Importance of C-H• • • π interactions in stabilizing the syn/anti arrangement of pendant alkoxy side arms in two manganese(IV) Schiff base complexes: exploration of catechol oxidase and phenoxazinone synthase like activities

Two new octahedral manganese(IV) complexes [Mn(HL1)(L-1)(NCS)](n) (1) and [Mn(HL2)(2)(OH)Cl] (2) [where H2L1 = 1-(5-hydroxy-3-oxapentyliminomethyl)-3-ethoxyphenol and H2L2 = 1-(5-hydroxy-3-oxapentyliminomethyl)- 4-chlorophenol] have been prepared and characterized. Unconventional C-H center dot center dot center dot pi((SCN)) interactions play a key role in stabilizing the unexpected syn arrangement of the ligand pending arms in 1, whereas conventional C-H center dot center dot center dot pi((phe)) interactions favour the anti arrangements in 2. The energetic features of these interactions have been studied by DFT calculations and characterized using Bader's theory of atoms in molecules in both complexes. Both complexes exhibit catechol oxidase and phenoxazinone synthase like activities.