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Polymorph Selective Growth of Sodium Tetrakis(2-pyridinecarboxylato) Lanthanides and Their Structure Sensitive Properties

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posted on 02.04.2008, 00:00 by Jung Hoon Hong, Yunghee Oh, Youngmee Kim, Sung Kwon Kang, Jungkweon Choi, Wan Seop Kim, Jong In Lee, Sung-Jin Kim, Nam Hwi Hur
Four new single crystals of sodium tetrakis(2-pyridinecarboxylato)Ln(III), where Ln is europium and terbium, with general formulas of Na[Ln(C6H4NO2)4]·2H2O were prepared from a reaction of solvent-mediated polymorph selection. All the crystal structures were determined by using temperature-dependent single crystal X-ray diffraction at 100(2) and 298(2) K. No phase transition was observed within this temperature range. Two isostructural compounds, IM (Eu3+ core) and IIIM (Tb3+ core), crystallize in the monoclinic space group C2h6 - C2/c (No. 15) and the other two compounds, IIH (Eu3+ core) and IVH (Tb3+ core), in the enantiomorphic hexagonal space group D63 - P6522 (No. 179). Both IM and IIH (or both IIIM and IVH) are homeotypic. Each structure consists of an extensive network of organo-lanthanide complex and has extremely long-ranged interlayer distances, about 10 Å. The parallel interlayer in IM (or IIIM) can be reconstructed into IIH (or IVH) via 6-fold angularly step-staggered packing. Such a phenomenon of crystal packing strongly depends not only on the nature of the applied solvent system but also on long-range ordering of the organo-lanthanides. Transmission electron microscopy analysis of IIH and IVH reveals the absolute configuration of parallel helical assemblies. Their optical and magnetic data show the salient features of topospecific chirality over those racemic counterparts.