Tatiana V. Dubinina

MCD spectroscopy and TD-DFT calculations of a naphthalene-ring-bridged coplanar binuclear phthalocyanine dimer

Magnetic circular dichroism (MCD) spectroscopy and TD-DFT calculations are used to analyze the electronic structure and optical properties of an alkyl-substituted naphthalene-ring-bridged coplanar binuclear phthalocyanine dimer. An analysis of the MCD spectrum of the naphthalene-ring-bridged dimer relative to those of benzene-bridged compounds reported previously, demonstrates that there is a significantly weaker interaction between the two phthalocyanine rings. TD-DFT results obtained using the B3LYP functional with 6–31G basis sets were found to be problematic. Closer agreement with the experimental data is obtained when the CAM-B3LYP functional is used instead. The naphthalene-ring-bridged compound is found to be unsuitable for use as a photosensitizer for the formation of singlet oxygen, because the ΦT values are negligible.

Electrochemical and spectroelectrochemical behavior of planar binuclear naphthalocyanines

The electrochemical and spectroelectrochemical behavior of two planar binuclear naphthalocyanines containing benzene and naphthalene π-conjugated bridges was investigated for the first time. Their intense absorption in the near infrared region was observed even in a low polar solvent such as o-dichlorobenzene after electrochemical reduction at a potential of -0.4 V vs. SCE, which was not enough to reduce the complexes into their first reduction state. These data and EPR studies allow us to conclude that the electrochemically generated form is the true neutral form of the synthesized compounds whereas the suppression of the near-infrared bands is a result of the presence of their cation radicals as one-electron oxidized forms.

A novel hybrid blend based on phenoxy-substituted boron subphthalocyanine for organic photodetectors

Phenoxy-substituted boron subphthalocyanine, blended with a conductive polymer MEH-PPV, is presented as a photoresistive organic material. Using an easily accessible drop casting technique, the blend produces a thin-layer organic photoresistor with a photoresistive ratio of ~2–12. Variations in the blend composition and morphology are shown to change the transport properties of the material. The photoelectrochemical characteristics of the photoresistor are discussed in terms of impedance spectroscopy and the morphology of the material is analyzed using confocal fluorescent microscopy. The device developed is a daylight detector.

Novel phenoxy-substituted subphthalocyanines possessing an extended π-system: synthesis and property investigation

Novel phenoxy-substituted subnaphthalocyanine and binuclear subphthalocyanine were synthesized. Structures of the target compounds were established by 1H NMR spectroscopy and high resolution MALDI-TOF/TOF mass spectrometry. Electronic absorption spectra of the synthesized complexes revealed the bathochromic shift of absorption maximum to the near IR spectral region as compared with subphthalocyanine.

Phenoxy-substituted boron subphthalocyanine as a ionophore of ion-selective electrodes

Phenoxy-substituted boron subphthalocyanine was synthesized and studied as an ionophore of plasticized polyvinyl chloride membranes of ion-selective electrodes. The electrodes exhibit reversible response to dobutamine, demonstrating the cation function, as well as reversible response to the salicylate anion. The effects of concentration of the ionophore (0.2–5 wt %) and ionic components (sodium tetraphenylborate, TPhBNa, and tributylhexadecylphosphonium bromide, TBGDPBr), including ionic liquids (ILs), such as diphenylbutylethylphosphonium bis(triflyl)imide, diphenylbutylethylphosphonium hexafluorophosphate, and 1,3-dihexadecylimidazolium chloride, as well as plasticizers, such as ortho-nitrophenyloctyl ether and diethyl sebacate, on the electrochemical characteristics of membranes were studied. For the electrode containing 2% of the phenoxy-substituted boron subphthalocyanine in dobutamine and salicylate solutions, the slopes of the electrode function were 36 ± 1 mV/dec and–46 ± 3 mV/dec and the limits of detection (LODs) were 4 × 10–5 M and 3 × 10–4 M, respectively. The addition of an ionic liquid containing the diphenylbutylethylphosphonium cation and the bis(triflyl)imide and hexaflurophosphate anions to the membrane composition had no effect on the response of membrane electrodes to both dobutamine and salicylate. The use of phenoxy-substituted boron subphthalocyanine in an amount of 2% and the TPhBNa additive significantly improved sensor characteristics: the slope of the electrode function (S) for the dobutamine-selective electrode was (54 ± 1) mV/dec and LOD was 1 × 10–5 M. Dobutamine can be determined in the presence of dopamine, adrenalin, and glucose. Electrodes based on 2% phenoxy-substituted boron subphthalocyanine and 0.5% (C16H33)2ImCl, or TBGDPBr in salicylate solutions demonstrate the slope of the electrode function close to the theoretical one and a low limit of detection: S = (–59 ± 1) mV/dec, LOD = 2 × 10–5 M and S = (–57 ± 1) mV/dec, LOD = 4 × 10–5 M, respectively. The anti-Hofmeister selectivity of sensors was observed. The electrode based on phenoxy-substituted boron subphthalocyanine and (C16H33)2ImCl was used for the assay of acetylsalicylic acid in the drug Cardiomagnyl.

Impact of scaling to the resistive switching effect in organic polymer – based structures

Abstract The resistive switching effect has been studied in a set of organic polymer - based structures of a different composition and size scale from macro to micro. It is shown that scaling down reduces both the threshold switching voltage Vth and the respective effective electric field Eth. Furthermore, introduction of metal micro particles into a macro scale polymer matrix provides the same effect. Therefore the metal particle incorporation may be regarded as an alternative method of effective scaling, depending on an application. Switching speed of less than 15 ns, threshold voltage Vth ~ (2 – 25) V, 105 cycle endurance, no significant moisture dependence and high retention time 3.5 months for scaled down samples aswell as for metal doped macro samples have been demonstrated. These characteristics are suitable for constructing memory devices. The switching effect mechanisms are discussed.

Resonant plasmon-stimulated nonlinear absorption in three-level systems.

Mechanisms of resonant nonlinear absorption in the hybrid exciton-plasmon systems based on gold nanoparticles and macroheterocyclical compounds are presented. We used novel substituted subphthalocyanines (SubPc) with 14 π-electronic system as powerful excitonic 3 – level systems, and 50 nm gold nanoparticles (AuNp) as plasmonic structures. We succeeded to define mechanisms of resonant nonlinearities and to show that local field factor (LFF) and Purcell factor (PF) lead to dramatic enhancement in SubPc nonlinearity. We suggest a theoretical model which describes exciton-plasmon interaction of porphyrin/phthalocyanine related compounds with gold nanoparticles in the resonant high power laser field.

In situ impedance spectroscopy of filament formation by resistive switches in polymer based structures

It is shown that the impedance spectroscopy allows identification of the resistive switching mechanisms in complex composite structures. This statement was demonstrated on an example of organic based sandwich structures with a modified polymer matrix as an active element. The impedance spectroscopy scanning was performed for a series of intermediate states formed within the switching process. Analysis of the experimentally obtained impedance spectra shows that the electron transport is provided by delocalized charge carriers and proceeds via conducting filaments formed in a highly resistive matrix. The filament configuration changes during the switching. With the shift from isolating to conducting states, single isolated filaments are reorganized into a branched network.

Strong saturable-absorption effect in subphthalocyanines caused by plasmonic nanoparticles

Nonlinear optical properties of subphthalocyanines coupled with gold nanoparticles have been studied. We have found out many-fold enhancement in the saturable-absorption effect which originated from the strong near-field and great increase in the decay rate of excited states. Such plasmon-induced phenomenon gives the unique opportunity to reduce saturation intensity and boost absorption modulation depth of organic saturable absorbers.