A series of silver(i)–lanthanide(iii) heterometallic coordination polymers: syntheses, structures and photoluminescent properties

Abstract

A series of new 4d–4f heterometallic coordination complexes based on 5-(4H-1,2,4-triazol-4-yl)benzene-1,3-dicarboxylic acid (H₂L), namely [AgLn(L)₂(H₂O)₄] [Ln = Nd (1), Eu (2) and Tb (3)], [AgLn(L)₂] [Ln = Nd (4), Eu (5) and Tb (6)] and [AgLn(L)₂(H₂O)]·H₂O [Ln = Er (7) and Yb (8)] were successfully synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR, elemental and thermogravimetric analyses. Complexes 1–3 consist of two-dimensional (2D) networks, which are further connected by hydrogen bonding and π–π interactions to give three-dimensional (3D) frameworks. Complexes 4–6 display a 3D (4,6)-connected framework containing 2D heterometallic bilayers. Complexes 7 and 8 are 3-fold interpenetrated (3,4,6)-connected 3D frameworks. The results show that the reaction temperature and the lanthanide have great influence on the structure of the complexes. Luminescent measurements revealed that 2, 3, 5 and 6 exhibit the characteristic emission bands of the lanthanide in the visible region with lifetimes in the range of 0.24–1.81 ms and the strongest emissions are ⁵D₀ → ⁷F₂ for 2 and 5, and ⁵D₄ → ⁷F₅ transitions for 3 and 6.