Publication: Taç eterli Ftalosiyanin ve metal koplekslerinin voltametrik incelenmesi
Abstract
Bu çalışmada, taç eterli serbest ftalosiyanin ( TCRH2Pc ), taç eterli bakır(II) ftalosiyanin ( TCRCuPc ) ve taç eterli molibdil (IV) ftalosiyanin ( TCRMoOPc ) komplekslerinin çeşitli çözücü ortamlarında ve civa damla elektrodu üzerindeki polarografik redüksiyonu incelendi. Yapılan tüm deneyler 25±1oC'de gerçekleştirildi. Referans elektrod olarak doymuş kalomel elektrod, taşıyıcı elektrolit olarak KNO3 kullanıldı. Polarogramlar Dimetilsulfoksit-Su ( DMSO-Su ), Tetrahidrofuran-Su ( THF-Su ) ve Dimetilformamid-Su ( DMF-Su ) çözücü ortamlarında ve değişik pH'larda çizildi. Söz konusu çözücü ortamlarında ve değişik pH'larda çizilen polarogramlarda TCRH2Pc kompleksine ait tek bir redüksiyon dalgası gözlenirken; TCRCuPc ve TCRMoOPc kompleksleri için ise iki ayrı redüksiyon dalgası gözlendi. Elde edilen akım-voltaj eğrilerinin logaritmik analizleri yapıldıktan sonra, çalışılan çözücü ortamlarındaki kinetik parametreler ( an ve kof,h ) hesaplandı. Yapılan çalışmalarda TCRH2Pc, TCRCuPc ve TCRMoOPc komplekslerinin çalışılan çözücü ortamlarında ve civa damla elektrodu üzerindeki redüksiyonlarının, difüzyon kontrollü ve irreversibil olduğu bulundu. Redüksiyon hız sabitleri incelendiğinde; genel olarak pH arttıkça, komplekslerin redüksiyon hızlarının azaldığı görüldü. TCRCuPc kompleksinin Dimetilsulfoksit-Su çözücü ortamındaki redüksiyonu Tetrahidrofuran-Su çözücü ortamına nazaran daha yavaş olarak gerçekleştiği anlaşıldı. TCRMoOPc kompleksinin Dimetilsulfoksit-Su çözücü ortamındaki redüksiyonu Dimetilformamid-Su çözücü ortamına nazaran daha yavaş olarak gerçekleştiği görüldü. Genel olarak pH arttıkça TCRCuPc ve TCRMoOPc komplekslerinin civa damla elektrodu üzerindeki redüksiyonuna ait yarım dalga potansiyellerinin daha negatif potansiyellere kaydığı görüldü. TCRCuPc kompleksine ait redüksiyon olayının DMSO-Su çözücü ortamında, THF-Su çözücü ortamına nazaran daha negatif potansiyellerde gerçekleştiği gözlendi. TCRMoOPc kompleksine ait redüksiyon olayının DMF-Su çözücü ortamında, DMSO-Su çözücü ortamına nazaran daha negatif potansiyellerde gerçekleştiği gözlendi.
In this study polarographic reduction of tetracrown metal-free phthalocyanine ( TCRH2Pc ), tetracrown copper(II) phthalocyanine ( TCRCuPc ) and tetracrown molybdenum(IV) oxide phthalocyanine ( TCRMoOPc ) complexes were examined in various solvent media on a dropping mercury electrode ( DME ). All measurements were carried out at 25±1oC. A saturated calomel electrode was employed as the reference electrode and KNO3 was the supporting electrolyte. Polarograms were recorded in the solvent media of dimethylsulphoxide-water (DMSO-H2O), tetrahydrofuran-water (THF-H2O ) and dimethylformamide-water ( DMF-H2O ) at different pH values. While only a single electrochemical reduction wave was observed for TCRH2Pc, both TCRCuPc and TCRMoOPc displayed two waves on the polarograms recorded in the related solvent media at different pH values. Kinetic parameters (an and kof,h) were determined by the logarithmic analysis of the current-voltage curves. As a result of the analysis electrochemical reductions of all complexes were found to be diffusion-controlled and irreversible in the given solvent media on a dropping mercury electrode ( DME ). The heterogeneous standart reduction rate constants ( kof,h ) showed that electrochemical reduction rates of complexes decrease with increasing pH. It was found that the reduction of TCRCuPc is slower in DMSO-H2O than in THF- H2O. Also the reduction of TCRMoOPc was found to occur more slowly in DMSO-H2O with respect to that in DMF-H2O. Generally the reduction half-wave potentials of the complexes were found to shift to more negative values with increasing pH. It was observed that the reduction of TCRCuPc occurs at more negative potentials in the solvent media of DMSO-H2O with respect to that in THF-H2O. On the other hand, the reduction of TCRMoOPc in DMF-H2O was observed to occur at more negative potentials than in DMSO-H2O.
In this study polarographic reduction of tetracrown metal-free phthalocyanine ( TCRH2Pc ), tetracrown copper(II) phthalocyanine ( TCRCuPc ) and tetracrown molybdenum(IV) oxide phthalocyanine ( TCRMoOPc ) complexes were examined in various solvent media on a dropping mercury electrode ( DME ). All measurements were carried out at 25±1oC. A saturated calomel electrode was employed as the reference electrode and KNO3 was the supporting electrolyte. Polarograms were recorded in the solvent media of dimethylsulphoxide-water (DMSO-H2O), tetrahydrofuran-water (THF-H2O ) and dimethylformamide-water ( DMF-H2O ) at different pH values. While only a single electrochemical reduction wave was observed for TCRH2Pc, both TCRCuPc and TCRMoOPc displayed two waves on the polarograms recorded in the related solvent media at different pH values. Kinetic parameters (an and kof,h) were determined by the logarithmic analysis of the current-voltage curves. As a result of the analysis electrochemical reductions of all complexes were found to be diffusion-controlled and irreversible in the given solvent media on a dropping mercury electrode ( DME ). The heterogeneous standart reduction rate constants ( kof,h ) showed that electrochemical reduction rates of complexes decrease with increasing pH. It was found that the reduction of TCRCuPc is slower in DMSO-H2O than in THF- H2O. Also the reduction of TCRMoOPc was found to occur more slowly in DMSO-H2O with respect to that in DMF-H2O. Generally the reduction half-wave potentials of the complexes were found to shift to more negative values with increasing pH. It was observed that the reduction of TCRCuPc occurs at more negative potentials in the solvent media of DMSO-H2O with respect to that in THF-H2O. On the other hand, the reduction of TCRMoOPc in DMF-H2O was observed to occur at more negative potentials than in DMSO-H2O.