Temperature Dependence of the Deactivation Behaviour of Substituted Acridizinium Derivatives in Dilute Solutions

Abstract

Fluoreszenz / Intersystem Crossing / Temperaturabhangigkeit / SubstituenteneinfluJThe energies of the excited states which are involved in the deactivation, the quantum yields of fluorescence and intersystem crossing, and the fluorescence decay times were determined for acridizinium and seven substituted acridizinium derivatives. Taking into account a contribution of temperature independent intersystem crossing the temperature dependence of the fluorescence quantum yield can be described by means of the Arrhenius equation. The thermally activated isc-process in acridizinium (kizc = 6 . lo8 s -I) which determines the radiationless deactivation, is equivalent to the S, ('B2J --t T3 ('B3,) transition observed in anthracene. The level inversion of the energetic sequence of S, and T2 which is known from the exocyclic substitution of anthracene, takes place during the endocyclic azinium-substitution, too. -Depending on their nature and position, additional exocyclic substituents will influence the activation energy, resulting in the case of heavy atoms in a drastic acceleration of ki:c or the rate constant for the temperature independent isc-process (I&).

Studies on the Mechanism of the Photo-Induced DNA Damage in the Presence of Acridizinium SaltsInvolvement of Singlet Oxygen and an Unusual Source for Hydroxyl Radicals

“…The fluorescence lifetimes of 1a and 1c were determined to be 6 ns and 14 ns. The value of 1a is similar to the one published earlier . Addition of DNA led to fluorescence decays that did not follow a monoexponential behavior.…”

“… a Determined by extrapolation to c( 1 ) = 0 M; b λ ex = 308 nm ( 1a and 1b ) and 455 nm ( 1c ); c In CH 3 CN; data for [1,3-CHD] ≤ 0.3 M; d No quenching by 1,3-CHD; e Ref ; f Ref c; g Ref ; counterion: ClO 4 - , in 0.1 M tetraethylammonium perchlorate in DMF; h Counterion BF 4 - , in DMF; i E red * = E 0 - 0 + E red . …”

The benzo[b]quinolizinium ion as a water-soluble platform for the fluorimetric detection of biologically relevant analytes

“…[77][78][79][80][81] In addition, a set of experimental 82 and computational 83 absorption data of quinolizinium derivatives was compiled. As a general trend, the benzo[b]quinolizinium (2a) absorbs and emits essentially in the same range as anthracene (1) (Figure 1) with an absorption maximum at 396 nm and an emission maximum at 407 nm in methanol, respectively.…”

“…As a general trend, the benzo[b]quinolizinium (2a) absorbs and emits essentially in the same range as anthracene (1) (Figure 1) with an absorption maximum at 396 nm and an emission maximum at 407 nm in methanol, respectively. 77,80 The emission lifetime of the parent compound 2a is 4.4 ns in CH 3 CN. 80 These data indicate that the benzo[b]quinolizinium ion has the ability to substitute an anthracene fluorophore while essentially maintaining the photophysical properties.…”

“…77,80 The emission lifetime of the parent compound 2a is 4.4 ns in CH 3 CN. 80 These data indicate that the benzo[b]quinolizinium ion has the ability to substitute an anthracene fluorophore while essentially maintaining the photophysical properties. Furthermore, the quinolizinium structure offers a special advantage regarding the integration of the anthracene chromophore in an electron donor-acceptor system, that is required to accomplish pronounced dye-type properties.…”