Ordering, Interaction, and Reactivity of the Low‐Lying nπ* and ππ* Excited Triplet States of Acetophenone Derivatives

Abstract

Im Gleichgewicht: Die niedrig liegenden nπ*‐ und ππ*‐Triplettzustände substituierter Acetophenone wurden mit zeitauflösender Nahinfrarotspektroskopie direkt beobachtet. Die effektiven Reaktivitäten der ππ*‐T1‐Zustände von Acetophenonen ergeben sich aus der thermischen Besetzung der höheren nπ*‐T2‐Zustände. Die T1‐ und T2‐Zustände der Acetophenone befinden sich im thermischen Gleichgewicht.

Is Our Way of Thinking about Excited States Correct? Time‐Resolved Dispersive IR Study on p‐Nitroaniline

“…Nanosecond time‐resolved dispersive IR spectroscopy : The apparatus for nanosecond time‐resolved dispersive IR spectroscopy has been described in detail elsewhere 34. 44 This apparatus utilizes a dispersive monochromator in combination with an alternating current (AC)‐coupled detection scheme 35. 45 Because the grating of the spectrometer must be scanned to record a spectrum, the dispersive method usually requires much longer acquisition time than the FTIR method.…”

“…45 Because the grating of the spectrometer must be scanned to record a spectrum, the dispersive method usually requires much longer acquisition time than the FTIR method. However, the dispersive method has higher sensitivity of up to Δ A ≈1×10 −6 ,44 which is hardly accessible with the FTIR method 46. Furthermore, the dispersive method is less susceptible to the instability of the measured transient event in comparison with the FTIR method 46…”

Theoretical Study of the Photochemical Initiation in Nitroxide-Mediated Photopolymerization

“…Ap is well-known for an ultrafast population of the triplet manifold . Ap photochemistry is strongly affected by the substituents, which can even change the nature of the lowest excited triplet state . Therefore, we first demonstrate that the low-lying states of Ap are preserved in the presence of the alkoxyamine moiety.…”

Effects of substituent position on aminobenzoate relaxation pathways in solution

“…Finally, we note here that states with nπ* character, for example, could also be particularly sensitive to solvent environment. 36 However, as the computational results presented in Table 1 suggest, the S 1 state of m-MA does not have nπ* character. While we have also found that the S 2 state of m-MA is indeed an nπ* state, the large S 1 -S 2 vertical energy difference for m-MA in all solvents (7582 cm -1 in CHX, 8630 cm -1 in ACN and 10082 cm -1 in EtOH) makes it highly unlikely for an S 2 →S 1 transition to take place in the vicinity of the Franck-Condon region.…”