Enone photochemistry. Dynamic properties of triplet excited states of cyclic conjugated enones as revealed by transient absorption spectroscopy

Internal Conversion vs. Intersystem Crossing – What Drives the Dynamics of Cyclic α,β-Enones?

“…A residual spectrum which is ctrum following excitation of TMCPO in acetonitrile at 228 nm is depicted in Figure 3. Besides the coherent artifact around time zero, one sees three processes, one on the 200 fs timescale originating from the 1 ππ*-state relaxation, one on the ps timescale ( 1 nπ*-state) and a residual spectrum peaking around 280 nm which can be assigned to the triplet states in agreement with [4]. When comparing the time constants for the 1 nπ*-decay, one sees no big changes between the solvents and the gas phase (between 3 and 4 ps).…”

Recent advances in 1,4-benzoquinone chemistry

“…This reaction has also been applied to the synthesis of a number of naturally occurring substances [330][331][332][333][334] and has attracted much attention from the mechanistic viewpoint. [335][336][337] Quinones occupy a very important position in the photoreactions with alkenes in which the conjugated C=C and C=O double bonds competitively take part in the [2+2] photocycloaddition to provide cyclobutane derivatives [338][339][340] and Paterno-Buchi adducts [341][342][343] respectively, depending on the identities of the quinone as well as the alkenes. We studied 344 the photocyclisation of benzoyl-1,4-benzoquinones leading to xanthones and phenyl gentisate esters while pursuing studies on the synthesis of anthracyclinones and heteroanthracyclinones.…”

Study of a Two-Stage Photobase Generator for Photolithography in Microelectronics

“…The singlet and triplet energies ( AP E S1 = 80 kcal mol −1 and AP E T1 = 74 kcal mol −1 ) 8 of the acetophenone (AP) moiety are higher than those of the cyclohexenone (CH) moiety ( CH E S1 = 75 kcal mol −1 and CH E T1 = 63 kcal mol −1 ). 9 Therefore, singlet and triplet energy transfer from excited states of the AP to CH moiety is energetically favorable. From the state energy diagram, photoexcitation of the acetophenone moiety generates AP S 1 , which could undergo intersystem crossing to AP T 1 or energy transfer to CH.…”