Title

Nonlinear Absorption In A Series Of Donor-Π-Acceptor Cyanines With Different Conjugation Lengths

Abstract

A detailed experimental and theoretical study of the linear and nonlinear absorption of a series of asymmetrical D-π-A cyanine dyes with the same trimethylindolin donor (D) and diethylamino-coumarin-dioxaborine acceptor (A) terminal groups and different conjugation lengths, is presented. Strong solvatochromic behavior affecting the fluorescence quantum yields, lifetimes, and the linear and nonlinear absorption properties is observed due to the presence of permanent ground state dipole moments. Detailed experimental studies of lifetime dynamics are performed by direct time-correlated single photon counting and pump-probe techniques. We find that an increase in π-conjugation in the investigated series of dyes leads to an enhancement of the excited-state absorption and two-photon absorption (2PA) cross-sections (δ 2PA). The 2PA spectra for all of the investigated dyes consist of two well-separated bands. The first band occurs at two-photon excitation into the vibrational levels and not into the absorption peak of the main transition, S0 → S1, which is more typical of that observed for symmetrical cyanines. The position of the second 2PA band for all the molecules remains unchanged in solvents of different polarity contrary to the large solvatochromic shift of the S0 → S1 band, resulting in a large intermediate state resonance enhancement and, therefore, a larger 2PA in acetronitrile (δ2PA ≈ 10000 GM) compared to toluene (δ2PA ≈ 4700 GM). © 2009 The Royal Society of Chemistry.

Publication Date

10-28-2009

Publication Title

Journal of Materials Chemistry

Volume

19

Issue

40

Number of Pages

7503-7513

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1039/b907344b

Socpus ID

77953451754 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/77953451754

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