Synthesis, Spectroscopy, and Theoretical Details of Uranyl Schiff-Base Coordination Complexes

Bonnie E Klamm; Cory J Windorff; Cristian Celis-Barros; Matthew L Marsh; Thomas E Albrecht-Schmitt

doi:10.1021/acs.inorgchem.9b00477

Synthesis, Spectroscopy, and Theoretical Details of Uranyl Schiff-Base Coordination Complexes

Inorg Chem. 2020 Jan 6;59(1):23-31. doi: 10.1021/acs.inorgchem.9b00477. Epub 2019 Apr 22.

Authors

Bonnie E Klamm¹, Cory J Windorff¹, Cristian Celis-Barros¹, Matthew L Marsh¹, Thomas E Albrecht-Schmitt¹

Affiliation

¹ Department of Chemistry and Biochemistry , Florida State University , 95 Chieftan Way, Room 118 DLC , Tallahassee , Florida 32306 , United States.

PMID: 31009208
DOI: 10.1021/acs.inorgchem.9b00477

Abstract

Two uranyl Schiff-base coordination complexes, UO₂L(MeOH) and UO₂Cl₂(H₂L) {L = N,N'-bis[(4,4'-diethylamino)salicylidene]-1,2-phenylenediamine}, have been synthesized that feature a rigid phenyl backbone. These complexes have been characterized by structural, spectroscopic, and theoretical analysis to offer an electronic structure basis to explain the bonding parameters and stability. Single-crystal X-ray analysis reveals that UO₂L(MeOH) adopts the typical "soft taco confirmation" characteristic of uranyl salophen complexes, whereas UO₂Cl₂(H₂L) features an unusual neutral ligand coordination that contains an internal hydrogen bond between the phenol and imine. Rate constants calculated from electrochemical experiments confirm a quasi-reversible UO₂²⁺/UO₂⁺ couple. Single-configurational and multiconfigurational methods were used to explore the bonding in UO₂L(MeOH) and UO₂Cl₂(H₂L). For UO₂Cl₂(H₂L), the U-Cl bond exhibits more covalent contributions than U-O_L.