title: Conjugated ligands modulated sandwich structures and luminescence properties of lanthanide metal-organic frameworks.
abstract: A conjugated ligand, 2-(carboxylic acid)-6-(2-benzimidazolyl) pyridine (Hcbmp), and a series of Lanthanide metal-organic frameworks (MOFs) [Ln(2)(cbmp)(ox)(3)(H(2)O)(2)](2)·2H(3)O(+)·7H(2)O (Ln = Sm (3), Eu (4), and Gd (5), H(2)ox = oxalic acid) have been designed and assembled. To elucidate how the conjugated ligands modulate the structures and luminescence properties, we carried out the structural characterizations and luminescence studies of complexes 3 and 4, and their corresponding oxalate complexes [Ln(ox)(1.5)(H(2)O)(3)]·2H(2)O (Ln = Sm (1) and Eu (2)) were also investigated for comparison. The changes of luminescence behaviors upon dehydration and D(2)O-rehydration processes are presented and discussed in detail. The results indicated that, the cbmp(-) ligands distribute on both sides of the ox(-)-Ln bilayer network to construct a sandwich structure. Moreover, the lowest triplet state of cbmp(-) ligands can match well the energy levels of the Sm(3+) and Eu(3+) cations which allow the preparation of new Ln-MOF materials with enhanced luminescence properties. Meanwhile, the crystallinity of solid states produces more substantial change in the luminescence behaviors than removal or replacement of effective nonradiative relaxers.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou, 350002, PR China.
authors.forename: Tian-Fu
authors.initials: TF
authors.lastname: Liu
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Zhang
authors.forename: Wen-Hua
authors.initials: WH
authors.lastname: Sun
authors.forename: Rong
authors.initials: R
authors.lastname: Cao
mesh_terms: D018360:Crystallography, X-Ray; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D008024:Ligands; D049449:Luminescence; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
chemical_list: D028581:Lanthanoid Series Elements; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines