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 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.     

Spectral and luminescent properties of ammonia cyclopalladated complexes

The synthesis of ammonia cyclometalated palladium(II) complexes [Pd(NH₃)₂C^N]ClO₄ (C^N is the deprotonated form of 2-phenylpyridine, 2-(para-tolyl)pyridine, 7,8-benzo(h)quinoline, 2,6-diphenylpyridine, and 4-phenylpyrimidine) is developed. The IR and electronic absorption and emission spectra of these complexes are studied. It is found that the ammine and analogous ethylenediamine cyclometalated Pd(II) complexes have similar spectral and luminescent properties and the same nature of the electronically excited ³(π-π*)-type state responsible for the long-lived luminescence, the π and π* orbitals being localized on the corresponding cyclometalating ligand. The efficient temperature quenching of the luminescence of Pd(II) complexes at room temperature is assigned to the thermally activated population of metal-centered electronically excited states with subsequent nonradiative deactivation.     

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 properties of metal complexes of 3,4,9,10-perylenetetracarboxylic acid

The spectral and luminescent properties of solutions of perylenetetracarboxylic acid (PTCA), its ionic forms, and its aggregates and complexes with rare-earth ions are studied. The mechanisms of the fluorescence quenching of PTCA upon complex formation are discussed. It is concluded that the complex formation in such systems is of the intrasphere type. Comparison between the measured intracomplex-deactivation energies of the fluorescing states of PTCA and pyrene tetrasulfonate indicates that the metal-ligand interaction is more efficient in carboxylic complexes.     

Spectral and luminescent specific features of phenylpyridine ethylenediamine complexes of Pt(II), Pd(II), and Au(III)

The orbital nature and basic photophysical parameters of phenylpyridine ethylenediamine complexes of Pt(II), Pd(II), and Au(III) are found from the comparative analysis of absorption and luminescence spectra and the luminescence decay kinetics. The orbital nature and properties of the lowest excited states responsible for luminescence are shown to depend on the type of metal and the energy of singlet-triplet splitting.     

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.     

Spectral and luminescent properties of coumarins in nanoparticles from metal ion complexes

We have studied the absorption spectra of complexes of trivalent ions Y, La, Lu, and Sc with p-phenylbenzoyltrifluoroacetone that were introduced into a solution of 90% H₂O + 10% iso-C₃H₇OH in the absence and presence of either 1,10-phenanthroline or coumarins 6, 7, or 30. We have shown that these coumarins, as well as phenanthroline, are synergistic bidentate ligands that are incorporated into complexes up to concentrations comparable with concentrations of complexes and that stabilize them in the solution. We have studied the dependences of the fluorescence (cofluorescence) intensity (I _cofl) of the coumarins on their concentration in nanoparticles from the complexes mentioned above. We have shown that, in nanoparticles from complexes of Y(III), Ln(III), and Sc(III), I _cofl of coumarin 30 at high concentrations is higher than I _cofl of coumarins 6 and 7. In addition, up to concentrations of coumarin 30 comparable with the concentration of complexes in nanoparticles, there is no concentration quenching of its fluorescence. For coumarins 6 and 7, which are prone to association in the solution under study, the process of incorporating coumarins into complexes competes with their association, which leads to concentration quenching and changes in the shape of their cofluorescence spectra.     

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...     

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.     

Peculiarities of crystal structures and magnetic properties of Cu(II) and Ni(II) mixed-ligand complexes on the 1,3-dithiole-2-thione-4,5-dithiolate basis

Mixed-ligand Cu(II) and Ni(II) complexes, [Cu(dmit)(bpy)]₂ (I), [Ni(dmit)(phen)₂] (II) and [Ni(dmit)(phen)₂]·CH₂Cl₂ (III) (dmit=1.3-dithiole-2-thione-4.5-dithiolate, phen=1.10-phenantroline, bpy=2.2′-bipyridine) have been prepared by ligand exchange between phen or bpy and (Bu₄N)₂[M(dmit)₂] (M=Ni, Cu) and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray analysis and by investigation of magnetic and resonance properties. In complex I, the monomeric units form dimers in a head-to-tail arrangement by weak coordination bonds between copper and dithiolate sulfur atoms and π–π interactions between dmit and bpy from neighboring monomers. Dimers in I are further extended into chains by weak Cu–S(thione) contacts. In crystal packing of complex II and III, there exists a weak π–π interaction between two parallel phen molecules of the adjacent complexes. As a consequence, the magnetic and resonance characteristics of copper complex may be described in approximation of exchange-coupled pairs of Cu²⁺ ions with ion spin S=1/2. The nickel complexes are described by isotropic exchange model for single-site spin S=1.     

Spectral and luminescent properties of triareno-substituted tetraazachlorins

Spectral and luminescent properties of recently synthesized compounds of a class of hydroporphyrazines, triarenotetraazachlorins, in polyvinylbutyral films have been studied. Fluorescence lifetimes have been measured in film and in solution. Fluorescence quantum yields have been estimated. It is found that annelation of aromatic rings to the pyrrole rings of the tetraazachlorin macrocycle enhances fluorescence. Quantum-chemical optimization of the geometrical structures of the free-base 1,2-trinaphthotetraazachlorins has been carried out using the AM1 method. The two isomers were shown to be highly non-planar. Spectral hole burning in absorption bands of both this compound and free-base 2,3-trinaphthotetraazachlorin in polyvinylbutyral films at 5 K in the wavelength region of titanium-sapphire laser radiation is possible and is ascribed to NH-photoisomerization. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 376–386, May–June, 2009.     

Spectral and luminescent properties of jet-cooled dinaphthofuran

The fluorescence and fluorescence excitation spectra of jet-cooled dinaphtho[2,1-b:1′,2′-d]furan (dinaphthofuran) molecules, as well as their complexation with inert gases Ar, Kr, and Xe, are studied. The indicatrices of the degree of polarization of fluorescence of dinaphthofuran molecules upon excitation of the electronic transitions S ₀?S ₁ and S ₀?S ₂ are calculated as functions of the intramolecular orientation of the transition dipole moments. The fluorescence polarization spectrum is measured under excitation within the rotational contour of the line of the purely electronic transition v ₀ ⁰ = 29 294 cm^?1. In contrast to complex planar molecules, the S ₀?S ₂ fluorescence excitation spectrum of dinaphthofuran is found to be continuous, with the Q branch of the rotational contour being absent. The fluorescence excitation spectra of van der Waals complexes of dinaphthofuran with inert gases exhibit multiplet lines, which is associated with the helical structure of the molecules studied.     

EPR study on the chemistry and photochemistry of copper(II) dithiocarbamate mixed-ligand complexes

The thermal and photochemical reactions of the 1∶1 mixed-ligand complexes Cu(dtc)X (X=Cl^?, NO₃ ^?, ClO₄ ^?) have been studied on the ground of their EPR spectra in acetone, CCl₄/i-PrOH (1∶1), and CHCl₃/i-PrOH (1∶1) solutions. The study allows us to get some insight into the behaviour of the mixed-ligand Cu^II(dtc)X complexes with respect to the acceptor properties of halocarbons. In CCl₄/i-PrOH (1∶1) both Cu^II(dtc)⁺…NO₃ ^? and Cu^II(dtc)⁺…ClO₄ ^? undergo thermal reactions within their donor-acceptor complexes with CCl₄ to yield Cu(dtc)Cl. On the time scale of the experiment the reaction does not occur thermally in CHCl₃/i-PrOH (1∶1), but occurs photochemically in both halocarbon/i-PrOH (1∶1) systems in which Cu(dtc)Cl is further photolyzed to CuCl₂. Continuous photolysis of the title compounds in acetone simply bleaches the solution without any intermediate EPR or light absorption.     

Photo- and electroluminescence of mixed-ligand Eu(III) complexes

Spectral and luminescent properties of mixed-ligand Eu(III) complexes were studied in solutions and in polyvinylcarbazole (PVC) thin films. Trends in their variations were found depending on the complex structure and excitation mode. The electroluminescence was observed in ITO/PEDOT/Eu complex:PVC/CaMg/Al devices. Their current-voltage and voltage-brightness characteristics were investigated.     

Spectral and luminescent properties of 1-substituted naphthalenes

Spectral, luminescent, and proton-acceptor properties of 1-substituted naphthalenes containing a CO group were investigated. Photophysical rate constants and quantum yields of fluorescence were calculated. The ability of the carbonyl oxygen to form a hydrogen bond was estimated for 1-naphthaldehyde, methyl 1-naphthoate, and 1-naphthyl acetate.     

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 and luminescent properties of chlorine-substituted derivatives of aniline

The effect of the position and number of chlorine atoms on spectral, geometrical, and photophysical characteristics of individual molecules of chlorine-substituted derivatives of aniline is studied by electronic spectroscopy and quantum-chemical calculations. It is shown that the long-wavelength absorption band of these compounds is formed by several electronic transitions of different nature and intensity. It is ascertained that electronically excited π σ* states involve C-Cl bonds, which weaken upon excitation. According to quantumchemical calculations, the quenching of fluorescence of chlorine-substituted derivatives of aniline is determined by the fact that intersystem crossing is more effective than radiative decay of the S ₁ state.