UV Photodissociation of Pyrroles: Symmetry and Substituent Effects
H (Rydberg) atom photofragment translational spectroscopy and ab initio electronic structure calculations are used to explore ways in which ring substituents affect the photofragmentation dynamics of gas phase pyrroles. S1 ← S0 (σ* ← π) excitation in bare pyrrole is electric dipole forbidden but gains transition probability by vibronic mixing with higher electronic states. The S1 state is dissociative with respect to N–H bond extension, and the resulting pyrrolyl radicals are formed in a limited number of (nontotally symmetric) vibrational levels (Cronin et al. Phys. Chem. Chem. Phys. 2004, 6, 5031–5041). Introducing σ-perturbing groups (e.g., an ethyl group in the 2-position or methyl groups in the 2- and 4-positions) lowers the molecular symmetry (to Cs), renders the S1–S0 transition (weakly) allowed, and causes some reduction in N–H bond strength; the radical products are again formed in a select subset of the many possible vibrational levels but all involve in-plane (a′) ring-breathing motions as expe...
Tolga N. V. Karsili; Barbara Marchetti; Roberta Moca; Michael N. R. Ashfold
In this article we have investigated intermolecular excited-state proton transfer (ESPT) of firefly’s chromophore D-luciferin in DMSO–water binary mixtures using steady-state and time-resolved fluorescence spectroscopy. The unusual behavior of DMSO–water binary mixture as reported by Bagchi ... more
Resonantly driven quantum emitters offer a very promising route to obtain highly coherent sources of single photons required for applications in quantum information processing (QIP). Realizing this for on-chip scalable devices would be important for scientific advances and practical applica ... more
The aryl hydrocarbon receptor (AhR) is a nuclear receptor regulating a wide range of biological and toxicological effects. Metabolites of l-tryptophan are able to bind and activate AhR, providing a link between tryptophan catabolism and a novel mechanism of protective tolerance, referred to ... more
Rohm and Haas Powder Coatings is delighted to announce that its Reading, Pennsylvania, facility is the first site in the world to receive the RCMS® Site Certification awarded by the American Chemical Council (ACC).
When Raj Gupta, Chairman and CEO of Rohm and Haas Company, became Chairman ... more