Introducing supramolecular interactions into robust bis(tetrabromocatecholate) chelated manganese(III) systems and biomimetic catalytic activity

Abstract

Click on the DOI link to access the article (may not be free).This report deals with the syntheses, structures, supramolecular interactions, and biomimetic catalytic activity of three new manganese(III) complexes (1-3) containing the tetrabromocatechol ligand. Three different amines were used, with the goal of introducing their protonated species into the crystal lattice as counter cations for the robust bis(tetrabromocatecholate) chelated manganese(III) anionic species. All these systems present interesting noncovalent interactions in their crystal packing, including hydrogen bonding, halogen bonding, pi stacking and anion-pi interactions. The geometrical differences (octahedral vs square pyramidal) have been analyzed by means of DFT studies, revealing that the strong anion-pi interaction of pyridine with the complex anion compensates for the absence of one apical methanol molecule in 3. All of the complexes exhibited leveling catalytic activity for aerobic oxidation of 3,5di-tert-butylcatechol. DFT calculations support the formation of a stable complex-substrate intermediate through hydrogen bonding, thereby disclosing the origin of catecholase activity of these complex anions.Department of Science and Technology (DST), New Delhi, under FAST Track Scheme (Order No. SB/FT/CS-016/2012, dated 20/12/2013) for financial support. A. B. and A. F. thank financial support by MINECO of Spain (projects CTQ2014-57393-C2-1-P and CONSOLIDER INGENIO 2010 CSD2010-00065, FEDER funds)