84559-64-8Relevant academic research and scientific papers
Absorption Kinetics of Photochemical Reactions of 2,4,6-Triisopropylbenzophenone and Its Derivatives in Benzene at Room Temperature Studied by Nanosecond Spectroscopy. 2. Laser Chemistry, Molecular Dynamics, collisions, and Energy Transfer
Nakayama, Toshihiro,Kuramoto, Tetsunobu,Hamanoue, Kumao,Teranishi, Hiroshi
, p. 5689 - 5695 (2007/10/02)
Nanosecond laser photolyses of 2,4,6-triisopropylbenzophenoses (TIB-X) have been performed in benzene at room temperature, and the characteristic absorption bands due to the highly hindered triplet states are observed around 600 about 800 nm.For the meta-
Intramolecular Hydrogen Abstraction from Triplet States of 2,4,6-Triisopropylbenzophenones: Importance of Hindered Rotation in Excited States
Ito, Yoshikatsu,Nishimura, Hiroaki,Umehara, Yasutoshi,Yamada, Yutaka,Tone, Mutsuto,Matsuura, Teruo
, p. 1590 - 1597 (2007/10/02)
Photochemically initiated benzocyclobutenol formation from a variety of 4'-substituted (4'-X) 2,4,6-triisopropylbenzophenones 1a-f (a, X = OMe; b, X = Me; c, X = H; d, X = CO2Me; e, X = CF3; f, X = CN) as well as from 2,4,6-trimethylbenzophenone (3a) and 2,4,6-triethylbenzophenone (3b) was studied.The quantum yields of the benzocyclobutenols 2a-f ranged from 0.60 for 2c to 0.06 for 2f in benzene.By usual Stern-Volmer quenching and sensitization methods using diene as quencher or sensitizer, various photokinetic data for these ketones, i.e., triplet lifetime (τT) and its temperature dependence (Ea and log A), rate constant for intramolecular hydrogen abstraction from o-isopropyl methine hydrogens (kr) and its isotope effect (kH/kD), rate constant for bimolecular triplet quenching (k2) with hydrogen donors (Bu3SnH, mesitylene, and cyclooctane), and intersystem crossing yield (ΘT), were estimated.The effect of 4'-substituents (4'-X) on kr (or kT) was unusual for a series of compounds 1a-c and 1e in that kr decreased in going from 1a (X = OMe) to 1e (X = CF3).This novel substituent effect was interpreted on the basis of hindered rotation in the excited state around the bond linking the 2,4,6-triisopropylphenyl and carbonyl groups.This interpretation was nicely supported by the results obtained for Ea (unusually large, e.g., Ea = 90 kcal/mol for 1c), kH/kD (1.5 for 1c), and k2 (increased in going from 1a to 1e).It is deduced that an increased n?* character of aromatic ketone triplets results in an increased barrier to rotation (viz., an increased double-bond character) about cAr-C(=O) single bond in triplet excited state.
Photocyclization Reaction and Triplet Lifetime of Hindered o-Alkyl Benzophenones
Ito, Yoshikatsu,Umehara, Yasutoshi,Yamada, Yutaka,Matsuura, Teruo
, p. 1160 - 1161 (2007/10/02)
The triplet lifetimes of hindered 4'-substituted-2,4,6-tri-isopropylbenzophenones decrease (increase) with the increasing electron-donating (withdrawing) ability of the ring substituents; this is the opposite effect to that expected from the rate of the i
