Effect of Redox Active Ligands on the Electrochemical Properties of Manganese Tricarbonyl Complexes.
The synthesis, structural characterization, and electrochemical behavior of the neutral Mn(azpy)(CO)3(Br) 4 (azpy = 2-phenylazopyridine) complex is reported and compared with its structural analogue Mn(bipy)(CO)3(Br) 1 (bipy = 2,2'-bipyridine). 4 exhibits reversible two-electron reduction at a mild potential (-0.93 V vs Fc+/0 in acetonitrile) in contrast to 1, which exhibits two sequential one-electron reductions at -1.68 V and -1.89 V vs Fc+/0 in acetonitrile. The key electronic structure differences between 1 and 4 that lead to disparate electrochemical properties are investigated using a combination of Mn-K-edge X-ray absorption spectroscopy (XAS), Mn-Kbeta X-ray emission spectroscopy (XES), and density functional theory (DFT) on 1, 4, their debrominated analogues, [Mn(L)(CO)3(CH3CN)][CF3SO3] (L = bipy 2, azpy 5), and two-electron reduced counterparts [Mn(bipy)(CO)3][K(18-crown-6)] 3 and [Mn(azpy)(CO)3][Cp2Co] 6. The results reveal differences in the distribution of electrons about the CO and bidentate ligands (bipy and azpy), particularly upon formation of the highly reduced, formally Mn(-1) species. The data show that the degree of ligand noninnocence and resulting redox-activity in Mn(L)(CO)3 type complexes impacts not only the reducing power of such systems, but the speciation of the reduced complexes via perturbation of the monomer-dimer equilibrium in the singly reduced Mn(0) state. This study highlights the role of redox-active ligands in tuning the reactivity of metal centers involved in electrocatalytic transformations.
View details for DOI 10.1021/acs.inorgchem.9b00652
View details for PubMedID 31117629
Control of clustering behavior in anionic cerium(III) corrole complexes: from oligomers to monomers
2016; 45 (46): 18653–60
The first synthesis of anion capped cerium corrole complexes is reported. Unusual clustering of the lanthanide corrole units has been found and the degree of aggregation can be controlled by the choice of the capping ligand. A polymeric structure 1a, with the general formula [Cor-Ce(THF)-Cp-Na]n (Cor = 5,15-bis(2,4,6-trimethylphenyl)-10-(4 methoxyphenyl)-corrole, THF = tetrahydrofuran), is formed using sodium cyclopentadienide (NaCp) and a dimeric structure 2a, with the general formula [Cor-Ce-Tp]2, is formed when potassium tris(pyrazolyl)borate (KTp) is used. Encapsulation of the counter-cation leads to the isolation of the monomeric structures 1b and 2b, with the general formulas [AM(2.2.2-cryptand)][Cor-Cp-X] (AM = Na or K, X = Cp or Tp). The structural and spectroscopic properties of the complexes have been investigated.
View details for DOI 10.1039/c6dt03884k
View details for Web of Science ID 000388369000030
View details for PubMedID 27827498
View details for PubMedCentralID PMC5127600