Title
Determination of zero-field splitting parameters for a MnIV center using variable-temperature, variable-field magnetic circular dichroism spectroscopy: Comparison to electron paramagnetic resonance spectroscopy
Author
Kevin Bane, Robert A. Geiger, Steven A. Chabolla, Timothy A. Jackson
Year
2012
Journal
Inorganica Chimica Acta
Abstract
The ground and excited state properties of [Mn(OMe)3(Me3TACN)]+ (Me3TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane), which features a mononuclear MnIV center, were investigated using electronic absorption, magnetic circular dichroism (MCD), and variable-temperature, variable-field (VTVH) MCD spectroscopies. Due to small zero-field splittings (ZFSs), MnIV centers are difficult to study using X-band electron paramagnetic resonance (EPR) spectroscopy. In this work, VTVH MCD spectroscopy was explored as an alternative method. [Mn(OMe)3(Me3TACN)]+ served as a test complex, because accurate ZFS parameters are available from high-field, high-frequency EPR (HF-EPR) data [33]. Using an E/D of 0, as determined from X-band EPR data, the VTVH MCD data collected for [Mn(OMe)3(Me3TACN)]+ yield an axial ground-state ZFS parameter (D) of similar accuracy, but lower precision, than that obtained from HF-EPR spectroscopy (D = +0.2(1) and +0.250(5) cm−1 from VTVH MCD and HF-EPR data, respectively). Thus, when combined with X-band EPR spectroscopy, the VTVH MCD method can serve as an alternative to HF-EPR spectroscopy even for systems with small ZFSs. In addition, analysis of electronic absorption and MCD spectral data collected for [Mn(OMe)3(Me3TACN)]+ permit the extraction of excited state parameters 10Dq and B(∼18 490 and 595 cm−1, respectively), which are comparable to those of other MnIVcomplexes.
Instrument
J-815
Keywords
Magnetic circular dichroism, Inorganic chemistry, Coordination chemistry,