Synthesis of new red photoluminescent Zn(II)-salicylaldiminato complex Vincenzo Liuzzo a, ⁎, Werner Oberhauser b , Andrea Pucci a,c a Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy b Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area di Ricerca CNR di Firenze, via Madonna del Piano 10, 50019, Sesto Fiorentino, Italy c INSTM, c/o DCCI, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy abstract article info Article history: Received 18 January 2010 Accepted 6 March 2010 Available online 17 March 2010 Keywords: Tetradentate Schiff base Zinc Luminiscence We report the preparation and photophysical properties of a new zinc (II) complex of the donor–acceptor– donor (D–A–D) type ligand N,N′-bis(2-hydroxy-1-naphthylidene)-diaminomaleonitrile (H 2 L). The mole- cular structure of the [(ZnL)·DMF]·DMF complex was determined by single crystal X-ray crystallography. The complex exhibits remarkable optical features attributed to the intramolecular charge transfer (ICT) with a striking red emission. Fluorescence studies of H 2 L and ZnL reveal that the quantum yield strongly increases upon coordination. © 2010 Elsevier B.V. All rights reserved. Since the first fabrication of thin-layer organic electroluminescent device, obtained from tris(8-hydroxyquinolinolate)aluminum(III) (Alq 3 ) [1], luminescent materials have attracted much attention due to their significant applications such as organic light emitting devices (OLEDs) and sensors [2]. In contrast to organic dyes and polymers, the organic metal– chelate complexes generally offer additional properties such as high thermal and optical stability as well as good electron transport and luminescent properties [3]. In this context, the metal complexes with salicylaldiminato ligands are promising materials for optoelec- tronic applications due to their outstanding photo- and electrolumi- nescent (PL and EL) properties and the easy preparation. One of the main appeals of this class of inorganic complexes is that molecular engineering permits systematically altering spectroscopic and chemical properties. This chemical flexibility allows for the designing of systems that respond to specific environmental variables [4,5]. Zn(II) complexes bearing salicylaldiminato ligands have been particularly employed as blue, greenish and red emitters in organic optoelectronics [6–8] but their absorption and emission properties appear scarcely investigated in detail. For this purpose, in the present work, we report the synthesis and the characterisation of a donor–acceptor–donor (D–A–D) type ligand N,N′-bis(2-hydroxy-1-naphthylidene)-diaminomaleonitrile (H 2 L) and its neutral Zn(II) complex, focusing the attention on their absorption and emission characteristics. To the best of our knowledge, no studies are reported in literature on the preparation and characterization of the ligand H 2 L while only one report describes the preparation and characterization of related cobalt(II), nickel(II) and copper(II) complexes [9]. H 2 L [10] and its zinc complex [11] were prepared using a method reported by Di Bella [12] and then characterized. In the IR spectra of H 2 L and ZnL similar frequencies were observed for the stretching of imines groups (H 2 L = 1618 cm -1 ; ZnL = 1615 cm -1 ) and nitrile groups (H 2 L = 2217 cm -1 ; ZnL = 2213 cm -1 ). In particular, the similar frequencies recorded for nitrile groups suggest that the coordination with the zinc atom slightly affects the charge distribu- tion of the π-electronic structure of the free ligand [12]. The crystal structure of [(ZnL)·DMF]·DMF (Fig. 1) exhibits one molecule of [(ZnL)·DMF] and one uncoordinated DMF in the asymmetric unit [13]. The Zn atom shows a distorted square-base pyramidal coordination geometry, with the two phenoxy oxygen atoms (O(1) and O(2)) and the two imino nitrogen atoms (N(1) and N (2)) occupying the basal coordination sites, while an O-coordinating DMF molecule occupies the apical position. The Zn atom deviates from Inorganic Chemistry Communications 13 (2010) 686–688 ⁎ Corresponding author. Tel.: +39 050 2219443; fax: +39 050 2219260. E-mail address: vinlz@dcci.unipi.it (V. Liuzzo). 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.03.020 Contents lists available at ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche