PAPER www.rsc.org/dalton | Dalton Transactions Structural, magnetic, high-frequency and high-field EPR investigation of double-stranded heterometallic [{Ni(en) 2 } 2 (l-NCS) 4 Cd(NCS) 2 ] n ·nCH 3 CN polymer self-assembled from cadmium oxide, nickel thiocyanate and ethylenediamine† Oksana V. Nesterova,* a Svitlana R. Petrusenko, a Vladimir N. Kokozay, a Brian W. Skelton, b Julia Jezierska, c Wolfgang Linert d and Andrew Ozarowski e Received 29th August 2007, Accepted 14th December 2007 First published as an Advance Article on the web 22nd January 2008 DOI: 10.1039/b713252b A novel heterometallic 1D coordination polymer [{Ni(en) 2 } 2 (l-NCS) 4 Cd(NCS) 2 ] n ·nCH 3 CN (en = ethylenediamine) has been prepared using the self-assembly process in a one-pot reaction of cadmium oxide, nickel and ammonium thiocyanates with an acetonitrile solution of ethylenediamine. The complex consists of an uncommon cis-Cd(SCN) 4 (NCS) 2 4− fragment and a rare combination of cis-Ni(en) 2 2+ and trans-Ni(en) 2 2+ building blocks linked by l 1,3 -NCS bridges into a double-stranded zigzag chain structure. Each chain is comprised of [Ni 2 Cd 2 (l-NCS–N,S) 4 )] macrocycles with chair-like and rectangular-like shapes arrayed alternately. The shortest intrachain Cd ··· Cd separations are 9.535(1) and 10.868(2) A ˚ , while the nearest Ni ··· Ni distances are 5.418(1) and 6.612(2) A ˚ . A network of weak N–H ··· S hydrogen bonds, involving the terminal NCS ligands and NH 2 -groups of en, links the infinite chains and results in the formation of an extended supramolecular three-dimensional framework. Variable-temperature (1.8–300 K) magnetic susceptibilities show a slight change of the l B value at low temperature, indicative of weak antiferromagnetic interactions (J = 1.55 cm −1 ) between magnetic canters. High-field, high-frequency (100–400 GHz) EPR spectra were simulated using S = 1 ground state for separate Ni 2+ ions with the spin Hamiltonian parameters g = 2.165, D = 0.45 cm −1 and E = 0.03 cm −1 . According to DFT calculations, the D and E parameters are −0.35 cm −1 and 0.049 cm −1 for the cis arrangement of Ni 2+ and 0.58 cm −1 and 0.012 cm −1 for trans. Introduction Synthesis of multidimensional homo- and heterometallic transi- tion metal polymers supported by pseudohalide NCO, 1 NCS, 2 NCSe 3 and N 3 4 bridges has attracted a special attention in view of the architectonical diversity and interesting magnetic properties of the complexes obtained. In this context, the thiocyanate ligand, which displays ambidentate character of end-to-end or end-on coordination modes, affords a number of discrete, one-, two- and three-dimensional structural assemblies that exhibit weak or strong magnetic interactions of various types. 5 However, despite of the various modes of the NCS-group coordination to the metal ions and its ability to act as an exchange pathway, it is not widely used in the design and synthesis of inorganic compounds. a Department of Inorganic Chemistry, National Taras Shevchenko Univer- sity, Volodymyrska str. 64, Kyiv, 01033, Ukraine. E-mail: nesterova@ univ.kiev.ua; Fax: +380 44 286 2467; Tel: +380 44 235 4371 b Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia c Faculty of Chemistry, University of Wroclaw, 14 Joliot-Curie Str., 50-383, Wroclaw, Poland d Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-AC, A-1060, Vienna, Austria e National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, Florida, 32310, USA †CCDC reference numbers 610955. For crystallographic data in CIF or other electronic format see DOI: 10.1039/b713252b While many homometallic complexes exist with single 6 or double 7 end-to-end NCS bridges, the heterometallic thiocyanato bridged species are comparatively less numerous. 8 Simultaneous presence of two different metal centers can potentially give rise to interesting physico-chemical properties and lead to attractive novel topologies and intriguing frameworks. To construct the novel heterometallic polymer we used a synthetic strategy named “direct synthesis of coordination com- pounds”, that is based on the one-pot self-assembly of building blocks, formed in situ, into supramolecular assemblies. This approach, in which a metal-containing ligand is formed from zerovalent metal or its oxide and subsequently self-assembles with a second metal center in the same reaction vessel 9 allowed the elimination of the separate step of building block construction. In previous work, it has been shown that heterometallic compounds may be obtained from the following systems (M (1) = Cu, Ni, M (2) = Zn, Cd; X = Cl, Br, I, NCS, CH 3 COO, N(CN) 2 (dca); L = ethylenediamine (en), Solv = dmf, dmso, CH 3 OH, CH 3 CN): 10 M (1) –M (2) O/M (2) X 2 –NH 4 X–L–Solv (in air) M (1) O–M (2) X 2 –NH 4 X–L–Solv (in air) Such investigations resulted in a series of thiocyanato-bridged heterometallic Cu/M (M=Zn, Cd) complexes showing zigzag and helical types of chain crystal structures based on Zn(NCS) 4 2− building blocks 10a and 2D structures built with Cd(NCS) 6 4− , 10b This journal is © The Royal Society of Chemistry 2008 Dalton Trans., 2008, 1431–1436 | 1431