Coordination complexes and polymers from the initial application of phenyl-2-pyridyl ketone azine in mercury chemistry Ali Akbar Khandar a,⇑ , Barindra Kumar Ghosh b,⇑ , Christos Lampropoulos c,⇑ , Masoumeh Servati Gargari a , Veysel T. Yilmaz d , Kishalay Bhar b , Seyed Abolfazl Hosseini-Yazdi a , John M. Cain c , Ghodrat Mahmoudi a a Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, P.O. Box 5166616471, Tabriz, Iran b Department of Chemistry, The University of Burdwan, Burdwan 713 104, India c Department of Chemistry, University of North Florida, 1 UNF Dr., Jacksonville, FL 32224, USA d Department of Chemistry, Faculty of Arts & Sciences, Uludag University, 16059 Bursa, Turkey article info Article history: Received 8 July 2014 Accepted 8 September 2014 Available online 18 September 2014 Keywords: Coordination polymer Mercury(II) halide/pseudohalide Azine X-ray structure Luminescence abstract A series of new mercury(II) azine Schiff base complexes have been synthesized and characterized from the initial use of phenyl-2-pyridyl ketone azine in Hg II chemistry. The synthetic/crystallization technique utilized involved the use of a branched tube, where temperature differential allowed for the slow crys- tallization of the products. The synthesized compounds are the mononuclear [Hg(L)Cl 2 ](1), [Hg(L)Br 2 ] (2), [Hg(L)(NO 2 ) 2 ](3), and the dinuclear [Hg 2 (l-L)(SCN) 4 ](4) coordination compounds, as well as a 1D coordination polymer [Hg(L)(l-I) 2 HgI 2 ] n (5) (L = phenyl-2-pyridyl ketone azine). From the X-ray data, it is evident that this versatile ligand functions as a bi- or tridentate chelate, and is also able to bridge two Hg II centers. The crystal structures of 1 and 2 are similar, both containing two crystallographically independent Hg II molecules, one tetrahedrally coordinated and one exhibiting trigonal bipyramidal geometry. The heptacoordinated Hg II center in 3 adopts a distorted capped trigonal prismatic coordina- tion sphere, while in the dinuclear complex 4, the metal ions are bridged via the bis(bidentate) L and each center is also bound to two S-bonded thiocyanate units. The one-dimensional coordination polymer in 5 consists of a tetrahedral HgI 4 and a trigonal bipyramidal HgN 3 I 2 chromophore unit, bridged by l-I  bridges. The thermal stability of the crystal lattice in 1–5 follows the pattern 3 > 1 > 2 > 5 > 4, as studied by TG/DTA, while the TG data of 1, 2, and 5 are similar, but different than the respective ones for 3 and 4, between which important similarities are observed. In the solid state, the ligand and compounds 1–5 exhibit intraligand p ? p ⁄ fluorescence at room temperature. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Mercury and its compounds [1–8] are of immense importance in chemistry and related disciplines due to their potential applica- tions in the paper industry and as preservatives, paints, cosmetics, fluorescent lamps, sensors and mercury batteries [9–12]. Exploit- ing the diversity in coordination geometries around this 5d 10 ion, different coordination frameworks may be accessed using a variety of organic ligands along with different inorganic/organic bridging units [1,13,14]. The coordination behavior of azines as organic spacers has spawned great interest in recent years due to the ease of their syntheses, their chelating abilities, and the various dentic- ities; additionally, subtle steric and/or electronic control on their frameworks has proven to lead to different monometallic and homo- or heterobimetallic complexes with interesting properties [15–17]. Halides [1,14b,14c,18,19], thiocyanates, ambidentate pseudohalides [13a,14a,20,21], and nitrites [22] are suitable termi- nal/bridging groups in mercury chemistry, and in combination with organic ligands often result in different molecular frame- works and crystalline networks through their versatile ligation modes and different non-covalent forces [23,24]. The ligand of choice for this work was phenyl-2-pyridyl ketone azine (L; Scheme 1). This ligand has previously afforded a small suite of products, including mono and/or dinuclear Cu, Ag, Ni, Zn, Co (all 3d metals) and Ag (4d metal) complexes [25]; however, there is no report of 5d metal complexes with L. Thus, we ventured to study the coordination behavior of this ligand in Hg II , and explore its coordination chemistry with a 5d metal ion. This work also focuses on the metal ion and its coordination geometry; along these lines we were particularly interested to investigate the syn- thesis of various complexes, and also structurally characterize the resulting products. Subtle changes to these geometries were also to http://dx.doi.org/10.1016/j.poly.2014.09.005 0277-5387/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: akhandar@yahoo.com (A.A. Khandar), barin_1@yahoo.co.uk (B.K. Ghosh), c.lampropoulos@unf.edu (C. Lampropoulos). Polyhedron 85 (2015) 467–475 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly