Optical and electrochemical characteristics of ethylenediamine complexes of Pt(II) and Ir(III) with metalated 2-phenyl- and 2-naphthylbenzothiazole

The cyclometalated complexes [Pt(С^N)En]PF₆ and [Ir(C^N)₂En]PF₆ ((C^N)^– are deprotonated forms of 2-phenylbenzothiazole or 2-naphthylbenzothiazole and En is ethylenediamine) are studied by ¹Н NMR, IR, electronic absorption, and emission spectroscopy, as well as by voltammetry. Metalation of heterocyclic ligands leads to the formation of five-membered {M(C^N)} cycles in the composition of squareplanar Pt(II) complexes and octahedral Ir(III) complexes of the cis-С,С structure. A bathochromic shift of the metal-to-cyclometalated ligand charge transfer bands and a decrease in the potential difference between the single-electron waves of metal-centered oxidation and ligand-centered reduction of complexes upon substitution of 2-phenylbenzothiazole by 2-naphthylbenzothiazole and of Pt(II) by Ir(II) are shown. The phosphorescence of complexes in the visible region is assigned to the radiative transition from the metal-modified intraligand electronic excited state.     

Theoretical study of Ir(III) complexes with cyclometalated alkenylquinoline ligands

Recently, it was reported that cyclometalated iridium(III) complexes of 2-((E)-2-phenyl-1-ethenyl)quinoline (PEQ) and 1-((E)-2-phenyl-1-ethenyl)isoquinoline (PEIQ) emitted saturated red light with high quantum efficiency and brightness. However, the energy difference between specific wavelengths due to the metal-to-ligand charge transfer (³MLCT) absorption and emission spectra showed rather large Stokes shifts, which originated at the predominant ³(π–π¹) ligand-based emission. In this paper, it is shown that these complexes are consistent with predominant ³(π–π¹) ligand-based emission. To develop the predominant ³MLCT emission of Ir complexes for a highly efficient phosphorescent complex suitable for red OLED devices, proper ligands having a highest occupied molecular orbital (HOMO) energy level similar to that of 2-phenylpyridine (ppy) ligand were designed to lead to strong mixing between π-orbitals of ligands and the 5d orbital of the centric iridium atom. In order to decrease the HOMO energy level and the lowest an occupied molecular orbital (LUMO) level simultaneously to maintain the same HOMO–LUMO energy gap, an electron accepting group such as F or CF₃ was introduced. By such manipulation of ligands in Ir complexes, it was theoretically possible to change the origin of emission in Ir complex from the predominant ligand-centered ³(π–π¹) excited state to the predominant ³MLCT excited state.     

Optical properties of cyclometalated Pd(II) and Rh(III) complexes based on 2-(4-biphenylyl)-6-phenylbenzoxazole luminophore with ethylenediamine

Using the methods of electronic absorption and emission spectroscopy, we have studied the optical properties of cyclometalated [Pd(C??N)En]CH₃COO and [Rh(C??N)₂En]Cl complexes of 2-(4-biphenylyl)-6-phenylbenzoxazole luminophore with ethylenediamine. We have shown that, along with a bathochromic shift of intraligand spin-allowed ??-??* optical transitions by 1000?C1800 cm^?1, complexes are characterized by the occurrence of long-wavelength bands of a mixed nature (intraligand-metal-ligand charge transfer) in the range of 369??392 nm and by competing intraligand fluorescence (419?C423 nm) and phosphorescence (511?C532 nm) processes under low-temperature (77 K) photoexcitation.     

Spectral,luminescent, and electrochemical properties of cyclometalated complexes of Rh(III) based on 1-phenylpyrazole with ethylenediamine and heterocyclic diimines

A series of [Rh(ppz)₂(N^N)]⁺ complexes (ppz^? is the deprotonated form of 1-phenylpyrazole and (N^N) is ethylenediamine, 2,2′-bipyridyl, 1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 2,2′-biquinoline) is obtained and characterized by ¹H NMR spectroscopy, electronic absorption and emission spectroscopy, and cyclic voltamperometry. A 0.75-V anodic shift of the ligand-centered reduction potentials of complexes compared to free heterocyclic (N^N) ligands is observed. The vibrationally structured luminescence spectra of complexes are attributed to intraligand spin-forbidden optical transitions localized on the {Rh(N^N)} metal-complex fragments.     

Spectral properties of 2-phenylpyridinate complexes of Au(III) with diimine ligands

The synthesis, identification, and optical spectra of 2-phenylpyridinate complexes of Au(III) with diimine ligands (2,2′-bipyridyl and 6,7-dimethyl-2,3-di(2-pyridyl) quinoxaline) are described. A difference in the nature of the energetically lowest electronically excited states responsible for the luminescence is established.     

Spectral and luminescent properties of new Pt(II) complexes with bis(salicylidene)ethylenediamine ligands

The results of synthesis of new Pt(II) complexes with N,N′-ethylene-bis(3-methoxysalicylideneiminate) and N,N′-2,3-dimethylbutane-2,3-diyl-bis(3-methoxysalicylideneiminate) ligands and their investigation by X-ray photoelectron spectroscopy and UV-visible absorption and emission spectroscopy are discussed. The degradation channels of excited electronic states of the complexes are determined.     

Synthesis and characterization of blue phosphorescent cyclometalated Ir(III) complexes containing 2-(imidazol-2-yl)pyridine as ancillary ligand

Four new blue phosphorescent iridium complexes containing 2-(fluoro substituted phenyl)pyridine as the cyclometalated ligands and 2-(imidazol-2-yl)pyridine as an ancillary ligand have been synthesized and characterized. The complexes have the general structure (C^N)₂Ir(pym), where C^N are cyclometalating ligands (e.g., 2-(2,4-difluorophenyl)pyridine (24f₂ppyH), 2-(3,4-difluorophenyl)pyridine (34f₂ppyH), 2-(3,5-difluorophenyl)pyridine (35f₂ppyH), and 2-(3,4,5-trifluorophenyl)pyridine (345f₃ppyH)), pym is 2-(imidazol-2-yl)pyridine (pymH). The absorption, emission, and cyclic voltammetry of the complexes were systematically investigated. The (46f₂ppy)₂Ir(pym) has been characterized using X-ray crystallography and the electronic ground state calculated using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) consists of a mixture of pym ligand (83.7%) and Ir orbitals (12.1%), while the lowest occupied molecular orbital (LUMO) is mostly on f₂ppy ligands (93.4%). By replacing the ancillary ligand pic with pym can finely tune emission of the iridium complexes, showing blue luminescence at a wavelength of 467-491 nm at room temperature in CH₂Cl₂.     

Synthesis,Optical Investigation and Biological Properties of Europium(III) Complexes with 2-(4-Chlorophenyl)-1-(2-Hydroxy-4-Methoxyphenyl)Ethan-1-one and Ancillary Ligands

Synthesis and photoluminescence behaviour of six novel europium complexes with novel β-hydroxyketone ligand, 2-(4-chlorophenyl)-1-(2-hydroxy-4-methoxyphenyl)ethan-1-one (CHME) and 2,2′-bipyridine (bipy) or neocuproine (neo) or 1,10-phenanthroline (phen) or 5,6-dimethyl-1,10-phenanthroline (dmphen) or bathophenanthroline (bathophen) were reported in solid state. The free ligand CHME and europium complexes, Eu(CHME)₃.2H₂O [1] Eu(CHME)₃.bipy [2], Eu(CHME)₃.neo [3], Eu(CHME)₃.phen [4], Eu(CHME)₃.dmphen [5] and Eu(CHME)₃.bathophen [6]were characterized by elemental analysis, FT-IR and ¹H-NMR. The photoluminescence emission spectra exhibited four characteristic peaks arising from the ⁵D₀ → ⁷F_J (J = 1–4) transitions of the europium ion in the solid state on monitoring excitation at λ_ex = 395 nm. The luminescence decay curves of these europium complexes possess single exponential behaviour indicating the presence of a single luminescent species and having only one site symmetry in the complexes. The luminescence quantum efficiency (η) and the experimental intensity parameters, Ω ₂ and Ω ₄ of europium complexes have also been calculated on the basis of emission spectra and luminescence decay curves. In addition, the antimicrobial and antioxidant activities were also studied of the investigated complexes.     

On a series of Ir(III) complexes with various numbers of fluorine atoms

In this paper, a series of acetylacetonate derived ligands with various numbers of fluorine atoms, as well as their corresponding Ir(III) complexes, are fabricated and studied. We investigate their single crystal structure, thermal stability, electrochemical property and photophysical performance of these Ir(III) complexes in detail. The effect of fluorine substituent effect on these Ir(III) complexes is also investigated. It is found that the introduction of fluorine atoms into acetylacetonate derived ligand has slim effect on emissive energy and absorption character due to the small contribution of acetylacetonate derived ligand to frontier molecular orbitals. But the introduction of fluorine atoms can improve emissive characters and thermal stability of Ir(III) complexes obviously, including spectral blue shift, excited state lifetime decrease and proper thermal stability. On the other hand excess fluorine atoms compromise above parameters on the contrary.     

Optical, spectroscopic, and electrochemical properties of cyclometalated complexes of platinum metals based on 2-tolylpyridine and benzo[h]quinoline in ethylenediamine

Cyclometalated [M(C∧N)En]PF₆ (M = Pd(II), Pt(II)) and [M(C∧N)₂En]PF₆ (M = Rh(III), Ir(III)) complexes ((C∧N)^? corresponds to the deprotonated forms of 2-tolylpyridine and benzo[h]quinoline, and En is ethylenediamine) are studied by ¹H NMR spectroscopy, electronic absorption and emission spectroscopy, and voltammetry. Metalation of heterocyclic ligands leads to the formation of five-membered {M(C∧N)} cycles in the composition of square planar and octahedral complexes of the cis-C,C structure. Correlation of the energy positions of the long-wavelength metal-to-ligand charge-transfer absorption bands with the difference between the potentials of one-electron waves of metal-centered oxidation and ligand-centered reduction of complexes is shown. The phosphorescence of the complexes in the visible region of 469–524 nm is attributed to the radiative transition from the metal-modified intraligand excited state. The temperature quenching of the phosphorescence of complexes is attributed to the thermally activated population of metal-centered electronically excited states with subsequent nonradiative deactivation.     

2-(2-喹啉偶氮)-4-甲基-1,3-苯二酚光度法测定铜的研究

合成了新试剂 2 - (2 -喹啉偶氮 ) - 4-甲基 - 1,3-苯二酚 (QAMDHB) ,并研究了其与铜的显色反应 ,在 p H=2 .2的磷酸 -磷酸二氢钾缓冲介质中 ,溴化十六烷基三甲基胺 (CTMAB)存在下 ,QAMDHB与铜反应生成 2∶ 1稳定络合物 ,λmax=5 5 0 nm,ε=4 .84× 10 4L· mol-1· cm-1。铜含量在 0— 2 0μg/ 2 5 m L范围内符合比耳定律 ,方法用于环境水样中铜含量的测定 ,结果令人满意     

2-(2-喹啉偶氮)-4-甲基-1,3-二羟基苯分光光度法测定钒

在 p H为 3.5的柠檬酸 -氢氧化钠缓冲介质中 ,溴化十六烷基三甲基铵 (CTMAB)存在下 ,新试剂 2 -(2 -喹啉偶氮 ) - 4-甲基 - 1,3-二羟基苯 (QAMDHB)与钒发生显色反应 ,生成 2∶ 1稳定络合物 ,最大吸收波长为 5 5 2 nm,摩尔吸光系数 ε=8.0 5× 10 4L· mol-1· cm-1,钒含量在 0— 0 .6 μg/ m L内符合比耳定律。用于几种合金样品中钒的分析 ,结果令人满意。     

Effect of electric fields on photoluminescence of 4-(dicyanomethylene)-2-methyl- 6-(p-dimethylaminostyryl)-4H-pyran

Electric-field-induced photoluminescent variation has been observed from the red-emitting dopant, 4-(di cyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). The layered structure of Al/tris-(8-hydroxyquinoline) aluminum (Alq)/DCM-doped Alq (Alq:DCM)/indium tin oxide studied, exhibits relatively enhanced red emission when a voltage is applied such that the electric field runs directly from the Alq:DCM layer to the Alq layer, and relatively enhanced green emission in the opposite direction of the field . This phenomenon is attributed to field-enhanced aggregation and permeation of DCM molecules due to the polarity of the molecule. PACS 78.55.Kz; 68.55.Ln; 85.60.Jb; 78.66.Qn; 78.20.Jq     

Polyethylene glycol (PEG-400) promoted one-pot,five-component synthesis of (E)-ethyl2-(2-((E)-2-(1-(4-methyl-2-(phenylamino)thiazol-5yl)ethylidene)hydrazinyl)-4-oxothiazol-5(4H)-ylidene)acetates

Molecular Diversity - A facile, inexpensive and eco-friendly synthesis of functionalised...     

New heteroleptic cyclometalated iridium(III) complexes containing 2-(2′,4′-difluorophenyl)-4-methylpyridine for organic light-emitting diode applications

Two phosphorescent iridium(III) complexes (dfpmpy)₂Ir(ppc) and (dfpmpy)₂Ir(prz) [dfpmpy=2-(2′,4′-difluorophenyl)-4-methylpyridine, ppc=pipecolinate, prz=2-pyrazine carboxylate] were synthesized from the reaction of the chloro-bridged dimeric complex [(dfpmpy)₂Ir(μ-Cl)]₂ and the ancillary ligand. Their structures and photoluminescence properties were investigated and device performances for application in organic light-emitting diodes (OLEDs) were studied. The complexes adopt a distorted, octahedral geometry around the iridium metal, exhibiting cis C-C and trans N-N arrangements. The photoluminescent (PL) properties reveal that (dfpmpy)₂Ir(ppc) emits in the blue-green region (λ_max=497 nm), whereas (dfpmpy)₂Ir(prz) shows red phosphorescence (λ_max=543 nm) in the film state (5% wt. doped in PMMA). The (dfpmpy)₂Ir(ppc)- and (dfpmpy)₂Ir(prz)-based OLEDs exhibited sky-blue and greenish-yellow electroluminescence with similar current-voltage characteristics, repectively. Maximum current efficiency of (dfpmpy)₂Ir(ppc) and (dfpmpy)₂Ir(prz) were 4.4 and 7.4 cd/A, respectively. Maximum luminance values were approximately 10,000 cd/m² for the both compounds.     

(2-(4-甲基-2-羟基苯基)苯并噻唑)锌的分子结构和光谱学性能

合成并研究了(2-(4-甲基-2-羟基苯基)苯并噻唑)锌(Zn(4-MeBTZ)2)的分子结构、热稳定性和光谱学特性.Zn(4-MeBTZ)2的单晶数据如下:三斜晶系,P-1空间群,晶胞参数为α=8.989 9(11)(A)b=12.161 7(15)(A),c=12.8719(16)(A),α=63.492(2)°,...     

Optical and electrochemical properties of cyclometalated Pd(II) and Pt(II) complexes with a metal-metal chemical bond

Cyclometalated [M(C^N)(μ-(N-S))]₂ complexes ((M = Pd(II), Pt(II)), (C^N)^? are the deprotonated forms of 2-tolylpyridine and benzo[h]quinoline, and (N-S)^? are pyridine-2-thiolate and benzothiazole-2-thiolate ions) are studied by ¹H NMR, IR, electronic-absorption, and emission spectroscopy, as well as by voltammetry. It is shown that the formation of the metal-metal chemical bond and the σ _dz2 ^* orbital as a HOMO of complexes leads to the long-wavelength spin-allowed (410–512 nm) and spin-forbidden (595–673 nm) optical transitions σ _dz2 ^* ?π _(C^N) ^* in the absorption and phosphorescence spectra, as well as to the two-electron and successive one-electron oxidation with the formation of binuclear Pt(III) and Pd(III) complexes. The substitution of Pt(II) by Pd(II) is characterized by hypso- and bathochromic shifts of the spin-allowed and forbidden σ _dz2 ^* ?π _(C^N) ^* optical transitions in the absorption and phosphorescence spectra of complexes, by phosphorescence quenching of Pd(II) complexes in liquid solutions, and by an anodic shift of the oxidation potential of Pd(II) complexes compared with Pt(II) complexes.     

NIR-luminescence from ternary lanthanide [Ho, Pr and Tm] complexes with 1-(2-naphthyl)-4,4,4-trifluoro-1,3-butanedionate

The ligand 1-(2-naphthyl)-4,4,4-trifluoro-1,3-butanedionate (Htfnd) has been employed to synthesize six novel ternary-lanthanide complexes in which the synergic ligands were 1,10-phenanthroline-5,6-dione (dione) and 4,5-diazafluoren-9-one (dafone), respectively. Two series of complexes Ln(tfnd)₃dione and Ln(tfnd)₃dafone (Ln=Ho, Pr, Tm) were obtained. These complexes were characterized by elemental analysis, Fourier Transform Infrared spectra and diffused reflectance. After ligand-mediated excitation, Ln(tfnd)₃dione and Ln(tfnd)₃dafone all show the characteristic NIR luminescence of the corresponding Ln³⁺ ions (Ln=Ho, Pr, Tm). This can be attributed to the efficient energy transfer from ligands to central Ln³⁺ ions, via an antenna effect. The indirect energy transfer in the complexes has been investigated and the differences in the luminescence intensity between Ln(tfnd)₃dione and Ln(tfnd)₃dafone were discussed in detail. The excellent luminescent performances enable these NIR-luminescent complexes to have potential applications in optical amplification operating at 1300 or 1500 nm.     

Intermolecular interaction and a concentration-quenching mechanism of phosphorescent Ir(III) complexes in a solid film

Solid-state self-quenching processes of highly efficient Ir(III) phosphorescent emitters are investigated by the measurement of thin film photoluminescence quantum efficiency and transient lifetime as a function of doping concentration in a host matrix. The radiative decay rate constant is found to be independent from the average distance between dopant molecules (R), and the concentration-quenching rate constant is shown to be dependent on R(-6). The quenching dependence on R strongly suggests that luminescent concentration quenching in a phosphorescent Ir(III) complex:host film is controlled by dipole-dipole deactivating interactions as described by the F?rster energy transfer model.