Single-Molecule Magnets DOI: 10.1002/ange.200905007 A Liquid-Crystalline Single-Molecule Magnet with Variable Magnetic Properties** Mathieu Gonidec, Fernando Luis, Àlex Vílchez, Jordi Esquena, DavidB. Amabilino,* and Jaume Veciana* Dedicated to Jean-Pierre Sauvage on the occasion of his 65th birthday Single-molecule magnets (SMMs) are attractive because they present magnetic bistability of each isolated molecule, [1] thus enabling the discovery of a wide variety of intriguing phenomena and the possibility of preparing multifunctional molecular nanosystems. [2] The so-called double-decker lan- thanide complexes of phthalocyanines, in which a lanthanide ion with a large total angular momentum is coordinated between two parallel phthalocyanine derivatives, are partic- ularly attractive because of their relatively high blocking temperatures. [3–5] Our interest in these systems arose from the possibility of using organic synthesis to functionalize the SMM core. In particular, we have been engaged in a program aimed at preparing chiral SMMs which might show interesting chirop- tical phenomena, [6, 7] such as magnetochiral dichroism (MChD), which could be useful for data storage and processing. [8] To facilitate processing of SMMs and related materials, the incorporation of long alkyl chains is advanta- geous, and we were particularly attracted by liquid-crystalline phases, as previously carried out with a Mn 12 SMM [9] and spin- crossover iron(II) compounds. [10] For this reason, we prepared compound 1, a chiral derivative of the double-decker terbium complex. It behaves both as a liquid crystal at room temperature and as a single- molecule magnet at low temperatures. Importantly, when the material is cooled at different rates, the magnetic properties vary because of different degrees of supramolecular order. Herein we describe the preparation and characterization of this liquid-crystalline terbium double-decker phthalocyanine complex and how its mesomorphic properties can be used as a tool to adjust its magnetic properties reversibly at will. The terbium ion is used as a direct and very sensitive probe of the structural changes occurring at low temperatures, at which magnetic relaxation is dominated by direct tunneling tran- sitions. The chiral metal-free (free-base) phthalocyanine 5, bear- ing eight identical stereocenters, was prepared in three steps from 4,5-dibromocatechol (Scheme 1) and the chiral bro- moalkyl compound 2 derived from methyl lactate by a known procedure. [11] Compound 3 was converted into the bis(cyano) derivative 4 using zinc(II) cyanide, [12] and the purified compound was cyclized in n-hexanol using lithium metal to give 5. The corresponding terbium double-decker complex 1 was pre- pared by reacting 5 with anhydrous terbium chloride and lithium bis(trimethylsilyl)amide with minor changes from a published method. [13] The new compound was thoroughly purified by column chromatography, and was characterized by MALDI-TOF mass spectrometry, IR, UV/Vis absorption spectroscopy, circular dichroism spectroscopy, and elemental [*] M. Gonidec, Prof. D. B. Amabilino, Prof. J. Veciana Departament de Nanocincia Molecular i Materials Orgànics, Institut de Cincia de Materials de Barcelona, Consejo Superior de Investigaciones Científicas (CSIC), Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN) Campus de la U.A.B., 08193 Bellaterra (Spain) Fax: (+ 34) 93-580-5729 E-mail: amabilino@icmab.es vecianaj@icmab.es Homepage: http://www.icmab.es/nmmo/ Dr. F. Luis Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, Universidad de Zaragoza C/Pedro Cerbuna 12, 50009 Zaragoza (Spain) À. Vílchez, Dr. J. Esquena Institut de Química Avançada de Catalunya, CSIC, Barcelona (Spain) [**] We warmly thank Amable BernabØ for recording the LDI-TOF MS and IR spectra. This work was supported by the Marie Curie EST FuMaSSEC, EU NoE MAGMANet (515767-2), EMOCIONA (CTQ2006-06333/BQU), Grup de Recerca de Catalunya (2009 SGR- 516) and Molecular Nanoscience (CSD2007-00010) and Molchip (MAT2009-13977-C03) projects Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200905007. Angewandte Chemie 1667 Angew. Chem. 2010, 122, 1667 –1670  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim