Serap Alp

Photophysical and photochemical characteristics of an azlactone dye in sol-gel matrix; a new fluorescent pH indicator

Abstract The photophysical and photochemical properties of an azlactone derivative, 4-(p-N,N-dimethylaminophenylmethylene)-2-phenyl-5-oxazolone, (DPO) in a sol-gel matrix have been examined. The fluorescence quantum yield, radiative lifetime, fluorescence lifetime, fluorescence rate constant and singlet energy values of the DPO dye were determined in a modified tetraethyl orthosilicate (TEOS) solid matrix by absorption and emission spectroscopy and obtained data were compared with the results of measurements in acetonitrile (MeCN) and tetrahydrofuran (THF) solution. The sol-gel matrix enhanced the fluorescence quantum yield (Qf=0.296) and fluorescence emission lifetime (τf=0.47 ns) compared to Qf=0.0027–0.0025 and τf=0.02–0.03 ns for solutions in MeCN and THF. The acidity constant of DPO was found to be as pKa=5.1 in the transparent sol-gel matrix. The dye doped sol-gel exhibited a pH sensitivity in pH range 3.0–7.0.

Fluorescence study on the interaction of bovine serum albumin with two coumarin derivatives

The interactions between bovine serum albumin (BSA) and two substituted hydroxychromone derivatives of coumarin, 3-hydroxy-7,8,9,10-tetrahydro-6H-benzo[c]chromen-6-on (C3) and 1,3-dihydroxy-7,8,9,10-tetrahy-dro-6H-benzo[c]chromen-6-on (C1.3), were investigated by fluorescence quenching spectra and UV-vis absorption spectra. It was proved that the fluorescence quenching of BSA by C3 and C1, 3 was mainly a result of the formation of C3 and C1.3-BSA complexes. The Stern-Volmer quenching constants, binding constants, binding sites and the corresponding thermodynamic parameters ΔHo, ΔSo and ΔGo at different temperatures were calculated. The results indicated that van der Waals interactions and hydrogen bonds were the predominant intermolecular forces in stabilizing each complex. The detection limits of C3 and C1.3 were 5.08 × 10−7 and 1.11 × 10−7 M in the presence of BSA, respectively.

Photostability studies of thermomesomorphic derivatives of 2, 5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione

Abstract In this study, the photophysical characteristics, like molar extinction coefficients, Stokes shifts, quantum yields, radiative and fluorescence lifetimes, fluorescence rate constants, radiationless deactivation rate constants, and singlet energies of the fluorescent mesomorphic diketopyrrolopyrrole derivatives, (DPPDs), 3,6-bis(4-octyloxyphenyl)-2,5-dihydro-2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4-dione (DPPD-1) and 3,6-bis(4′-butylbiphenyl-4-yl)-2,5-dihydro-2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4-dione (DPPD-2) have been determined. The photostability studies were carried out under xenon arc lamp, direct and concentrated sunlight in solution of chloroform and tetrahydrofuran as well as in solid state, embedded in matrices of polyvinyl chloride (PVC) and sol-gel. The studies reveal that the photostabilities of the DPPD derivatives in PVC and sol-gel matrices are enhanced compared to solutions of chloroform and tetrahydrofuran.

Synthesis and spectroscopic studies of 3,6-diphenyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dion's N,N'-dialkyl derivatives.

Abstract3,6-diaryl-2,5-dihydro-1,4-diketopyrrolo[3,4-c]pyrrole-1,4-dione (DPPD) derivatives are used commercially as red pigments, because of their color strength, brightness, and very low solubility in most common solvents. These products, although highly colored, appear to be of limited value as dyes, since they show a tendency to form an aggregate when incorporated into a solvent. Monoalkyl and dialkyl derivatives of DPPD were synthesized and then characterized with IR, 1HNMR, UV-Vis absorption and emission spectroscopy. Molar absorption coefficient, singlet energy level and Stokes’ shift values of DPPD derivatives were declared. Monoalkyl and dialkyl derivatives of DPPD’s solubilities were measured from saturated solutions of dimethylformamide (DMF), tetrahydrofuran (THF), dichloromethane (DCM), acetonitrile (ACN) and toluene and they are compared with each other.

Dissolved Carbon Dioxide Sensing with Phenyl-Linked Carbazole Oxazolones in Ionic Liquid and Ethyl Cellulose Moieties

ABSTRACT A new optical dissolved carbon dioxide (dCO2) sensor based on the spectrofluorimetric signal changes of the fluorescent carbazole derivative in room temperature ionic liquid was proposed. Response of the offered sensor composition to gaseous and dissolved carbon dioxide was tested in ethyl-cellulose- and imidazolium-based ionic liquid moieties. The detection limit was found to be 5 × 10−7 M [ ] for dCO2. When embedded in ionic liquid, the employed molecule exhibits excitation wavelength beyond 465 nm, extinction coefficients around 185,000 cm−1 M−1, and Stokes shifts extending to 56 nm. The ionic liquid—1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4)—provided longer storage time and highly stable microenvironment for the indicator molecule due to the buffering effect. The dissolved carbon dioxide sensor based on dye-doped RTIL does not need extra protection from the ambient air of the lab.

Crystal Structure and Conformational Analysis of 4-[(p-N,N-Dimethylamino) benzylidene]-2-(3,5-dinitrophenyl)oxazole-5-one

ABSTRACT An azlactone derivative, 4-[(p-N,N-dimethylamino)benzylidene]-2-(3,5-dinitrophenyl)oxazol-5-one (DNPO), C18H14N4O6, has been synthesized, and its crystal structure has been investigated by single crystal X-ray analysis and ab initio method. DNPO is monoclinic, with a = 9.3628(4) Å, b = 13.5148(9) Å, c = 13.7701(6) Å, β = 92.921(4)°, Z = 4, Dx = 1.46 g/cm3, μ(MoKα) = 0.112 mm−1, and space group P 121/c1. The whole molecule is almost planar. The crystal structure is stabilized by C–H · · · N type intramolecular, C–H · · · O type intermolecular interactions. To determine the flexibility of DNPO, the selected torsion angle is varied from − 180° to 180° in steps of 10°, and the molecular energy profile is calculated and analyzed.

Photophysical and Complexation Properties of Benzenesulfonamide Derivatives with Different Donor and Acceptor Moieties

Pyrrolobenzosulfonamide, indolobenzosulfonamide and carbazolobenzosulfonamide derivatives with different acceptor groups were synthesized and their photophysical properties were compared. The electron donor linking sites are found to influence the emission characteristics of these compounds while acceptor linking sites have no noticeable effects on the spectral properties. P2-A5 which is a C–C linked pyrrole derivative exhibited different spectral properties from the C–N linked pyrrole derivatives. The complexation properties of the molecules were also investigated employing Na (I), Ca (II), Li (I), Mg (II), Zn (II) and Cu (II) ions.

Optical Determination of Glucose with Glucose Oxidase Immobilized in PVC together with Fluorescent Oxazol‐5‐One Derivatives

Abstract Fully reversible biosensors for glucose monitoring based on solid polyvinylchloride (PVC) films where the enzyme glucose oxidase (GOx) was incorporated together with 2‐phenyl‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐1), 2‐(3,5‐dinitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐2), 2‐(4‐nitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐3) and 2‐(4‐tolyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐4) derivatives have been developed. The limit of detection (LOD) values for glucose were found to be 1.47×10−5 M, 2.01×10−5 M, 0.89×10−5 M, and 0.12×10−5 M for CPO‐1, CPO‐2, CPO‐3, and CPO‐4, respectively (n=7). Sensor films were found to have excellent photostability.

Tuning Photoinduced Intramolecular Electron Transfer by Electron Accepting and Donating Substituents in Oxazolones

The solvatochromic and spectral properties of oxazolone derivatives in various solvents were reported. Fluorescence spectra clearly showed positive and negative solvatochromism depending on substituents. The solvatochromic plots and quantum chemical computations at DFT-B3LYP/6-31 + G(d,p) level were used to assess dipole moment changes between the ground and the first excited singlet-states. The electron accepting nitro substituent at the para-position increased the π-electron mobility, however, the 3,5-dinitro substituent decreased the π-electron mobility as a result of inverse accumulation of the electronic density as compared with that of its ground state. Experimental and computational studies proved that the photoinduced intramolecular electron transfer (PIET) is responsible for the observed solvatochromic effects. We demonstrate that PIET can be finely tailored by the position of the electron accepting and donating substituents in the phenyl ring of the oxazolone derivatives. We propose that the photoactive CPO derivatives are new molecular class of conjugated push-pull structures using azlactone moiety as the π-conjugated linker and may find applications in photovoltaic cells and light emitting diodes.

2,5-Dihexyl-3,6-diphenyl-pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dione.

The asymmetric unit of the title compound, C30H36N2O2, contains one half-molecule, the other half being generated by a crystallographic inversion centre. The crystal structure is devoid of any classical hydrogen bonds however, non-classical C—H⋯O interactions link the molecules into chains propagating in [001] and a C—H⋯π interaction leads to the formation of a two-dimensional network in (011).