Photochemical reactivity of para-aminobenzophenone in polar and non-polar solvents

Synthesis of Benzophenone Nucleosides and Their Photocatalytic Evaluation for [2+2] Cycloaddition in Aqueous Media

“…The triplet state of 4‐aminobenzophenone 1a is E T = 2.91 eV in benzene,14 which is still sufficient to sensitize substrate 2 . The major drawback, however, for the substitution of 4‐aminobenzophenone 1a is that the quantum yield of intersystem crossing is reduced to Φ T = 0.82 in nonpolar solvents 15. Herein, we follow this approach and present the synthesis of C ‐nucleosides that contain 4‐aminobenzophenone (i.e., 1a ), 4‐(dimethylamino)benzophenone (i.e., 1b ), 4‐methoxybenzophenone (i.e., 1c ), and 4‐methylbenzophenone (i.e., 1d ) as aglycons.…”

Influence of the chloro substituent position on the triplet reactivity of benzophenone derivatives: a time‐resolved resonance Raman and density functional theory study

“…The TR 3 results obtained after 266 nm photolysis of 2‐Cl‐BP in IPA with a 319.9 nm probe wavelength clearly showed that the 2‐Cl‐DPK radical forms slower than the parent and other chloro‐substituted DPK radicals, which demonstrates that the 2‐chloro substituent reduces the hydrogen abstraction ability of the 2‐Cl‐BP triplet. In general, carbonyl compounds having a ππ* triplet as the lowest excited state exhibit no or low photoreduction efficiency, such as some electron‐donating group substituted BP derivatives . In addition, the solvent polarity can affect the hydrogen abstraction ability of the carbonyl compound triplet.…”

“…Therefore, the efficiency of the photoreduction of BP derivatives can be affected significantly by the solvent polarity and the nature and position of the substituent on the phenyl ring. For example, an electron‐donating substituent group on the phenyl ring such as NH 2 , OH, OCH 3 usually reduces the reactivity of the substituted BP towards a hydrogen donor, because of the relative position of the n π* and ππ* states being largely altered in polar and nonpolar solvents . In addition, the electron‐donating group could decrease the electrophilicity at the carbonyl oxygen and hence make the corresponding BP derivative less reactive towards a hydrogen atom donor compared with the unsubstituted molecule.…”

Photodimerization of enaminoketonatoboron difluorides

“…Unfortunately, the mass spectra (CI, EI) of each of these photoproducts showed identical molecular ion signals as the initial monomer. Furthermore, other spectra ( 1 H-NMR, 13 C-NMR and IR) did not yield sufficient useful information to allow the structure of the photoproducts to be assigned. Therefore, we turned to single crystal structure analysis by X-ray diffraction to show that these products are the anti head-to-tail (H-T) dimer ( 2) and syn H-T dimer (3) of the parent compounds (Figs.…”

“…The excited triplet state lifetime is known to decrease with increasing solvent polarity. 11,13 Therefore, it is reasonable that the dimer yield from photoreaction of complex 1a in the presence of benzophenone decreases in polar solvents.…”