Bipyridyl Ligands Research Articles

Synthesis of dielectric polymers with bipyridyl ligand and metal complex by ring-opening metathesis polymerization

Block copolymers with bipyridyl ligand and metal ion complex were synthesized by ring-opening metathesis polymerization. The combination of high dipolar polarization induced by bis(trifluoromethyl) group in polymer, the long-range polaron hopping process produced by the introduction of metal-bipyridyl side group, and the self-assembled nanostructure significantly improved the dielectric properties of polymers. The iridium(III)-contained block copolymer exhibited outstanding comprehensive dielectric and energy storage performance with high dielectric constant of 23.0–20.3 and low dielectric loss of 0.032–0.013 at 102–106 Hz, and high polarizability of 3.14 μC cm−2 at 280 MV m−1. Besides, the released-stored energy density reached 4.17/4.86 J cm−3 accompanied with the charge-discharge efficiency of 86%. Therefore, it would have potential applications as a metal-organic dielectric material with good dielectric and energy storage properties.

PCET-Based Ligand Limits Charge Recombination with an Ir(III) Photoredox Catalyst.

Upon photoinitiated electron transfer, charge recombination limits the quantum yield of photoredox reactions for which the rates for the forward reaction and back electron transfer are competitive. Taking inspiration from a proton-coupled electron transfer (PCET) process in Photosystem II, a benzimidazole-phenol (BIP) has been covalently attached to the 2,2'-bipyridyl ligand of [Ir(dF(CF3)ppy)2(bpy)][PF6] (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-(trifluoromethyl)pyridine; bpy = 2,2'-bipyridyl). Excitation of the [Ir(dF(CF3)ppy)2(BIP-bpy)][PF6] photocatalyst results in intramolecular PCET to form a charge-separated state with oxidized BIP. Subsequent reduction of methyl viologen dication (MV2+), a substrate surrogate, by the reducing moiety of the charge separated species demonstrates that the inclusion of BIP significantly slows the charge recombination rate. The effect of ∼24-fold slower charge recombination in a photocatalytic phthalimide ester reduction resulted in a greater than 2-fold increase in reaction quantum efficiency.

Trinuclear Organometallic Pt-Ir-Pt Complexes: Insights into Photophysical Properties, Amino Acid Binding and Protein Sensing.

The rational synthesis of trinuclear emissive organometallic complexes with two equivalent platinum(II) centres appended to the ancillary substituted 2,2'-bipyridyl ligand of the cyclometalated iridium(III) centre is reported here. The alkynyl-platinum moiety and cyclometalated iridium(III) centres have been separated through a non-conjugated CH2 -O-CH2 linkage. The emission titration with amino acids reveals that the complexes sense free amino acids. The luminescence sensing of BSA is thus attributed to the amino acid sensing ability of the complexes and confirmed by emission anisotropy and Far-UV CD spectral study. The decrease in α-helix in the CD spectra signifies the changes in the secondary structure of protein in presence of the complexes.

Structures of alkali metal salts with [W(CN)6(bpy)]− ion. Comparative studies to W(IV) analogues

Three complexes with the formula Na[W(CN)6(bpy)]·H2O (1), K[W(CN)6(bpy)] (2) and Rb[W(CN)6(bpy)] (3) have been synthesized and structurally characterized based on the X-ray analysis of single crystals, as well as described and compared with analogues in which the tungsten atom is in the fourth oxidation state. All salts crystallize in orthorhombic (Pbca for 1) or monoclinic (P21/c for 2 and 3) space groups. Contrary to the layered systems containing the negative anionic complexes of W(IV), the compounds described in the publication containing the negative anionic complexes of W(V) form much more complex structural systems, the arrangement of which is based on an extensive network of bridging cyanido ligands. This network is additionally stabilized by π-π type interactions of bipyridyl ligands. This phenomenon of a different spatial arrangement of the structure in the studied compounds compared to the layered W(IV) systems is surprising and proves that the structure of the bridge cyanido systems is influenced by many, previously unpredictable factors, and the knowledge of crystal engineering of cyanido polymers itself is not field too vast.

Dual luminescent coordination polymers based on flexible aliphatic carboxylate ligands supplemented by rigid bipyridyl ligands for 2,4-dinitrophenol (DNP) and iron(III) ion detection

Based on flexible aliphatic carboxylate ligands supplemented by rigid bipyridyl ligands with isomerized structures, three novel Zn(II) coordination polymers, namely Zn2(dpe)(glutarate)2(H2O)2 (1), Zn2(glutarate)2(tdpe)2(H2O)2 (2) and Zn(H2O)(succinate)(tdpe)2 (3) [dpe = 1,2-di(4-pyridyl)ethylene, tdpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene)], were synthesized by appropriate methods. The crystallographic data of all the complexes present diverse geometries of the Zn(II) centers. There are two independent Zn(II) ions where one is intermediate between square pyramidal and trigonal pyramidal and the other is distorted tetrahedral [in 1] or distorted octahedral [in 2 and 3]. Both carboxylate ligands act as bridging ligands with various coordination modes to build up the main structures, whereas the bipyridyl ligands show only coordination of the 4-pyridyl site with the metal centers, indicating that only dpe acts as a bridging ligand, building up the principal framework in 1. The tdpe ligand presents a monodentate coordination mode in the other two complexes. The structures of all complexes indicate that the coexistence of two ligand types could support higher dimensionalities in the complexes. Complex 1 was further used as a nitroaromatic compound (NAC) and a heavy metal ion sensor. The complex showed highly sensitive and selective sensing of 2,4-dinitrophenol (DNP) and Fe(III) ions, based on its fluorescence quenching effect.

Electrocatalytic synthesis of heterocycles from biomass-derived furfuryl alcohols

It is very attractive yet underexplored to synthesize heterocyclic moieties pertaining to biologically active molecules from biomass-based starting compounds. Herein, we report an electrocatalytic Achmatowicz reaction for the synthesis of hydropyranones from furfuryl alcohols, which can be readily produced from biomass-derived and industrially available furfural. Taking advantage of photo-induced polymerization of a bipyridyl ligand, we demonstrate the facile preparation of a heterogenized nickel electrocatalyst, which effectively drives the Achmatowicz reaction electrochemically. A suite of characterization techniques and density functional theory computations were performed to aid the understanding of the reaction mechanism. It is rationalized that the unsaturated coordination sphere of nickel sites in our electrocatalyst plays an important role at low applied potential, not only allowing the intimate interaction between the nickel center and furfuryl alcohol but also enabling the transfer of hydroxide from nickel to the bound furfuryl alcohol.

Investigation of iron(III) ionic structural complexes for seebeck coefficient enhancement using variation of ligand lengths with extended Π-conjugated bipyridyl ligands

Five new octahedral spin-crossover magnetic complexes with general formulae, [Fe(LCn)3](BF4)3, where L = ligand, and n = 8, 10, 12, 14, 16, were synthesized and characterized. The influence of different ligand lengths on the diffusion and Seebeck coefficient, and the effect of counterions were investigated. It was found that diffusion and Seebeck values were highly dependent on magnetic properties of the complexes and the agglomeration formed from the long ligand lengths. Hence, it was found that ionic complexes with higher percentage of low-spin have recorded the highest diffusion and Seebeck values due to the presence of N-donor ligand as an effective electron donor to the metal centre. Thus, it is easier to break the Coulombic interaction, consequently increase the ionic mobility in solution that accounted for the entropy formed. Therefore, these findings provide a systematic pathway in the designing and synthesising SCO complex to obtain optimum performance of thermo-electrochemical materials.

Structural Characterization, Magnetic and Luminescent Properties of Praseodymium(III)-4,4,4-Trifluoro-1-(2-Naphthyl)Butane-1,3-Dionato(1-) Complexes

Four new Pr(III) mononuclear complexes of formula [Pr(ntfa)3(MeOH)2] (1), [Pr(ntfa)3(bipy)2] (2), [Pr(ntfa)3(4,4′-Mt2bipy)] (3) and [Pr(ntfa)3(5,5′-Me2bipy)] (4), where ntfa = 4,4,4-trifuoro-1-(naphthalen-2-yl)butane-1,3-dionato(1-), 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-dipyridine, 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-dipyridine, have been synthesized and structurally characterized. The complexes display the coordination numbers 8 for 1, 3 and 4, and 10 for 2. Magnetic measurements of complexes 1–4 were consistent with a magnetically uncoupled Pr3+ ion in the 3H4 ground state. The solid state luminescence studies showed that the ancillary chelating bipyridyl ligands in the 2–4 complexes greatly enhance the luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Pr3+ ion; behaving as “antenna” ligands.

Dual Luminescent Coordination Polymers Based on Flexible Aliphatic Carboxylate Ligands Supplementing by Rigid Bipyridyl Ligands for 2,4-Dinitrophenol (DNP) and Iron (III) Ion Detections

Based on flexible aliphatic carboxylate ligands supplementing by isomerized structure of rigid bipyridyl ligands, three novel Zn(II) coordination polymers, namely Zn 2 (dpe)(glutarate) 2 (H 2 O) 2 (1), Zn 2 (glutarate) 2 (tdpe) 2 (H 2 O) 2 (2), and Zn(H 2 O)(succinate)(tdpe) 2 (3) (dpe = 1,2-di(4-pyridyl)ethylene, tdpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene)), have been synthesized by appropriate methods. The crystallographic data of all complexes presented the diverse geometries of Zn(II) center such as two independent of square pyramidal and tetrahedral (in (1)), trigonal bipyramidal (in (2)), and octahedral (in (3)). Both the carboxylate ligands act as bridging ligands with the various coordination mode to build up the main structures. While bipyridyl ligand showed only 4-pyridyl site in coordination bond with metal center providing only dpe acted as bridging ligand to build up the principal framework in (1). Whereas tdpe ligand presented monodentate coordination mode in the other. All structures of complexes indicated that the coexistence of two ligand types could support the higher dimensionality in the complexes. Complex 1 was further used as nitro-aromatic compounds (NACs) and heavy metal ion sensors. It shows highly sensitive and selective sensing to 2,4-dinitrophenol (DNP), and Fe(III) ion, respectively based on fluorescence quenching effect.

Синтез и строение продуктов реакции 2,2’-дипиридила с треххлористой сурьмой

Adducts have been obtained from antimony trichloride and 2,2'-bipyridyl in acetonitrile: [C10H9N2]2+[OSb2Cl6]2 (1) и [C10H9N2]+ {[(C10H8N2)SbCl3]2[Cl]} (2). The compounds have been identified by IR spectroscopy and X-ray diffraction analysis. According to the X-ray diffraction data, the pale green crystals 1 consist of two types of bipyridyl cations and binuclear anions [OSb2Cl6]2, in which two SbCl3 fragments are linked through an oxygen atom and two bridged chlorine atoms. The coordination polyhedron of the antimony atom is a square pyramid with two terminal (SbClterm 2.418(5)2.497(4) Å) and two bridged chlorine atoms (SbClbr 3.044(4)–2.849(5) Å) at the base and the oxygen atom at the fifth vertex (SbO 1.95(1) and 1.93(9) Å). The Sb–O–Sb group has been curved (119.3(5)o) so that the antimony atoms approach each other at a distance of 3.348(2) Å, which is greater than the sum of the covalent radii of these atoms (2.08 Å), but less than the sum of their van der Waals radii (4.4 Å). The antimony atom shifts from the equatorial plane [Cl4] towards the carbon atom by 0.254 Å. Along with the main product of the reaction, there are minor amounts of yellow-orange crystals 2, consisting of two types of bipyridyl cations and binuclear chlorine-containing anions {[(C10H8N2)SbCl3]2[Cl]}, in which two antimony-containing fragments (distorted octahedron) (C10H8N2)SbCl3 are linked by a chlorine bridging atom (SbClbr 2.59(8) Å). The bridging chlorine atom occupies the sixth vertex of the octahedron (SbCl 3.13(1) Å), the opposite vertex is occupied by one of the nitrogen atoms of the bipyridyl ligand, the second nitrogen atom (SbN 2.22(9) Å) of which lies in the equatorial plane with three chlorine atoms (SbCl 2.58(1), 2.61(1), 2.56(1) Å). Complete tables of atom coordinates, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Center ((№ 2041289; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif).

1,2-Bis-perfluoroalkylations of alkenes and alkynes with perfluorocarboxylic anhydrides via the formation of perfluoroalkylcopper intermediates.

A novel, Cu-mediated protocol toward the 1,2-bis-perfluoroalkyaltion of alkenes/alkynes was developed. The method proceeded with perfluorocarboxylic anhydrides as inexpensive and readily available perfluoroalkyl sources. Diacyl peroxide was generated in situ from the perfluorocarboxylic anhydrides and H2O2. The key step in this reaction is the formation of a stable perfluoroalkylcopper intermediate that is achieved with the aid of a bipyridyl ligand. Subsequent reaction of the intermediate with perfluoroalkyl-containing alkyl or vinyl radicals affords the desired products.

Analysis of the effects of Cu-MOFs on fungal cell inactivation.

Three dimensional (3D) copper metal organic frameworks (Cu-MOFs) containing glutarates and bipyridyl ligands (bpa = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene, or bpp = 1,3-bis(4-pyridyl)propane) were synthesized by using previously reported hydrothermal reactions or a layering method. All three Cu-MOFs contained well-defined one dimensional (1D) channels with very similar pore shapes and different pore dimensions. The bulk purities of the Cu-MOFs were confirmed using powder X-ray diffraction (PXRD) and infrared spectroscopy (IR) spectra. When the three types of Cu-MOFs were applied to Candida albicans cells and Aspergillus niger spores, an average of about 50–80% inactivation was observed at the highest concentration of Cu-MOFs (2 mg mL−1). The efficiency of the fungal inactivation was not significantly different among the three different types (bpa, bpe, bpp). Treatment of the fungi using Cu-MOFs induced an apoptosis-like death and this was more severe in A. niger than C. albicans. This may be due to elevation of the intracellular level of reactive oxygen species (ROS) in A. niger. Generation of the reactive species in solution by Cu-MOFs was observed. However, there was a dramatic variation in the levels observed among the three types. Our results suggest that Cu-MOFs can produce antifungal effects and induce apoptosis-like death of the fungi, which was probably caused by the elevated level of intracellular reactive species.

Same knot, longer rope: altering ligand geometry provides control over nuclearity in self-assembled trefoil knots.

Taking advantage of the accumulation of a number of noncovalent intramolecular interactions, octanuclear and hexanuclear trefoil knots are self-assembled based on half-sandwich rhodium fragments. The selective synthesis of either the octanuclear or hexanuclear knot can be controlled by altering different dipyridyl arms.

Slow magnetic relaxation and luminescence properties in neodymium(iii)-4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dionato complexes incorporating bipyridyl ligands

A new series of eight-coordinated Nd(iii) complexes derived from 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate and bi-pyridyl ligands revealed multifunctional molecular materials as photoluminescent single-molecule magnets (SMMs).

Substrate-Dependent Electron-Transfer Rate of Mixed-Ligand Electrolytes: Tuning Electron-Transfer Rate without Changing Driving Force.

To meet various requirements for electron transfer (ET) at the substrate/electrolyte interface, mixed redox couples assigned to different functions have been applied. While in all studies the mixed redox species had different redox potentials, such redox systems inherently lose energy by ET between the species. We report interfacial ET kinetics employing mixed-ligand electrolytes based on Co2+/3+ complexes with mixtures of dimethyl- and dinonyl-substituted bipyridyl (bpy) ligands with the same redox potential. The ET rates of the mixed electrolytes decrease with the increasing ratio of the dinonyl-bpy ligand, with substrates adsorbed by molecules without alkyl chains due to a blocking effect. However, when the molecules on substrates have four alkyl chains, the ET rate between the molecules and the electrolytes with increasing ratio of the dinonyl-bpy ligand is enhanced. The substrate-dependent behavior is explained by selective intermolecular interactions. The results open design flexibility for mixed-redox electrolyte systems to control ET at multi-substrate interfaces and provide a novel means to tune ET rates simultaneously for various ET processes in a system without losing energy by the ET.

Synthesis and Characterization of Serendipitous Dioxovanadates and Their DNA/BSA Interaction Studies and In Vitro Cytotoxic activity

In the current study, we have synthesized and characterized two, hitherto unreported, bis (N,N) donor dioxovanadium(V) complexes based on 1,10-phenanthroline (complex 1) and 2,2′-bipyridyl (complex 2) ligands with 3,5-dinitrosalicylic acid counter anion. The structure of the complexes are confirmed by single crystal X-ray crystallography. The binding interactions of the metal complexes with deoxyribonucleic acid (DNA) and bovine serum albumin (BSA) have been investigated by UV absorption titration and tryptophan emission quenching methods respectively. The complexes quench the intrinsic fluorescence of BSA with increasing amount of the complex concentration. Furthermore, the cytotoxic effect of the complexes against cervical cancer cell lines (HeLa) has been ascertained by MTT assay. The complexes are found to show good DNA/BSA binding ability. Based on the results obtained, it has been observed that the complexes bind preferably to groove as implicated by hyperchromic effect with increasing amount of the DNA. The binding constants (Kb) of the complexes 1 and 2 are 9.02 × 103 M−1 and 2.13 × 103 M−1 respectively. The quenching constants (KBSA) and quenching rate constant (Kq) of the complexes 1 & 2 are 0.1075 × 106 M−1 & 0.076 × 106 M−1 and 1.075 × 1013 M−1S−1 and 0.76 × 1013 M−1S−1, respectively.

Ancillary Ligand Effects on Heteroleptic IrIII Dye in Dye‐Sensitized Photocatalytic CO2 Reduction: Photoaccumulation of Charges on Arylated Bipyridine Ligand and Its Control on Catalytic Performance

Herein, we report the synthesis, and photochemical and -physical properties, as well as the catalytic performance, of a series of heteroleptic IrIII photosensitizers (IrPSs), [Ir(C^N)2 (N^NAryl )]+ , possessing ancillary ligands that are varied with aryl-substituents on bipyridyl unit [C^N=(2-pyridyl)benzo[b]thiophen-3-yl (btp); N^NAryl =4,4'-Y2 -bpy (Y=-Ph or -PhSi(Ph)3 ]. We found that the π-extension of bipyridyl ligand by aryl-substitution put bipyridyl ligand in use as an electron relay unit that performed charge accumulation before delivering to the catalytic center, greatly improving the overall CO2 -to-CO conversion activities. In a typical run, the aryl-substituted IrPS (tBu IrP-PhSi )-sensitized homogeneous systems (IrPS+ReI catalyst) gave a turnover number of 1340 (ΦCO =24.2 %) at the early stage of photolysis (<5 h). This study demonstrates that the π-character modulation on the ancillary bipyridyl ligand is critical for forthcoming catalytic performance.

The Milstein Bipyridyl PNN Pincer Complex of Ruthenium Becomes a Noyori-Type Catalyst under Reducing Conditions.

Hydrogenation of the dearomatized PNN ligand of the Milstein bipyridyl complex RuH(CO)[PNN] (2) gives a square-pyramidal Ru(II) product RuH(CO)[pPNN] (5). The central ring of the pPNN ligand is a piperidine. A minor byproduct of the hydrogenation reaction is complex 6 which has a dimeric structure made of two Ru(II) fragments each possessing a partly hydrogenated PNN ligand. The structures of 5 and 6 have been elucidated by NMR spectroscopy and X-ray crystallography. The PNN ligand of 2 is also hydrogenated under the conditions of the catalytic dehydrogenative coupling of ethanol to ethyl acetate. No direct evidence of the aromatized dihydride RuH2(CO)[PNN] (4) was found in this study. However, treating RuHCl(CO)[PNN] with Li[HBEt3] or reacting 2 with H2 at low temperature resulted in a structurally characterized hydride-bridged dimer (7) bearing intact aromatized bipyridyl ligands. M06-L/def2-QZVP DFT calculations provided insights into the thermodynamics of the stoichiometric reactions of this work and into the nature of the intermediates of the catalytic ester hydrogenation facilitated by RuH2(CO)[pPN(H)N] (8) formed from 5 under H2.

Enantioconvergent Cu-Catalyzed Intramolecular C-C Coupling at Boron-Bound C(sp3) Atoms of α-Aminoalkylboronates Using a C1-Symmetrical 2,2'-Bipyridyl Ligand Attached to a Helically Chiral Macromolecular Scaffold.

Enantioconvergent intramolecular coupling of α-(2-bromobenzoylamino)benzylboronic esters was achieved using a copper catalyst having helically chiral macromolecular bipyridyl ligand, PQXbpy. Racemic α-(2-bromobenzoylamino)benzylboronic esters were converted into (R)-configured 3-arylisoindolinones with high enantiopurity using right-handed helical PQXbpy as a chiral ligand in a toluene/CHCl3 mixed solvent. When enantiopure (R)- and (S)-configured boronates were separately reacted under the same reaction conditions, both afforded (R)-configured products through formal stereoinvertive and stereoretentive processes, respectively. From these results, a mechanism involving deracemization of organocopper intermediates in the presence of PQXbpy is assumed. PQXbpy switched its helical sense to left-handed when a toluene/1,1,2-trichloroethane mixed solvent was used, resulting in the formation of the corresponding (S)-products from the racemic starting material.

New Organometallic Ruthenium(II) Compounds Synergistically Show Cytotoxic, Antimetastatic and Antiangiogenic Activities for the Treatment of Metastatic Cancer.

In this study, we newly designed and synthesized a small library of ten structurally related C,N-cyclometalated ruthenium(II) complexes containing various pyridine-functionalized NHC ligand and chelating bipyridyl ligands (e.g., 2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, and 1,10-phenanthroline (phen)). The complexes were well characterized by NMR, electrospray ionization-mass spectrometry, and single-crystal X-ray structure analyses. Among the new ruthenium(II) derivatives, we identified that the complex Ru8 bearing bulky moieties (i.e., phen and pentamethyl benzene) had the most potent cytotoxicity against all tested cancer cell lines, generating dose- and cell line-dependent IC50 values at the range of 3.3-15.0 μm. More significantly, Ru8 not only efficiently inhibited the metastasis process against invasion and migration of tumor cells but also exhibited potent antivascular effects by suppressing HUVEC cells migration and tube formation in vitro and blocking vessel generation in vivo (chicken chorioallantoic membrane model). In a metastatic A2780 tumor xenograft-bearing mouse model, administration of Ru8 outperformed antimetastatic agent NAMI-A and clinically approved cisplatin in terms of antitumor efficacy and inhibition of metastases to other organs. Overall, these data provided compelling evidence that the new cyclometalated ruthenium complex Ru8 is an attractive agent because of synergistically suppressing bulky tumors and metastasized tumor nudes. Therefore, the complex Ru8 deserves further investigations.