Investigation on structures, luminescent and magnetic properties of Ln III-M (M = FeIIHS, CoII) coordination polymers

摘要

The structures, luminescent and magnetic properties of three series of coordination polymers with formulas-{[Fe3Ln2(L 1)6(H2O)6]·xH 2O}n (Ln = Pr-Er; 1-9), {[Co3Ln 2(L1)6(H2O)6] ·yH2O}n (Ln = Pr-Dy, Yb; 10-17) and {[Co 2Ln(L2)(HL2)2(H2O) 7]·zH2O}n (Ln = Eu-Yb; 18-25) (H 2L1 = pyridine-2, 6-dicarboxylic acid, H3L 2 = 4-hydroxyl-pyridine-2, 6-dicarboxylic acid) were systematically explored in this contribution. [FeIIHS-L 1-LnIII] (1-9) and [CoII-L1-Ln III] (10-17) series are isostructural, and display 3D porous networks with 1D nanosized channels constructed by Fe/Co-OCO-Ln linkages. Furthermore, two types of "water" pipes are observed in 1D channels. [Co II-L2-LnIII] (18-25) series exhibit 2D open frameworks based on double-stranded helical motifs, which are further assembled into 3D porous structures by intermolecular hydrogen bonds between hydroxyl groups. The variety of the resulting structures is mainly due to the HO-substitution effect. These 3D coordination polymers show considerably high thermal stability, and do not decomposed until 400 °C. The high-spin Fe II ion in [FeIIHS-L1-Ln III] was confirmed by X-ray photoelectron spectroscopy, M?ssbauer spectroscopy and magnetic studies. The luminescent spectra of coordination polymers associated with SmIII, EuIII, TbIII and DyIII were systematically investigated, and indicate that different d-metal ions in d-f systems may result in dissimilar luminescent properties. The magnetic properties of [FeIIHS-L1-LnIII] (3, 6, 7, 9, 13), [Co II-L1-LnIII] (15-17) and [Co II-L2-LnIII] (19-24) coordination polymers were also studied, and the χMT values decrease with cooling. For the single ion behavior of CoII and LnIII ions, the magnetic coupling nature between FeIIHS/CoII and Ln III ions cannot be clearly depicted as antiferromagnetic coupling.