In situ recrystallization of lanthanide coordination polymers: from 1D ladder chains to 1D linear chains

Abstract

Reactions of LnCl₃·6H₂O (Ln = La, Ce, Pr, Nd, Gd and Lu), L-dibenzoyl tartaric acid (L-DBTA) and triethylamine in a methanol–water solution afford four complexes 1a–4a with 1D ladder chain structures, e.g. {[Ln₂(L-DBTA)₃(CH₃OH)_x(H₂O)_y]·zH₂O}_n (x = 3 or 4, y = 3 or 4, z = 2 or 5; Ln = La (1a), Ce (2a), Pr (3a) and Nd (4a)) and two complexes 5 and 6 with 1D linear chain structures, e.g. {Et₃NH[Ln(L-DBTA)₂(CH₃OH)₂(H₂O)₂]·2H₂O}_n (Ln = Gd (5) and Lu (6)). Accidentally, an in situ irreversible SCSC transformation from the kinetically stabilized 1D ladder chain structures of 1a–4a to thermodynamically stabilized 1D linear chain structures of 1–4 was observed, which was seldom reported for lanthanide coordination polymers. The coordination stability around a lanthanide cation was investigated to expatiate on the irreversible SCSC transformation. The solid-state NIR luminescence for complexes 3a, 3, 4a and 4 was also studied.