Title

Efficient Two-Photon Absorbing Acceptor-Π-Acceptor Polymethine Dyes

Abstract

We present an experimental and theoretical investigation of the linear and nonlinear optical properties of a series of acceptor-φ-acceptor symmetrical anionic polymethine dyes with diethylamino-coumarin-dioxaborine terminal groups and different conjugation lengths. Two-photon absorption (2PA) cross sections (δ2PA) are enhanced with an increase of π-conjugation length in the investigated series of dyes. 2PA spectra for all dyes consist of two well-separated bands. The first band, located within the telecommunications window, occurs upon two-photon excitation into the vibrational levels of the main S0 →' S1 transition, reaching a large δ2PA = 2200 GM (1 GM = 1 × 10-50 cm 4 s/photon) at 1600 nm for the longest conjugated dye. The position of the second, and strongest, 2PA band for all anionic molecules corresponds to the second-excited final state, which is confirmed by quantum-chemical calculations and excitation anisotropy measurements. Large δ2PA values up to 17 000 GM at 1100 nm are explained by the combination of the large ground-and excited-state transition dipole moments. The three shortest dyes show good photochemical stability and surprisingly large fluorescence quantum yields of ≈0.90, ≈0.66, and ≈0.18 at the red to near-IR region of ≈640, ≈730, and ≈840 nm, respectively. The excited-state absorption spectra for all samples are also studied and exhibit intense bands throughout the visible wavelength region with peak cross section close to 5 × 10 -16 cm2 with a corresponding red shift with increasing conjugation lengths. © 2010 American Chemical Society.

Publication Date

6-17-2010

Publication Title

Journal of Physical Chemistry A

Volume

114

Issue

23

Number of Pages

6493-6501

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/jp100963e

Socpus ID

77953440609 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/77953440609

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