11,11,12,12-Tetracyano-4,5-pyrenoquinodimethanes: Air-Stable Push–Pull o-Quinodimethanes with S₂ Fluorescence

Abstract

The synthesis and properties of 11,11,12,12-tetracyano-4,5-pyrenoquinodimethanes (4,5-TCNPs), a new family of isolable and air-stable o-quinodimethanes, are reported. The ortho disposition of the dicyanomethane substituents strongly polarizes the pyrene framework to promote broad and intense intramolecular charge-transfer transitions. In addition, spectroscopic studies reveal that 4,5-TCNPs violate Kasha's rule and emit from the S2 level.

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

“…The product was isolated as a white solid (3.46 g, 10.8 mmol, 51 %). The spectroscopic data match those reported previously . 1 H NMR (500 MHz, CD 2 Cl 2 ): δ =7.98 (dd, J= 7 Hz, J= 1 Hz, 2 H), 7.97 (dd, J= 8 Hz, J= 1 Hz, 2 H), 7.82 (s, 2 H), 7.73 (dd, J= 8 Hz, J= 7 Hz, 2 H), 4.29 (br, 4 H), 3.75 (br, 4 H) ppm.…”

Prompt and Long-Lived Anti-Kasha Emission from Organic Dyes

“…Violation of the Kasha rule was attributed to the large S1-S2 energy gap (0.98 and 0.94 eV in 71 and 72, respectively, as determined by DFT and TDDFT calculations at B3LYP/6-31G(d,p) level) favoring emission from S2 over S2-S1 IC as a consequence of the reduced overlap between vibrational levels of S1 and S2. While pyrene, previously reported as an exception to Kasha rule [9], was recently demonstrated [14] to emit uniquely from S1, the introduction of dicyano methane substituents on the pyrene scaffold to generate compounds 71 and 72 (Scheme 25) promotes, in DCM solution, an intense ICT emission that originates from S2, while no radiative deactivation is obtained upon S0-S1 excitation [71] (see Figure 19). Violation of the Kasha rule was attributed to the large S1-S2 energy gap (0.98 and 0.94 eV in 71 and 72, respectively, as determined by DFT and TDDFT calculations at B3LYP/6-31G(d,p) level) favoring emission from S2 over S2-S1 IC as a consequence of the reduced overlap between vibrational levels of S1 and S2.…”

A short pyrene-fused pyrazaacene with red to near-infrared photoluminescence

“…To do so, pyrene diketone 7 was first transformed into diketal-protected 8 and then was subsequently oxidised to pyrene diketone 9, following a previously reported procedure. 10 Compounds 4 and 6 were obtained by cyclocondensation of diketone 9 with 2,3-diamino-5,6-dicyanopyrazine and diaminomaleonitrile in good yields (52% and 43%, respectively). Compounds 3-6 are soluble in a wide variety of organic solvents, including CH 2 Cl 2 , CHCl 3 and THF.…”