Spectral characteristics of europium phthalocyaninates with different axial ligands

Europium (acetylacetonato)phthalocyanine Eu(acac)Pc and europium (oxyquinolinato)phthalocyanine Eu(q)Pc with different axial ligands have been synthesized and their photophysical characteristics (electronic absorption and photoluminescence spectra) have been studied. An energy level diagram of the complexes has been proposed. The influence of the axial ligand on the optical and luminescence characteristics of the complexes has been revealed.     

The formation of new adsorption centers on platinized SiO2 surfaces

Kinetic and spectral characteristics of luminescence and excitation of luminescence of magnesium phthalocyanine (MgPc) molecules adsorbed on silicon dioxide (SiO₂) are studied. They are found to be affected by finely divided platinum (Pt) present at the surface and hydration. The deposition of a Pt catalyst on SiO₂ leads to the formation of new centers. Adsorption of MgPc molecules at these centers increases the lifetime of excited states of the former. Luminescence of charge transfer complexes and the protonized form of phthalocyanine is detected at the platinized surface of silicon dioxide.     

Spectroscopy of polymorphic forms of Mg phthalocyanine

Some specific features of the absorption, luminescence, and internal photoelectric effect spectra of nanocrystals of Mg phthalocyanine of the β and X aggregate forms obtained by crystallization from molecular solutions of Mg phthalocyanine are revealed and studied. The complex structure of the spectra of the crystalline forms is attributed to the simultaneous presence of both crystalline phases and the molecular phase of Mg phthalocyanine in the samples. Comparison of the absorption and luminescence spectra is an effective diagnostic tool for optimization of the methods of preparation of single-phase Mg-phthalocyanine objects. Similar results were also observed in the spectroscopic study of other metal phthalocyanine derivatives.     

Influence of the molecular structure of copper phthalocyanines on their ordering in thin films and photoluminescence and absorption spectra

Thin films consisting of copper phthalocyanine (CuPc) molecules and copper phthalocyanine molecular complexes with different structures on glass and glass-ceramic substrates are studied using reflectance anisotropy, photoluminescence, and photoconductivity (constant photocurrent method) spectroscopies. It is established that, in the studied films, the CuPc molecules and CuPc molecules containing peripheral phthalimide substituents are located in planes virtually parallel to the surface of the substrate. In thin films consisting of μ-peroxo dimer complexes, the angle between the CuPc molecular planes and the surface of the substrate is close to 90°. The thin films formed by CuPc molecules containing peripheral phthalimide substituents are characterized by the highest luminescence intensity in the range of ～ 1.12 eV and the lowest absorption intensity in the range of energies less than the band gap. These properties are explained by the lower concentration of non-radiative recombination centers in the film.     

Interaction of indium metal with phthalocyanine molecules: Luminescence enhancement

Absorption and luminescence studies of phthalocyanine molecules coated onto thin, variable thickness, indium films showed a strong optical overlap of the metal and molecular resonances. Fluorescence from the phthalocyanine is increased by a factor of 30 due to excitation transfer from the indium particles. The enhancement of the luminescence due to optical coupling between metal particles and semiconductors has important implications in the development of efficient metal/semiconductor Schottky junction solar cells.     

Properties of uncharged water-soluble tetra(ω-methoxypolyethyleneoxy)phthalocyanine free base: Viable switching of the optical response by means of H3O+ ions

An uncharged water-soluble tetra (ω-methoxypolyethyleneoxy)phthalocyanine was characterized by MALDI-TOF mass spectrometry, UV–vis and luminescence measurements. The polyether substituents render water soluble this uncharged phthalocyanine. Relevant changes are observed in emission measurements upon protonation. The phthalocyanine free base and its protonated forms can be switched alternating H₃O⁺ and OH^? ions as inputs, being the intensity of the luminescence spectra the output. Binary codes 1 or 0 can be assigned to the high luminescent phthalocyanine free base state or to the low luminescent protonated state, respectively. The read-out procedure is fast and the system is reversible. In addition, the exploiting of the luminescent properties of the present water soluble phthalocyanine could be of relevance also for biological applications (photosensitizers for the photodynamic therapy).     

Effect of finely dispersed platinum on the structure of luminescence spectra of the adsorbates of magnesium phthalocyanine on silicon dioxide

The luminescence and excitation spectra and kinetic characteristics of the luminescence of the adsorbates of magnesium phthalocyanine (MgPhc) on SiO₂ and the effect on them of surface hydration and finely dispersed platinum are studied. It is found that a structure that improves hydration of the adsorbent surface appears on the platinized surface in the luminescence and excitation spectra. It is assumed that the spectral structure is due to the complexes of MgPhc formed with water molecules, the hydroxyl cover of the surface, and the surface centers of SiO₂ modified by a Pt-catalyst. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 552–555, July–August, 1999.     

Influence of nanoparticles and thin layers of gold, europium phthalocyanine, and erbium nanoparticles on the formation of luminescence spectra of structures with InGaN/GaN quantum wells

The influence of nanoparticles and thin layers of Au, Eu phthalocyanine, and Er nanoparticles on the formation of luminescence spectra of InGaN/GaN quantum-well structures has been investigated. It has been shown that the influence of localized plasmons on the generation of charge carriers is determined by the size of Au nanoparticles under the assumption that the interaction of plasmons with surface states of the structures plays a dominant role. The influence of Au nanoparticles on the formation of luminescence spectra of multiple quantum-well structures based on InGaN/GaN, unlike the case of Au layers, is determined by the indium concentration. The influence of Eu phthalocyanine films, which are deposited onto the surface of the studied structures, on their photoluminescence spectra is similar to the influence of doping of these structures with europium.     

Aggregation and photophysical properties of phthalocyanines in supramolecular complexes

The concentration dependence of the degree of association of zinc and aluminum phthalocyanines in supramolecular systems is determined. Complexes containing rare photoactive associates with an absorption maximum significantly shifted to longer wavelengths are obtained. The radiative lifetimes, extinction coefficients, and energy of HOMO-LUMO electronic transitions of isolated and associated metal phthalocyanine complexes are determined. It is demonstrated that the existence of the metal phthalocyanine largely in an aggregated state is characteristic of zinc phthalocyanine systems, while aluminum phthalocyanine, having an additional extraligand, chloride ion, is stabilized in the isolated state.     

Branching ratio and L2 + L3 intensities of 3d-transition metals in phthalocyanines and the amine complexes

L(2,3) inner-shell excitation spectra were obtained by electron energy-loss spectroscopy (EELS) for the divalent first transition series metals in phthalocyanine complexes (MPc) such as titanium oxide phthalocyanine (TiOPc), fluoro-chromium phthalocyanine (CrFPc), manganese phthalocyanine (MnPc), iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), nickel phthalocyanine (NiPc) and copper phthalocyanine (CuPc). It was found that the value of normalized total intensity of I(L2 + L3) was nearly proportional to the formal electron vacancies of each 3d-state, and the values of the branching ratio, I(L3)/I((L2 + L3), represented a high-spin-state rather than low-spin-state for MnPc, FePc and NiPc. EELS was also applied to charge-transfer complexes of FePc with an amine such as pyridine or gamma-picoline. It was concluded that their I(L2 + L3) intensity of Fe showed the decrease in vacancies of 3d-states on the formation of the charge-transfer complex with these amines, which suggests some electron transfer from the amine to Fe in phthalocyanine. The EELS study provides beneficial information for investigating the electronic states of the specific metal sites in organic materials.     

Investigation of the ionization of phthalocyanines by luminescence spectra

On the basis of absorption and luminescence spectra and polarization measurements on phthalocyanine solutions in acid medium, it has been established that successive protonation probably occurs at the bridge nitrogen atoms; the protonated forms are asymmetric in acid medium.     

UV-visible spectral study on the stability of lead phthalocyanine complexes

UV-visible electronic spectral study has been done on lead phthalocyanine (PbPc), lead tetranitro phthalocyanine (PbTNP) and lead tetraamino phthalocyanine (PbTAP) in dimethyl sulphoxide (DMSO) and H₂SO₄ media. Metal free phthalocyanine (H₂Pc) is insoluble in DMSO and soluble in conc. H₂SO₄. The study has been extended to H₂Pc to compare the stability of phthalocyanine structure with the PbPc complexes in H₂SO₄ medium. PbPc complexes are stable in DMSO, and all the complexes are more stable in 36 N H₂SO₄ than in 30 N and 28 N H₂SO₄ media. Further, complete demetallation and degradation of the phthalocyanine structure have been observed for all the PbPc complexes in 36 N H₂SO₄ medium within a week's time. The stability of these complexes is compared with H₂Pc in H₂SO₄ medium. The decomposition reactions in H₂SO₄ media for H₂Pc, PbPc, PbTNP and PbTAP are followed spectrophotometrically and rate constants were calculated. The decomposition reactions were found to follow the first-order kinetics with respect to the concentration of their respective phthalocyanine derivatives.     

Luminescence quenching of complexes immobilized on a cation-exchange membrane by molecular oxygen

A technique is developed and luminescence quenching of complexes immobilized on cation-exchange membranes is considered. The mechanism of the luminescence quenching of the complexes by molecular oxygen is discussed.     

Isomerism in dihalogenometal porphyrins and phthalocyanines: a theoretical study of dihalogenotitanium complexes

Trans- and cis-isomers of dihalogenotitanium porphyrins and phthalocyanines, TiX₂P and TiX₂Pc (X = F, Cl, Br, I; P = porphyrin, Pc = phthalocyanine), which provide a good example of isomerism in dihalogenometal porphyrin and phthalocyanine complexes, have been studied by density functional theory calculations using the B3LYP hybrid method and triple-ζ valence basis sets. All eight complexes have two isomers, trans-isomer of D _4h symmetry and cis-isomer of C _2v symmetry with halogen atoms located in the same plane with two meso-atoms. In the case of difluorotitanium phthalocyanine the cis-isomer is preferable in the gas phase, while in all porphyrin complexes and remaining three phthalocyanine complexes the trans-isomers have lower energies than cis-isomers. Electrostatic repulsion between the halogen atoms and central nitrogen atoms of the macroheterocycle seems to play the major role in determining the preference of the trans- or cis-isomer.     

带-NH2的嘧啶环对钌配合物与DNA相互作用的瞬态发光特性的影响

采用时间分辨的发光光谱技术,分别测量了两种新合成的钌配合物[Ru(bpy)2 (dpbpd(NH2)2)]2 和[Ru(phen)2(dpbpd(NH2)2)]2 与小牛胸腺脱氧核糖核酸(ctDNA)相互作用时的瞬态发光动力学过程,并与以往对[Ru(phen)2dppz]2 等的研究结果进行对比,从而研究带-NH2的嘧啶环对配合物与DNA作用动力学过程的影响.结果表明:这两种含有带-NH2的嘧啶环的钌配合物与DNA相互作用时的发光按双指数规律衰减,发光寿命为几十纳秒,比dppz类钌配合物与DNA作用时的发光衰变寿命(几百纳秒)小一个数量级.归因于嘧啶环上的N和-NH2可能与水分子、DNA的碱基对或磷酸骨架形成氢键,从而加快激发态的无辐射弛豫,削弱发射光强,缩短发光寿命.该结论为进一步研究配合物分子与DNA的相互作用的机理提供了一定的依据.     

Spectral-luminescence study of the formation of QD-sulfophthalocyanine molecule complexes in an aqueous solution

The spectral-luminescence manifestations of the formation of quantum dot (QD)-phthalocyanine complexes as a result of electrostatic interaction have been investigated. Effective QD luminescence quenching has been found in complexes of this type. The luminescence of the molecules associated in complexes with QDs is also partially quenched. A mathematical model of the formation of QD-organic molecule complexes is proposed.     

两亲性金属酞菁的催化性能研究

采用耗氧法研究了4种金属酞菁配合物[α-四(对羧基苯氧基)金属酞菁(Zn,Co)、β-四(对羧基苯氧基)金属酞菁(Zn,Co)]对0.1mol.L-1亚硫酸钠的催化氧化性能,考察了配合物中心金属和取代基的位置对催化活性的影响。研究结果表明中心离子相同时,β位四取代(对羧基苯氧基)金属酞菁的催化活性优于α位;取代基位置相同时,酞菁钴的催化氧化性优于酞菁锌。且β-四(对羧基苯氧基)酞菁钴的浓度为1.00×10-4mol.L-1时,对亚硫酸钠的催化氧化性能最高。     

Formation of QD-porphyrin molecule complexes in aqueous solutions

The spectral and luminescent manifestations of the electrostatic formation of quantum dot (QD)-porphyrin complexes are studied. The QD luminescence in these complexes is found to be efficiently quenched. The luminescence of molecules complexed with QDs is also partially quenched. The luminescence excitation spectra of porphyrin molecules associated with QDs exhibit a contribution of the QD absorption spectrum, which indicates that energy is transferred from QDs to porphyrin. The efficiency of the nonradiative resonant energy transfer from a QD to a porphyrin molecule is estimated. The observed experimental data agree well with a proposed model of formation of complexes of the QD-organic molecule type.     

Effect of vapors of water and organic solvents on the luminescence of cation-exchange membranes immobilized with cyclometalated Pt(II) complexes

The luminescence quenching of cation-exchange membranes immobilized with cyclometalated Pt(II) complexes by vapors of water and some organic solvents (methanol, ethanol, isopropanol, n-butanol, acetonitrile, and acetone) is studied. The mechanism of the luminescence quenching of complexes is discussed.     

Observation of luminescence from bound multiexciton complexes in gallium doped germanium

Spectrally resolved luminescence associated with the decay of bound multiexciton complexes in optically excited Ge:Ga is observed. This is the first reported observation of multiexciton complexes in p-type germanium. The observed spectra are consistent with the shell model for bound multiexciton complexes.No-phonon, TA, LA, and TO phonon assisted luminescence are observed. From these spectra, the energies of the LA, TA, and TO phonons in Ge:Ga are determined.