Spectroscopic and electrochemical properties of dichlorobenzoquinoline complexes of Au(III), Pt(II), and Pd(II)

The dichloride complexes of Au(III), Pt(II), and Pd(II) with 2,2′-biquinoline are obtained and characterized by ¹H NMR spectroscopy, electronic spectroscopy, and cyclic voltammetry. It is shown that the low efficiency of the metal-ligand (2,2′-biquinoline) interaction leads to almost the same positions of the intraligand bands in the absorption and fluorescence spectra of the complexes and to the closeness of their reduction potentials.     

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.     

Spectral and luminescent properties of mono- and binuclear cyclometalated complexes of Pd(II) and Pt(II) based on 4,6-diphenylpyrimidine with ethylenediamine and orthophenanthroline

The [M(N_^∧N)(Hdphpm)]ClO₄ and [(M(N_^∧N))₂(μ-dphpm)](ClO₄)₂ complexes (M = Pd(II), Pt(II); (N_^∧N) is ethylenediamine (En) and orthophenanthroline (Phen); Hdphpm^? and dphpm^2? are the mono- and bisdeprotonated forms of 4,6-diphenylpyrimidine) are obtained and characterized by ¹H NMR spectroscopy and electronic absorption and emission spectroscopy. The magnetic nonequivalence of protons of (N_^∧N) ligands is explained by a difference in the trans-effect of the carbanion and pyrimidine parts of the cyclometalated ligand. The long-wavelength absorption bands and the vibrationally structured luminescence bands of ethylenediamine complexes are attributed to optical transitions in the {M(Hdphpm)} and {M₂(μ-dphpm)} metal-complex fragments. The complexes with orthophenanthroline exhibit two low-energy optical transitions involving π* orbitals localized on the cyclometalated and chelating ligands; the difference in their energies depends on the metal and is much larger for Pt(II) than for Pd(II). It is found that the replacement of Pd(II) by Pt(II) in the [(M(phen))₂(μ-dphpm)]²⁺ complexes changes the direction of the photoexcitation energy degradation due to the energy transfer between the {M₂(μ-dphpm)} bridging fragment and peripheral phenanthroline ligands.     

Spectral and luminescent investigations of ammonia cyclometalated Pt(II) complexes

A method of synthesis of ammonia cyclometalated Pt(II) complexes [Pt(NH₃)₂C∧N]ClO₄, where C∧N is 2-phenylpyridinate or 2-phenylbenzothiazole ion, is developed. The electronic absorption and emission properties of the complexes are studied. It is found that the state responsible for intense long-lived luminescence is the excited charge-transfer state of the ³(d-π*) type, the π* orbital being localized at the corresponding cyclometalating ligand. Formation of platinum blue is observed in air-saturated aqueous solutions of ammonia cyclometalated complexes.     

Specific features of spectra of cyclometalated Pt(II) and Pd(II) complexes in polyvinyl alcohol

The absorption spectra and luminescent properties of ethylenediamine complexes of Pt(II) and Pd(II) with cyclometalating ligands (2-phenylpyridinate and 2-2’-thienyl)pyridinate) in polyvinyl alcohol are studied. It is ascertained that, upon an increase in temperature, the nonradiative degradation of energy in palladium complexes occurs according to the mechanism of strong vibronic coupling, whereas platinum complexes show weak vibronic coupling.     

Effect of the nature of heterocyclic ligands on spectral and luminescent properties of Pt(II) and Pd(II) complexes

Optics and Spectroscopy - The spectral and luminescent properties of Pt(II) and Pd(II) complexes with heterocyclic imine ligands—1-phenylpyrazolate, 2-phenylpyridinate, and...     

Mixed-ligand complexes of Pt(II) and Pd(II) with 2-phenylbenzothiazole

The mixed-ligand cyclometalated [M(Bt)(μ-Cl)]₂ and [(M(N∧N))(Bt)]⁺ complexes (M = Pd(II), Pt(II); Bt^? is the deprotonated form of 2-phenylbenzothiazole; and ( N∧N) is ethylenediamine (En) and orthophenanthroline (Phen)) are studied and described by ¹H NMR spectroscopy, electronic absorption and emission spectroscopy, and voltammetry. The one-electron reduction of complexes is attributed to the electron transfer to the π * orbitals of both diimine and cyclometalated ligands. The long-wavelength absorption bands and vibrationally structured luminescence bands are assigned to optical transitions that are localized mainly on the M(Bt) metal-complex fragment.     

过渡金属Mn（Ⅲ）,Fe（Ⅲ）,Rh（Ⅱ）和Pd（Ⅱ）卟啉配合物的共振拉…

讨论了金属离子Ｍｎ（Ⅲ），Ｆｅ（Ⅲ），Ｒｈ（Ⅲ）和Ｐｄ（Ⅱ）原卟啉Ⅸ－二甲酯（ＰＰ）和四苯基卟啉（ＴＰＰ）配合物及Ｐｄ（Ⅱ）间氯四苯基卟啉（ＴＰＰｍ－ｃｌ）配合物的共振拉曼光谱。利用金属离子外层ｄ电子与卟啉环的作用，解释了配合物结构灵敏带的变化规律，同时讨论了不同卟啉及卟啉环上取代基团对结构灵敏带的影响。     

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.     

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.     

Spectral and luminescent properties of mixed-ligand complexes of palladium(II) and 7,8-benzoquinoline

Spectral and luminescent properties of mixed-ligand palladium(II) complexes—[PdBhq(μ-Cl)]₂, [PdBhqEn]ClO₄, and [PdBhqBpy]ClO₄, where Bhq stands for the 7,8-benzoquinoline ion—were studied. The absorption spectra of these complexes in the 25000–40000-cm^? range were found to have a number of spin-allowed transitions of the ₁(π-π*) type involving orbitals of the 7,8-benzoquinoline ligand. The luminescent characteristics of these compounds in a glass-forming matrix at 77 K are primarily determined by the participation of the ₃(π-π*) states of the 7,8-benzoquinoline ligand.     

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.     

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.     

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.     

Synthesis and spectral-luminescent properties of Pt(II) and Pd(II) complexes with 2,3,5,6-tetrakis(2-pyridyl)pyrazine

A method for synthesis of seven Pt(II) and Pd(II) complexes with 2,3,5,6-tetrakis(2-yridyl)pyrazine is developed. The spectral-luminescent properties of the complexes in the solid phase and solution are studied at 77 and 298 K. The types of excited electronic states responsible for the luminescence and nonradiative excitation energy relaxation in the complexes are determined.     

Effect of acidification on spectral parameters of solutions of mixed-ligand cyclometalated Pt(II) and Pd(II) complexes

The effect of acidification of water-ethanol solutions of cyclometalated Pt(II) and Pd(II) complexes with ethylenediamine and cyanide ligands is studied. It is found that, unlike the ethylenediamine complexes, the cyclometalated complexes with cyanide ligands are unstable and undergo irreversible decyclometalation.     

Synthesis and luminescent properties of Cu(II), Zn(II) polymeric complexes with electron- and hole-transporting groups

A novel ligand 3,6-bis(1,10-phenathroline-[5,6-d] imidazole-2-yl)carbazole (Bpic) containing hole- and electron-transporting groups was firstly designed. Its polymeric complexes of Bpic with Cu(∥), Zn(∥) were successfully synthesized. The UV-vis absorption, fluorescence spectra and thermal properties of these complexes were investigated. At room temperature, complexes 2, 3 emit blue luminescence from 445 to 485 nm in DMSO solution, and emit green/yellow and orange luminescence from 523 to 585 nm in solid state. In comparison with the free ligand, the polymeric complexes exhibit a bathochromic shift. It can be assigned to the extended π-conjugation of the complexes.     

Specific features of spectra of cyclometalated Pt(II) complexes in polystyrene and polymethyl methacrylate

A method of obtaining polystyrene and polymethyl methacrylate films containing cyclometalated complexes of Pt(II) with 2-phenylpyridinate and 2-(2′-thienyl)pyridinate is described. The spectral and luminescent properties of these films at 77 and 298 K are studied. It is ascertained that the Pt(II) complexes in the films are in a monomolecular state.     

Highly luminescent europium(III) complexes with naphtoiltrifluoroacetone and dimethyl sulphoxide

The synthesis, luminescence properties, experimental determination and theoretical calculation of the emission quantum yield of Eu(NTA)₃.2L complexes, where NTA is naphtoiltri-fluroacetone and L denotes H₂O or DMSO (dimethyl sulphoxide), were reported. The compounds were characterized by elemental analysis (carbon, hydrogen and europium), thermal analysis, UV-visible absorption and photoluminescence spectroscopies. The experimental quantum yields were determined based on a method previously proposed by Bril and collaborators. The Eu(NTA)₃.2DMSO compound shows a high value for the Ω₂ intensity parameter (35.8 × 10^?20 cm²), reflecting the hypersensitive nature of the ⁵D₀ → ⁷F₂ transition and indicating that the lanthanide ion is in a highly polarizable chemical environment. The experimental quantum yield measured for that compound, 0.75, is one of the highest so far reported for solid-state europium complexes. The theoretical calculations of the quantum yield were carried out by solving an appropriate set of rate equations and by using empirical spectroscopic parameters and energy transfer rates. The theoretical results agree well with the experimental data for both complexes. The photostability of Eu(NTA)₃.2DMSO at 358K was evaluated in order to verify whether this complex can be applied as a phosphor for blue light emitting devices.