Concomitant Crystallization of Copper(II) Sachharinato Complexes with 2-methylpyrazine as a Monomer and an One-dimensional Polymer: Syntheses, Crystal Structures, Spectroscopic and Thermal Properties Veysel T. Yilmaz Æ Evrim Senel Æ Canan Kazak Received: 20 May 2008 / Accepted: 3 June 2008 / Published online: 13 June 2008 Ó Springer Science+Business Media, LLC 2008 Abstract The reaction of [Cu(sac) 2 (H 2 O) 4 ] Á 2H 2 O with 2-methylpyrazine (mpyz) leads two complexes, concomi- tant crystallization of a mononuclear complex [Cu(sac) 2 (mpyz)(H 2 O) 2 ](1) and a polymeric complex [Cu(sac) 2 (l-mpyz)] n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three- dimensional network by p–p stacking interactions. Com- plex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled to form two-dimensional frameworks by p–p and C–HÁÁÁp stacking interactions. Keywords Saccharinate Á 2-methylyrazine Á Copper(II) complex Á Coordination polymer Á One-dimensional chain Á Two-dimensional framework 1 Introduction Saccharin (sacH; o-benzosulfimide) is the most widely used non-caloric artificial sweetener and is commercially available as water soluble alkali salts. SacH is readily deprotonated when dissolved. Its deprotonated form, the saccharinate anion (sac), behaves as a versatile ligand by coordinating to dif- ferent metal ions due to the presence of the negatively charged imino nitrogen atom and the carbonyl and sulfonyl oxygen atoms. It can act in mono- (N or O), bi- (N, O) and tridentate (N, O, O) coordination modes to form metal com- plexes from mononuclear to coordination polymers [1]. Pyrazine (pyz) and related 1,4-diazines are known to behave as exo-bidentate ligands. Extensive studies on metal complexes of 1,4-diazines have demonstrated the potential of pyz and its C-substituted derivatives to bridge metal centers and form one-dimensional linear chains [2–20]. Following our work in this field, here we report a case of spontaneous crystallization of two complexes, [Cu(sac) 2 (mpyz)(H 2 O) 2 ](1) and [Cu(sac) 2 (l-mpyz)] n (2) that are obtained from the reaction of [Cu(sac) 2 (H 2 O) 4 ] Á 2H 2 O with 2-methylpyrazine (mpyz) in aqueous solution. Species 1 is a mononuclear complex, while species 2 exists as a coordination polymer with bridging mpyz ligands. This paper reports the synthesis, structural characterization and thermal properties of these two copper(II) saccharinato complexes with mpyz. 2 Experimental 2.1 Materials and Measurements All chemicals are at least reagent grade quality and are used without further purification. The starting compound, V. T. Yilmaz (&) Department of Chemistry, Faculty of Arts and Sciences, Uludag University, 16059 Gorukle, Bursa, Turkey e-mail: vtyilmaz@uludag.edu.tr E. Senel Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit, Samsun, Turkey C. Kazak Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayis University, 55139 Kurupelit, Samsun, Turkey 123 J Inorg Organomet Polym (2008) 18:407–413 DOI 10.1007/s10904-008-9218-8