions catalyzed by efficient and recyclable Fe3O4@SiO2@mSiO2–Pd(II) catalyst

In this study, a novel Pd(II) complex functionalized core–shell magnetic mesoporous catalyst (Fe₃O₄@SiO₂@mSiO₂–Pd(II)) was synthesized by a simple cost effective procedure. It was characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and nitrogen physical adsorption. The Fe₃O₄@SiO₂@mSiO₂–Pd(II) catalyst offered high surface area and exhibited excellent activity towards Suzuki–Miyaura cross-coupling reaction of halides with aryl boronic acids in ethanol in air. The Fe₃O₄@SiO₂@mSiO₂–Pd(II) catalyst was stable, reusable, and conveniently recovered by applying an external magnetic field. Moreover, it provided 91% conversion after the sixth catalytic run. The Fe₃O₄@SiO₂@mSiO₂–Pd(II) catalyst examined in this study combined both the efficiency of a homogeneous catalyst and the durability of a heterogeneous catalyst. The results revealed that the Fe₃O₄@SiO₂@mSiO₂–Pd(II) catalyst is promising as a candidate for various Pd-based catalytic applications.     

Synthesis,antiapoptotic biological activity and structure of an oxo–vanadium(IV) complex with an OOO ligand donor set

The oxo–vanadium(IV) complex VO(oda)(H₂O)₂ (1) (oda=oxydiacetate, O(CH₂COO⁻)₂) was obtained by reaction of aerobic aqueous solutions of VO(acac)₂ with oxydiacetic acid, O(CH₂COOH)₂. The antiapoptotic biological activity of 1 was studied in insulin-producing cells. Chemically generated nitric oxide (NO) triggers apoptotic events, such as the appearance of oligonucleosomes in cytosol, and this response was prevented by the presence of 1 in the culture medium. The molecular structure of 1 has been determined by X-ray diffraction analysis.     

Synthesis of a ruthenium complex of a cyclic trifunctional η6, η1, η1-arene–diphosphine ligand by intramolecular dehydrofluorinative carbon–carbon coupling

Treatment of the ruthenium complex cation [(η⁶-C₆H₃Me₃-1,3,5)(RuCl(dfppe)]⁺ {dfppe=(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂} with proton sponge yields [{η⁶,η¹,η¹-C₆H₃Me-5-[CH₂-2-C₆F₄P(C₆F₅)CH₂]₂-1,3}RuCl]⁺ by stepwise intramolecular dehydrofluorinative carbon–carbon coupling.     

Reversal of enantioselectivity by change of solvent with clay-immobilized bis(oxazoline)–copper catalysts

The reduction in the polarity of the solvent induces the approach of the bis(oxazoline)–copper complex to the clay sheet in the immobilized catalyst. This proximity strongly influences the stereochemical course of the cyclopropanation reaction, even leading to a reversal in the enantioselectivity.     

Stepwise synthesis of a pentanuclear copper(II)–manganese(II) cluster by using a versatile Schiff base ligand derived from 3-formylsalicylic acid

The Schiff base 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H₂L) is a useful ligand for the design of heteronuclear complexes. A pentanuclear copper(II)–manganese(II) cluster was synthesized by using H₂L as a ligand. The compound was characterised by analytical and spectral methods. Cryomagnetic investigations over the temperature range 1.9–300 K reveal antiferromagnetic interactions between the copper(II) and manganese(II) ions.     

Epoxidation of alkenes with molecular oxygen catalyzed by a manganese porphyrin-based metal–organic framework

The flexible nature of reticular assemblies and high specific surfaces of metal–organic frameworks (MOFs) offers new opportunities for the design of heterogeneous catalysts capable of industrially relevant reactions. We demonstrate the first instance of alkene epoxidation at mild conditions using molecular oxygen by a manganese porphyrin containing MOF, MOF-525-Mn [Zr₆O₄(OH)₄(MgC₄₈H₂₄O₈N₄Cl)₃]. This zirconium MOF with a manganese porphyrin catalyst shows minimal deactivation over long periods and maintains its structure and high activity after multiple catalytic cycles. Kinetic studies of styrene epoxidation are in agreement with theoretical and experimental studies of homogeneous reactions with the same porphyrin unit, suggesting that the heterogeneous catalyst operates according to a similar mechanism as its homogeneous counterpart.     

Tris(N,N′-dimethylurea)bis(nitrato-O,O′)manganese(II), the first example of a seven-coordinate manganese(II) complex with a monodentate organic ligand

Employing a variety of solvents and molar ratios, the reactions of Mn(NO₃)₂·6H₂O with N,N′-dimethylurea (DMU) afforded the adduct [Mn(NO₃)₂(DMU)₃] (1). X-ray analysis shows that the high-spin complex has a pentagonal bipyramidal geometry with two DMU oxygen atoms in axial positions and with two types of monodentate O-bonding for the DMU molecules, one of them being very unusual. The spectroscopic properties of the prepared complex are also discussed.     

Catalytic hydration of alkynes to ketones by a salen–gold(III) complex

A general atom-economical approach for the synthesis of ketones is demonstrated through hydration of a wide range of alkynes catalyzed by a salen–gold(III) complex in the presence of trifluoroacetic acid as the cocatalyst. Various terminal and internal alkynes were suitable substrates for the catalytic system.     

Photocleavage of DNA and adenine–thymine inclined binding by a novel ruthenium(II) complex with 3,4-dibromo-imidazo[4,5-f][1,10]phenanthroline ligand

A new ruthenium(II) complex [Ru(phen)2(ODBIP)]^2 + (phen = 1,10-phenanthroline; ODBIP = 3,4-dibromo-imidazo[4,5-f][1,10]phenanthroline) has been synthesized. Binding of this complex to poly(dG–dC) DNA, supercoiled pBR322 plasmid DNA, calf thymus DNA (CT DNA), and poly(dA–dT) DNA was investigated by spectroscopic methods. The photocleavage on pBR322 DNA was also studied by agarose gel electrophoresis, and the cleavage mechanisms were further explored. The results indicated that [Ru(phen)2(ODBIP)]^2 + preferentially bound to DNA at adenine–thymine base pairs by intercalation, and the complex exhibited higher DNA cleavage efficiency under visible light irradiation than under UV light irradiation. The singlet oxygen may be responsible for the DNA photocleavage.     

A multifunctional reduced molybdophosphate-based 3D metal–organic framework induced by a rigid triazole and a flexible bis(triazole) mixed ligand

A novel reduced molybdophosphate-based metal–organic framework (MOF) Zn[(MoO₂)₆(HPO₄)₂(PO₄)₂(OH)₃]₂[Zn₂(L¹)][Zn(HL²)₂]₂·10H₂O (1) (L¹ = 1,6-bis(1,2,4-triazol-1-yl)hexane, L² = 1,2,4-triazol) has been hydrothermally synthesized and structurally characterized. Compound 1 is constructed from the [Zn(P₄Mo₆)₂]-based 2D layer and μ₂-bridging L¹ ligands, which shows a (2,3,8)-connected three-dimensional framework with {{4·6²}2{4⁴·6²·8¹⁸·12⁴}{4}²} topology. 1 represents the first 3D P₄Mo₆-based MOF constructed by mixed N-donor ligands. The electrocatalytic and photocatalytic activities of compound 1 have been investigated.     

A luminescent pH sensor based on a diruthenium(II) complex: `off–on–off' switching via the protonation/deprotonation of an imidazole-containing ligand

Complex [(bpy)₂Ru(bpibH₂)Ru(bpy)₂](ClO₄)₄·3H₂O (1) (bpy=2,2′-bipyridine and bpibH₂=1,4-bis([1,10]phenanthroline[5,6-d]imidazol–2-yl)benzene), which contains two metallolumophores and a two receptor system, acts as an `off–on–off' luminescent pH sensor through protonation and deprotonation in MeOH–H₂O (1:1 v/v) solution at room temperature.     

Structural analysis and electronic properties of a homodinuclear erbium(III) complex bridged by the polyazine ligand 2,2′-bipyrimidine

Structural analysis of the previously reported homodinuclear complex [Er(tfa)₃]₂bpm (where tfa = 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione and bpm = 2,2′-bipyrimidine) synthesized by reaction of two equivalents of ErCl₃ with six equivalents of tfa and one equivalent of bpm in a basic ethanol solution is presented. X-ray quality crystals were grown by slow evaporation of concentrated methanol solution containing the complex. The complex crystallizes in the monoclinic space group P2₁/n, with a planar bpm ligand. The erbium…erbium distance is 6.715(5) Å. Each erbium center is eight coordinate from six tfa oxygens and two bpm nitrogens. Electronic transitions of concentrated solutions of the complex reveal three sharp lines corresponding to the 4f–4f1 transitions at 486 nm, 520 nm and 657 nm with the lowest energy transition corresponding to ⁴I_15/2 → ⁴F_9/2.     

Cleavage of the C–N bond of a peptide group by a copper(II)-peroxide adduct with an η1-coordination mode

We have obtained clear evidence that a copper(II)-peroxide adduct with an η¹-coordination mode can cleave the C–N bond of a peptide group and hydroxylate the alkyl group nearby; this may provide helpful information for elucidation of the reaction mechanism of PAM, peptidylglycine α-amidating monooxygenase.