Diphenolate Ligand Research Articles

Achieving efficient and stable blue thermally activated delayed fluorescence organic light-emitting diodes based on four-coordinate fluoroboron emitters by simple substitution molecular engineering.

Achieving both high efficiency and high stability in blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) is challenging for practical displays and lighting. Here, we have successfully developed a series of sky-blue to pure-blue emitting donor-acceptor (D-A) type TADF materials featuring a four-coordinated boron with 2,2'-(pyridine-2,6-diyl)diphenolate (dppy) ligands, i.e.1-8. Synergistic engineering of substituents on the phenyl bridge as well as the electronic properties and the attached positions of heteroatom N-donors not only enables fine-tuning of the emission colors, but also modulates the nature and energies of their triplet excited states that are important for the reverse intersystem crossing (RISC). Particularly for the compound with two methyl substituents on the phenyl bridge (compound 8), RISC is significantly facilitated through the vibronic coupling of the energetically close-lying triplet charge transfer (3CT) and the triplet local excited (3LE) states, when compared to analogue 7. Efficient sky-blue to pure-blue OLEDs with electroluminescence peaks (λ EL) at 460-492 nm have been obtained, in which ca. five-fold higher external quantum efficiencies (EQEs) of 18.9% have been demonstrated by 8 than that by 7. Moreover, ca. thirty times longer device operational half-lifetimes (LT50) of 9113 hours for 8 than that for 7 as well as satisfactory LT50 reaching 26 643 hours for 6 at an initial luminance of 100 cd m-2 have also been demonstrated. To the best of our knowledge, these results represent one of the best high-performance blue OLEDs based on tetracoordinated boron TADF emitters. Moreover, the design strategy presented here has provided an attractive strategy for enhancing the device performance of blue TADF-OLEDs.

Fluorescence, cyclic voltammetric, computational, and spectroscopic studies of Mn(II), Co(II), Pd(II), Zn(II) and Cd(II) complexes of salen ligand and their biological applications

2,2′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidiene))bis(methanylylidene))diphenol (H2L) ligand and its Mn(II), Co(II), Pd(II) Zn(II) and Cd(II) chelates have been isolated and characterized by conventional and spectroscopic techniques including FTIR spectrum, 1HNMR , 13CNMR , powder X-ray diffraction [PXRD], UV–visible, mass spectroscopy besides elemental analyses, and magnetic susceptibility measurements. The DMOL3 tool in the material studio package was also used to optimize the structures. The ligand behaves as binegative N2O2 tetradentate in Pd(II) and Zn(II) complex, neutral N2 bidentate in Mn(II), Co(II) and Cd(II)-complexes. Horowitz–Metzger and Coats–Redfern approaches were used to estimate the various kinetic and thermodynamic parameters. Zeta Potentials for the H2L ligand and its Pd(II), Cd(II) and Co(II) complexes in ethanol as a dispersive medium were measured. Ligand and its complexes were tested for their biological potency as anti-bacterial activity against gram (-) E. coli, P. aeruginosa, and gram (+) B. subtilis, S. aureus bacteria as well as antifungal activity against C. albicans. The antioxidant potentials of the isolated compounds were also screened by using DPPH scavenging methods. The isolated compounds were examined for cytotoxic activity using the MTT assay on MDA-MB-231 and HepG2 cell lines, and the results were verified using molecular docking simulations.

Fe‐Based Complexes as Styrene Aziridination Catalysts: Ligand Substitution Tunes Catalyst Activity

AbstractAs part of our effort to improve our understanding of aziridination mechanism, we used tetra substitution of a diphenol ligand to modify the redox properties of corresponding Fe complexes. This allowed us to confirm that aziridination catalysis by Fe‐based complexes is governed by electron affinity of the active species and further show that it correlates with the FeIII/FeII redox potential.

Four-Coordinate Boron Emitters with Tridentate Chelating Ligand for Efficient and Stable Thermally Activated Delayed Fluorescence Organic Light-Emitting Devices.

A new class of four-coordinate donor-acceptor fluoroboron-containing thermally activated delayed fluorescence (TADF) compounds bearing a tridentate 2,2'-(pyridine-2,6-diyl)diphenolate (dppy) ligand has been successfully designed and synthesized. Upon varying the donor moieties from carbazole to 10H-spiro[acridine-9,9'-fluorene] to 9,9-dimethyl-9,10-dihydroacridine, these boron derivatives exhibit a wide range of emission colors spanning from blue to yellow with a large spectral shift of 2746 cm-1 , with high PLQYs of up to 96 % in the doped thin film. Notably, vacuum-deposited organic light-emitting devices (OLEDs) made with these boron compounds demonstrate high performances with the best current efficiencies of 55.7 cd A-1 , power efficiencies of 58.4 lm W-1 and external quantum efficiencies of 18.0 %. More importantly, long operational stabilities of the green-emitting OLEDs based on 2 with half-lifetimes of up to 12 733 hours at an initial luminance of 100 cd m-2 have been realized. This work represents for the first time the design and synthesis of tridentate dppy-chelating four-coordinate boron TADF compounds for long operational stabilities, suggesting great promises for the development of stable boron-containing TADF emitters.

Four‐Coordinate Boron Emitters with Tridentate Chelating Ligand for Efficient and Stable Thermally Activated Delayed Fluorescence Organic Light‐Emitting Devices

AbstractA new class of four‐coordinate donor‐acceptor fluoroboron‐containing thermally activated delayed fluorescence (TADF) compounds bearing a tridentate 2,2′‐(pyridine‐2,6‐diyl)diphenolate (dppy) ligand has been successfully designed and synthesized. Upon varying the donor moieties from carbazole to 10H‐spiro[acridine‐9,9′‐fluorene] to 9,9‐dimethyl‐9,10‐dihydroacridine, these boron derivatives exhibit a wide range of emission colors spanning from blue to yellow with a large spectral shift of 2746 cm−1, with high PLQYs of up to 96 % in the doped thin film. Notably, vacuum‐deposited organic light‐emitting devices (OLEDs) made with these boron compounds demonstrate high performances with the best current efficiencies of 55.7 cd A−1, power efficiencies of 58.4 lm W−1 and external quantum efficiencies of 18.0 %. More importantly, long operational stabilities of the green‐emitting OLEDs based on 2 with half‐lifetimes of up to 12 733 hours at an initial luminance of 100 cd m−2 have been realized. This work represents for the first time the design and synthesis of tridentate dppy‐chelating four‐coordinate boron TADF compounds for long operational stabilities, suggesting great promises for the development of stable boron‐containing TADF emitters.

Fabrication of selective and sensitive Pb2+ detection by 2,2′-(−(1,2-phenylenebis(azaneylylidene))bis(methaneylylidene))diphenol by electrochemical approach for environmental remediation

The Tetradentate Schiff base was easily prepared from o-phenylenediamine and salicylaldehyde and used as a ligand for the detection of heavy metal ions in phosphate buffer medium by electrochemical approach. To fabricate the selective lead (Pb2+) ion sensor, a slurry of the synthesized 2,2′-(−(1,2-phenylenebis(azaneylylidene))bis(methaneylylidene))diphenol (TDL) ligand was deposited onto glassy carbon electrode (GCE) as uniform thin-layer. The calibration curve of the proposed Pb2+ ion sensor in form of a current vs. concentration plot is found to be linear over Pb2+ ion concentration range (0.1 nM ~ 0.01 mM). The sensitivity of the sensor is very high (8.84 μAμM−1 cm−2) and detection limit is as low as 98.02 ± 0.50 pM (Limit of quantification is 316.73 pM). The projected Pb2+ sensor with active TDL shows reliability, precise reproducibility and short response time (16.0 s.) during sensing performances. Above all, it was showed successive applicability to detect the real environmental samples. In the field sensor development, this methodology using TDL onto GCE might be ae efficient and reliable innovative technique for the detection of heavy metal ions by electrochemical methods.

Synthesis, Characterization and Photo-Kinetic Study of DiphenolSchiff Base and its Metal Complexeswith (Co+2, Ni+2, Cu+2) Ions

In this research 3, 3`-[benzene-1, 4-diylbis (nitromethylylidene)diphenol (ligand)was prepared from reaction of 1, 4phynilindiamine with 3-Hydroxy Benzoic acid. This ligand was investigated using GC-Mass, (H1, C13)NMR, FT-IR and UV-Vis spectral studies. Complexes of ligand with the transition metal ions (Co+2, Ni+2, Cu+2) were prepared and investigated by using the techniques FTIR, Uv-visible, molar conductivity and magneticsusceptibility.

Redox-Active Bis(phenolate) N-Heterocyclic Carbene [OCO] Pincer Ligands Support Cobalt Electron Transfer Series Spanning Four Oxidation States.

A new family of low-coordinate Co complexes supported by three redox-noninnocent tridentate [OCO] pincer-type bis(phenolate) N-heterocyclic carbene (NHC) ligands are described. Combined experimental and computational data suggest that the charge-neutral four-coordinate complexes are best formulated as Co(II) centers bound to closed-shell [OCO]2- dianions, of the general formula [(OCO)CoIIL] (where L is a solvent-derived MeCN or THF). Cyclic voltammograms of the [(OCO)CoIIL] complexes reveal three oxidations accessible at potentials below 1.2 V vs Fc+/Fc, corresponding to generation of formally Co(V) species, but the true physical/spectroscopic oxidation states are much lower. Chemical oxidations afford the mono- and dications of the imidazoline NHC-derived complex, which were examined by computational and magnetic and spectroscopic methods, including single-crystal X-ray diffraction. The metal and ligand oxidation states of the monocationic complex are ambiguous; data are consistent with formulation as either [(SOCO)CoIII(THF)2]+ containing a closed-shell [SOCO]2- diphenolate ligand bound to a S = 1 Co(III) center, or [(SOCO•)CoII(THF)2]+ with a low-spin Co(II) ion ferromagnetically coupled to monoanionic [SOCO•]- containing a single unpaired electron distributed across the [OCO] framework. The dication is best described as [(SOCO0)CoII(THF)3]2+, with a single unpaired electron localized on the d7 Co(II) center and a doubly oxidized, charge-neutral, closed-shell SOCO0 ligand. The combined data provide for the first time unequivocal and structural evidence for [OCO] ligand redox activity. Notably, varying the degree of unsaturation in the NHC backbone shifts the ligand-based oxidation potentials by up to 400 mV. The possible chemical origins of this unexpected shift, along with the potential utility of the [OCO] pincer ligands for base-metal-mediated organometallic coupling catalysis, are discussed.

Conductometric studies and application of new Schiff base ligand as carbon paste electrode modifier for mercury and cadmium determination

ABSTRACTA new chemically modified carbon paste electrode by 2,2ʹ-((pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))diphenol (L) ligand has been made and used as a sensor for determination of trace mercury and cadmium ions with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. Complexation studies of the ligand with Cu2+, Zn2+, Hg2+, Ni2+ and Cd2+ ions by conductometric method in acetonitrile–ethanol mixture at 25°C show that the ML complexes have formed. The formation constants of complexes were calculated from the computer fitting of the molar conductance–mole ratio data, and the stability of the resulting complexes varied in order of Cd2+ > Hg2+ > Cu2+ > Zn2+ > Ni2+. Then a simple and effective chemically modified carbon paste electrode with L was prepared, and the electrochemical properties and applications of the modified electrode were investigated. Under the optimal conditions, the detection limit was 0.0494 μg L−1 and 0.0782 μg L−1 for cadmium and mercury ions, respectively, and the linear range for both metal ions were from 1 to 100 μg L−1. The electrode shows high sensitivity, reproducibility and low cost, and was successfully applied to determination of Cd2+ and Hg2+ ions in water samples with recovery in the range of 97–101%.

Lactide/trimethylene carbonate triblock copolymers: Controlled sequential polymerization and properties

Controlled synthesis and characterization of a series of copolymers comprising repeating units derived from D,D-lactide (D,D-LA) and trimethylene carbonate (TMC) is reported. Diblock PTMC-b-PDLA or PDLA-b-PTMC and finally triblock PTMC-b-PDLA-b-PTMC or PDLA-b-PTMC-b-PDLA copolymers have been prepared for the first time in a controlled way via sequential polymerization of the corresponding comonomers. The initiating/catalytic system based on Al-alkoxide that bears a bulky, optically active diphenolate ligands has been chosen for this purpose, since it quantitatively depresses a segmental exchange side-reactions. In order to improve the thermal properties of thus obtained materials, triblock copolymers: PTMC-b-PDLA-b-PTMC and PTMC-b-PLLA-b-PTMC of the opposite configuration of PLA sequence, have been used for the preparation of the corresponding stereocomplex. Microstructure, morphology, and thermal properties of thus prepared copolymers have been investigated by 13C NMR, SEM, DSC, and TGA measurements.

Coordinating effect in ring-opening polymerization of ε-caprolactone using aluminum complexes bearing bisphenolate as catalysts

A series of Al complexes bearing diphenolate ligands was synthesized and their application for the ring-opening polymerization of ε-caprolactone was studied.

Zirconium complexes of phenylene-bridged {ONSO} ligands: coordination chemistry and stereoselective polymerization of rac-lactide.

Sequential tetradentate dianionic thio-imine diphenolate ligands featuring an ortho-phenylene core and their zirconium complexes are described for the first time. Ligands that include different combinations of bulky-alkyl groups and halo groups on the two phenol arms were prepared by a substitution/condensation reaction sequence. An unexpected fac-fac wrapping mode was found in the solid state for the ligands in the octahedral [{ONSO}Zr(O(t)Bu)2] complexes. The complexes were all fluxional, and the barrier for enantiomer interconversion was found to depend on the phenolate substituents. The complexes were found to catalyze the polymerization of rac-lactide to poly(lactic acid) in solution with polymer tacticities varying from heterotactic to atactic which showed correlation to the nature of phenolate substituents but not to the degree of complex fluxionality.

Chlorido[2,2′-[1,2-phenylenebis(nitrilomethanylylidyne)]diphenolato-κ4O,N,N′,O′]manganese(III) methanol monosolvate

In the title complex, [Mn(C20H14N2O2)Cl]·CH3OH, the central MnIII atom displays a distorted square-pyramidal coordination by two N and two O atoms from the tetradentate 2,2′-[1,2-phenyl­enebis(nitrilo­methanylyl­idyne)]diphenolate ligand and one chloride ligand. The MnIII atom is 0.525 (4) Å out of the square basal N2O2 least-squares plane. The complex mol­ecule is hydrogen bonded to the methanol solvent mol­ecule.

Catena-Poly[{μ3-4,4′,6,6′-tetrabromo-2,2′-[butane-1,4-diylbis(nitrilomethanylylidene)]diphenolato}{μ2-4,4′,6,6′-tetrabromo-2,2′-[butane-1,4-diylbis(nitrilomethanylylidene)]diphenolato}dicopper(II)

The asymmetric unit of the title coordination polymer consists of a dinuclear neutral complex mol­ecule of formula [Cu2(C18H14Br4N2O2)2]n. One of the CuII ions is coordinated in a distorted square-planar geometry, whereas the other is coordinated in a distorted square-pyramidal geometry, the long apical Cu—O bond [2.885 (4) Å] of the square-pyramidal coordination being provided by a symmetry-related O atom creating a one-dimensional polymer along [010]. π–π stacking inter­actions [centroid–centroid distance = 3.783 (4) Å] and short inter­chain Br⋯Br inter­actions [3.6142 (12)–3.6797 (12) Å] are observed.

Catena-Poly[{μ3-4,4′,6,6′-tetrachloro-2,2′-[butane-1,4-diylbis(nitrilomethanylylidene)]diphenolato}{μ2-4,4′,6,6′-tetrachloro-2,2′-[butane-1,4-diylbis(nitrilomethanylylidene)]diphenolato}dicopper(II)

The asymmetric unit of the title compound, [Cu2(C18H14Cl4N2O2)2]n, contains two independent CuII ions which are bridged by a pair of 4,4′,6,6′-tetra­chloro-2,2′-[butane-1,4-diylbis(nitrilo­methanylyl­idene)]diphenolate ligands, forming a dinuclear unit. One of the CuII ions is coordinated in a distorted square-planar environment and the other is coordinated in a distorted square-pyramidal environment. The long apical Cu—O bond of the square-pyramidal coordinated CuII ion is formed by a symmetry-related O atom, creating a one-dimensional polymer along [010]. In addition, short inter­molecular Cl⋯Cl distances [3.444 (2) Å] and weak π–π inter­actions [centroid–centroid distances = 3.736 (2)–3.875 (3) Å] are observed. The crystal studied was an inversion twin with a refined twin component ratio of 0.60 (1):0.40 (1).

Trichlorido{μ-6,6′-dimethoxy-2,2′-[cyclohexane-1,2-diylbis(nitrilomethanylylidene)]diphenolato}dimethanolcopper(II)samarium(III)

In the title hetero-dinuclear complex, [CuSm(C22H24N2O4)Cl3(CH3OH)2], the CuII cation is N,N′,O,O′-chelated by a 6,6′-dimeth­oxy-2,2′-[cyclo­hexane-1,2-diylbis(nitrilo­methanylyl­idene)]diphenolate ligand, and one Cl− anion further coordinates to the CuII cation to complete the distorted square-pyramidal coordination geometry, while the SmIII cation is chelated by four O atoms from the same ligand, and is further coordinated by two methanol mol­ecules and two Cl− anions in an bicapped trigonal–prismatic geometry. Intra- and inter­molecular O—H⋯Cl hydrogen bonds are present in the structure.

Aquachlorido{6,6′-dimethoxy-2,2′-[ethane-1,2-diylbis(nitrilomethanylylidene)]diphenolato-κ2O1,N,N′,O1′}cobalt(III) dimethylformamide monosolvate

In the title compound, [Co(C18H18N2O4)Cl(H2O)]·C3H7NO, the CoIII ion is six-coordinated by a tetra­dentate 6,6′-dimeth­oxy-2,2′-[ethane-1,2-diylbis(nitrilo­methanylyl­idene)]diphenolate ligand, with a chloride ion and an aqua ligand in the apical positions. The compound crystallized as a dimethyl­formamide (DMF) monosolvate. In the crystal, complex mol­ecules are linked via O—Hwater⋯O hydrogen bonds to form a dimer-like arrangement. These dimers are linked via a C—H⋯Cl inter­action, and the DMF mol­ecule is linked to the complex mol­ecule by C—H⋯O inter­actions.

Synthesis and characterization of a trianionic pincer supported Mo-alkylidene anion and alkyne insertion into a Mo(IV)-C pincer bond to form metallocyclopropene( η2-vinyl) complexes

This report describes two approaches to form complexes featuring Mo–C multiple bonds and a trianionic pincer ligand. Treating the trianionic pincer ligand precursor [ t BuOCO]H 3 (1) with MeLi provides the corresponding dilithio salt [ t BuOCHO]Li 2(THF) 3 ( 6) in situ, which further reacts with Mo(NAr) (CHCMe 2Ph)(OTf) 2(DME) to provide the terphenyl diphenolate complex [ t BuOCHO]Mo(NAr)CHCMe 2Ph ( 5). Complex 5 is characterized by 1H, 13C{ 1H} NMR spectroscopy, combustion analysis, and single crystal X-ray diffraction. The solid state structure of 5 reveals a distorted trigonal pyramidal geometry for the Mo(VI) ion. Treating 5 with one equiv. of phosphorane in toluene converts the diphenolate ligand into a trianionic pincer ligand by deprotonation of the pincer C ipso -H proton to give the alkylidene salt {[ t BuOCHO]Mo(NAr)(CHCMe 2Ph)}{Ph 3PCH 3} ( 7). Treating [ t BuOCO]MoNMe 2(NHMe 2) 2 ( 2), containing a d 2 Mo(IV) ion, with terminal alkynes (H–C≡CR, R = Ph, 3,5-F 2C 6H 3, 3,5-(CF 3) 2C 6H 3 and SiMe 3) produces in excellent yield the corresponding metallocyclopropylidene complexes 10-R (R H, F, CF 3) and 11 (R = SiMe 3). X-ray diffraction studies on single crystals of 10-H and 11 reveal three important features: 1) a highly distorted hexacoordinate Mo(VI) center, 2) a metallocyclopropene( η 2-vinyl) fragment, and 3) a highly distorted CH group in the metallocyclopropene unit. A single point calculation and an NBO analysis performed on 10-H′ confirms the multiple bond between Mo1 and C28. The highest occupied Kohn–Sham molecular orbital (HOMO) represents a π-combination between d yz of Mo1 and the p y orbital of C28, and the corresponding π∗-combination of those orbitals constitutes the lowest unoccupied molecular orbital (LUMO).

Amine influence in vanadium-based ethylene polymerisation pro-catalysts bearing bis(phenolate) ligands with ‘pendant’ arms

Two families of vanadium complexes bearing diphenolate ligands with different ‘pendant’ arms have been screened under various conditions for the polymerisation behaviour of ethylene. The presence of a bound amine arm was found to favour enhanced thermal stability.

{6,6′-Dimethoxy-2,2′-[(cyclohexane-1,2-diyl)bis(nitriliomethylidyne)]diphenolato}trinitratolanthanum(III) methanol monosolvate

In the title mononuclear complex, [La(NO3)3(C22H26N2O4)]·CH3OH, the LaIII ion is coordinated by three bidentate nitrate counter-ions and one zwitterionic 6,6′-dimeth­oxy-2,2′-[(cyclo­hexane-1,2- di­yl)bis­(nitriliomethyl­idyne)]diphenolate ligand through two phenolate and two meth­oxy O atoms, while the protonated N atoms remain uncoordinated. H atoms located on the two N atoms are involved in intra­molecular hydrogen bonds with the deprotonated phenol O atoms, indicating that proton migration occurs during the lanthanum complexation.