Dual fluorescence emission of azulene derivatives in solution

Dual emission in purely organic materials for optoelectronic applications

“…15 An interesting but often overlooked DE phenomenon stems simply from the existence of two (or more) emissive singlet states in a molecule. 16 Originally discovered in azulene, 17 the rare occurrence of simultaneous emission from the first and second singlet excited states violates Kasha's rule. 18 The DE phenomenon was further explored in the intramolecular charge transfer (ICT) states in a push-pull 4-N,N-dimethylaminobenzonitrile (DMABN) compound by Lippert et al in 1959.…”

Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines

“…In the case of 4a , by excitation with 375 nm, a dual fluorescence emission is observed at 435 nm and 530 nm, respectively (Table 3). According to literature reports on azulene fluorescent behavior, the first emission wavelength is attributed to the S 2 →S 0 transition, whereas the second emission can be a consequence of the S 1 →S 0 transition [18]. By comparison the fluorescence intensity of 4b , not only increases but it also shows a strong hypsochromic shift for both transitions with the emission wavelengths at 427 nm and 522 nm, respectively (Fig.…”

“…Owing to its unique fluorescent and remarkable optical and redox properties, azulene proved to be an excellent building block for developing a large variety of materials ranging from NLO chromophores [13] to molecular switches [14–15] and liquid crystals [16] or high-conductance materials [17]. In contrast to most aromatic compounds which exhibit S 1 →S 0 fluorescence under low excitation intensity, azulene shows fluorescence predominantly from the S 2 excited state and only very weakly from S 1 [18]. The control of the optical and electronic properties of the azulene-based materials can be finely tuned by careful selection of the substitution patterns.…”

Azulene‐Moiety‐Based Ligand for the Efficient Sensitization of Four Near‐Infrared Luminescent Lanthanide Cations: Nd3+, Er3+, Tm3+, and Yb3+

“…It is known that the electronic structure and photophysical properties of derivatives of azulene are affected by their substituents. [52] This perturbation of the molecular orbitals of the azulene moiety can be rationalized by a qualitative pictorial description of the low lying molecular orbitals ( Figure 6). [53] The HOMO, LUMO, and LUMO+1 orbitals of azulene, which correspond to S 0 , S 1 and S 2 levels, respectively, are depicted in the Figure 6.…”

“…It has been found that the aldehyde group causes a blue shift of the S 1 state because of its inductive electron withdrawing effect, but causes red shift of the S 2 state due to the conjugation effect. [52] On the other hand, the hydroxyl group at C-2, which is a resonance donating group, will destabilize the LUMO orbital of azulene. This will lead to an increased S 0 -S 1 gap and to a corresponding blue shift, which explains why the energy position of the maximum of the S 0 -S 1 transition of 1,3-dicarboxaldehyde azulene is at approximately 500 nm (20 000 cm À1 ), while it is around 428 nm for our ligand.…”