Bismuth(iii)-thiophenedicarboxylates as host frameworks for lanthanide ions: synthesis, structural characterization, and photoluminescent behavior

Abstract

Three bismuth-2,5-thiophenedicarboxylates (Bi-TDC) and two europium-2,5-thiophenedicarboxylates (Eu-TDC) were synthesized under ambient conditions. The structures were determined through single crystal X-ray diffraction, and three of the phases were further characterized by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Reactions of bismuth nitrate, 2,5-thiophenedicarboxylate, and pyridine in an acidic solution of acetic acid and ethanol yield Hpy[Bi(TDC)₂(H₂O)]·1.5H₂O (1), whereas reactions in a water/ethanol mixture produce a minor phase, [Hpy]₃[Bi₂(TDC)₄(HTDC)(H₂O)]·xH₂O (2) along with a major product, (Hpy)₂[Bi(TDC)₂(HTDC)]·0.36H₂O (3). The structures of 1–3 are all built from anionic Bi-TDC chains that are further bridged through additional TDC linkages into interpenetrated 2D sheets. Addition of an aqueous lanthanide solution to the reaction mixtures that yielded 1 and 2–3 resulted in the formation of doped phases, Hpy[Bi_1−xLn_x(TDC)₂(H₂O)]·1.5H₂O (Bi_1−xLn_x-1), where Ln = Nd, Sm, Eu, Tb, Dy, and Yb, and (Hpy)₂[Bi_0.99Eu_0.01 (TDC)₂(HTDC)]·0.36H₂O (Bi_0.99Eu_0.01-3). Using europium nitrate rather than the bismuth precursor resulted in the formation of two homometallic europium based phases, [Eu(TDC)(NO₃)(H₂O)]_n (4) and [Eu₂(TDC)₃(H₂O)₉]·5H₂O (5), which adopt an extended 3D network and an interpenetrated 2D structure, respectively. Photophysical measurements were carried out for 1 and the lanthanide containing phases and quantum yield and lifetime values were determined for the visible light emitters. Herein, the structural chemistry, spectroscopic properties, and luminescence of the bismuth phases, their lanthanide doped analogs, and the europium compounds are presented.