FULL PAPER Tetracyanoquinodimethanido Derivatives of (Terpyridine)- and (Phenanthroline)metal Complexes  Structural and Magnetic Studies of Radical-Ion Salts [‡] Cristina Alonso, [a] Loreto Ballester, [a] Angel Gutie ´rrez,* [a] M. Felisa Perpin ˜a ´n, [a] Ana E. Sa ´nchez, [a] and M. Teresa Azcondo [b] Keywords: Radical ions / Stacking interactions / Supramolecular chemistry / Magnetic properties Several derivatives of formulae [M(terpy) 2 ](TCNQ) 2 or [M(terpy) 2 ](TCNQ) 3 (M = Ni, Cu, Zn; terpy = 2,2':6',2"-terpyr- idine; TCNQ= 7,7,8,8-tetracyanoquinodimethane) and [M(phen) 3 ](TCNQ) 2 or [M(phen) 3 ](TCNQ) 4 (M = Fe, Ni; phen = 1,10-phenanthroline) have been obtained. The crystal structures of [M(terpy) 2 ](TCNQ) 2 (M = Ni, Cu) show that the metal is surrounded by the terpyridine nitrogen atoms in a closed octahedral environment and the TCNQ anions are dimerised by π overlap. The cationic [M(terpy) 2 ] 2+ and the anionic [TCNQ] 2 2- groups alternate in the crystal. For the de- rivatives with three TCNQ groups, the existence of a stack of trimeric [TCNQ] 3 2- ions having electronic delocalisation is Introduction In the field of molecular networks containing organic radicals, macroscopic properties such as magnetic order or electric conductivity can be produced when the appropriate supramolecular arrangement is achieved. [1,2] On this basis, when paramagnetic metallic centres are integrated within organic radicals as building blocks in molecular networks, ‘‘hybrid’’ materials combining the properties of the organic and inorganic components can be formed. [3,4] Special attention has been given to the assembly of orga- nonitrile radical complexes with transition metals because of their rich interaction possibilities. One of the most exten- sively used radicals in these studies has been the planar or- ganic molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) since it shows a low reduction potential which makes it a suitable acceptor in charge transfer processes and also [‡] A portion of this work was previously published in communication form: L. Ballester, A. Gutie ´rrez, M. F. Perpin ˜a ´n, M. T. Azcondo, A. E. Sa ´nchez, Synth. Met. 2001, 120, 965. [a] Departamento de Quı ´mica Inorga ´nica I, Facultad de Ciencias Quı ´micas, Universidad Complutense, 28040 Madrid, Spain Fax: (internat.) + 34-913944352 E-mail: alonso@quim.ucm.es [b] Departamento de Ciencias Quı ´micas, Facultad de Ciencias Experimentales y de la Salud, Universidad San Pablo, CEU, 28668 Boadilla del Monte, Madrid, Spain 486 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/ejic.200400540 Eur. J. Inorg. Chem. 2005, 486-495 proposed. The compound [Fe(phen) 3 ](TCNQ) 2 , which shows a strong interaction between TCNQ anions, led to the forma- tion of a σ bond in the diamagnetic species [TCNQ-TCNQ], while the nickel analogue is expected to have a localised structure formed by alternation of cationic metal complexes and dimeric [TCNQ] 2 2- anions similar to those observed in the analogous terpy derivatives. The derivatives having four TCNQ groups also show electronic delocalisation and a 1D stack based on the magnetic data is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) shows, in its anion-radical form, a high σ-donor ability for coordinating to transition metals. [5-8] Another typical fea- ture of this acceptor is the tendency to overlap its π-delocal- ised system with neighbouring molecules to form stacks with different degrees of electronic delocalisation. [9-12] The compounds having vacant positions around the me- tal react with TCNQ salts forming new compounds where the anion-radical is coordinated via one or more of its ni- trile groups. [6,8,13-15] When complexes with a fully coordi- nated metal environment are used, new species without di- rect bonding interactions between the metal and the TCNQ are formed. When TCNQ is fully reduced, dimerisation to [TCNQ] 2 2- is usually observed [7,8,16] but when TCNQ is partially reduced, a greater electronic delocalisation along with the formation of infinite stacks is observed. [9-12] The present work reports our studies on the interactions of TCNQ in different formal oxidation states with closed shell first row transition metal complexes aimed at looking for electronic delocalisation in our systems. We have used nitrogen donor ligands with aromatic rings such as terpy (2,2':6',2"-terpyridine) or phen (1,10-phenanthroline) which are susceptible to forming weak π interactions with the TCNQ rings. [17-26] These interactions are more common when neutral TCNQ is present and can modulate the TCNQ overlap responsible for the stacking.