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Abstract. Compounds 1 were synthesized, in good to excellent yields (72-87%), through
condensation of formyl-arylthiophene precursors 2 with 1,2-diaminoanthraquinone in ethanol at
reflux, followed by cyclisation of the imine intermediate with Pb(OAc)
4
in acetic acid at room
temperature. Evaluation of the thermal, linear and NLO properties of these compounds was carried
out. The β values of chromophores 1, measured by hyper-Rayleigh scattering (HRS) technique, are
several times larger (49-67) than that of the standard reference molecule p-nitroaniline (pNA). Due
to their excellent thermal stability, (T
d
= 341-446
o
C), and good NLO properties, arylthienyl-
imidazo-anthraquinones 1 could be used as new efficient and thermally stable NLO materials.
Introduction
Push-pull chromophores, with the electron donor and acceptor separated by π-conjugated bridges
(D-π-A), have been investigated for decades. Nevertheless, they continue to attract growing interest
as one of the best paradigms for engineering new molecules for strong second-order nonlinear
optical (NLO) reponses, and their potential for application as advanced materials in molecular
devices [1]. In particular, imidazole derivatives have received increasing attention as NLO
chromophores due to their excellent thermal stability in guest-host systems. The incorporation of
thiophene rings is also desirable to enhance molecular nonlinearity. As a result of the optical and
conductive properties, conjugated materials containing thiophene and imidazole heterocycles have
found many applications including uses in OLED-PLEDs, in flexible light displays, solar cells, flat
panel displays, field effect transistors, NLO materials, sensors, etc. [2-6]. Following our interest in
heterocyclic derivatives for optical applications, we report in this work the synthesis and
characterization of the thermal, linear and nonlinear optical properties of NLO chromophores 1,
containing a functionalized arylthienyl- π-conjugated bridge linked to the imidazo-anthraquinone
electron-withdrawing moiety, which is original and different from the few anthraquinone
chromophores previously reported [7-10].
Results and discussion
Synthesis. Arylthienylimidazo-anthraquinones 1 were synthesised with different arylthienyl
substituents at position 2, in order to evaluate the effect of the electronic nature of the π-conjugated
bridge on the solvatochromic and nonlinear optical properties of chromophores 1. Therefore,
compounds 1a-e containing functionalized arylthienyl moieties (substituted with donor or acceptor
groups) linked to the imidazo-anthraquinone system, were synthesized in good to excellent yields
(72-87%), by condensation of 1,2-diaminoanthraquinone with formyl-arylthiophenes 2a-e [2] in
Materials Science Forum Vols. 636-637 (2010) pp 387-391
Online available since 2010/Jan/12 at www.scientific.net
© (2010) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/MSF.636-637.387
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
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