Syntheses of mixed chelate copper(II) complexes containing b-ketoaminato and diamine ligands: Solvatochromism study Hamid Golchoubian a,⇑ , Ehsan Rezaee a , Giuseppeh Bruno b , Hadi Amiri Rudbari b a Department of Chemistry, University of Mazandaran, Babol-sar 47416-95447, Iran b Dipartimento di Chimica Inorganica, Vill. S. Agata, Salita Sperone 31, Università di Messina, 98166 Messina, Italy article info Article history: Received 29 June 2012 Received in revised form 24 July 2012 Accepted 2 August 2012 Available online 24 August 2012 Keywords: Mixed-chelate b-Ketoamine Solvatochromism SMLR method Copper(II) complexes Diamine abstract Three new mixed-chelate Cu(II) complexes incorporating N,N,N 0 ,N 0 -tetramethylenediamine (tmen) or N,N-dimethyl, N 0 -benzyl-ethylenediamine (dmben) as diamine chelate and a b-ketoaminato such as 4-amino-3-penten-2-onato (APO) or 3-amino-3-phenyl-2-buten-1-onato (APBO) with the general formula [Cu(b-ketoamine)(diamine)]ClO 4 were prepared and characterized. Their solvatochromic proper- ties were studied by visible spectroscopy. X-ray crystal analysis confirmed that copper (II) ion in [Cu(APO)(tmen)]ClO 4 and[Cu(APBO)(tmen)]ClO 4 is almost in a square planar environment. Structure of [Cu(APO)(dmben)]ClO 4 was investigated by DFT calculation. The solvent-dependent visible spectroscopic absorption maxima, m max , were analyzed using stepwise multiple linear regression (SMLR) method to find the best model explaining the observed positive solvatochromism. The analysis demonstrated that among different solvent parameters, donor number (DN) is a dominant factor responsible for the shift in the d–d absorption band of the complexes to the lower wavenumber with increasing its values. The importance of steric effect in the diamine ligand and more delocalization of pi-bands in the b-ketoamine on the spectral and SMLR measurements are discussed. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Through the past decade, chromotropism behaviors of inorganic complexes have been interested and investigated by many researchers [1–3]. Chromotropism means the reversible color transformation of the materials due to the surrounding physical and chemical conditions such as temperature (thermochromism), solvent (solvatochromism), pressure (piezochromism), light (photochromism) and electro-redox reaction (electrochromism) [4]. This phenomenon has many applications in thermo-sensitive, imaging, photo-switching and sensor materials [5,6]. One of the most attractive applications in inorganic chemistry is the use of solvatochromism behavior of complexes in Lewis acid–base indica- tors [7]. The origin of solvatochromism phenomena in metal com- plexes are classified into two general types [8,9]; in the first type, metal complexes in solution are interacted by solvent molecules in a direct fashion due to the direct attachment of the solvent mole- cules onto metal center and by indirect interactions between sol- vent molecules and ligands in the second type. In copper(II) and nickel(II) complexes with square planar structures the first type solvatochromism often observed while coordinatively saturated complexes are examples of the second type. Although there are a vast collection of solvatochromic complexes and compounds, a certain class of complexes such as mixed-chelate complexes of copper(II) exhibit considerable color change over a wide range of solvent used [1,10,11]. This is due to presence of strong John–Teller effect in these complexes, the d–d transition of copper(II) can be shifted because of the interactions of the solvent molecules with the axial sites of the copper center. Although there are many reports for syntheses and solvatochromic properties of mixed- chelate copper(II) complexes derived by b-diketones and diamines [12–15], based on our knowledge, such investigations have not been employed on synthesis and solvatochromism of mixed-che- late complex containing b-ketoaminato. By now, only some reports are available in literature concerning preparation of bis(b-ketoam- inato) complexes and their properties and applications [16–20]. Therefore, the solvatochromism of this class of mixed-chelate com- plexes is still unexplored. In this report we synthesized and char- acterized three new mixed-chelate copper(II) complexes with a general formula [Cu(b-ketoamine)(diamine)]ClO 4 shown in Fig. 1, where b-ketoamine is 4-amino-3-penten-2-onato (APO) or 3- amino-3-phenyl-2-buten-1-onato (APBO) and diamine stands for N,N-dimethyl, N 0 -benzylethylenediamine (dmben) or N,N,N 0 ,N 0 -tet- ramethylethylenediamine (tmen). Furthermore, solvatochromism behaviors of the mixed-chelate complexes in a number of organic solvents have been investigated. The effects of substitutions attached to the diamine and b-ketoaminato ligands on the solvatochromism of these complexes have been examined. There 0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ica.2012.08.008 ⇑ Corresponding author. Tel./fax: +98 (112) 5342350. E-mail addresses: h.golchobian@umz.ac.ir (H. Golchoubian), gbruno@unime.it (G. Bruno), hamirirudbari@unime.it (H.A. Rudbari). Inorganica Chimica Acta 394 (2013) 1–9 Contents lists available at SciVerse ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica