Design of Organic Molecules with Large Two-Photon Absorption Cross Sections

Abstract

A strategy for the design of molecules with large two-photon absorption cross sections, delta, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of delta. Synthesized bis(styryl)benzene derivatives with donor-pi-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of delta, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide delta values in good agreement with experimental values. The combination of large delta and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.

Five Orders-of-Magnitude Enhancement of Two-Photon Absorption for Dyes on Silver Nanoparticle Fractal Clusters

“…We estimated that these films have a fractal dimension of 1.45-1.65 from optical and scanning electron microscopy (imaged perpendicular to film), using the area-perimeter method. 22 The chromophoric polymer (A), whose structure is shown in Figure 1, contains donor-acceptor-donor units 23,24 in the main chain that exhibit a large TPA cross section and high fluorescence quantum efficiency. It was synthesized via a Heck coupling of a divinyltriarylamine, 3, and a dicyano-substituted, diiodobis(stryryl)benzenze, 6, as shown in Scheme 1.…”

Vibronic contributions to resonant NLO responses: two-photon absorption in push–pull chromophores

“…Among other properties, large two-photon absorption (TPA) cross-sections are promising for different applications, ranging from optical storage to biological optical imaging 1 . As a consequence, both experimental and theoretical work [2][3][4][5][6][7] have received strong impetus and several interesting strategies have been proposed to improve NLO responses in general 8,9 and TPA cross-section in particular 1,10 . A presently highly debated topic concerns the importance of vibrational contributions to NLO responses of organic materials [11][12][13][14] .…”

Three Novel Seminaphthorhodamines: Synthesis, Structure, and Spectral Properties

“…In aqueous solution, the Stokes shift is more pronounced with increased alkylation of the nitrogen at position 10, likely due to the electron donating abilities of the N-alkyl groups. 8 The extinction coefficients, absorption maxima, and Stokes shift of each compound can be seen in Table 1 in the various solvents probed. Stokes shifts grew larger with increasing alkylation of the position 10 nitrogen in aqueous solvents.…”