Polyimide and Imide Compound Exhibiting Bright Red Fluorescence with Very Large Stokes Shifts via Excited-State Intramolecular Proton Transfer II. Ultrafast Proton Transfer Dynamics in the Excited State

Abstract

A novel polyimide (PI) and imide compound emitting prominent reddish-orange fluorescence under excitation by UV light were prepared based on 3-hydroxypyromellitic dianhydride (PHDA), and their fluorescence properties were examined. The steady-state fluorescence spectrum of a PI film displayed an emission band at 590 nm with a very large Stokes shift (ν = 10 448 cm −1 ) via the excited-state intramolecular proton transfer (ESIPT), while the time-resolved fluorescence spectrum showed a rapid decay of the emission band of the enol form at around 400 nm within 15 ps. Transient absorption measurements showed an induced absorption and stimulated emission of the keto form with a time constant of ca. 3.0 ps, implying that ESIPT occurs on this time scale. Consequently, introduction of a hydroxy group into the pyromellitic moiety of PIs and imide compounds led to the long-wavelength ESIPT emission applicable to spectral converters having high thermal, mechanical, and environmental stabilities.

Iridium‐Catalyzed Direct C−H Amidation Polymerization: Step‐Growth Polymerization by C−N Bond Formation via C−H Activation to Give Fluorescent Polysulfonamides

“…[13] Theprevious examples of fluorescent polymers exhibiting the ESIPT process contained ap henolic À OH moiety as ahydrogen-bond donor and displayed large Stokes shifts (86-255 nm) with only weak fluorescence (F F = 0.003-0.06). [14] However,strong fluorescence (quantum yields of up to 0.45;s ee Table S7) was observed from P1-P6,w hich contain the sulfonamide N À Hg roup as the hydrogen-bond donor because the sulfonamide moiety is conformationally locked and rigid, thereby reducing the probability of other non-radiative decay processes.T hese intriguing fluorescence properties were also observed in the film state,w here large Stokes shifts (153-173 nm) and high quantum yields of up to 0.49 without significant self-quenching were observed (see Table S7 and Figure S2). This is the first example of the ESIPT mechanism observed in polysulfonamides,w hich demonstrated excellent fluorescent behavior.…”

Crystal structure of 2,6-dibenzylpyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetrathione

“…Recently, pyromellitic diimide derivatives have been spotlighted due to their use in energy-storage materials (Nalluri et al 2016). They also show potential applications in photovoltaic devices (Kanosue et al, 2016) and organic semiconductors (Zheng et al, 2008). Not only pyromellitic diimide derivatives, but also pyromellitic diimides substituted with sulfur have potential applications in organic semiconductors (Yang et al, 2015).…”

Photoluminescence Properties of Novel Fluorescent Polyimide Based on Excited State Intramolecular Proton Transfer at The End Groups

“…Polyimides (PIs) are a group of condensation polymers which have high thermal stability, good mechanical strength, excellent chemical stability, low dielectric constant, and low thermal expansion [1][2][3][4][5][6][7][8]. Thus, PIs have been widely used as insulating interlayer films in microelectronic industry and thermal controlling films in aerospace industry.…”

“…Because of the poor solubility of PIs, optical characteristics of the PIs, such as absorption and fluorescence properties, can be evaluated only in the solid state. However, the formation of aggregation, charge-transfer (CT) complex, and oriented structures in solid samples make interpretation of the optical properties difficult [4].…”

“…However, owing to the low oscillator strength originated from the spatially separated orbitals of HOMO and LUMO, florescent emission from the CT state always results in low photoluminescent efficiency [10]. Furthermore, aromatic PIs with strong CT transitions exhibit strong coloration, which is undesirable for practical applications of the florescent PIs [4].…”