Triphenylamine/4,4′-Dimethoxytriphenylamine-Functionalized Thieno[3,2-b]thiophene Fluorophores with a High Quantum Efficiency: Synthesis and Photophysical Properties

Abstract

A wide series of 10 new triphenylamine (TPA)/4,4′dimethoxytriphenylamine (TPA(OMe) 2 )-functionalized thieno[3,2b]thiophene (TT) fluorophores, 4a−e and 5a−e, bearing different electron-donating and electron-withdrawing substituents (-PhCN, -PhF, -PhOMe, -Ph, and -C 6 H 13 ) at the terminal thienothiophene units were designed and synthesized by the Suzuki coupling reaction. Their optical and electrochemical properties were investigated by experimental and computational studies. Solid-state fluorescent quantum yields were recorded to be from 20 to 69%, and the maximum solution-state quantum efficiency reached 97%. Moreover, the photophysical characterization of the novel chromophores demonstrated a significant Stokes shift, reaching 179 nm with a bathochromic shift. They exhibited tuning color emission from orange to dark blue in solution and showed fluorescence lifetime reaching 4.70 ns. The relationship between triphenylamine (TPA)/ 4,4′-dimethoxytriphenylamine (TPA(OMe) 2 )-derived triarylamines and different functional groups on thieno[3,2-b] thiophene units was discussed.

Solution-processable donor–π–acceptor type thieno[3,2-b]thiophene derivatives; synthesis, photophysical properties and applications

“…Thienothiophenes (TTs) (5a,b) were synthesized according to our previously reported methods. [23][24][25][26][27][28] Initially, the synthesis of the core units, thieno[3,2-b]thiophens 3a,b, was conducted starting from 3-bromothiophene 1, from which monoketones, 2a,b, were constructed in a one-pot three step reaction, (i) lithiation of 1 with n-butyllithium at À78 1C, (ii) additions of elemental sulfur and, then, (iii) 4-(2-bromoacetyl)benzonitrile. Their precursors, monoketones (2a,b), were prepared in 81 and 77% yields, respectively.…”

“…51 The gas-phase geometries were optimized by the Gaussian 09 program at the B3LYP/6-31G(d) level, considering that experimental results of organic materials produce good agreement with the predicted results by B3LYP. 22,25,54,55 Optical properties were investigated by time dependent DFT (TD-DFT), including the solvent effect incorporated by the set of polarizable continuum model (PCM) as implemented in the Gaussian 09 package. In order to have absorption bands with the number of states (NStates) of 50, 38,56 the structures and HOMO-LUMO orbitals (isosurface value 0.04 a.u.)…”

“…Thieno [3,2-b]thiophenes (TT) have rigid, electron-rich and flat delocalized structures, making them promising p-bridges and donors to construct conjugated and low band gap organic semiconductors for organic light-emitting diodes (OLEDs), organic solar cells (OSCs), organic field-effect transistors (OFETs), lighting lasers and photosensitizers. [22][23][24][25][26][27][28][29][30][31][32][33] Another important building block is triphenylamine (TPA), having an ionization potential of 6.80 eV, lower than many organic/inorganic skeletons, which makes TPA a very strong electron-donating group for electronic materials. Moreover, TPA has a propeller-like shape with a torsion angle of 41.71 leading to a nonplanar structure with limiting intramolecular motion, which provides the resultant fluorescent molecule in solution with aggregation-induced emission (AIE) in the solid-state.…”

Pyrimidine‐Based Fluorescent Probe for Monitoring Mitophagy via Detection of Mitochondrial pH Variation

“…This "D-π-A" structure exerts a high quantum yield due to the intramolecular charge transfer (ICT). [25,26] A benzyl alcohol moiety was incorporated into the probe to interfere which the electron-withdrawing effect of the pyrimidine moiety, decreasing the ICT efficiency and reducing the fluorescence quantum yield. This inhibitory effect on the ICT is disrupted by protonation of the dimethylaniline moiety upon pH decrease, endowing the probe with a "turn-on" fluorescence mechanism.…”

“…The Z2 fluorescent probe has a donor‐π‐acceptor (D‐π‐A) photoelectric molecular structure that integrates an electron donor (D, dimethylaniline), a π‐conjugated link (olefinic bond), and an electron acceptor (A, pyrimidine). This “D‐π‐A” structure exerts a high quantum yield due to the intramolecular charge transfer (ICT) [25,26] . A benzyl alcohol moiety was incorporated into the probe to interfere which the electron‐withdrawing effect of the pyrimidine moiety, decreasing the ICT efficiency and reducing the fluorescence quantum yield.…”