Structural and magnetic modulation of a purely organic open framework by selective guest inclusion

Solvent inclusion/evacuation caused variations in the structural and magnetic characteristics of the purely organic porous magnet based on the tricarboxylic-substituted PTMTC radical. Whereas no inclusion is observed for nonpolar solvents, the exposure of crystals of the α-phase of PTMTC to vapors of polar organic solvents with hydrogen acceptor and/or donor functionalities, such as, ethanol, benzoic alcohol, n-decanol, THF, and DMSO results in the inclusion of these solvents in the highly polar tubular channels of the α-phase. The resulting inclusion compounds of formula PTMTC. x(guest) show several structural rearrangements, as confirmed by IR and XRPD (X-ray powder diffraction) measurements. The crystal transformations have been studied for a specific case: the PTMTC·EtOH adduct. The crystal structure reveals that included guest solvent molecules participate in the formation of new hydrogen bonds with the carboxylic groups of PTMTC radicals, inducing the disruption of several direct hydrogen bonds among these radicals. As expected, the interruption of direct hydrogen bonds between PTMTC radicals induces large transformations in the magnetic properties. From the ferromagnetic behavior of the α-phase, predominant antiferromagnetic interactions are observed for the inclusion adducts. Interestingly, both structural and magnetic changes are reversible after removal of guest solvent molecules.This work was supported by Dirección General de Investigación (Spain), under project CONSOLIDER-C EMOCIONa (contract CTQ2006–06333/BQU) and Generalitat de Catalunya (2005 SGR-00591). We also thank the European Commission for the Marie Curie Research Training Network (contract QUEMOLNA, number MRTN-CT-2003—504880) and the NoE MAGMANet (contract NMP3-CT-2005–515767) and also to ESRF for providing synchrotron radiation beam time (experiment number CH-1236) on the ID.11 beam line. D.M. is grateful to the Generalitat de Catalunya for a predoctoral and postdoctoral grant. N.D. is also grateful to the Ministerio de Educación y Ciencia (Spain) for the predoctoral grant No. AP2000–1842 of the FPU program.Peer Reviewe