取代基对双酞菁铥LB膜及光谱特性的影响

采用紫外-可见吸收光谱的方法研究了三种稀土夹心双酞菁铥化合物在溶液和LB膜中的聚集性和光谱特性。实验结果表明三种稀土双酞菁化合物在氯仿溶液中形成了H-聚集体,但当浓度比较低时,溶液中表现出单体的吸收。取代基OC₈H₁₇的加入使氯仿溶液中双酞菁铥化合物的聚集性减弱,而且使得吸收峰发生红移,对吸收峰的强度也有较大的影响,造成了Soret吸收带的分裂。另外,取代基OC₈H₁₇对LB膜中双酞菁分子的存在状态有较大的影响,在LB膜中,TmPc₂和TmPcPc*分子以H-聚集体的形式存在,而TmPc*₂分子以T-聚集体的形式存在。形成LB膜后,由于双酞菁分子之间排列紧密,相互作用加强,使得薄膜中分子聚集体的吸收峰相对于溶液中聚集体的吸收峰发生了一定的红移,薄膜中分子排列方向的不同对吸收光谱也有一定的影响。     

Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines

A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir–Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc₂) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV–vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc₂:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir–Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc₂ and SAuNPs inserted in the films and limits of detection in the range of 10⁻⁷ mol L⁻¹ were attained.     

Thin‐Film Voltammetry of a Lutetium Bisphthalocyanine at Ionic Liquid|Water Interface

At room temperature, tetraoctylphosphonium bromide is a viscous ionic liquid, this gel‐like organic phase can be cast over a basal‐plane graphite electrode (BPGE). Cyclic voltammetry at such a modified electrode, in contact with an aqueous solution have revealed one reversible oxidation and five reversible reduction steps for a Lu^III bisphthalocyanine dissolved in the ionic liquid film, a proof that the highly reactive reduced species were protected from interaction with water in this highly lipophilic phase. It has also been shown that the redox properties are influenced by the ions in the aqueous phase, a property which has been attributed to ion‐pairing effects; obviously, the ion transfers at the organic|aqueous interface has been ignored. Electrochemistry of Lu(III)[(_tBu)₄Pc]₂ (cyclic voltammetry and square wave voltammetry) under similar conditions shows that the nature and concentration of the anion in the aqueous solution in contact with the ionic liquid film influences the potential of the electrode reaction. This can be attributed to variations of the interfacial potential and also because the organic phase is an anion exchanger. Moreover, SWV experiments suggest that the rate of the overall reaction varies with the nature and concentration of the anion of the aqueous electrolyte, which implies that the ion transfer through the organic|aqueous interface is slower than the electron exchange rate of the molecule at the surface of graphite.     

Synthesis, characterization, and electrochemical, and electrical measurements of novel 4,4′-isopropylidendioxydiphenyl bridged bis and cofacial bis-metallophthalocyanines (Zn, Co)

4,4′-Isopropylidendioxydiphenyl bridged bis-metallophthalocyanines Zn(II) (5) and Co(II) (6) were synthesized from the compound 4,4′-isopropylidendioxydiphthalonitrile (3) and 4,5-bis(hexylthio)phthalonitrile (4). The new cofacial bis-phthalocyanines Zn(II) (7) and Co(II) (8) were synthesized from the corresponding 3 which can be obtained by the reaction of 4,4′-isopropylidendiphenol (1) with 4-nitrophthalonitrile (2). These complexes have been characterized by elemental analysis, UV/Vis, FT-IR, ¹H NMR and MALDI-TOF mass spectroscopies. The electrochemical properties of the complexes were examined by cyclic voltammetry, differential pulse voltammetry and controlled potential coulometry in nonaqueous media. Electrochemical results showed that while there is not any considerable interaction between the two phthalocyanine rings in bisphthalocyanine complexes 5 and 6, the splitting of the molecular orbitals occurs as a result of the strong interaction between the phthalocyanine rings in cofacial complexes 7 and 8.

Measurements of capacitance showed a well defined decrease with increasing frequency and an increase with increasing temperature at lower frequencies.     

Reverse saturable absorption of lanthanide bisphthalocyanines and their application for optical switches

We have investigated reverse saturable absorption (RSA) of tetrakis(2,9,16,23-tert-butyllanthanide bisphthalocyanines)(M(TBPc)₂, M=Lu, Dy, Tb) with Z-scan technique. Furthermore, lanthanide bisphthalocyanines have also been utilized for optical switches based on their RSA performance. However, the experimental results reveal that the performances of RSA and optical switches for M(TBPc)₂ (M=Lu, Dy, Tb) are poorer than that of tetrakis(2,9,16,23-tert-butylcopper phthalocyanines) (Cu(TBPc)) due to strong intramolecular π-π interaction between the two Pc rings.     

Array of biosensors for discrimination of grapes according to grape variety,vintage and ripeness

A bioelectronic tongue based on nanostructured biosensors specific for the simultaneous detection of sugars and phenols has been developed. The array combined oxidases and dehydrogenases immobilized on a lipidic layer prepared using the Langmuir-Blodgett technique where Glucose oxidase, d-Fructose dehydrogenase, Tyrosinase or Laccase were imbibed. A phthalocyanine was co-immobilized in the sensing layer and used as electron mediator. The array thus formed has been used to analyze grapes and provides global information about the samples while providing specific information about their phenolic and their sugar content. Using Principal Component Analysis (PCA) the array of voltammetric biosensors has been successfully used to discriminate musts prepared from different varieties of grapes (Tempranillo, Garnacha, Cabernet-Sauvignon, Prieto Picudo and Mencía). Differences could be also detected between grapes of the same variety and cultivar harvested in two successive vintages (2012 and 2013).     

Synthesis,characterization, and electrochemical,spectroelectrochemical and electrical measurements of novel ball-type four 1,1′-methylenedinaphthalen-2-ol bridged metal-free,zinc(II) and cobalt(II), and metal-free clamshell phthalocyanines

The new ball-type bisphthalocyanines [metal-free 6, Zn(II) 7 and Co(II) 8] were synthesized from the corresponding 4,4′-[1,1′-methylenebis(naphthalene-2,1-diyl)]bis(oxy)di-phthalonitrile 4, which can be obtained from the reaction of 4-nitrophthalonitrile (2) with 1,1′-methylenedinaphthalen-2-ol 3. A novel clamshell type bisphthalocyanine 5 was synthesized from compound 4 and 4,5-bis(hexylthio)phthalonitrile 1. The novel compounds have been characterized by elemental analysis, UV/Vis, IR, ¹H NMR and MALDI-TOF Mass spectroscopies. The electrochemical and spectroelectrochemical measurements showed the formation of various mixed-valence oxidation and reduction species, due to the strong intramolecular interactions between the two phthalocyanine rings, especially in the ball-type phthalocyanines. The conduction properties of the compounds have been examined by d.c. and impedance spectroscopy measurements as function of temperature and frequency. D.c. conductivity, measured between 290 and 480 K, is thermally activated with the activation energy ranging between 0.62 and 0.84 eV. The a.c. results gave a power law behaviour, σ_a.c. = A(T)ω^s, in which the frequency exponent s decreases with temperature for 6, 7 and 8. The bulk resistance of the samples was derived from complex impedance spectra. It was found that the bulk resistance shows a typical negative temperature coefficient of resistance, decreasing with a rise in temperature, like that of a semiconductor.     

Synthesis,characterization, and electrochemical and electrical properties of novel mononuclear and binuclear ball-type Zn(II) and Co(II) phthalocyanines substituted with 1a,8b-dihydronaphtho[b]naphthofuro-[3,2-d]furan-7,10-diyl

New mononuclear phthalocyanines [Zn(II) 4 and Co(II) 6] and ball-type bisphthalocyanines [Zn(II) 5 and Co(II) 7] have been synthesized from the corresponding compound 3, which can be obtained from the reaction of 4-nitrophthalonitrile 1 with 1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]furan-7,10-diol 2. The novel compounds have been characterized by elemental analysis, UV/Vis, IR, ¹H NMR and MASS spectroscopy. The electrochemical measurements show the formation of various mixed-valence oxidized and reduced species, due to intramolecular interactions between the two phthalocyanine units in the ball-type binuclear metallophthalocyanines. Detailed studies of the effect of temperature on the electronic properties of the films were investigated by dc conductivity and impedance spectroscopy techniques at temperatures between 290 K and 460 K. Thermally activated conductivity dependence on temperature was observed from the dc measurements. The ac results give a power law behavior in which the frequency exponent decreases with temperature. It was observed that the impedance spectra consist of a curved line at low temperature. These curved lines transform into a full semicircle with increasing temperature.     

THE ELECTROCHROMIC BEHAVIOUR OF LANTHANIDE BISPHTHALOCYANINES: THE ANOMALOUS NATURE OF THE GREEN LUTETIUM SPECIES

Abstract

Double integration of the electron paramagnetic resonance signal associated with the green form of lutetium bisphthalocyanine in dimethylformamide solution indicates it is a minor species. Magnetic circular dichroism spectroscopy strongly suggests the chromophore is not a radical. These findings are in keeping with the recently resurrected hypothesis [Daniels et al., J. Coord. Chem. (1993) 28, 23–31] that the “electrochromic” color changes observed in lanthanide bisphthalocyanine chemistry are acid-base in nature and not due to oxidation-reduction processes involving the phthalocyanine rings.