Ligand control of low-frequency electron paramagnetic resonance linewidth in Cr(iii) complexes. Issue 15 (31st March 2021)

• Record Type: Journal Article
• Authors: Campanella, Anthony J.; Nguyen, Manh-Thuong; Zhang, Jun; Ngendahimana, Thacien; Antholine, William E.; Eaton, Gareth R.; Eaton, Sandra S.; Glezakou, Vassiliki-Alexandra; Zadrozny, Joseph M.
• Is Part Of: Dalton transactions. Volume 50:Issue 15(2021)
• Page Start: 5342
• Page End: 5350
• Publication Date: 2021-03-31
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d1dt00066g
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : This study reveals, for the first time, the extent to which ligand design strategies can modulate L-band EPR linewidths for an S > 1/2 metal complex. Abstract : Understanding how the ligand shell controls low-frequency electron paramagnetic resonance (EPR) spectroscopic properties of metal ions is essential if they are to be used in EPR-based bioimaging schemes. In this work, we probe how specific variations in the ligand structure impact L-band ( ca . 1.3 GHz) EPR spectroscopic linewidths in the trichloride salts of five Cr(iii ) complexes: [Cr( RR -dphen)3 ] 3+ ( RR -dphen = (1 R, 2 R )-(+)-diphenylethylenediamine, 1 ), [Cr(en)3 ] 3+ (en = ethylenediamine, 2 ), [Cr(me-en)3 ] 3+ (me-en = 1, 2-diaminopropane, 3 ), [Cr(tn)3 ] 3+ (tn = 1, 3-diaminopropane, 4 ) [Cr( trans -chxn)3 ] 3+ ( trans -chxn = trans -(±)-1, 2-diaminocyclohexane, 5 ). Spectral broadening varies in a nonintuitive manner across the series, showing the sharpest peaks for 1 and broadest for 5 . Molecular dynamics simulations provide evidence that the broadening is correlated to rigidity in the inner coordination sphere and reflected in ligand-dependent distribution of Cr–N bond distances that can be found in frozen solution.