Lanthanide Coordination Polymers of Mixed Phthalate/Adipate for Ratiometric Temperature Sensing in the Upper-Intermediate Temperature Range

Abstract

Based on the mixed phthalate (phth^2-) and adipate (ad^2-), [Nd₂(ad)(phth)₂(H₂O)₄] (I) and [Ln(ad)_0.5(phth)(H₂O)₂] (Ln = Eu^III (II), Gd^III (III), Tb^III (IV), Dy^III (V), Er^III (VI), Tm^III (VII), 1Eu^III:10Tb^III (VIII), 3Eu^III:10Tb^III (IX), and 5Eu^III:10Tb^III (X)) were synthesized and characterized. Complexes VIII-X show excellent ratiometric temperature sensing behavior in physiological and higher temperature ranges (303-423 K) rendered by the Tb^III-to-Eu^III energy transfer process. The efficiency of the process as illustrated through the lifetime measurements depends on both the Eu^III:Tb^III mole ratio and the temperature. The performance of X in terms of relative sensitivity ( S_r), temperature resolution, and measurement repeatability were determined, revealing the maximum S_r ( S_m) of 1.21%·K^-1 at 303 K with reliable temperature resolution and excellent repeatability.