Self-assembly of Ligands Designed for the Building of a New Type of [2 × 2] Metallic Grid. Anion Encapsulation and Diffusion NMR Spectroscopy Blanca R. Manzano,* ,² Fe ´lix A. Jalo ´ n, ² Isabel M. Ortiz, ² M. Laura Soriano, ² Felipe Go ´ mez de la Torre, ² Jose ´ Elguero, ‡ Miguel A. Maestro, § Kurt Mereiter, | and Tim D. W. Claridge ⊥ Departamento de Quı ´mica Inorga ´ nica, Orga ´ nica y Bioquı ´mica, Facultad de Quı ´micas, IRICA, UniVersidad de Castilla-La Mancha, AVda Camilo Jose ´ Cela, 10, E-13071 Ciudad Real, Spain, Instituto de Quı ´mica Me ´ dica, Centro de Quı ´mica Orga ´ nica ‘Manuel Lora-Tamayo’, CSIC, Juan de la CierVa 3, E-28006 Madrid, Spain, SerVicios Xerais de Apoio a ´ InVestigacio ´ n, UniVersidad de A Corun ˜ a, Campus de A. Zapateira, E-15071 A Corun ˜ a, Spain, Faculty of Chemistry, Vienna UniVersity of Technology, Getreidemarkt 9/164 SC, A-1060 Vienna, Austria, Chemistry Research Laboratory, Department of Chemistry, UniVersity of Oxford, Mansfield Road, Oxford, OX1 3TA, UK Received June 7, 2007 The ligands 4,6-bis(pyrazol-1-yl)pyrimidine (bpzpm), 4,6-bis(3,5-dimethylpyrazol-1-yl)pyrimidine (bpz*pm), 4,6-bis- (4-methylpyrazol-1-yl)pyrimidine (Mebpzpm), and 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine (ppdMe) were synthesized and were made to react with Cu(I) centers in the presence of different counteranions. Different [2 × 2] metallic grids were obtained. With ligands bpzpm, bpz*pm, and Mebpzpm, a new type of grid was obtained where the facing ligands were divergent and two counteranions (BF 4 - or PF 6 - ) were hosted in the resulting cavities and exhibit C-H‚‚‚F and anion‚‚‚π interactions in the solid state. The presence of methyl groups on the pyrazolyl rings induced several distortions in the structure. In complexes with the ligand ppdMe, there were found two groups of parallel ligands in the grid, and the cavities generated were smaller. The counteranions were situated outside the grid, and the facing ligands exhibited aromatic π-π stacking interactions. Anion-π interactions involving the pyridazine ring were found. The behavior in solution of the new derivatives with a special emphasis on the cation-anion interactions was studied by UV-vis and NMR spectroscopy. Diffusion NMR experiments performed for some complexes allowed us to conclude that weak cation-anion interactions exist in solution, with the counteranions undergoing fast exchange on the diffusion time scale between the free and ion-paired states. Introduction There is a great interest in developing strategies for the synthesis of complex molecular architectures that could exhibit new properties and potential applications in nano- technology. During the past few years, supramolecular chemistry, with the development of self-assembly processes, has provided important achievements in this direction. 1 Whereas the self-assembly of organic components has been a traditional area, the synthesis of inorganic architectures from organic ligands and metal ions is nowadays a very active area. The spontaneous generation of supramolecular entities is based on metal-ion-directed self-assembly, with the organic ligands having encoded information that is mainly related to the arrangement of the binding sites. 2,3 Different authors have recently presented 4 overviews in supramolecular inorganic building on the basis of the idea that different coordination geometries enable the controlled design of * To whom correspondence should be addressed. E-mail: Blanca. Manzano@uclm.es. Fax: (internat.) + 34-926/295318. ² Universidad de Castilla-La Mancha. ‡ Centro de Quı ´mica Orga ´nica ‘Manuel Lora-Tamayo’. § Universidad de A Corun ˜a, Campus de A. Zapateira. | Vienna University of Technology. ⊥ University of Oxford. (1) Lehn, J.-M. Supramolecular Chemistry - Concepts and PerspectiVes; VCH, Weinheim: Weinheim, Germany, 1995. (2) Baxter, P. N. M. In ComprehensiVe Supramolecular Chemistry; Atwood, J. L., Davies, J. E. D., MacNicol, D. D., Vo ¨gtle, F., Lehn, J.-M., Eds.; Pergamon Press: Oxford, U.K.; Vol. 9, pp 165-211.; Constable, E. C. in the same reference, pp 213-252; Fujita, M. in the same reference, pp 253-282. (3) Ward, M. D. Annu. Rep. Prog. Chem. Sect. A 2001, 97, 293. Inorg. Chem. 2008, 47, 413-428 10.1021/ic701117a CCC: $40.75 © 2008 American Chemical Society Inorganic Chemistry, Vol. 47, No. 2, 2008 413 Published on Web 10/02/2007