Mehmet Yıldırım

Synthesis and characterizations of poly(ether)/poly(phenol)s including azomethine coupled benzothiazole side chains: the effect of reaction conditions on the structure, optical, electrochemical, electrical and thermal properties

A new Schiff base, 4-((6-ethoxybenzothiazole-2-ylimino)methyl)benzene-1,2-diol (3,4-HBAEBT) was synthesized by the condensation reaction of 3,4-dihydroxybenzaldehyde (3,4-HBA) and 2-amino-6-ethoxybenzothiazole. The Schiff base, then, was converted to its polymer derivatives by oxidative polycondensation reaction in both organic (P-1) and aqueous alkaline medium (P-2). Spectral observations indicated different structural properties for each polymerization condition. Organic and aqueous alkaline medium produced poly(ether) and poly(phenol) structures, respectively. The obtained polymers were separately studied with respect to optical, electrochemical, electrical and thermal properties. With exception of thermal degradation behaviors, the other investigated properties as well as morphological characteristics of both polymers were considerably different. In the fluorescence measurements a solvatochromic effect was recorded and the emission colors of the polymers could be changed as turquoise-green by solvent change.

Biosynthesis and characterization of organosoluble conjugated poly(2-aminofluorene) with the pyrazine bridged.

In this paper, the results on horseradish peroxidase (HRP)-catalyzed oxidative polymerization of amine-functionalized fluorene monomer, 2-amino fluorene (AF), are reported. The resulting polymer exhibits an exciting molecular structure and spectral properties. FT-IR and NMR studies show that the two fluorene units come together by forming an intermediate six-membered pyrazine ring and these formed dimeric units are linked to the each other through C-C couplings to produce fully conjugated polymer structure (AFP). Further characterizations were performed by means of GPC, TGA, DSC, SEM, CV (cyclic voltammetry), fluorescence analyses, and solubility tests. Optical band gaps of this electroactive polymer was found to be 2.60 eV. AFP emits red light and its emission maxima is drastically affected by the kind of the solvents used. In addition, obtained polymer is soluble in common polar and apolar organic solvents.

Synthesis and Spectrophotometric PH Sensing Applications of Poly-2-[4-(diethylaminophenyl)imino]-5-nitro-phenol and its Schiff Base Monomer for Two Different PH Ranges

Poly-2-[4-(diethylaminophenyl)imino]-5-nitro-phenol (PEAPINP) and 2-[4-(diethylaminophenyl)imino]-5-nitro-phenol (EAPINP) were prepared as new pH sensors. Spectrophotometric and spectrofluorometric response of the novel sensors in various pH values were investigated. EAPINP has the ability to respond linearly at alkaline PH values, 8 to 9, and can be utilized in absorption and wavelength radiometric methods. PEAPINP has the ability to respond linearly at lower pH values, 6 to 7, and can be used as an alternative pH sensor in this range. The new sensors are yellow-colored in acidic and neutral media and red-colored in alkaline PHs. With their colorimetric responses at different pH ranges EAPINP and PEAPINP can be used to develop color-tunable PH sensors.

Syntheses and pH Sensing Applications of Imine-Coupled Phenol and Polyphenol Species Derived from 2-Amino-4-Nitrophenol

Developing of new generation optical polymeric pH sensors has increasing importance due to their stable structures. Available polymeric sensors for different pH ranges are already needed. In the present study new kinds of monomeric and polymeric absorption pH sensors (HBANP and PHBANP) derived from 2-amino-4-nitrophenol were prepared. The novel sensors were investigated in various pH values using spectrophotometric, spectrofluorometric, and electrochemical techniques. The sensors showed sigmoidal correlations vs. pH range in optical measurements. These correlations were improved as mathematical formula to obtain the solution pH. HBANP and PHBANP differed from each other by response fields. HBANP had a sharp absorption increase between the pH of 6.5→7.5 while PHBANP spectrophotometrically responded at lower pHs. HBANP was colorless in acidic pHs, yellow-colored in neutral media and red-colored in alkaline pHs. With its colorimetric responses in various pHs HBANP can be used to develop color-tunable pH sensors. Electrochemical oxidation peak potentials and currents also particularly changed in various pHs.

Synthesis, Characterization, and Naked-Eye Sensor Application of Fully Substituted Urea-Based Cyclotriphosphazene Compound

GRAPHICAL ABSTRACT Abstract A novel sensor with a hexacenter containing nitrophenylurea groups on a cyclotriphosphazene core was synthesized by “click” reaction of N-propargyl-substituted urea with a hexaazide-substituted cyclotriphosphazene compound. It was characterized by spectroscopic techniques such as Fourier transform infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy. This compound was used for naked-eye and spectrophotometric detection of F− anions. The optical sensor properties of compound were investigated using ultraviolet–visible spectroscopy.

Synthesis, structural characterization, and anion interactions of new triazole-linked urea derivative fully substituted cyclotriphosphazene compounds

GRAPHICAL ABSTRACT ABSTRACT Three novel fully substituted urea derivative cyclotriphosphazene compounds 5–7 were synthesized by alkyne-azide 1,3-dipolar cycloaddition reaction of propargyl substituted ureas 2–4 with hexaazide substituted cyclotriphosphazene 1 in the presence of Cu(I) catalyst. All compounds were characterized with spectroscopic techniques such as FT-IR, 1H, 13C, and 31P nuclear magnetic resonance and mass spectroscopy. Also, the usefulness of compounds 5–7 as anion carriers was investigated by 1H NMR spectroscopy. For this purpose, 1H NMR spectra of compounds 5–7 were recorded in the presence of tetrabutylammonium fluoride in DMSO-d6. It was determined, that the urea protons in the compounds interact with fluoride.