Functional heterometallic coordination polymers with metalloligands as tunable luminescent crystalline materials

Abstract

Five heterometallic luminescent crystalline materials with the metalloligand, [Zn(HL)Eu_xTb_y(H₂O)₂][ZnBr₄]·H₂O (x = 1, y = 0, IFMC-21; x = 0.75, y = 0.25, IFMC-22; x = 0.5, y = 0.5, IFMC-23; x = 0.25, y = 0.75, IFMC-24; x = 0, y = 1, IFMC-25; H₄L = 4,4′,4′′,4′′′-(2,2′,2′′,2′′′-(ethane-1,2-diylbis(azanetriyl))tetrakis(methylene)-tetrakis-(1H-benzo[d]imidazole-2,1-diyl))tetrakis(methylene)-tetrabenzoic acid; IFMC = Institute of Functional Material Chemistry), were prepared by the combination of hydrothermal and ionothermal methods for the first time. IFMC-21–25 can be obtained by introducing the desired Eu(III) and Tb(III) in the initial experiments. In these crystalline materials, the metalloligand Zn(HL) was connected by bi-lanthanide cores leading to a 2D sheet-structure and [ZnBr₄]²⁻ ions were distributed in the interspaces of the sheet. The luminescent properties of IFMC-21 to 25 were investigated and the results reveal that they exhibit characteristic Eu(III) and Tb(III) ion emissions, and the intensities of red and green arising from Eu(III) and Tb(III) emissions are shifted correspondingly by tuning the ratios of Eu(III) : Tb(III).