Butterfly-shaped π-extended benzothiadiazoles as promising emitting materials for white OLEDs

Abstract

A series of butterfly-shaped D–A–D and D–A–A compounds composed of a benzothiadiazole core and corresponding terminal alkynes were synthesized.

Preparation and Photoluminescent Properties of Three 5‐Amino Benzothiadiazoles (5‐amBTDs)

“…On the contrast, the D−A conjugation through 5‐position of BTD was seldom reported [3] . In our previous reports, the butterfly‐shaped 5,6‐disubstituted BTDs tended to crystalize much easier than the linear‐shaped 4,7‐disubstituted BTDs and finely tuned the emissive light of the bright crystals ranging from 473 nm to 627 nm by simply changing the substituted groups [4] . In the screening of the various donors by surfing the literature, azepane, [5] was selected in this study for its easier structural modification by installing phenyl groups, [6] the magnified absorptivity in comparison with other nitrogen‐containing rings, such as aziridine, azetidine, pyrrolidine and piperidine [7] and so far their multiple achievements in thermally activated delayed fluorescence emitter, [8] dye‐sensitized solar cell, [9] polymer LEDs [10] and the ultrasensitive fluorescence sensor [11] .…”

“…[3] In our previous reports, the butterfly-shaped 5,6-disubstituted BTDs tended to crystalize much easier than the linear-shaped 4,7-disubstituted BTDs and finely tuned the emissive light of the bright crystals ranging from 473 nm to 627 nm by simply changing the substituted groups. [4] In the screening of the various donors by surfing the literature, azepane, [5] was selected in this study for its easier structural modification by installing phenyl groups, [6] the magnified absorptivity in comparison with other nitrogen-containing rings, such as aziridine, azetidine, pyrrolidine and piperidine [7] and so far their multiple achievements in thermally activated delayed fluorescence emitter, [8] dye-sensitized solar cell, [9] polymer LEDs [10] and the ultrasensitive fluorescence sensor. [11] Combining with our previous works on benzothiadiazole (BTD) on the development of new fluorescent compounds for optoelectronic materials and fluorescent probes, [12] azepane (AP), iminodubenzyl (IDB) and iminostilbene (ISB) were respectively installed on 5-position of BTD, affording compounds 1, 2 and 3 for the systematical investigation of the fluorescent structure-property relationship (FSPR).…”

Identification of the Irreversible Redox Behavior of Highly Fluorescent Benzothiadiazoles

“…All compounds show the lowest Φ fl in EtOH, the solvent with the highest polarity and highest hydrogen bonding strength. [33] Compounds 1 and 2 show a remarkably strong reduction of Φ fl in EtOH (15 % and 16 %) and reduced τ of 4.12 ns (1) and 2.42 ns (2). This effect is ascribed to hydrogen bonding to the nitrogen atom of the BTD core, which is rather unprotected in 1 and 2 but sterically shielded by the phenyl substituents in 3 and 4.…”

“…Subsequent coupling reactions like Sonogashira, Suzuki, and Buchwald-Hartwig coupling give access to a plethora of symmetrical and unsymmetrical derivatives. [1][2][3][4] BTDs can be applied in organic light-emitting diode (OLED) materials, [5][6][7] polymers with defined electronic and optical properties, [8][9][10] in sensory metal-organic frameworks, [11] solar cells [12] or in field-effect transistors (FET). [13] Furthermore, BTDs can act as ortho-diamine protecting groups and can thus be used as precursors for other molecular compounds, e. g. diaminodicyanoquinones and quinoxalines.…”

“…Moreover, the Φ fl SS values observed in this study for solid 1-4 (Table 1) considerably exceed the Φ fl SS values published for BTDs so far, that are below 25 %, even though these values were measured in spin-coated thin films. [2] To gain more insights into the redox behavior of our BTD dyes we performed cyclic voltammetry (CV) as well as spectroelectrochemical (UV/Vis/NIR) measurements for 1-4 in a 0.1 M Bu 4 NPF 6 solution of DCM ( Figure 5 and S16-S18). The values of the electrochemical potentials are given relative to the ferrocene/ferrocenium couple (Fc/Fc + ).…”