Abstract
The dyes (P-1 and P-2) of perylenebisimide (PBI) conjugated with 2-(2-hydroxyphenyl)benzothiazole (HBT) were prepared by Sonogashira coupling reaction. The new compounds have special photophysical properties, such as near infrared absorption/emission and large Stokes shift. The UV-vis absorption (range from 651 nm to 690 nm) and emission wavelength (range from 732 nm to 756 nm) of P-1 and P-2 extend to near infrared range. Importantly, they have much larger Stokes shifts (range from 73 nm to 105 nm) compared with the conventional PBI derivatives, such as 7 (from 19 nm to 65 nm) and 9 (from 81 nm to 86 nm). TD-DFT calculation was used to rationalize UV-vis absorption, emission and especially large Stokes shift from the theoretical point of view. We found geometry relaxation of P-1 and P-2 in the excited state is an important reason for the origin of large Stokes shift besides intramolecular electron transfer (ICT).
Highlights
HBT is a conventional dye with excited intramolecular proton transfer (ESIPT),[34,35] which has been applied to uorescent molecular probes[36,37,38,39,40,41,42,43,44,45,46,47,48,49] and luminescent materials.[50,51]
In order to compare the photophysical property with P-1, we synthesized P-2 which is alkylation of the hydroxyl group in HBT
In the weak polarity solvent, the Stokes shi s of P-1 and P-2 are 82 nm and 73 nm in PhCH3 respectively (Table 1). It indicates that some internal structural feature result in the large Stoke shi besides intramolecular electron transfer (ICT) effect57(see the later DFT calculation section)
Summary
Perylenebisimide (PBI) and its derivatives have been widely applied to the areas of uorescence probe and intracellular uorescence imaging image,[1,2,3,4,5] organic photovoltaic devices,[6,7,8,9,10,11,12] charge transporting materials,[13,14,15,16,17,18] luminescent materials[19,20,21,22,23,24] and triplet photosensitizers[25,26,27,28,29,30,31,32] due to its excellent luminous performance, photo-stability and electronic transmission capacity. PBI dyes with near infrared absorption/emission, as well as large Stoke shi are very meaningful. HBT is a conventional dye with excited intramolecular proton transfer (ESIPT),[34,35] which has been applied to uorescent molecular probes[36,37,38,39,40,41,42,43,44,45,46,47,48,49] and luminescent materials.[50,51] By connecting PBI with 2-(2-hydroxyphenyl)benzothiazole (HBT), p-conjugation structure is enlarged by the introduction of substituents in PBI, so the absorption wavelength may be extended to near infrared region. Our work will provide a new way to obtain such special dyes
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