Synthesis, spectroscopic, magnetic and thermal properties of copper(II), nickel(II) and iron(II) complexes with some tetradentate ligands: Solvatochromism of iron(II)–L 2 Alper Onder a , Murat Turkyilmaz b , Yakup Baran a,⇑ a Onsekiz Mart University, Art and Science Faculty, Department of Chemistry, Canakkale 17100, Turkey b Trakya University, Science Faculty, Department of Chemistry, Edirne, Turkey article info Article history: Received 10 February 2012 Received in revised form 27 April 2012 Accepted 10 May 2012 Available online 19 May 2012 Keywords: Azomethines Thermal stability Spectroscopic Solvatochromism Complexes abstract The tetradentate azomethines were prepared by condensation of 2-piperazin-1-ylethanamine, (3-mor- pholin-4-ylpropyl)amine with 3-methylthophene-2-carbaldehyde, salicylaldehyde and 1H-imidazole- 5-carbaldehyde. The ligands were characterized based on mass, 1 H and 13 C NMR, FTIR, and elemental analyses. New complexes of ligands with copper(II), iron(II) and nickel(II) were synthesized. Metal com- plexes are reported and characterized by magnetic, conductivity measurements, FTIR, elemental and thermal analyses (TG–DTA). Spectral analyses show that all the ligands behave as neutral tetradentate ligands and bind to the metal via azomethine N, piperazine N, salicylaldehyde O, morpholine O, imidazole N and thiophene S. Results of magnetic measurements and thermal studies show that the geometrical structures of the nickel(II) complexes are square planar while copper(II) and iron(II) are octahedral. The thermal behaviors of these complexes show that the hydrated complexes lose the hydration water molecule in the first step, followed immediately by decomposition of the anion and ligand molecules in subsequent steps. The solvatochromic behavior of the iron(II)–L 2 complex was investigated using the electronic spectra of 1  10 3 M in four different solvents. The solvatochromism was explained in terms of MLCT transition and solvent characteristics such as polarity, nature and acceptor–donor properties. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The synthesis of a new ligand is the most important step in the development of metal complexes with unique properties and novel reactivity. Four tetradentate azomethines were prepared. L 3 and L 4 are new and L 2 is patented [1].L 1 was prepared and its cadmium(II) and nickel(II) complexes were reported. These are X-ray structure reports and solution equilibrium respectively. Azomethines can be considered an important class of organic compounds which are good chelating agents because of the presence of both hard nitro- gen and oxygen, and soft sulfur donor atoms in the backbones of these ligands [2]. Tetradentate azomethines, with N 2 O 2 donor sets resulting from the condensation of aliphatic diamines, have been extensively studied [3–6]. Azomethine complexes are studied for their antitumor, antimicrobial, antiviral, catalytic, enzymatic and mesogenic characteristics [7–13]. Nickel–L 1 complex has been studied for planar-octahedral equilibrium in solution [14]. Synthe- sis, crystal structure, and magnetic properties of copper–L 2 were studied. The inhibitory bioactivities of nickel–L 2 against urease and xanthine have been studied [15,16]. Azomethine metal com- plexes are also a focus for scientific interest, due to their important role in biological systems, and represent an interesting model for metalloenzymes which efficiently catalyze the reduction of oxy- gen. Thermal decomposition of the metal complexes is used to in- fer the structures of the metal complexes together with the other spectroscopic and elemental analysis data [17–19]. Salicylaldehyde derivatives of azomethine compounds show a variety of biological activities, such as antibacterial activity [20]. The electronic spectra of the inorganic compounds can be affected by solvents. These complexes are usually referred to as solvatochromic substances and recent papers indicate continuing interest in this field [21– 25]. The solutions of [FeL 2 Cl 2 ] range in color from yellow to purple in solvents. These colors are due to intense charge transfer bands involving electron transfer from the metal t 2g orbital in low spin d 6 to low lying p / orbital in the azomethine. This color change occurs without any structural change in the chromophor. This is where the MLCT transition between iron(II) and azomethine takes place. Stronger acceptor properties of the solvent leads to a greater MLCT blue shift observed. This work deals with the synthesis, characterization and thermal behavior of new tetradentate azomethine complexes of 0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.ica.2012.05.006 ⇑ Corresponding author. Tel.: +90 286 2180018; fax: +90 286 2180533. E-mail address: yakupbaran@yahoo.com (Y. Baran). Inorganica Chimica Acta 391 (2012) 28–35 Contents lists available at SciVerse ScienceDirect Inorganica Chimica Acta journal homepage: www.elsevier.com/locate/ica