2D/3D coordination polymers based on di-, tri-, tetranuclear and polymeric chain units with a tricarboxylate ligand: Structures, magnetic and luminescent properties

Abstract

Six novel coordination polymers (CPs), [M2(HL)2(4,4′-bipy)(H2O)2] (M = Co, for 1; Ni, for 2), [M3(L)2(CH3CN)2(H2O)2]·2H2O (M = Co, for 3; Ni, for 4), [Co4(OH)2(L)2(4,4′-bipy)(H2O)4]·2H2O (5) and [Zn4(OH)2(L)2(DMA)2(H2O)2] (6) have been synthesized by using different metal ions and 5-(2-nitro-4-carboxylphenyl)isophthalic acid (H3L) ligand in the absence/presence of 4,4′-bipyridine (4,4′-bipy) ancillary ligand. Interestingly, these CPs exhibit different structures based on di-, tri-, tetranuclear and chain units, respectively. CPs 1 and 2 are isomorphous and possess a (4,4) 2D layer in which dinuclear [M2(µ2-Ocarboxylate)2]2+ clusters are interlinked by the HL and 4,4′-bipy ligands. In isomorphous CPs 3 and 4, the linear trinuclear [M3(μ2-COO)2(μ2-Ocarboxylate)]3+ clusters are linked by the L ligands to give a 2D layer with a (3,6)-connected kgd topology. In 5, the chair-shaped tetranuclear [Co4(μ3-OH)2]6+ clusters are interlinked by organic spacers into a 2D layer with a (3,8)-connected net with point symbol (3·42)2(34·46·56·68·73·8). Compared with 5, the cluster structures of 5 and 6 are very similar, but in 6, the chair-shaped tetranuclear [Zn4(μ3-OH)2]6+ clusters are connected by the double (μ2-syn, anti-COO)2 bridges to form a 1D chain. The chains further are cross-linked by the L ligands to build a 3D framework. Magnetic analyses suggest that all of the short bridging moieties in 1–5 transmit antiferromagnetic couplings between metal(II) ions. Moreover, CP 6 shows an intense solid-state emission at room temperature. This work opens up the use of this tricarboxylate ligand for generating CPs with interesting structures and functional properties.