SEARCH

SEARCH BY CITATION

Keywords:

  • Metallacrown compounds;
  • Copper;
  • Sorption;
  • Magnetic properties

Abstract

Metathesis of the perchlorate anions in [Cu5(ahpha)4](ClO4)2·4H2O, where ahpha2– is the dianion of 3-amino-3-hydroximinopropane hydroxamic acid, with m- and p-phthalates resulted in formation of [Cu5(ahpha)4(m-C8H4O4)(H2O)]·9H2O (1), [Cu5(ahpha)4(m-C8H4O4)(H2O)]·2MeOH·DMF (1a) and [Cu5(ahpha)4(p-C8H4O4)(H2O)2]2·14H2O (2). Molecules in the structures of 1, 1a and 2 are held together by noncovalent interactions, and the lattices contain voids filled with water molecules. Compounds 1 and 1a differ in the mode of m-phthalate coordination, solvent type, and crystal lattice content. Desolvated 1 and 2 sorb gaseous MeOH and EtOH. Whereas the MeOH sorption capacity was very similar for 1 and 2 (about 0.14 cm3/g at PPS–1 = 0.9, where P is the current methanol pressure and PS the saturation vapor pressure of methanol at 293 K), the capacity of 2 to sorb EtOH was about 1.5 times as high as that of 1. To a certain extent, the structures of 1 and 1a can be considered as models of compounds that can form at different stages during alcohol sorption by desolvated 1. The χMT vs. T data for 1 and 2 could be fitted with a model based on the Hamiltonian H(CuII5) = –2J1(S1·S2 + S1·S3 + S1·S4 + S1·S5) – 2J2(S2·S5 + S2·S3 + S3·S4 + S4·S5), where S1 represents the spins of the central CuII ions and S2–S4 correspond to the spins of the peripheral CuII ions. The best fits corresponded to J1 = –129(3) cm–1, J2 = –66(1) cm–1 and zJ′ = –2.5(2) cm–1 at gCu = 2.12(1) for 1, and J1 = –163(3) cm–1, J2 = –78(1) cm–1 and zJ′ = –1.5(1) cm–1 at gCu = 2.05(1) for 2.