Structure-function correlation of mononuclear nonheme copper(ii) compounds based on a ligand backbone effect and phenoxazinone synthase activity

Mononuclear nonheme copper(ii) compounds [Cu(BQEN)(CH3CN)](2+)1 and [Cu(BQPN)(CH3CN)](2+)2 (BQEN = N,N & PRIME;-dimethyl-N,N & PRIME;-di(quinolin-8-yl)ethaneane-1,2-diamine; BQPN = N,N & PRIME;-dimethyl-N,N & PRIME;-di(quinolin-8-yl)propane-1,2-diamine) were synthesized and characterized by elemental analysis, ESI-MS, EPR, and single-crystal X-ray diffratrometry. Compound 1 crystalized in the P1 space group, while 2 crystallized in the P2(1)/n group. Compounds 1 and 2 exhibited distorted square pyramidal geometry, which deviated interestingly by 4.8% and 46.0% from a regular square pyramidal structure in 1 and 2, respectively. This was attributed to the marginal increase in the carbon chain backbone of the ligand in 2. Compounds 1 and 2 were used in the aerial oxidation of 2-aminophenol (H(2)AP) to 2-amino-phenoxazine-3-one (APX), which revealed phenoxazinone synthase activity. DFT steric maps were utilized to understand the catalytic activity of 1 (% Vbur, 71.3%) and 2 (% Vbur, 75.6%). The current results clearly demonstrate an interesting structure-function relationship based on the effect of the ligand backbone on the geometry.

Automated summary

Mononuclear nonheme copper(ii) compounds were synthesized and characterized. These compounds exhibited phenoxazinone synthase activity in the aerial oxidation of 2-aminophenol to 2-amino-phenoxazine-3-one.