23 research outputs found
Utilization of a Pt(II) di-yne Chromophore incorporating a 2,2Ęš-bipyridine-5,5Ęš-diyl spacer as a Chelate to Synthesize a Green and Red Emitting d-f-d Heterotrinuclear Complex
A new heterotrinuclear (d-f-d) complex [Eu(btfa)31c] (btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1c = [(Ph)(Et3P)2PtâCâĄCâRâCâĄCâPt(Et3P)2(Ph)] (R = 2,2â-bipyridine-5,5â-diyl) has been synthesized by utilizing the N,N-donor sites of the organometallic chromophore. The complex was characterized by analytical and spectroscopic methods. Photophysical properties of the complex were analysed in detail using both steady-state and time-resolved emission and excitation spectroscopy. The optical absorption spectrum of the complex is dominated by the spin allowed ĎâĎ* transitions of the btfa and 1c units in the UV-visible region (200 â 418 nm) and thus is excitable over a wide range of wavelengths across the UV into the visible region of the electromagnetic spectrum. The complex displays typical red Eu(III) emission when excited at 345 nm. However, it also shows green emission when excited at 464 nm and, thus could be an interesting candidate for full colour display applications. The change in the colour could be a result of the high value of the energy back-transfer rate (6.73 105 sâ1) from the triplet state of the organometallic chromophore to the 5D1 state of Eu(III). Judd-Ofelt (J-O) intensity parameters ( and ), radiative (AR), non-radiative (AR) decay rates and intrinsic quantum yield ( ) have been calculated
Utilization of a Pt(II) di-yne Chromophore incorporating a 2,2Ęš-bipyridine-5,5Ęš-diyl spacer as a Chelate to Synthesize a Green and Red Emitting d-f-d Heterotrinuclear Complex
A new heterotrinuclear (d-f-d) complex [Eu(btfa)31c] (btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1c = [(Ph)(Et3P)2PtâCâĄCâRâCâĄCâPt(Et3P)2(Ph)] (R = 2,2â-bipyridine-5,5â-diyl) has been synthesized by utilizing the N,N-donor sites of the organometallic chromophore. The complex was characterized by analytical and spectroscopic methods. Photophysical properties of the complex were analysed in detail using both steady-state and time-resolved emission and excitation spectroscopy. The optical absorption spectrum of the complex is dominated by the spin allowed ĎâĎ* transitions of the btfa and 1c units in the UV-visible region (200 â 418 nm) and thus is excitable over a wide range of wavelengths across the UV into the visible region of the electromagnetic spectrum. The complex displays typical red Eu(III) emission when excited at 345 nm. However, it also shows green emission when excited at 464 nm and, thus could be an interesting candidate for full colour display applications. The change in the colour could be a result of the high value of the energy back-transfer rate (6.73 105 sâ1) from the triplet state of the organometallic chromophore to the 5D1 state of Eu(III). Judd-Ofelt (J-O) intensity parameters ( and ), radiative (AR), non-radiative (AR) decay rates and intrinsic quantum yield ( ) have been calculated
Two is Better Than One? Investigating the Effect of Incorporating Re(CO)<sub>3</sub>Cl Side-Chains into Pt(II) Diynes and Polyynes
Pt(II) di-ynes and poly-ynes incorporating 5,5â- and 6,6â-disubstituted 2,2â-bipyridines were prepared following conventional Sonogashira and Hagihara dehydrohalogenation reaction protocols. Using Pt(II) dimers and polymers as a rigid-rod backbone, four new hetero-bimetallic compounds incorporating Re(CO)3Cl as a pendant functionality in the 2,2â-bipyridine core were obtained. The new hetero-bimetallic Pt-Re compounds were characterized by analytical and spectroscopic techniques. The solid state structures of a Re(I)-coordinated diterminal alkynyl ligand and a representative model compound were determined by single-crystal X-ray diffraction. Detailed photo-physical characterization of the hetero-bimetallic Pt(II) di-ynes and poly-ynes was carried out. We find that the incorporation of the Re(CO)3Cl pendant functionality in the 2,2â-bipyridine-containing main-chain Pt(II) di-ynes and poly-ynes has a synergistic effect on the optical properties, red shifting the absorption profile and introducing strong long-wavelength absorptions. The Re(I) moiety also introduces strong emission into the monomeric Pt(II) di-yne compounds, whereas this is suppressed in the poly-ynes. The extent of the synergy depends on the topology of the ligands. Computational modelling was performed to compare the energetic stabilities of the positional isomers and to understand the microscopic origin of the major optical absorptions. We find that 5,5â-disubstituted 2,2â-bipyridine systems are better candidates in terms of yield, photophysical properties and stability than their 6,6â-substituted counterparts. Overall, this work provides an additional synthetic route to control the photo-physical properties of metalla-ynes for a variety of optoelectronic applications
Salts of Lanthanide(III) Hexafluoroacetylacetonates [Ln = Sm(III), Eu(III) and Tb(III)] with Dipyridylammonium Cations: Synthesis, Characterization, Photophysical Properties and OLED Fabrication
A series of tetrakis lanthanide complexes with the general formula [Ln(hfaa) 4] -(DpaH) + [Ln = (Sm-1), (Eu-1) and (Tb-1)], hfaa = hexafluroacetylacetonate and Dpa â2,2â˛-dipyridylamine] has been synthesized by the reaction of LnCl 3, hfaa and Dpa in the presence of ammonia solution (25%). The complexes have been characterized by analytical and spectroscopic methods. The solution molecular structure of the complexes was elucidated by one- and two-dimensional NMR spectroscopy which shows that the DpaH + cation retains a close interaction with the lanthanide anion in solution. The crystal structure of Eu-1, determined by single crystal X-ray diffraction, confirms this intermolecular interaction in the solid-state through a NâHâŻO hydrogen bond of 2.187 Ă
. In the [Eu(hfaa) 4] - anion the EuO 8 coordination polyhedron has a distorted triangular dodecahedron geometry with approximate D 2d-symmetry around the metal centre. Photophysical, thermal, and electroluminescent properties of the complexes have been investigated. The Sm-1 and Eu-1 complexes displayed efficient typical red emission with a sizeable photoluminescence quantum yield (PLQY) while Tb-1 displayed near-white light emission. The complexes have been used as dopants to fabricate single- and double-emitting layer (EML) OLEDs through the thermal evaporation method. At the optimum doping concentration, double-EML Eu-1 based device displayed orange electroluminescence (EL) with a brightness (B) of 417 cd/m 2 and very low V turn-on = 3.4 V. Interestingly, the Sm-1 based single-EML device exhibited pure red emission with the Commission internationale de l'Êclairage [(CIE) x,y = 0.613, 0.321], which is rare. The Sm-1 based device performance [B = 145 cd/m 2, current efficiency (Ρ c) = 0.35 cd/A, power efficiency (Ρ p) = 0.15 lm/W with an external quantum efficiency (EQE) = 0.3% and V turn-on = 7.1 V] surpassed that of the only reported Sm-based single red-OLED (R-OLED). </p
Synthesis and Photophysical Properties of Ternary β-Diketonate Europium(III) Complexes Incorporating Bipyridine and its Derivatives
Two new octa-coordinated ternary europium(III) complexes of the type [Eu(btfa)3(Br2-bpy)] (Eu-1) and [Eu(btfa)3(PhE2-bpy)] (Eu-2) (where btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione, Br2-bpy = 5,5'-dibromo-2,2'-bipyridine, PhE2-bpy 5,5'-bis(phenylethynyl)-2,2'-bipyridine) together with a previously reported complex [Eu(btfa)3(bpy)] (Eu-3) have been synthesized. The complexes have been characterized by analytical and spectroscopic methods. The photophysical properties of the complexes have also been analyzed both experimentally and theoretically. The contribution of each ligand to the sensitized Eu(III) photoluminescence (PL) has been analyzed and is discussed. An energy transfer (ET) mechanism is proposed and discussed for the sensitized Eu(III) emission using experimental and theoretical data. The Eu(III) complex incorporating the parent bpy showed impressive performance as a double-emitting layer (EML) red organic light emitting diodes (R-OLEDs)
Two is Better Than One? Investigating the Effect of Incorporating Re(CO)<sub>3</sub>Cl Side-Chains into Pt(II) Diynes and Polyynes
Pt(II) di-ynes and poly-ynes incorporating 5,5â- and 6,6â-disubstituted 2,2â-bipyridines were prepared following conventional Sonogashira and Hagihara dehydrohalogenation reaction protocols. Using Pt(II) dimers and polymers as a rigid-rod backbone, four new hetero-bimetallic compounds incorporating Re(CO)3Cl as a pendant functionality in the 2,2â-bipyridine core were obtained. The new hetero-bimetallic Pt-Re compounds were characterized by analytical and spectroscopic techniques. The solid state structures of a Re(I)-coordinated diterminal alkynyl ligand and a representative model compound were determined by single-crystal X-ray diffraction. Detailed photo-physical characterization of the hetero-bimetallic Pt(II) di-ynes and poly-ynes was carried out. We find that the incorporation of the Re(CO)3Cl pendant functionality in the 2,2â-bipyridine-containing main-chain Pt(II) di-ynes and poly-ynes has a synergistic effect on the optical properties, red shifting the absorption profile and introducing strong long-wavelength absorptions. The Re(I) moiety also introduces strong emission into the monomeric Pt(II) di-yne compounds, whereas this is suppressed in the poly-ynes. The extent of the synergy depends on the topology of the ligands. Computational modelling was performed to compare the energetic stabilities of the positional isomers and to understand the microscopic origin of the major optical absorptions. We find that 5,5â-disubstituted 2,2â-bipyridine systems are better candidates in terms of yield, photophysical properties and stability than their 6,6â-substituted counterparts. Overall, this work provides an additional synthetic route to control the photo-physical properties of metalla-ynes for a variety of optoelectronic applications
Single component white-OLEDs derived from tris(β-diketonato) europium(iii) complexes bearing the large bite angle N^N 2-(4-thiazolyl)benzimidazole ligand
Two new organo-europium complexes (OEuCs) [Eu(tfac)3(TB-Im)] (Eu1) [Eu(hfac)3(TB-Im)] (Eu2) incorporating fluorinated (hexafluoroacetylacetone; Hhfaa) or hemi-fluorinated (trifluoroacetylacetone; Htfac) β-diketones together with the large bite angle N^N ligand (2-(4-thiazolyl)benzimidazole; TB-Im) have been synthesized and characterized. The structure of the complexes has been established by single crystal X-ray diffraction (SC-XRD) analysis and shows that the coordination sphere is composed of a EuO6N2 core (octacoordinated). Continuous shape measures (CShMs) revealed that the geometry around Eu(III) is trigonal dodecahedral with approximate D2d-symmetry. Efficient red emission is observed for both the complexes in solution with a fairly large photoluminescence quantum yield (PLQY (QLEu) = 39.00â47.00%). Furthermore, by utilizing the experimental photoluminescence (PL) data and theoretical modelling employing density functional theory (DFT) in conjunction with LUMPAC, energy transfer (ET) and back energy transfer rates were calculated, and an ET mechanism for the sensitized PL is proposed and discussed in detail. Finally, the complexes were used as an emitting layer (EML) to fabricate 20 organic light emitting diodes (OLEDs) by varying the doping concentration. Interestingly, both the complex-based OLEDs at 4 wt% doping concentration display white electroluminescence (EL) with the brightness (B) = 100.5â364.1 cd mâ2 at very low turn-on voltage (Vturn-on) = 3.9â4.6 V. The overall electroluminescence performance of Eu1 and Eu2 is higher than that of the reported europium based single component white-OLEDs
Bimetallic Pt(II)-bipyridyl-diacetylide/Ln(III) tris-diketonate adducts based on a combination of coordinate bonding and hydrogen bonding between the metal fragments: syntheses, structures and photophysical properties
The luminescent Pt(II) complex [Pt(4,4'-Bu-t(2)-bipy){CC-(5-pyrimidinyl)}(2)] (1) was prepared by coupling of [Pt(4,4'-Bu-t(2)-bipy)Cl-2] with 5-ethynyl-pyrimidine, and contains two pyrimidinyl units pendant from a Pt(H) bipyridyl diacetylide core; it shows luminescence at 520 nm which is typical of Pt(II) luminophores of this type. Reaction with [Ln(hfac)(3)(H2O)(2)] (hfac = anion of hexafluoroacetylacetone) affords as crystalline solids the compounds [1 center dot {Ln(hfac)(3)(H2O)}{Ln(hfac)(3)(H2O)(2)}] (Ln = Nd, Gd, Er, Yb), in which the {Ln(hfac)(3)(H2O)} unit is coordinated to one pyrimidine ring via an N atom, whereas the {Ln(hfac)(3)(H2O)(2)} unit is associated with two N atoms, one from each pyrimidine ring of 1, via N center dot center dot center dot HOH hydrogen-bonding interactions involving the coordinated water ligands on the lanthanide centre. Solution spectroscopic studies show that the luminescence of 1 is partly quenched on addition of [Ln(hfac)(3)(H2O)(2)] (Ln = Er, Nd) by formation of Pt(II)/Ln(III) adducts in which Pt(II)-> Ln(III) photoinduced energy-transfer occurs to the low-lying f-f levels of the Ln(Ill) centre. Significant quenching occurs with both Er(Ill) and Nd(III) because both have several f-f states which match well the (MLCT)-M-3 emission energy of 1. Time-resolved luminescence studies show that Pt(II)-Er(III) energy-transfer (7.0 x 10(7) M-1) is around three times faster than Pt(II)-> Nd(III) energy-transfer (approximate to 2 x 10(7) M-1) over the same distance because the luminescence spectrum of l overlaps better with the absorption spectrum of Er(111) than with Nd(III). In contrast Yb(111) causes no significant quenching of 1 because it has only a single f-f excited level which is a poor energy match for the Pt(II)-based excited state
Dicopper(I) Complexes Incorporating Acetylide-functionalized Pyridinyl-based Ligands::Synthesis, Structural and Photovoltaic Studies
Heteroaryl incorporated
acetylide-functionalized pyridinyl ligands (<b>L1âL6</b>) with the general formula Py-CîźC-Ar (Py = pyridine and Ar
= <i>thiophene-2-yl</i>, 2,2â˛<i>-bithiophene]-5-yl</i>, 2,2â˛<i>:5</i>â˛,2âł<i>-terthiophene]-5-yl</i>, <i>thienoÂ[2,3-<i>b</i>]Âthiophen-2-yl</i>, <i>quinoline-5-yl</i>, <i>benzoÂ[c]Â[1,2,5]Âthiadiazole-5-yl</i>) have been synthesized by Pd(0)/CuÂ(I)-catalyzed cross-coupling reaction
of 4-ethynylpyridine and the respective heteroaryl halide. Ligands <b>L1âL6</b> were isolated in respectable yields and characterized
by microanalysis, IR spectroscopy, <sup>1</sup>H NMR spectroscopy,
and ESI-MS mass spectrometry. A series of dinuclear CuÂ(I) complexes <b>1</b>â<b>10</b> have been synthesized by reacting <b>L1âL6</b> with CuI and triphenylphosphine (PPh<sub>3</sub>) (<b>R1</b>) or with an anchored phosphine derivative, 4-(diphenylphosphino)
benzoic acid (<b>R2</b>)/2-(diphenylphosphino)Âbenzenesulfonic
acid (<b>R3</b>), in a stoichiometric ratio. The complexes are
soluble in common organic solvents and have been characterized by
analytical, spectroscopic, and computational methods. Single-crystal
X-ray structure analysis confirmed rhomboid dimeric structures for
complexes <b>1</b>, <b>2</b>, <b>4</b>, and <b>5</b>, and a polymeric structure for <b>6</b>. Complexes <b>1</b>â<b>6</b> showed oxidation potential responses
close to 0.9 V vs Fc<sup>0/+</sup>, which were chemically irreversible
and are likely to be associated with multiple steps and core oxidation.
Preliminary photovoltaic (PV) results of these new materials indicated
moderate power conversion efficiency (PCE) in the range of 0.15â1.56%
in dye-sensitized solar cells (DSSCs). The highest PCE was achieved
with complex <b>10</b> bearing the sulfonic acid anchoring functionality