Unexpected influences of solvents on excited state properties of solute molecules

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

“…Later, on the basis of new experiments, he tended toward the TICT hypothesis (vide infra). The Chandross hypothesis 91 was revitalized and substantiated by Varma and his students. ,, In alkane solutions of 1 , on addition of a polar solvent P, the F B fluorescence is quenched while F A grows, as shown by the linearity of the intensity ratio plots, F A / F B = k [P], indicating a formation of 1:1 exciplexes (for alternative interpretations, see section III.A.1). On the basis of ample evidence of measurements in mixed solvents, they concluded that the solvent effect is due not to dielectric polarization but to specific interactions.…”

“…The fluorescence quantum yield of the primary excited state of DMABN in nonpolar hydrocarbon solvents is reported to be φ B = 0.27, φ B ≥ 0.2, or φ B = 0.18 . With increasing polarity of the solvents, the quantum yield of F B drops by 2 orders of magnitude because a new and faster depopulation channelthat of the excited-state ICT reaction  is being switched on.…”

“…The derivatives of 1 which are rigidized with respect to the twist around the N amino −C benzonitrile ring bond, e.g., 20 , 29 , 55 , and 56 , emit only the F B fluorescence. ,,,,,,, …”

“… 22 a HEX 0.95 9.5 0.75 3.4 BN a , e HEX 0.51 0.33 0.28 0.35 11 c n -heptane ∼1.0 THF 0.50 ACN 0.24 107 f HEX 1.42 CH 3 COOEt 0.88 CH 2 Cl 2 0.54 ACN 0.49 108 f HEX 1.15 CH 3 COOEt 1.08 CH 2 Cl 2 1.06 ACN 0.76 292 h cyclopentane 0.05 BCN 0.03 a Data from ref . b Data from ref . c Data from ref .…”

The effect of gold(i) coordination on the dual fluorescence of 4-(dimethylamino)pyridine

“…Thus, for instance among the former several theories have been proposed. Chandross 4,5 and later Varma [6][7][8] suggested the existence of exciplexes in the excited state. McGlynn et al proposed that the low energy band found in DMABN arose from an excimer, while the high energy band corresponded to the monomer.…”