In this paper we report the deprotonation yields, the pKa, and decay kinetics of the aci-nitro intermediates of some substituted 2-nitrobenzaldehydes that can be used as photoactivatable caged proton compounds. The decay of the aci-nitro absorbance for 2-nitrobenzaldehyde occurs within a few nanoseconds from photoexcitation. Addition of electron donating methoxy substituents at positions 4 and 5 leads to lower deprotonation yields, higher pKa, and slower decays of the aci-nitro intermediates. On the contrary, the decay rate is accelerated by the introduction of an electron-withdrawing Cl atom at position 4 in the phenyl ring, with little influence on the deprotonation yield and pKa of the aci-nitro intermediate.
Deprotonation yields, pKa, and aci-nitro decay rates in some substituted o-nitrobenzaldehydes / Abbruzzetti, Stefania; Carcelli, Mauro; Rogolino, Dominga; Viappiani, Cristiano. - In: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. - ISSN 1474-905X. - 2:(2003), pp. 796-800. [10.1039/b301818k]