Preparation and characterization of Mn II Mn III complexes with relevance to class Ib ribonucleotide reductases

The Mn 2 complex [Mn II 2 (TPDP)(O 2 CPh) 2 ](BPh 4 ) ( 1 , TPDP = 1,3-bis(bis(pyridin-2-ylmethyl)amino)propan-2-ol, Ph =phenyl) was prepared and subsequently characterized via single-crystal X-ray diffraction, X-ray absorption, electronic absorption, and infrared spectroscopies, and mass spectrometry. 1 was prepared in order to explore its properties as a structural and functional mimic of class Ib ribonucleotide reductases (RNRs). 1 reacted with superoxide anion (O 2 center dot - ) to generate a peroxido-Mn II Mn III complex, 2 . The electronic absorption and electron paramagnetic resonance (EPR) spectra of 2 were similar to previously published peroxido-Mn II Mn III species. Furthermore, X-ray near edge absorption structure (XANES) studies indicated the conversion of a Mn II 2 core in 1 to a Mn II Mn III state in 2 . Treatment of 2 with para-toluenesulfonic acid ( p-TsOH) resulted in the conversion to a new Mn II Mn III species, 3 , rather than causing O -O bond scission, as previously encountered. 3 was characterized using electronic absorption, EPR, and X-ray absorption spectroscopies. Unlike other reported peroxidoMn II Mn III species, 3 was capable of oxidative O -H activation, mirroring the generation of tyrosyl radical in class Ib RNRs, however without accessing the Mn III Mn IV state.