A Photophysical Study of Purines and Theophylline by Using Laser‐Induced Optoacoustic Spectroscopy

Abstract

The photophysics of purinic compounds (purine, 6-methylpurine, 6-aminopurine [adenine], 6-chloropurine, 6-methoxypurine) and theophylline in acetonitrile solution were studied by pulsed laser-induced optoacoustic spectroscopy (LIOAS) exciting at 266 nm. The effect of O2, Xe and MnCl2 on the photophysical behavior of these compounds was studied; as well, the formation quantum yield of purine and 6-methylpurine triplet states were determined, with phi T = 0.88 +/- 0.03 for both compounds. Multiphotonic and depletion processes were observed at high laser fluences. In order to explain this behavior, theoretical UV-visible absorption electronic spectra from both the S0 and S1 state have been calculated for purines and theophylline by using the semiempirical PM3 and ZINDO/S methods.

UVC induced oxidation of chloropurines: excited singlet and triplet pathways for the photoreaction

“…Literature values only concern e T(max) of purine and pyrimidine nucleotides (AMP and GMP) which lie in the range 4 × 10 3 -1.3 × 10 4 M −1 cm −1 and appear to be higher for purine than for pyrimidine nucleotides. 25 By setting also a value of e T(max) = 10 4 M −1 cm −1 for 2ClPu, one obtains a U T value close to unity, which agrees with an earlier study of Murgida et al 26 for unsubstituted purine in aqueous solution (Table 1). Assuming similar e T(max) values for 6ClPu and 2,6diClPu, much lower values of triplet formation quantum yields close, to 0.1 were obtained for these two chloropurines (Table 1).…”

Time-resolved photothermal methods: accessing time-resolved thermodynamics of photoinduced processes in chemistry and biology

“…132 Using similar methodologies, the triplet yield and the singlet oxygen quantum yield was also determined for tetraphenylporphyrin and its Zn and Cu complexes, 139 as well as for halogenated chlorins. 140 The photophysical properties of caffeine, theophylline, and theobromine, 141 and their benzophenone-photosensitized reactions in acetonitrile 38 were investigated by time-resolved LIOAS. In the three cases, global quenching rate constants of triplet benzophenone were measured as a function of temperature and it was observed that this is a non-activated process.…”

Photosensitized Oxidation of Oxopurines by Rose Bengal†

“…In previous papers we described the sensitized photooxidation of oxopurines (OP) (xanthines) by benzophenone, which take place by a type I mechanism via a hydrogen abstraction process (16) and different aspects of the photophysics of several purine derivatives (17)(18)(19). In the present work, we study the photosensitized oxidation of OP such as CF, TF, TB and 1,3,7-trimethyluric acid (TMU) (Scheme l), by RB.…”