The photochemical characteristics of aromatic enediyne compounds substituted with electron donating and electron withdrawing groups

Abstract

trans- and cis-1-(4-Dimethylaminophenyl)-6-(4-nitrophenyl)hex-3-ene-1,5-diynes (trans- and cis-DANE) were synthesized and their photochemical properties were studied. The absorption spectra of trans-DANE red-shifted compared with the parent compound bisphenylethynylethene (BEE) due to intramolecular charge transfer. The fluorescence spectra, Stokes shift, fluorescence lifetime, fluorescence quantum yield, and quantum yield of trans-to-cis photoisomerization of trans-DANE showed strong dependence upon the solvent polarity in the less-polar region. No fluorescence emission from trans-DANE was observed in medium-polar and polar solvents. The quantum yield of cis-to-trans isomerization was almost solvent independent. The donor-acceptor substituents shifted the equilibrium between the trans perpendicular triplet state and the trans planar triplet state to the trans triplet state, and resulted in an increase in the triplet lifetime. Comparison of the photochemical properties of trans-DANE with trans-4-dimethylamino-4'-nitrostilbene (DANS) suggests that trans-DANE is a possible fluorescent probe in the non-polar region.

Synthesis and Characterization of Extended Tetrathiafulvalenes with Di‐, Tri‐, and Tetraethynylethene Cores

“…Interestingly, the CT absorption band of trans ‐ 22 exhibits almost twice the molar absorptivity as that of cis ‐ 22 . This isomeric difference is similar to that exhibited by trans/cis ‐1‐(4‐dimethylaminophenyl)‐6‐(4‐nitrophenyl)hex‐3‐ene‐1,5‐diyne, as reported by Arai and co‐workers 24e. No decomposition or thermal isomerization was observed according to 1 H NMR spectroscopy upon heating any of the isomers at 125 °C in [D 6 ]DMSO.…”

“…The photostationary state is characterized by a cis / trans ratio of 8:2. Similarly as to what was found by Arai,24e the ratio of quantum yields φ trans→cis / φ cis→trans can be estimated to 6:4 as judged from the ratio of ϵ trans / ϵ cis ≈ 7:3.…”

Revisiting the non-fluorescence of nitroaromatics: presumption versus reality

“…102 On the other hand, the data reported for nitrostilbenes and related compounds rationalize the fluorescence quenching under similar conditions in terms of the formation of a charge transfer state with the twisted geometry, resulting in efficient IC via bond rotation. 63–67,69,71 In the light of these publications, the hypothesis of ISC dominating the non-radiative deactivation pathways in polar media is rather dubious.…”

Synthesis and molecular design of 4,8‐diaryl‐ and 4,8‐di(arylethynyl)pyrido[4,3‐d]pyrimidines: Potential applications in nonlinear optics. Diazines Part 49

“…Coupling of 4-N,N-dimethyl-aminophenylethyne [13,14] (1.2 equiv.) with 2 (373 mg, 1 mmol) according to the general procedure B (t = 24 hours) gave after purification by column chromatography (silica gel, eluent: petroleum ether:ethyl acetate (7:3)) 274 mg (79%) of 15 as a yellow solid, mp >250°C; ir : 3177, 2201, 1673, 1607, 1586, 1558, 1520, 1462, 1391, 1359, 1222, 1151, 1115, 810 ,72.81;N,16.17;H,6.40.…”