Electronic Polarization Reversal and Excited State Intramolecular Charge Transfer in Donor/Acceptor Ethynylpyrenes

Abstract

An attempt to tune the electronic properties of pyrene (Py) by coupling it with a strong electron donor (-PhNMe2, DMA)/acceptor (anthronitrile, AN) through an ethynyl bridge has been undertaken. A moderate electron donor (iPrOPh-, IPP)/acceptor (2-quinolinyl, 2Q) has also been incorporated, and all four molecules were studied with reference to a neutral molecule, namely, 1-phenylethynylpyrene (PhEPy). All the arylethynylpyrenes (ArEPy's) have been thoroughly characterized, and their electronic properties were studied by absorption and emission spectral properties of these ArEPy's. The electrochemical characteristics were also studied for arriving at the electrochemical band gap which has been compared with the HOMO-LUMO energy gap derived from the photophysical measurements and theoretical calculations performed by density functional theory (DFT) using B3LYP/6-31G basis sets. The results obtained from experimental and theoretical studies are critically discussed.

Regioselective Substitution at the 1,3- and 6,8-Positions of Pyrene for the Construction of Small Dipolar Molecules

“…4 Pyrene 5 belongs to a family of polycyclic aromatic hydrocarbons (PAHs) with a natural electron-donating and an electron-accepting role. 6 Apart from other PAHs such as anthracene, 7 fluorene, 8 pyrene possess the equivalent activity of the sites at the 1-, 3-, 6-and 8-positions, it is different to develop an effectively rational synthetic strategy to asymmetric functionalization of pyrene. Typically, tetrabromopyrene and pyrene tetraone derivatives as key precursor were extensively utilized in the construction of PAHs for semiconductor applications, via the introduction of terminal moieties.…”

3-Pyrenylacrylates: Synthetic, Photophysical, Theoretical and Electrochemical Investigations

“…However, the bands are superposed by each other which prevents making proper assignments. In general the emission spectrum shows fewer details than the spectra of ethynylpyrenes [2] or 1-(arylalkenyl)pyrenes [24]. The absorption spectrum contains a distinct fine structure but the emission spectrum in n-hexane has less fine structure as in case of 3d.…”

“…1) [25,26]. In earlier studies it was pointed out that the shape of electronic absorption spectra of these classes of compounds depends strongly on the pyrene-type backbone [2,24]. While the bands in the spectrum of parent pyrene occur at 1 B a : 241 nm, 1 B b : 273 nm, and 1 L a : 335 nm [26], the 1 L a band in the spectra of pyrenylacrylate appear at higher wavelengths.…”

“…Its photophysical properties [1 -5] and its supramolecular chemistry [4 -9] have been widely studied. Structural modifications [10] allow for many applications, which include the development of fluorescent dyes [11], molecular electronics [2,12], optical sensors [13], fieldeffect transistors [13] and photovoltaic cells [14,15]. A wide range of fabrication techniques in combination with modern synthetic methods allow for the development of new materials which meet special demands and applications.…”

“…The synthesis and photophysical properties of 1-ethynylpyrenes and 1-arylpyrenes have been previously studied as well. They were prepared by Sonogashira and Suzuki-Miyaura cross-coupling reactions of halogenated pyrenes and characterized with regard to their absorption and emission spectral properties [2,3,22]. In this respect, the fluorescence properties of the parent pyrenes are well known to be characterized by long excited-state lifetimes and distinct solvatochromic shifts.…”