A new family of coumarin-based pH indicators was synthesized. They are sensitive to pH in either weakly acidic or weakly basic solution. The indicators possess moderate to high brightness, excellent photostability and compatibility with light-emitting diodes. The indicators were covalently immobilized on the surface of amino-modified polymer microbeads which in turn were incorporated into a hydrogel matrix to obtain novel pH-sensitive materials. When a mixture of two different microbeads is used, the membranes are capable of optical pH sensing over a very wide range comparable to the dynamic range of the glass electrode (pH 1-11).

Novel coumarin-based fluorescent pH indicators, probes and membranes covering a broad pH range.

Novel iminocoumarin dyes as photosensitizers for dye-sensitized solar cell

Optical properties of new fluorescent iminocoumarins. Part 2. Solvatochromic study and comparison with the corresponding coumarin

The electronic structures and photophysical properties of rigid coumarin dyes have been studied by using quantum chemical methods. The ground-state geometries of these dyes were optimized using the Density Functional Theory (DFT) methods. The lowest singlet excited state was optimized using Time -Dependent Density Functional Theory [TD-B3LYP/6-31G(d)]. On the basis of ground- and excited-state geometries, the absorption and emission spectra have been calculated using the DFT and TD-DFT method. All the calculations were carried out in gas phase and in acetonitrile medium. The results show that the absorption maxima and fluorescence emission maxima calculated using the Time-Dependent Density Functional Theory is in good agreement with the available experimental results. To understand the Non- Linear Optical properties of coumarin dyes we computed dipole moment (μ), electronic polarizability (α), mean first hyperpolarizability (βo) and second hyperpolarizability (γ) using B3LYP density functional theory method in conjunction with 6-31G(d) basis set.

Rigid Coumarins: a Complete DFT, TD-DFT and Non Linear Optical Property Study

The synthesis and optical characterization of novel iminocoumarin derivatives

Bichromophoric 3-diethylamino-7-phenyl-7H-benzo-[4,5]-imidazo-[1,2-c]-chromeno-[3,2-e]-pyrimidines were synthesized by the condensation of 7-diethylamino-3-(2-benzimidazolyl)-iminochromene with several aromatic aldehydes. Fluorescence properties of these compounds were studied in solvents of various polarity and acidity. The excited state intramolecular electron transfer was shown as the reason for the fluorescence quenching of the studied dyes with electron donor substituents in the minor chromophoric moiety. Prospects for the usage of these compounds as fluorescence probes sensitive to polarity and pH of their surrounding were elucidated.

Mikhail I Rubtsov

Papers

Bichromophoric fluorescent dyes with rigid molecular structure: fluorescence ability regulation by the photoinduced intramolecular electron transfer