This article prepared a variety of novel singlet oxygen photosensitizers containing different numbers of bromine atoms, which
could be divided into two groups (G1, G2) according to parent chemical structural characteristics. Effects of numbers of substituted bromine
atoms on one- and two-photon optical properties of singlet oxygen photosensitizers were surveyed experimentally and theoretically.
One-photon fluorescence emission spectra of the photosensitizers were affected more remarkably by numbers of substituted bromine atoms
than one-photon absorption spectra. Two-photon absorption (TPA) properties of these photosensitizers were determined under
700~880nm near-infrared laser frequencies at 20nm step tuning. The photosensittizers with two substituted bromine atoms showed the
largest TPA cross sections in two groups respectively. The generation of singlet oxygen by these photosensitizers under one- and twophoton
irradiation was confirmed by photochemical methods and ESR (electron spin resonance) experiments. Singlet oxygen quantum
yields of these photosensitizers were improved with increasing substituted bromine atoms, but the enhancement extents were different between
G1 and G2. Molecular geometry optimization was performed to analyze further the fundamental reasons of influence of number of
substituted bromine atoms on the ground and excited states of various photosensitizers.
Keywords: Two-photon, Heavy atom effect, Singlet oxygen, Photosensitizer, Triplet state, Molecular geometry optimization, Near-IR laser, Organic photochemistry
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