SHORT COMMUNICATION DOI: 10.1002/ejic.200600477 New Dimeric Copper(II) Complex [Cu(5-MeOsal) 2 (μ-nia)(H 2 O)] 2 with Magnetic Exchange Interactions through H-Bonds Dus ˇan Valigura,* [a] Jan Moncol, [a] Maria Korabik, [b] Zuzana Púc ˇeková, [a] Tadeusz Lis, [b] Jerzy Mrozin ´ski, [b] and Milan Melník [a] Keywords: Copper / Carboxylate ligands / Nicotinamide / Dimer / Structure / Magnetic properties The synthesis and characterization (elemental analysis, IR, electronic and EPR spectra as well as magnetization mea- surements over the temperature range 1.8 K–300 K) of solid complex [Cu(5-MeOsal) 2 (μ-nia)(H 2 O)] 2 (1; 5-MeOsal = 5- methoxysalicylate, nia = nicotinamide) is reported together with the crystal structure. In blue–green complex 1, two Cu(5-MeOsal) 2 (H 2 O) units are held together by a pair of bi- dentate nonchelating nicotinamide ligands, which form a (CuNC 3 O) 2 ring. Each Cu atom adopts a distorted square- pyramidal geometry. The oxygen atoms from two unidentate 5-MeOsal anions occupy the trans position, a water molecule and the pyridine N atom of nicotinamide build the basal plane and a carboxamide O atom occupies the apical posi- tion. The separation between two Cu atoms within the cen- trosymmetric dimer is 6.940(2) Å. The dimeric units are self- Introduction For quite some time, copper complexes with various or- ganic ligands have been a subject of intense study because of their interesting properties which include biomedical ac- tivities. Nicotinamide (also known as a niacin derivative or vitamin B 3 ) is a nitrogen donor ligand that has been used in the treatment of various skin diseases (atopic eczema, [1,2] psoriasis and skin cancer [3–5] ), and the biological activity of its copper complexes have also been studied. [6] In addition, the biological activity of different salicylic acid derivatives and their copper(II) complexes is well known. [7–10] Mean- while, salicylatocopper(II) complexes that contain nicotin- amide are rarely studied in spite of their possible structural diversities. There are only two examples (out of 26 known structures) [6,11] of polymeric copper(II) complexes where nicotinamide acts as a bridging ligand – [Cu 2 (CH 3 COO) 4 - (μ-nia)] n and {[Cu(sacharinato) 2 (μ-nia)(H 2 O)]·H 2 O} n . With the purpose to obtain and study the properties of all possible products that could be prepared by the reac- tions under study, we report the synthesis, structural char- [a] Department of Inorganic Chemistry, Slovak Technical Univer- sity, Radlinského 9, 81237 Bratislava, Slovakia Fax: +421-2-52493198 E-mail: dusan.valigura@stuba.sk [b] Faculty of Chemistry, University of Wroclaw, 50-383 Wroclaw, Poland Eur. J. Inorg. Chem. 2006, 3813–3817 © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3813 assembled across a centre of symmetry by the formation of two pairs of strong hydrogen bonds, which create a one-di- mensional polymeric structure with the interdimer Cu···Cu separation 4.901(2) Å. It is believed that these hydrogen bonds between the copper(II) atoms are responsible for the unique magnetic properties of compound 1. The magnetic susceptibility of complex 1 exhibits a maximum at 6 K. A sat- isfactory explanation was found with the Bleaney–Bowers equation for Cu–Cu interaction through carboxylato groups and H-bond bridges (2J = –6.83 cm –1 ). An additional molecu- lar field correction that was used to characterize the interac- tion across the nia bridges is assumed to be extremely weak (zJ' = –0.28 cm –1 ). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) acterisation and properties of the unusual dimeric complex [Cu(5-MeOsal) 2 (μ-nia)(H 2 O)] 2 (1), which exhibits rare in- tradimer and/or interdimer interactions that result in mag- netic properties that are of interest. Results and Discussion The molecular structure of 1 (Figure 1) consists of di- meric [Cu(5-MeOsal) 2 (μ-nia)(H 2 O)] 2 molecules that are located at a centre of symmetry. Two equivalent Cu(5- MeOsal) 2 (H 2 O) moieties are connected by a pair of biden- tate nonchelating nicotinamide ligands, which creates a twelve-membered metallocyclic (CuNC 3 O) 2 ring. Each Cu atom adopts a distorted square-pyramidal geometry with the oxygen atoms of two unidentate 5-MeOsal anions in the trans position [Cu–O12 = 1.945(2) Å]. A water molecule [Cu–O1W = 1.989(2) Å] and the pyridine N atom of nico- tinamide [Cu–N1 = 2.030(3) Å] build the basal plane; a car- boxamide O atom of the bridging nicotinamide assumes the apical position [Cu–O1 = 2.267(2) Å]. The copper atom is displaced from the basal plane towards the carboxamide O atom by 0.047(1) Å. The τ value [12] of 0.066 implies an al- most perfect square-pyramidal geometry. The separation between Cu···Cu i (1– x,1– y ,1– z) within the dimeric mole- cule is 6.940(2) Å(Figure 1). The amide H atoms of the api- cally coordinated carboxamide group are linked to the co-