Synthesis, structure, magnetic properties and molecular mechanics study on the dinuclear copper (II) with biradical

Dinuclear copper complex with biradicals Cu(hfac)2]2PhBNM(PhBNM = 2,5-bimethyl- 1,4-bis(4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide)phenyl,hfac=hexafluoroacetylacetonate) has been synthesized and characterized. It crystallized in the monoclinic system, with space group C2/c, a=1.9012(4), b=1.3718(3), c=2.1620(4) nm, β=97.55(3)°,Z=4. The X-ray structure analysis shows that the molecular structure consists of two kinds of conformations. The ratio of them is 7:3. The energy of two conformations, calculated with molecular mechanics, are different, E1=740 kJ/mol, and E2=771 kJ·mol-1. The CNDO/k results on the complex indicate that the orbital energy of low spin state is lower than that of high spin state, which correspond with the results of magnetic measurement.