FULL PAPER DOI:10.1002/ejic.201402314 Synthesis and Structure of [Et 3 NH][Fe(HL) 2 ] [H 3 L= L-2- (3,5-Di-tert-butyl-2-hydroxybenzylamino)succinic Acid] and Its Catalytic Activity towards Efficient Photodegradation of Dyes in the Presence of H 2 O 2 Sohaham Dasgupta, [a] Sanghamitra Atta, [a] N. D. Pradeep Singh,* [a] Dibakar Deb, [a] W. Scott Kassel, [b] and Manish Bhattacharjee* [a] Keywords: Photodegradation / Green chemistry / Dyes/pigments / Iron / Amino acids / Biomimetic synthesis A new biogenic potentially tetradentate ligand, L-2-(3,5-di- tert-butyl-2-hydroxybenzylamino)succinic acid, has been synthesized. Upon reaction with FeCl 3 in the presence of tri- ethylamine, it afforded the complex [Et 3 NH][Fe(HL) 2 ](1). The complex was structurally characterized and was used for Introduction Iron-promoted photo-Fenton systems have been used for the photodegradation of pollutants such as phenols, [1–5] chlorophenoxy herbicides [6] and different dyes [7,8] because they exhibit an accelerated rate of oxidation. [9] The two im- portant steps that occur in photo-Fenton processes are (i) photoreduction of iron(III) to iron(II) by photoinduced metal–heteroatom bond cleavage [10] or by ligand-to-metal charge transfer [11] and (ii) reaction of H 2 O 2 with iron(II) to produce a reactive hydroxyl radical. Photo-Fenton pro- cesses that involve various iron complexes such as ferrioxal- ate/H 2 O 2 [12] by using UV radiation have been used for effec- tive photodegradation of wastewater and organic pol- lutants. Since the major portion of sunlight falls in the vis- ible region, utilization of visible light to degrade pollutants is highly desirable. Recently, complexes such as iron tetra- sulfophthalocyanine, [Fe(PcS)], iron(II) bipyridine complex, [Fe(bipy) 3 ] 2+ , and iron salen complex, [Fe III –salen]Cl [salen = 2,2'-ethylenebis(nitrilomethylidene)diphenol], in the pres- ence of hydrogen peroxide have been shown to be effective catalysts for the photodegradation of organic pollutants un- der visible light. [13–15] It has been mentioned in the litera- ture that [Fe(PcS)] is the best choice, since it is a biomimetic catalyst and can be anchored to Amberlite. It might be [a] Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India E-mail: mxb@iitkgp.ac.in; ndpradeep@chem.iitkgp.ernet.in http://www.chemistry.iitkgp.ac.in/~mxb/ http://www.chemistry.iitkgp.ac.in/faculty/NDPS/ [b] Department of Chemistry, Villanova University, Villanova, PA 19085, USA Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201402314. Eur. J. Inorg. Chem. 2014, 5125–5134 © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 5125 homogeneous photocatalytic degradation of methylene blue (MB), malachite green (MG), crystal violet (CV) and rhod- amine B (RhB) under visible-light irradiation in aqueous solution in the presence of H 2 O 2 . noted that, although [Fe(Pcs)] is available commercially, it is not very cheap. Thus, reports on efficient photocatalysts for degradation that contain iron complexes of environmen- tally friendly biomimetic ligands are not numerous and the development of such complexes still remains a challenge. Among the various organic pollutants, different synthetic dyes are widely used to colour products in many industries such as textile, paper, rubber, plastics and cosmetics. Such colouring agents, when mixed with water and used for in- dustrial processes, produce highly coloured effluent. These common industrial pollutants are subsequently discharged mostly into surface water resources. Even at low concentra- tions, dyes can be detected visually and their presence in surface water affects aquatic life. [16] These highly persistent coloured compounds are not only the first visually detect- able contaminant present in the water; they also inhibit the admission of sunlight into water and thus affect photosyn- thesis by aquatic plants. [17] Hence, it has become essential to develop a suitable process that can mineralize these kinds of contaminants present in wastewater. Previous studies suggest that a complex with broad ab- sorption in the visible region can be utilized in the photo- Fenton reaction to harvest visible light. It should be noted that some of the reported complexes employ ligands that are not environmentally benign. Thus there is a need to develop iron complexes that contain environmentally friendly ligands and that show ligand-to-metal charge- transfer (LMCT) transitions in the visible region. Therefore we thought of synthesizing a ligand based on a naturally occurring amino acid that contained a phenolate group. Herein we report the synthesis of a new amino acid based ligand, -2-(3,5-di tert-butyl-2-hydroxybenzylamino)suc- cinic acid (LH 3 ), and its iron complex, [Et 3 NH][Fe(LH) 2 ]