Photochromic Lanthanide(III) Materials with Ion Sensing Based on Pyridinium Tetrazolate Zwitterion

Lanthanide­(III)
ion (Ln­(III)) sensing has become a major research
area owing to its intriguing prospect in clinic, biology, and environmental
studies. However, the existing methods have limitations like requirement
of expensive instrumentation, long analytical times, and sample pretreatments,
revealing the necessity of other methods. In this work, by using N-methyl-4-pyridinium tetrazolate (mptz) zwitterion as an
electron acceptor, we obtained several new Ln­(III) compounds with
electron-transfer (ET) photochromic properties: [Ln­(NO3)3(H2O)4]·mptz [Ln = Sm (1), Eu (2), Gd (3), La (4), Ce (5), Pr (6), Nd (7),
Tb (8), Dy (9), Ho (10), Er
(11), Tm (12), Yb (13), Lu
(14)]. Notably, different Ln­(III) ions in these compounds
can be visually identified by their different photoinduced color changes
related to the ET process. This work may not only contribute to the
more understanding of the structure–photosensitivity relationships
of pyridinium-based compounds, but also provide a new approach for
Ln­(III) ion sensing.