Fluorescence and two-photon absorption of push—pull aryl(bi)thiophenes: structure—property relationships

Abstract

Photophysical and TPA properties of series of push-pull aryl(bi)thiophene chromophores bearing electron-donating (D) and electron-withdrawing (A) end-groups of increasing strength are presented. All compounds show an intense intramolecular charge transfer (ICT) absorption band in the visible region. Increasing the D and/or A strength as well as the length of the conjugated path induces bathochromic and hyperchromic shifts of the absorption band as reported for analogous push-pull polyenes. Yet, in contrast with corresponding push-pull polyenes, a significant increase in fluorescence is observed. In particular, chromophores built from a phenyl-bithienyl conjugated path and bearing strong D and A end-groups were found to combine very large one and two-photon brightness as well as strong emission in the red/NIR region. These molecules hold promise as biphotonic fluorescent probes for bioimaging.

Vectorization and Intracellular Distribution of a Two‐Photon‐Absorbing, Near‐Infrared‐Emitting π‐Extended Boranil Dye

“…PEB displays two absorption bands centred at λ =800 and 960 nm with high TPA cross sections (σ 2 ; 320 and 420 GM, respectively), much higher than the rhodamine reference. The absorption band centred at 960 nm is approximately twice the wavelength of the linear absorption of the S 0 →S 1 transition band of the chromophore ( λ abs =473–495 nm) which indicates that the excited‐state can be reached by one or two‐photon excitation, a feature frequently observed for push–pull derivatives . The higher energy band located at 800 nm can be likely associated with a vibronic replica; a statement supported by similar measured anisotropy values (0.07) obtained via vertically polarized excitations at 800 and 960 nm.…”

“…The absorption band centreda t9 60 nm is approximatelyt wice the wavelength of the linear absorption of the S 0 !S 1 transition band of the chromophore( l abs = 473-495 nm) whichi ndicates that the excited-state can be reached by one or two-photon excitation,afeature frequently observed for push-pull derivatives. [22] The highere nergy band located at 800 nm can be likely associated with av ibronic replica;astatements upported by similarm easured anisotropy values (0.07) obtained via vertically polarized excitations at 800 and 960 nm. This clearly does evidencet hat both fluorescenceb ands originate from the same excited state.…”

Experimental and Theoretical Studies of Quadrupolar Oligothiophene‐Cored Chromophores Containing Dimesitylboryl Moieties as π‐Accepting End‐Groups: Syntheses, Structures, Fluorescence, and One‐ and Two‐Photon Absorption

“…When compared to the branching strategy applied in references 10, 12, 13 to both quadrupolar8–10 and dipolar10, 11 analogues, the effectiveness of our BMes 2 ‐based compounds is clearly evident. The compounds reported herein have normalized TPA cross‐sections approaching that of the best‐performing bithiophene push–pull chromophores,16 despite the large contribution to the molecular weight of the mesityl groups required for stability and applications. Further comparison of σ 2 /MW values of our oligothiophene‐BMes 2 chromophores to other reported BMes 2 containing compounds (Table 5),8–13 shows red‐shifted fluorescence maxima, that is, closer to the biological transparency window, especially for the elongated compounds.…”

Reduced voltage losses yield 10% efficient fullerene free organic solar cells with >1 V open circuit voltages

“…S1a, ESI†) due to replacing the rhodanine end group with a stronger dye chromophore – thiobarbituric acid – which effectively contributes to the photon harvesting. 28 The low band gap acceptor IDTBR has also shown to work nicely with P3HT; however, the high lying HOMO energy level of P3HT limited the V oc below 1 V in these devices. 29 …”