Structure−Property Relationships for Two-Photon Absorbing Chromophores:  Bis-Donor Diphenylpolyene and Bis(styryl)benzene Derivatives

Abstract

The two-photon absorption properties of a series of bis dialkylamino- or diarylamino-substituted diphenylpolyenes and bis(styryl)benzenes have been investigated. Two-photon absorption cross sections, δ, as large as 1420 × 10-50 cm4 s/photon-molecule have been observed for molecules with this general bis-donor structure. The effect of the type and length of the conjugated chain and of dialkylamino or diarylamino substitution on the position and magnitude of the peak two-photon absorptivity is reported. The transition dipole moments for the transitions between the ground state and the first excited singlet state (M ge) and between the first and second excited singlet states (M ee ‘) have been estimated using experimental data from the one- and two-photon spectra. It was found that increases in chain length result mainly in an increase in M ge, whereas the addition of donor end groups or going from diphenylpolyene- to phenylene-vinylene-type bridges leads primarily to an increase in M ee ‘. The trends in the energy of the lowest excited singlet states and in the transition moments for the diphenylpolyene series as a function of chain length are in agreement with those calculated by quantum mechanical methods. These results furnish a link between structural features in these classes of molecules and the electronic dipole couplings and state energies that control the strength of the two-photon absorption. In bis(aminophenyl)polyenes containing up to four double bonds (m) the lowest excited singlet state is a Bu state, as opposed to the case of simple polyenes and diphenylpolyenes, for which it is an Ag state for m > 2. The relationship of the state ordering in these systems with the observed values of the radiative and nonradiative decay rates is also discussed.

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.…”

Theoretical study of one- and two-photon absorption spectra of azoaromatic compounds

“…In particular, numerous aspects affecting the nonlinear absorption, such as molecular symmetry, molecular planarity and extension of the conjugation length of the compounds have been considered. [7][8][9] More recently, theoretical methods have been employed to support the understanding of experimental 2PA spectrum of several compounds, 8,[10][11][12] including azoaromatic compounds, which have also been the target of theoretical studies. [11][12][13] Among several theoretical methods used to study electronic transitions of compounds, the density functional theory ͑DFT͒ combined with linear response function formalism 14 has been shown to provide accurate excitation energies particularly when employing hybrid exchange-correlation functionals.…”

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] .…”