An Oxido‐Bridged Diiron(II) Complex as Functional Model of Catechol Dioxygenase. Issue 9 (21st June 2016) - Dey, Dhananjay
Abstract: An oxido‐bridged diiron(II)‐phenanthroline complex, [Fe2 O(phen)2 Cl2 ] (1 ) [phen =1, 10‐phenanthroline] has been synthesized from an oxido‐bridged diiron(III) precursor in presence of sodium azide and structurally characterized by different spectroscopic tools including single crystal X‐ray diffraction study.From X‐ray crystal structure of1, it is revealed that each of the Fe(II) centre is in distorted octahedral geometry with FeN4 OCl core and the molecule crystallizes in P nc2 space group. Bond valence sum (BVS) calculation confirms the existence of iron ions in +2 oxidation state in1 . The diiron(II) complex has been evaluated as model system for the catechol dioxygenase enzyme by using 3, 5 ‐ di‐ tert ‐butylcatechol (DTBC) as the substrate in acetonitrile medium, revealing that1 efficiently mimics the catalytic cycle of catechol dioxygenase. Upon stoichiometric addition of DTBC pretreated with two equivalents of triethylamine (Et3 N) to the diiron complex, two catecholate‐to‐iron(III) LMCT bands (515 nm and 734 nm) are observed. The in situgenerated catecholate adduct from1 in acetonitrile solution react with dioxygen to afford exclusively extradiol cleavage products along with a small amount of benzoquinone, which is also discerned from the appearance and decrease in intensity of the electronic spectral bands around (708 nm; 507 nm) nm. Nucleophilic attack by molecular oxygen on catecholate adduct in solution provides substantial evidence for the regioselective extradiol cleavage products. Abstract : An oxido‐bridged diiron(II)‐phenanthroline complex, [Fe2 O(phen)2 Cl2 ] (1 ) [phen =1, 10‐phenanthroline] has been synthesized andevaluated as model system for the catechol dioxygenase enzyme by using 3, 5 ‐ di‐ tert ‐butylcatechol (DTBC) as the substrate in acetonitrile medium, which efficiently mimics the catalytic cycle of catechol dioxygenaseand provide substantial evidence for the substrate activation mechanism proposed for the extradiol cleavage of catechols.