Synthesis and Full Characterization of Molybdenum and Antimony Corroles and Utilization of the Latter Complexes as Very Efficient Catalysts for Highly Selective Aerobic Oxygenation Reactions

Abstract

Two molybdenum and three antimony corroles were isolated and characterized by NMR, EPR, and electrochemistry. The very negative reduction potentials of the (oxo)molybdenum(V) corroles are clearly related to their inactivity as oxygen transfer reagents and the unsuccessful attempts to isolate lower-valent molybdenum corroles. X-ray crystallography of the (oxo)molybdenum(V) corrole 1a and the trans-difluoroantimony(V) corrole 2c, the first of their kind, revealed that their molecular structures represent extreme cases of such complexes: a highly domed corrole with very large out-of-plane metal displacement for 1a (0.73 Angstroms) and a very flat corrole with the metal ion in its center for 2c. All three antimony corroles displayed high activity and selectivity as catalysts for the photoinduced oxidation of thioanisole by molecular oxygen, with superior results obtained in alcoholic solvents with 2c as catalyst. Allylic and tertiary benzylic CH bonds were also oxidized under those conditions, with absolute selectivity to the corresponding hydroperoxides.

Coordination chemistry of corroles with focus on main group elements

“…The affinity of corrolechelated metal ions for a sixth ligand as to form 6-coordinated complexes is quite low (vide infra) and most reported complexes of this kind contain pyridines as axial ligands. All 6-coordinate metallocorroles, including with NMe 3 and fluorides, display a very planar macrocyclic structure [17,18]. Selected X-ray crystallographic structural information is presented in Tables 1 and 2, the latter of which contains all pyridine-coordinated metallocorroles.…”

“…In addition, they have rich redox chemistry and interesting catalytic properties. The isolated complexes consist of 5-coordinate Sb(tpfc)(py) and Sb(tpfc)(O) and 6-coordinate Sb(tpfc)(F) 2 (9a-9c, Scheme 8) [18]. The reaction of 1 with SbCl 3 in pyridine afforded Sb(tpfc)(py) in 95% yield: both its 1 H and 19 F NMR spectra are consistent with the dominant species in solution to be 5-coordinate, i.e., an antimony(III) corrole with only one pyridine ligated to the axial position.…”

“…110 K. Selected bond lengths: Sb-F1 = 1.940(1)Å, Sb-F2 = 1.932(1)Å, Sb-N(pyrrole) average = 1.975Å. The corrole is essentially planar.Figure wasreproduced from Ref [18],. with permission of the copyright holders.…”

Ultrafast electronic and vibrational dynamics in brominated aluminum corroles: Energy relaxation and triplet formation

“…The simple and efficient procedure of corroles synthesis combined with readily tuned physical and chemical characteristics by varying the peripheral substituents, 3–6 central metal, 5,7 and axial ligands 8,9 has revived substantial interest in employing these contracted porphyrinoids in various fields. Examples for application of the corroles include dye-sensitized solar cells, 7,10 photodynamic therapy, 11–13 photodynamic detection, 14 photodynamic inactivation of mold fungi and green algae, 15,16 regular and sophisticated optical imaging, 17,18 formation of singlet oxygen for catalysis, 19–21 and corrole-based electron and energy transfer systems 22–24 . In this context, the ability to control the corrole's parameters such as fluorescence, 6,25 phosphorescence, 26–29 and singlet oxygen quantum yield, 30 energy, 31 and lifetime of their photoexcited states 26,32–34 is fundamental in optimizing the corrole based photocatalysts for their specific application 35 .…”

Investigating photoexcitation-induced mitochondrial damage by chemotherapeutic corroles using multimode optical imaging

“…The combination of the inherent targeted cytotoxicity of HerGa with its newly discovered photoreactivity may facilitate an even greater potency and specificity for tumor cell destruction, thus yielding a therapeutic with optimized efficacy and safety. 26 …”