Synthesis and Optical Properties of Donor–Acceptor-Type 1,3,5,9-Tetraarylpyrenes: Controlling Intramolecular Charge-Transfer Pathways by the Change of π-Conjugation Directions for Emission Color Modulations

Abstract

In dipolar organic π-conjugated molecules, variable photophysical properties can be realized through efficient excited-state intramolecular charge transfer (ICT), which essentially depends on the π-conjugation patterns. Herein, we report a controllable regioselective strategy for synthesis and optical properties of two donor–acceptor (DA)-type 1,3,5,9-tetraarylpyrenes (i.e., 1,3-A/5,9-D ( 4b ) and 1,3-D/5,9-A ( 4c )) by covalently integrating two phenyl rings and two p -OMe/CHO-substituted phenyl units into the 2- tert -butylpyrene building block, in which the two phenyl rings substituted at the 1,3-positions act as acceptors for 4b or as donors for 4c and the two p -OMe or p -CHO-substituted phenyl moieties substituted at the K-region of 5,9-positions act as donors for 4b or as acceptors for 4c , respectively. Density functional theory calculations on their frontier molecular orbitals and UV–vis absorption of S 0 → S 1 transition theoretically predicted that the change of π-conjugation directions in the two DA pyrenes could be realized through a variety of substitution patterns, implying that the dissimilar ground-state and excited-state electronic structures exist in each molecule. Their single-crystal X-ray analysis reveal their highly twisted conformations that are beneficial for inhibiting the π-aggregations, which are strikingly different from the normal 1,3,5,9-tetraphenylpyrenes ( 4a ) and related 1,3,6,8-tetraarylpyrenes. Indeed, experimental investigations on their optical properties demonstrated that the excited-state ICT pathways can be successfully controlled by the change of π-conjugation directions through the variety of substitution positions, resulting in the modulations of emission color from deep-blue to green in solution. Moreover, for the present DA pyrenes, highly fluorescent emissions with moderate-to-high quantum yields both in the thin film and in the doped poly(methyl methacrylate) film were obtained, suggesting them as promising emitting materials for the fabrication of organic light-emitting diodes.

Triflic Acid-Promoted Adamantylation and tert-Butylation of Pyrene: Fluorescent Properties of Pyrene-Decorated Adamantanes and a Channeled Crystal Structure of 1,3,5-Tris(pyren-2-yl)adamantane

“… 2 Two alkyl-substituted pyrene derivatives, 2- tert -butylpyrene 2 and 2,7-di- tert -butylpyrene 3 , have been widely used as useful starting materials in numerous syntheses of dyes that feature special molecular shapes and suppressed aggregation properties. 3 Moreover, the latter compound proved to be an efficient acceptor for triplet–triplet annihilation 4 and a π–donor for semiconductive charge-transfer cocrystals. 5 To date, both compounds could be obtained via Friedel–Crafts alkylation of pyrene with tert -butyl chloride in the presence of a Lewis acid (aluminum chloride or bromide).…”

Synthesis, Photophysical and Electronic Properties of New Red‐to‐NIR Emitting Donor–Acceptor Pyrene Derivatives

“…There are also reports on pyrenes that have donor and acceptor moieties on alternative positions, besides the typical three categories (vide supra). Hu and co‐workers developed unsymmetric pyrenes with donors at the 1,3‐positions and acceptors at the 5,9‐positions that emit in the blue‐green region (Scheme ) . Sutherland and co‐workers combined the 2,7‐ and 1,8‐positions with the K‐region ( V and VI , Scheme ), respectively, and obtained an S 1 ←S 0 absorbance up to 900 nm, as it was their objective to obtain strongly redshifted absorptions with high molar absorptivities.…”

Regioisomeric BODIPY Benzodithiophene Dyads and Triads with Tunable Red Emission as Ratiometric Temperature and Viscosity Sensors

“…[53] Interestingly however, studies on the effecto fr egioisomerismi nr elation to TICT/AIE in organic rotor molecules are rather few. [49,[54][55][56][57][58] To our knowledge, regioisomericB ODIPY based multichromophoric TICT rotors with large Stokes shift, tunable emission in red region and unique temperature and viscosity sensingc apabilities have not been reported.…”