Solvent Influence in Obtaining Diverse Coordination Symmetries of Dy(III) Metal Centers in Coordination Polymers: Synthesis, Characterization, and Luminescent Properties

Six new Dy­(III)-containing coordination polymers (CPs) have been synthesized emphasizing the role of solvent molecules in directing the formation of the Dy­(III) coordination sphere which in turn influences the dimensionality of the coordination polymer, thermal stability, and emission properties. An isophthalate-based flexible ligand 5-[(anthracen-9-ylmethyl)-amino]-isophthalic acid (H₂L) with different solvents such as dimethylformamide (DMF), dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), diethylformamide (DEF), and N-donor linkers phen (1,10-phenanothroline) and pyridine (py) was employed to obtain six different coordination polymers, viz., [Dy₂(L)₂(HCOO)₃(DMF)·Me₂NH₂·H₂O]_n (1), [Dy₄(L)₆(DMA)₂(H₂O)₄·4DMA·4H₂O]_n (2), [Dy₂(L)₃(DMSO)₃(H₂O)₂·2DMSO·2H₂O]_n (3), [{Dy­(L)­(DEF)}₂(μ₂-OH)]_n (4), [Dy₂(L)₃(phen)₂·DMA·7H₂O]_n (5), and [Dy­(L)­(NO₃)­(py)₂·py]_n (6), respectively. All the compounds were characterized by IR spectroscopy and thermogravimetric analysis, and unambiguously characterized by single crystal X-ray crystallography. The bulky anthracenyl group of the linker H₂L in combination with the solvent molecules significantly alters the coordination symmetry of the Dy­(III) coordination sphere in the polymers in the manner: D_2d in 1, C_2v and D_4d in 2, C_4v and C_s in 3, C_5v in 4, D_4d in 5, and D_2d in 6. The coordination symmetry plays an interesting role in sensitization of lanthanide emission. The emission maxima of compounds 1–6 vary from the blue region to the yellow region significantly due to coordination symmetry expressed by the Dy­(III) centers, which in turn depends upon the coordinated solvent molecule. The thermogravimetric profile indicates the thermal stability of the solvent free compounds up to 300 °C.