ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2009, Vol. 35, No. 7, pp. 512–518. © Pleiades Publishing, Ltd., 2009. 512 1 INTRODUCTION Throughout the synthesis of crown ethers, the selec- tivity behaviors of these compounds were recognized by Pedersen [1, 2]. The primary crown ethers contain only oxygen binding sites, which have tendency for selective binding with alkali and alkaline-earth metal ions [3, 4]. The selectivity is the prime request for most chemical measurements, especially, in analytical tech- niques [5]. The synthesis of new crown ethers, which have more tendencies for binding with transition and post-transition metal ions, was the more stimulated goal for research [6]. Therefore, new macrocyclic poly- ethers, which introduced N, S, and pyridyl unit onto macrocyclic ring, have been synthesized later [7, 8]. One of these new synthesized crown ethers is diben- zopyridino–18-crown–6 (DBPY18C6). Currently, our research group have studied the chemical behavior of DBPY18C6 in several areas, such as charge-transfer reactions with iodine [9], designing of ion-selective electrode and ion-transport for Pb 2+ [10, 11], and poten- tiometric study of it with both some alkaline and alka- line-earth and post-transition metal ions in methanol [12–14]. We also studied the chemical behavior of DBPY18C6 with some alkaline-earth and lanthanides metal ions by spectrophotometry [15, 16]. In continu- ing these studies for approaching the analytical aspects, 1 The article is published in the original. we have interested in studying complexation reactions of DBPY18C6 with some transition and post-transition metal ions by spectrophotometry, because there is no report about them in the literature [17, 18]. In spectrophotometric method, metal ion indicators have a considerable potential for obtaining reliable complex stability constants. The concentration of both the free ligand and the complex can be accurately mea- sured without disturbing the equilibrium [19]. An important application of this approach is the measure- ment of stability constants of a metal ion with other ligands in solution. A competitive spectrophotometric method for the complexation studies of some transition and post-transition metal ions with crown ethers and cryptands have been developed [20–24], using murex- ide (Mu) as a suitable metallochromic indicator [23]. However, reports about murexide reaction with post- transition metal ion are quiet sparse [19, 25, 26]. Because of biological, industrial, and environmental importance of Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Pb 2+ , Ag + , and Hg 2+ the study of the complexation, reactions of these metal ions with DBPY18C6 by the spectrophtometric method through using murexide was the major goal of this research. In this study, we have reported the stability con- stants of complexation reactions of dibenzopyridino– 18-crown–6 with Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Pb 2+ , Ag + , and Spectrophotometric Study of Complexation of Dibenzopyridino–18-Crown–6 with Some Transition and Post-Transition Metal Ions in DMSO Solution Using Murexide as a Metallochromic Ligand 1 J. Zolgharnein*, H. Tahmasebi, and S. Amani Department of Chemistry, Arak University, Arak, 38156, Iran *E-mail: J-Zolgharnein@araku.ac.ir Received October 27, 2008 Abstract—The complexation reaction of dibenzopyridino-18-crown-6 (DBPY18C6) with Co 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ , Hg 2+ , and Ag + have been studied in DMSO at 25°C by the spectrophotometric method. Murexide was used as a competitive colored ligand. The stoichiometry of metal ion-murexide and metal ions with DBPY18C6 complexes were estimated by mole ratio and continuous variation methods and emphasized by the KINFIT program. The sto- ichiometry of all the complexes was found to be 1 : 1 (metal ion/ligand). The order of stability constants for the ob- tained metal ion–murexide complexes (1 : 1) varies in the order Cu 2+ > Cd 2+ > Co 2+ ~ Pb 2+ > Zn 2+ > Ag + > Hg 2+ . This trend shows that the transition metal ions clearly obey the Irving–Williams role. For the post-transition metal ions, the ionic radius and soft-hard behavior was the major affects in varying of this order. The dibenzopyridino-18- crown-6 complexes with the used metal ions vary as Ag + > Pb 2+ > Cu 2+ > Cd 2+ > Hg 2+ > Zn 2+ > Co 2+ . DOI: 10.1134/S1070328409070082