Tuning the structure and Zn(ii) sensing of lanthanide complexes with two phenylimidazophenanthrolines by acetonitrile hydrolysis

Abstract

Exploring lanthanide complexes as luminescence sensors is an interesting topic. By utilizing 2-(4-carboxyphenyl)imidazo[4,5-f][1,10]phenanthroline (Hcpip) and 2-phenylimidazo[4,5-f][1,10]phenanthroline (pip), two series of lanthanide complexes, one-dimensional [Ln₂(cpip)₂(OAc)₄]_n (1-Ln; Ln = Sm, Eu) and zero-dimensional [Ln₂(pip)₂(OAc)₆] (0-Ln; Ln = Sm, Eu, Tb, Dy), have been synthesized and crystallographically characterized. The in situ hydrothermal hydrolysis of acetonitrile yields the acetate anions. For both series, the main feature is the existence of [Ln₂(μ-η¹:η²-COO)₂(μ-η¹:η¹-OAc)₂(η²-OAc)₂] subunits, in which μ-η¹:η²-COO⁻ refers to the carboxylate group when the ditopic Hcpip is used, but in the case of the monotopic pip, μ-η¹:η²-COO⁻ comes from the acetate. Insoluble polymeric 1-Eu in its water suspension exhibits specific but slow luminescence response (emission colour changes from red to bluish green). As an improvement, the dimeric 0-Eu is soluble in DMSO and shows the luminescence response immediately.