Aggregation-induced emission: phenomenon, mechanism and applications.

6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Interpretation of europium(III) spectra

Cyanines during the 1990s: A Review

Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated.Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtos...

Hydrogen bonding in the electronic excited state.

Environmental and magnetic field effects on exciplex and twisted charge transfer emission

The polarized low‐temperature absorption spectrum, emission spectrum, and excitation spectrum of benzil and benzil‐doped stilbene crystals have been recorded. It has been found that the 3800 A (n–π*) band system of benzil is split by the weak interaction between the two halves of the molecule. The excitation spectrum reveals the presence of a S→T transition hidden underneath the S→S transition. The crystal spectrum of benzil‐doped stilbene is different from the benzil spectrum. The new sharp band at 4850 A has been interpreted in terms of a trans–planar configuration of benzil. A weak (π*→n) fluorescence has been detected in this crystal.

Spectra of Benzil

Effect of environment on the magnetic field modulation of exciplex luminescence

Conformational relaxation in the excited electronic states of benzil and naphthyl

The effect of variation of dielectric constant on the relative magnetic field effect in singlet luminescence has been studied using a typical exciplex system at a saturating field. The study indicates strong specificity in the perturbation of the magnetic field effect by alcoholic solvents. In contrast to alcohols where relative singlet magnetic field effect is of the order of 2% only, the magnetic field effect in non-alcoholic medium reaches as high as 9%. Moreover, dielectric constant variation in alcohols yields curves which are distinctly different from those in non-alcoholic media. It turns out that this dependence of magnetic field effect on dielectric constant is similar in all non-alcoholic solvent mixtures. An analytical study based on Hong and Noolandi’s solution of Smoluchowski equation has been made. Derived expressions can interpret experimental curves reasonably well.

Mihir Chowdhury

Papers

Environmental and magnetic field effects on exciplex and twisted charge transfer emission

Spectra of Benzil

Effect of environment on the magnetic field modulation of exciplex luminescence

Conformational relaxation in the excited electronic states of benzil and naphthyl

Effect of variation of dielectric constant on the magnetic field modulation of exciplex luminescence