Synthesis and physicochemical characterization of lanthanide complexes coordinated with spiropyran derivatives

Abstract

Among many molecules, spiropyran derivatives are still a target of interest for various research fields due to the distinctive physicochemical properties of their isomers in response to a variety of triggers, including light irradiation and solvent–solute interaction. Herein, 14 coordination complexes (LnMC) using the lanthanide ion series (from La³⁺ to Lu³⁺, excluding the Pm ion) were coordinated with a spiropyran derivative (SPCOOH—l-(b-carboxyethyl)-3′,3′-dimethyl-6-nitrospiro(indoline-2′,2[2H-1]benzopyran). The ligand binding to these metal ions was achieved in organic solvent solution, using UV radiation to precipitate the complex. These complexes were characterized using electronic and spectrometric techniques, revealing that more than one structure can be obtained for the same metal ion by coordinating two or three SPCOOH in the lanthanide ion. The photochromic properties of these complexes were evaluated using electronic spectroscopy, with absorption maxima wavelengths ranging from 463 to 479 nm. The emission results showed no significant wavelength variation for most of the ions (ranging from 560 to 578 nm), suggesting that data emission is primarily dependent on the merocyanine isomer. The solvatochromic data exhibited a strong linear correlation for these LnMC complexes using 1-propanol, compared to other alcohols tested.

Graphical abstract