Structural and spectroscopic characterization of thorium pyrasal complexes

• Published in: Inorganica Chimica Acta 2023-08, Vol.553 (C), p.121542, Article 121542
• Main Authors: Eralie, Dylan M.T., Hoang, Tessa M., Williamson, Justin A., Unruh, Daniel, Gorden, Anne E.V.
• Format: Article
• Language: English
• Subjects: Actinides; Fluorescence; Thorium; UV–vis; X-ray crystallography
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2023.121542

[Display omitted] •Th(IV)-pyrasal complexes crystallize as stable 8-coordinate complexes from chloroform.•Electron-withdrawing pyrazine induces solid state extended structure minimizing pi-pi stacking.•Highly symmetric planar Th(IV)-pyrasal complexes result in less fluorescence. To explore the coordination chemistry of thorium, the most abundant radioactive element on earth, we examine the synthesis and characterization of two Th (IV)-pyrasal complexes, L1 “pyrasal” ((2,2'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))diphenol), and L2 “naphthylpyrasal” (1,1'-((1E,1'E)-(pyrazine-2,3-diylbis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol). These complexes demonstrate little or no fluorescence when compared to similar naphthylsalophen thorium complexes previously published. Each complex was synthesized and characterized by IR, NMR (1H), and mass spectrometry. The photometric properties of the complexes were characterized using UV–Vis and fluorescence spectroscopy and their solid-state molecular structures were established by single-crystal X-ray crystallography. The electron-withdrawing effects of the pyrazine ring creates changes in the thorium coordination environment resulting in a secondary solid-state extended structure that minimizes the pi-pi stacking. This subsequently causes an overall decrease in the intensity of fluorescence demonstrated previously in by naphthylsalophen thorium complexes.