Synthesis and characterisation of oxygenated magnesium phthalocyanine

Two crystals of oxygenated magnesium phthalocyanine complex (MgPc)2O2 with a composition of (MgPc)2O2·2(MgPcDBU)·2DBU – crystal 1 (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene) and (MgPc)2O2·4(4-Mepy) – crystal 2 were obtained. In both crystals the (MgPc)2O2 molecule is centrosymmetric and exhibits similar conformation, but different to that in the gas phase as obtained by DFT calculations. The Mg centre of both MgPc molecules of (MgPc)2O2 is 4+1 coordinated by four isoindole N atoms of Pc(2−) macrocycle in an equatorial position, and by oxygen atom of bridged dioxygen molecule in an axial position. Owing to the interaction of the electropositive Mg centre of MgPc molecules with the bridged dioxygen molecule, the Mg atom is significantly displaced (∼0.73 Å) from the plane defined by four isoindole N atoms of Pc(2−) macroring. In the MgPcDBU molecule in crystal 1 the interaction of Mg centre of MgPc with N atom of DBU in the axial position leads to the displacement of Mg from the N4-plane by ∼0.63 Å. The interactions of Mg centre of MgPc with dioxygen molecule forming the oxygenated (MgPc)2O2 complex as well as the interactions of Mg centre of MgPc with N atom of DBU forming MgPcDBU complex lead a distortion of a planar Pc(2−) macrocycle to the saucer-shape form. The displacement of Mg from the N4-plane as well as the distortion of Pc(2−) macrocycle from planar conformation is more pronounced in the crystals than that in the gas phase structure. Both crystals were also characterised by the thermal analysis. EPR and magnetic susceptibility measurement show the diamagnetic character (no net unpaired electrons) of oxygenated (MgPc)2O2 complex. The calculated three-dimensional MESP maps are helpful for understanding of the interactions between the MgPc and dioxygen molecule forming the oxygenated (MgPc)2O2 complex. The 3D MESP maps are also helpful for understanding the arrangement of molecules in a solid (crystal).

Two crystals of the oxygenated magnesium phthalocyanine (MgPc)2O2 with the composition of (MgPc)2O2·2(MgPcDBU)·2DBU and (MgPc)2O2·4(4-Mepy) were obtained. The conformation of (MgPc)2O2 supramolecule in both crystals is very similar. EPR and magnetic susceptibility measurements have shown the diamagnetic (no net unpaired electron) character of (MgPc)2O2. The MESP maps are helpful for understanding the interaction between MgPc and dioxygen molecule.Figure optionsDownload as PowerPoint slide