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The gas-phase dynamics of two classes of photochromic molecules, three spiropyrans and one spirooxazine, is investigated using both time-resolved mass spectrometry and photoelectron spectroscopy approaches. The comparison of the dynamics and their ionization cross sections has helped to verify a sequential photoisomerization mechanism involving four steps.

Strong connections have been made since the 1970s between responses of biological systems and ongoing advances in light-induced condensed-phase dynamics involving chemical reactions. Recent experimental measurements illustrate the great utility of transient spectroscopy measurement, especially with infrared femtosecond pulses, to many biology questions. Ultrafast laser techniques are important in the study of biology. Protein dynamics are often not easy to mimic in chemical systems, given the structural and electronic motifs that often represent them.

A crystallographic analysis of the phase dynamics of (1R*,2S*,5R*)-5-tert-butyl-2-hydroxycyclopentanecarboxylic acid reveals the importance of hydrogen bonding interactions in crystallization kinetics and differentiating between the phases. The enthalpy of activation of the tert-butyl (phase II) is lower than that for the other phases, while the tert-butyl rotations have considerable, positive entropies of activation.

Abstract: A novel two-step procedure involving the formation of 1-arylidene-2-tetralones from 2-tetralone and subsequent Michael addition of a cyclic secondary amine on the alkenone followed by in situ aerial oxidation [...]