DOI: 10.1002/zaac.200700229 Comparative Study of Reactivity of Copper(II) Salts with N,N-Dipyridyl Ligands. Structural Diversity and Magnetic Properties S. Delgado* ,a , M. E. Medina b , C.J. Pastor b , R. Jime ´nez-Aparicio c , and J. L. Priego c Madrid/Spain, Universidad Auto ´noma de Madrid, Facultad de Ciencias, a Departamento de Quı ´mica Inorga ´nica and b Servicio Interdepartamental de Investigacio ´n. Laboratory of SingleCrystal XR Diffraction c Madrid/Spain, Universidad Complutense de Madrid, Facultad de Ciencias Quı ´micas, Departamento de Quı ´mica Inorga ´nica Received March 22nd, 2007. Dedicated to Professor Alfonso Castin ˜eiras on the Occasion of his 65 th Birthday Abstract. The coordination chemistry of 1,2-bis(2-pyridyl)buta- diyne (dpb) , 2,5-bis(2-pyridylethynyl)thiophene (dpet) (rigid li- gands) and 4,4-dipyridyldisulfide (4-dpds) (flexible ligand) with Cu(tfac) 2 (tfac trifluoroacetylacetonate) and Cu(BF 4 )·xH 2 O have been investigated in order to test the influence of different anions on the overall structure. Three of the resulting metal-organic as- semblies have been determined. These crystal structures have shown that the geometry and coordinating properties of the corre- sponding anions together with the positional orientation of the ni- trogen atoms in the ligands are essential in determining the final structures of the assemblies. So, reactions with Cu(tfac) 2 lead to Introduction The coordination chemistry of metal-nitrogen and/or me- tal-oxygen bonds under mild conditions is currently an ac- tive research area in solid-state supramolecular chemistry due to the promise of molecule-based electronic, magnetic and optical devices [13]. As a consequence of the dynamic nature of the metal-ligand bonds and the different potential geometries around the metal centres, it is often difficult to predict the exact nature of the final metal-organic assembl- ies. Their structures are highly dependent on the geometries, bulkiness and flexibility of the ligands that are used as building blocks. Furthermore, the experimental conditions employed (such as the solvent, temperature, order of ad- dition of the reactive, etc) and the nature of the metal’s counterions can also have an important impact on the final structure. In particular, much research have been concen- trated on the use of bridging 4,4-bipyridine based rodlike ligands [4] whereas bent ligands are relatively less used as building blocks due to the difficulty in predicting the re- sulting structures. * Professor S. Delgado Departamento de Quı ´mica Inorga ´nica Facultad de Ciencias Universidad Auto ´ noma de Madrid, E-28049 Madrid / Spain Fax: 34 91 4974833. E-mail: salome.delgado@uam.es. 1860  2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Z. Anorg. Allg. Chem. 2007, 633, 18601868 dimeric compounds [Cu 2 (tfac) 4 (L)] for L  dpb 1 and dpet 2 and one-dimensional polymer [Cu(tfac) 2 (4-dpds)] n (3) for 4-dpds li- gand. On the other hand analogous reactions with Cu(BF 4 )·xH 2 O afforded the copper(II) complexes [Cu(dpb)(BF 4 ) 2 ·(CH 3 OH) 1.5 ] n (4) and [Cu(4-dpds) 2 /(BF 4 ) 2 (MeOH)(CH 2 Cl 2 )] n (6) for dpb and 4-dpds ligands as well as the copper(I) compound [Cu(dpet) 2 ] n (BF 4 )·CH 2 Cl 2 (5) for dpet ligand. In addition to this, magnetic properties have been studied. Keywords: Copper; Coordination polymers; Dipyridyl ligands In previous work, we have studied how the effect of the 2,2-positional orientation of the nitrogen atoms in bis-pyri- dine-type ligands, (rigid such as 1,2-bis(2-pyridyl)butadiyne (dpb) or 2,5-bis(2-pyridylethynyl)thiophene (dpet); or flex- ible like 2,2-dipyridyldisulfide(2-dpds)), and the nature of the counterions in the employed copper salts influences on the coordination framework and affects the polymeric structures of the crystalline materials when we carried out reactions with Cu(hfac) 2 , Cu(NO 3 ) 2 and Cu(OAc) 2 ·H 2 O and the previously pointed out ligands [57]. To our knowledge, other relevant examples showing the influence of the anionic counterions on the final structure of the materials obtained have been reported [810]. As a continuation of our interest in understanding the ability of anions to direct the assembly process, herein we have carried out a systematic study in order to determine the role that the counterions play in determining the struc- ture of the final assemblies. The synthesis, crystal structures and magnetic properties of new copper(II) compounds formed upon mixing Cu(tfac) 2 or Cu(BF 4 )·xH 2 O with the dpb, dpet and 4-dpds ligands, are presented (see Scheme 1). The influence of the anionic counterions and the orien- tation of the ligands on the self-assembly process are dis- cussed. Results and Discussion When methylene chloride solutions of dpb, dpet and 4-dpds were allowed to diffuse, at room temperature, into a solu-