Symmetric and asymmetric charge transfer process of two­photon absorbing chromophores: bis­donor substituted stilbenes, and substituted styrylquinolinium and styrylpyridinium derivatives

Abstract

Two-photon absorption properties of a series of symmetrically substituted stilbenes and asymmetrically substituted stilbene-type derivatives with the same conjugated length have been investigated. The effective twophoton absorption cross sections, d TPA , as large as 62.0610 248 cm 4 s photon 21 for D-p-D molecules and 48.5610 248 cm 4 s photon 21 for D-p-A counterparts have been observed. The effect of these two types of chromophores on the peak position of the linear absorption, one-photon fluorescence as well as two-photon absorptivity is reported. Dipole moment change between the ground and the first excited states (Dm ge ), and the transition dipole moment between the first and second excited states (M ee' ) have also been calculated. It was found that the asymmetrically substituted derivatives possess relatively large Dm ge , whereas the symmetrical counterparts show an increase in M ee' . Although a large two-photon absorption resonance is due to the simultaneously high values of M ee' and Dm ge , correlated to intramolecular charge transfer, the former function is larger. These results obtained have demonstrated that the magnitude and the peak position of two-photon absorption depend not only on the amount but also on the direction of the intramolecular charge transfer.

Cooperative enhancement of two-photon absorption based on electron coupling in triphenylamine-branching chromophore

“…2). Strangely, the triphenylamine subunit on the terminal of monobranch 1 adopts the propeller-shaped, while the three of triphenylamine subunits in multibranch 2 lie in one common plane that is in agreement with the crystallographic data in BDPAS (E-4,4'-bis(diphenylamino)stilbene) [34] and in triphenylamine [35,36]. This can be explained by the sp 2 -hybridization of nitrogen and resulting effective electron delocalization within entire molecular skeleton [37].…”

Octupolar Polycyclic Aromatic Hydrocarbons as New Two‐Photon Absorption Chromophores: Synthesis and Application for Optical Power Limiting

“…Such intramolecular charge transfers were favored in more polar solvents and would result in enhanced TPA responses. [26,27] Compounds HBCÀCN and HBCÀCF 3 exhibited well-resolved emission bands. However, there was no clear spectral shift in different solvents (Figure S2 in the Supporting Information).…”

Two-photon absorption spectrum in diazoaromatic compounds

“…The spatial confinement of excitation and the ability to excite molecules with half of the energy required for linear absorption can be employed in three-dimensional microfabrication [2,3], three-dimensional optical storage [4,5], two-photon fluorescence imaging [6][7][8], two-photon photodynamic cancer therapy [9,10] and optical power limiting [11,12]. Motivated by these applications, efforts to understand the relationship between molecular structure and 2PA, aiming to design compounds with larger 2PA cross-section, have been carried out, leading to design strategies for novel organic materials [13][14][15][16][17].…”