DOI: 10.1002/zaac.200500395 Ion Pairing, H-bonding, and π-π Interactions in Cobalt(II) Compound Containing Guanidinium Counter Ion Shabnam Sheshmani a , Hossein Aghabozorg* ,b , Fahimeh Mohammad Panah c , Robabeh Alizadeh b , Guido Kickelbick d , Bahar Nakhjavan b , Abolghasem Moghimi e , Farshid Ramezanipour b , and Hamid Reza Aghabozorg f Tehran / Iran, a Department of Chemistry, Islamic Azad University, Shahr-e Rey Branch, b Department of Chemistry, Teacher Training University, c Department of Chemistry, Islamic Azad University, North Tehran Branch, e Department of Chemistry, Imam Hossein University, f NIOC Research Institute of Petroleum Industry, d Wien / Austria, Institute of Materials Chemistry, Vienna University of Technology Received October 9th, 2005. Abstract. A novel proton transfer compound, (GH) 2 (phendc), (1), was synthesized from the reaction of 1,10-phenanthroline-2,9-di- carboxylic acid, phendcH 2 , and guanidine hydrochloride, (GH)(Cl), (G: guanidine). The characterization was performed using IR, 1 H and 13 C NMR spectroscopy. The cobalt(II) com- pounds were synthesized using proton transfer compounds contai- ning guanidinium counter ion. These proton transfer compounds are (GH) 2 (phendc), and (GH) 2 (pydc) (pydcH 2 : 2,6-pyridinedicar- 1 Introduction Existing design strategies for the synthesis of extended inor- ganic networks follow two principal methods based on the different nature of the interactions responsible for net- working. In one approach, which are the most frequently used, coordinative covalent bonds engaged between tran- sition-metal ions and various organic linkers [1-5]. The other method, still far less common, exploits weaker inter- molecular forces (particularly π-π interactions, H-bonding, and halogen bonding) as a guide to the assembly of molecu- lar coordination complexes into extended organized net- works [2]. Recently, a project was defined to prepare water-soluble proton transfer compounds [3] as novel self-assembled sys- tems that can function as suitable ligands in the synthesis of metal complexes. The success of the synthesis of these systems depends on the choice of the appropriate carboxylic acid, as proton donor, and amine, as proton acceptor, which interact to each other. Several examples of proton transfer self-assembled systems, prepared by employing this strategy, include organic heterocyclic amine carboxylates [5], oxa- lates [6], and squarates [7]. Our research group have re- ported cases in which proton transfer from 2,6-pyridined- * Prof. Hossein Aghabozorg Department of Chemistry, Teacher Training University, 49 Mofateh Avenue, 15614, Tehran / Iran, Fax: +98 21 88820993, E-mail: aghabozorg@saba.tmu.ac.ir Z. Anorg. Allg. Chem. 2006, 632, 469-474  2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 469 boxylic acid). The chemical formulae and space groups are (GH) 2 [Co(phendc) 2 ]·4H 2 O, P1 ¯ (2), and (GH) 2 [Co(H 2 O) 6 ]- [Co(pydc) 2 ] 2 , P2 1 /n (3). Non-covalent interactions such as ion- pairing, hydrogen bonding and π-π stacking are discussed. Keywords: Cobalt; 1,10-Phenanthroline-2,9-dicarboxylic acid; 2,6-Pyridinedicarboxylic Acid; Guanidine hydrochloride; Crystal structure; Ion pairs; Hydrogen bonds icarboxylic acid, pydcH 2 , to 2,6-pyridinediamine, pyda, guanidine, G, 1,10-phenanthroline, phen, creatinine, creat, and 2,4,6-triamino-1,3,5-triazine, tata, resulted in the for- mation of proton transfer compounds, (pydaH)(pydcH) [8], (GH) 2 (pydc) [9], (phenH) 2 (pydc) [10] (creatH)(pydcH)·H 2 O [11], and (tataH) 2 (pydc) [12]. The importance of proton transfer compounds resides in their ability to act as com- plexing agents in polar solvents such as H 2 O to form water- soluble complexes. Several complexes of these systems have been synthesized and their X-ray crystal structures have been reported [9, 10, 13]. In continuation of our research project, we report herein the synthesis, characterization and crystal structure deter- minations of cobalt(II) compounds obtained from two pro- ton transfer compounds containing guanidinium counter ion. These proton transfer compounds are (GH) 2 (phendc), and (GH) 2 (pydc)(G: guanidine; phendcH 2 : 1,10-phen- anthroline-2,9-dicarboxylic acid; pydcH 2 : 2,6-pyridine- dicarboxylic acid). Non-covalent interactions in these com- pounds play an important role in the crystal lattice. 2 Results and Discussion 2.1 Synthesis and Characterization of (GH) 2 (phendc), (1) The reaction between 1,10-phenanthroline-2,9-dicarboxylic acid, phendcH 2 , and guanidine hydrochloride, (GH)(Cl), in 1:2 molar ratio under reflux leads to the formation of a light yellow crystalline 1 (Scheme 1). Our effort on crystalli- zation of the proton transfer compound to obtain single crystals suitable for X-ray diffraction study was not success-