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Ceyhan T.,Gulhane Medical Academy GATA | Altindal A.,Marmara University | Ozkaya A.R.,Marmara University | Salih B.,Hacettepe University | Bekarolu O.,Technical University of Istanbul
Dalton Transactions | Year: 2010

The phthalodinitrile derivative 3 was prepared by the reaction of 1,4-dithioerythritol 1 and 4-nitrophthalonitrile 2 in dry DMF as the solvent in the presence of K 2CO 3 as the base by the method of nucleophilic substitution of an activated nitro group in an aromatic ring. The template reaction of compound 3 with the corresponding metal salts gave the novel binuclear MPcs of ball-type (M = Zn 4, Co 5, Cu 6) and their water soluble phthalocyanines 7-9 were obtained from refluxing a suspension of the compounds bearing eight OH side groups, in aqueous NaOH (%30) solution. Newly synthesized compounds were characterized by elemental analysis, UV/VIS, IR, MALDI TOF mass and 1H-NMR spectroscopy techniques. The electronic spectra exhibit an intense π→π* transition of characteristic Q and B bands of the phthalocyanine core. The electrochemical measurements showed the formation of various mixed-valence oxidation and reduction species of 4 and 6 due to weak intramolecular interactions between the two MPc units. Complex 5 displayed a much higher catalytic activity than those of 4 and 6. It was found that oxygen reduction on the 5-based catalyst occurs through a direct 4-electron transfer pathway with a high water selectivity. However, the overpotential for oxygen reduction is high, probably due to a long distance between the two CoPc units in 5. A.c. and d.c. conductivity measurements were performed as a function of temperature (300-543 K) and frequency (40-10 5 Hz). It was found from d.c. measurements that the values of the pre-exponential factor σ 0 for the investigated samples are in the interval from 1.36 × 10 -3 to 6.20 × 10 2 Ω -1 cm -1, inferring that the conduction occurs most probably by hopping between the localized states in band tails. Based on the existing theory of a.c. conduction, it has been concluded that for the low frequency region the dominant conduction mechanism is multihopping at high temperatures (>390 K) whereas for the high frequency region the correlated barrier hopping model is the dominant mechanism. The sensing properties of the films for CO 2 gas were also investigated. © 2010 The Royal Society of Chemistry.

Ozdag M.A.,Ankara University | Ceyhan T.,Gulhane Medical Academy GATA | Unver H.,Ankara University | Elmali A.,Ankara University | Bekaroglu O.,Technical University of Istanbul
Optics Communications | Year: 2010

The nonlinear absorption and optical limiting (OL) performance of a supramolecular hexa-phthalocyaninato-hexazinc (II) with hexylthio substituents in solution and in the solid-state have been described using the open-aperture Z-scan technique. The measurements were performed using collimated 4 ns pulses generated from a frequency-doubled Nd:YAG laser at 532 nm wavelength. The results indicated that OL performance of the investigated compound in the polymeric film is much better compared to properties in solution. With the excellent combination of OL parameters the investigated compound in the solid-state is a candidate for the use as optical limiter. © 2009 Elsevier B.V. All rights reserved.

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