Syntheses, crystal structures and luminescence properties of lanthanide-based coordination polymers constructed from a functionalized terpyridyl carboxylate ligand

Abstract

Six families of new lanthanide coordination polymers, [Ln 2 (L) 6 (H 2 O) 2 ] n •3nH 2 O (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb ( 9 14), Gd (15), Er ( 16)), (HL = 4′-(2-carboxyphenyl)-4,2′:6′,4″-terpyridine, H 2 ox = oxalic acid, H 2 glu = glutaric acid, H 2 adip = adipic acid, H 2 (1,2-bdc) = benzene-1,2-dicarboxylic acid) were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compounds 1-9 are isomorphic 1D chain structures based on binuclear Ln(III) units. Compound 10 is a 1D chain, where L − ligands dangle on two sides of the Pr-ox zigzag chain. Compounds 11 and 12 exhibit distinct 2D-layer structures consisting of Ln 2 (COO) 4 binuclear units. Compound 13 displays an appealing 3D network structure, where the auxiliary ligand H 2 adip plays a significant role in the self-assembly process. Compounds 14-16 present a 1Dchain structure which is extended to a 2D-supramolecular framework by means of weak interactions. The diverse structures further verify the potential of HL ligand in the preparation of coordination polymers with new structures and properties. The effects of auxiliary ligands and coordination modes of HL ligand on the crystal architectures are discussed. The solid-state luminescence and thermal stabilities of compounds 1-16 also were studied. Based on the luminescent properties, we have designed and constructed successfully a series of doped-lanthanide MOF by adjusting the co-doping ratio of Eu(III) and Tb(III) into the same framework as that of 1-9. Interestingly, the luminescent colors of the Eu(III)-doped Tb(III) compounds can be tuned with change of excitation wavelength. Moreover, white-light emission was achieved on excitation at 330 nm.

A Series of New Eu/Tb Mixed MOFs with Tunable Color Luminescence

“…According to previous work, compared with single carboxylate‐coordinated Eu/Tb complexes, mixed oxalate‐assisted coordinates have paid much attention due to their polydentate, easy to synthesize and noticeable synergy effects on fluorescence properties. Li and Hu et al, , reported that mixed Eu/Tb frameworks display highly efficient red/green emissions based on the mixed ligand. But the application of mixed Eu/Tb single‐oxalate complexes for the fluorescence modulation has merely not investigated.…”

“…The mixed Ln ‐MOFs materials, especially Eu/Tb mixed MOFs, play an important role in the preparation of luminescent materials with application in display devices, greatly improving the deficiency of the traditional physical mixing methods in fabrication process, stability, and reproduction . In general, multiple color emission can be accomplished by adjusting the proportion of different color via controlling the Ln III ions ratio and the excitation wavelength of mutually doped Ln ‐MOFs . For example, Hu et al reported two Eu/Tb doped compounds exhibiting tunable white‐light emission, whose luminescent colors can be turned easily …”

“…However, by using oxalic acid as the main ligand to construct the Ln ‐MOFs, possessing good luminescence performance, is still sporadic . To best of our knowledge, the application of mixed Eu/Tb oxalate complexes for the fluorescence modulation has not been investigated …”

Two topologically different 3D CuII metal–organic frameworks assembled from the same ligands: control of reaction conditions

“…The architectures of the numerous carboxylate-based MOFs are well defined with reticular chemistry, partly due to their prominent metalcarboxylate secondary building units (SBUs) (Furukawa et al, 2013;Du et al, 2014). Carboxylic acids as bridging ligands usually have two advantages: first, carboxylic acids have rich coordination modes with metal ions; secondly, depending on the degree of deprotonation, the carboxyl group itself can act as a hydrogen-bond acceptor and donor (Deacon & Phillips, 1980;Xu et al, 2016;. Based on these considerations, recently, a few novel 3D MOFs with a rare lsz topology (Zhang et al, 2018), a unique binodal 3,20-connected network (Zhao et al, 2016), an unprecedented 3D/3D heterointerpenetrating framework composed of a dia and a bcu topology (Xu et al, 2012;Luo et al, 2014), and an unusual infinite nano-sized ribbon (Zhang et al, 2011) have been successfully assembled from the symmetrically substituted biphenyldicarboxylic acids (H 2 BPDC).…”

Lanthanide coordination polymers based on designed bifunctional 2-(2,2′:6′,2″-terpyridin-4′-yl)benzenesulfonate ligand: syntheses, structural diversity and highly tunable emission

“…Hence, the selection of appropriate organic ligands, which function as chromophores that transfer absorbed energy efficiently to the excited states of Ln 3+ ions, is significant for Ln 3+ compounds to optimize their luminescence and enhance their emission efficiency (Moore et al, 2009;Zheng et al, 2007;Mahapatra et al, 2018;Zheng et al, 2014). Terpyridine-based derivatives are admirable chromophoric antenna ligands, and they are widely used as effective building blocks for lanthanide coordination compounds (Zheng et al, 2014;Smith et al, 2012;Wu et al, 2011b;Xu et al, 2016;Liu et al, 2012;Bretonniè re et al, 2002).…”