Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 147–151 Contents lists available at ScienceDirect Journal of Photochemistry and Photobiology A: Chemistry journal homepage: www.elsevier.com/locate/jphotochem Optical properties of a donor–acceptor-substituted “hemi-cruciform” catechol derivative Christophe Aronica a , Juliette Guérin a , Jérôme Chauvin b , Vincent Robert a , Gilles Lemercier c,∗ a Laboratoire de Chimie, UMR n ◦ 5182, CNRS/ENS-Lyon, 46 Allée d’Italie, 69364 Lyon Cedex 07, France b Laboratoire de Spectrométrie Physique, UMR n ◦ 5588, CNRS/Université Joseph Fourier and CNRS, 140 rue de la physique, BP 87 - 38402 Saint Martin d’Hères Cedex, France c Université de Reims Champagne-Ardenne, ICMR, UMR n ◦ 6229, BP 1039 - 51687 Reims Cedex 2, France article info Article history: Received 3 December 2009 Received in revised form 16 February 2010 Accepted 20 February 2010 Available online 3 March 2010 Keywords: Catechol derivatives Luminescence properties Solvatochromism Polarizability Charge-transfers abstract The optical properties of a novel catechol derivative have been studied; a very large solvatochromism of the emission spectra was observed, revealing an important low-energy intra-molecular charge- transfer. From our experiment, a chemical structure–polarizability relationship is studied according to the Lippert–Mataga correlation and compared to results obtained previously for analogous compounds. This synthetic strategy complemented with characterizations and theoretical analysis allows one to design specific charge-transfer compounds to be used as nonlinear chromophores and ligands in multifunctional complexes. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Organic molecules and related polymers [1] dedicated to appli- cations such as electroluminescence devices (OLEDs), thin film transistors, optical storage devices, optical biosensors and solar cells are commonly based on conjugated electro-withdrawing (A) and electro-donating (D) groups linked via a -conjugated sys- tem [2]. In this area, new chemosensors for the luminescent detection of relevant ions and molecules have been reported [3]. Among them, catechol derivatives displaying a pH-sensitive flu- orescence emission have been proposed and described recently [4]. In order to target specific properties and applications, a better knowledge of the materials structure–property relation- ship would be desirable. With this goal in mind, we have recently published [5], the synthesis and optical properties of several novel 4,5-substituted-(tert-butyldimethylsilyl)-protected- catechols involving (D,D), (D,A) and (A,A) pairs as Z 1 and Z 2 substituents (see Fig. 1 for the general structure of this family of compounds). These molecules appeared to be promising candidates as well as for the fine-tuning of the internal charge-transfers than as potential nonlinear chromophores, luminophores and ligands within related multifunctional coordination complexes. ∗ Corresponding author at: Université de Reims Champagne-Ardenne, ICMR UMR no 6229, BP 1039 – 51687 Reims cedex 2, France. Tel.: +33 03 26 91 32 40; fax: +33 03 26 91 32 43. E-mail address: gilles.lemercier@univ-reims.fr (G. Lemercier). On one hand, the (D,D) and (A,A) combinations allow for charge-transfers (CTs) between the catecholate functions and the -delocalized substituents in the 4th and 5th positions. On the other hand, the (D,A) substitutions favour a low-energy inter- branch CT. Since our purpose is to enhance the polarizabilities for nonlinear optical (NLO) applications, large- and low-energy intra- molecular CTs must be favoured through chemical engineering [6]. In this study, the synthesis and optical properties of a novel 4,5-[(4-phenylethynyl)-substituted]-TBDMS-protected- catecholate compound pCat-PECF 3 -PENMe 2 are reported. The substitution with an electro-donating (NMe 2 ) and -withdrawing (CF 3 ) groups at the 4th and 5th positions, respectively, gives rise to different CT strengths and pathways within the chromophore. A correlation between the optical properties (more particularly, polarizability) and structures is suggested and complementary the- oretical investigations are performed. 2. Results and discussion 2.1. Synthesis pCat-I-PENMe 2 was prepared according to procedures already described in the literature (see Section 4 for references). 4,5- Substituted-TBDMS-protected-catechol compound pCat-PECF 3 - PENMe 2 was obtained via a Sonogashira cross-coupling reac- tion [7], starting from commercially available 1,1-ethynyl-4- 1010-6030/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jphotochem.2010.02.012