Toward Highly Active Two-Photon Absorbing Liquids. Synthesis and Characterization of 1,3,5-Triazine-Based Octupolar Molecules

Abstract

Three novel two-photon absorbing (TPA) chromophores with 1,3,5-triazine as the π-electron deficient core, dialkylfluorene as aromatic bridges, and diphenylamino groups as the electrondonating end-groups were prepared. Designated as AF-450 (2,4,6-tris[7-(diphenylamino)-9,9-didecylfluoren-2-yl]-1,3,5-triazine), AF-455 (2,4,6-tris[9,9-bis(3,7-dimethyloctyl)-7-(diphenylamino)-fluoren-2yl]-1,3,5-triazine), and AF-457 (2,4,6-tris[(7-(diphenylamino)-9,9-diprop-2-enylfluoren-2-yl]-1,3,5-triazine), their overall molecular structure and local symmetry (D 3h ) are similar to those of previously reported three-armed AF-350 (N,N,N-tris[4-{7-(2benzothiazolyl)-9,9-diethylfluoren-2-yl}phenyl]amine) and AF-380 (N,N,N,-tris[7-(2-benzothiazolyl)-9,9-diethylfluoren-2-yl]amine). Among the family of AFX chromophores previously reported by us, AF-450 possesses one of the largest effective TPA cross-sections (σ 2 ′ ) 39 500 × 10 -50 cm 4 -sec/photon-molecule, or 39 500 GM) as determined by nonlinear transmission method in the nanosecond regime at 800 nm. In contrast, AF-455, a mixture of stereoisomers with the same chemical formula as AF-450, is a glassy material that becomes fluid (molasses-like) upon heating at 70-80 °C and has noticeably smaller effective σ 2 ′ value (33 300 GM). AF-457 (σ 2 ′ ) 27 800 GM) with six allyl side groups was prepared as a precursor toward the synthesis of a TPA liquid. The intrinsic TPA cross-sections of these chromophores were also determined as a function of excitation wavelengths via a femtosecond white-light continuum generation and direct degenerate-TPA measurement technique. At the TPA peaks ∼779 nm, their σ 2 ′ values are 216, 214, and 199 GM ((15%) for AF-450, AF-455, and AF-457, in that order. They are in the same trend as the nanosecond values, albeit two orders of magnitude lower.

Two-photon fluorescence measurements of reversible photodegradation in a dye-doped polymer

“…AF455 is known to have a large two-photon absorption cross-section and is therefore a promising optical material for many applications. [7] Figure 2 shows the experimental layout. The laser beam is filtered to remove all parasitic light and is split into two parts.…”

Facile synthesis of two-photon absorbing polymers through radical copolymerization

“…1 H NMR spectra were measured by a Bruker AM 250 (250 MHz) spectrometer. 13 C NMR spectra were recorded at 62.9 MHz on a Bruker AM 250 (250 MHz) spectrometer. All samples were referenced to the deuterated solvents.…”

“…The fulfillment of above technological applications relies greatly on the development of organic materials with superior two-photon absorption (TPA) activities. Since 1990s, intensive studies have been conducted and great progress has been made on the discovery of structure-activity relationship in TPA molecules [11][12][13][14][15][16][17][18][19]. Earlier studies have focused on linear quadrupolar molecular structures, and found that the conjugation length, π-electron center, and chemical functional groups at the end of electron conjugation are three important factors for the enhancement of TPA activities [11,15,16].…”

“…Earlier studies have focused on linear quadrupolar molecular structures, and found that the conjugation length, π-electron center, and chemical functional groups at the end of electron conjugation are three important factors for the enhancement of TPA activities [11,15,16]. Recent studies have demonstrated superior TPA properties of octupolar multi-branched structures in comparison to linear structures [12,13,20]. Despite the advances in molecular structure development, most TPA molecules need to be incorporated into polymers to form thin films for many practical applications [21].…”

Two-Photon Absorbing Molecules as Potential Materials for 3D Optical Memory

“…Several well-known π-bridges that have been reported are trans-stilbene [8,10,11], fluorene [9], dithienothiophene [12,13], and butadiyne [13,14] linkers (Scheme 1). Elongation and dendrimerization [15,16] of the molecules also results in the enhancement of 2PA (Scheme 2). Scheme 1.…”