Structural investigations of the axially ligated beryllium phthalocyanine derivatives

The BePc(H2O)·py (I), BePc(3-CNpy) (II) and BePc(4-CNpy)·(4-CNpy) (III) complexes in the crystalline form were obtained by recrystallisation of beryllium phthalocyanine (BePc) in wet pyridine, in liquid 3-cyanopyridine (3-CNpy) and in 4-cyanopyridine (4-CNpy), respectively. Single crystal analyses show 4 + 1 coordination of the Be(II) ion in these complexes. It is equatorially ligated by the four N-isoindole atoms of Pc macrocycle and axially by the O atom of water molecule in I and by the N-ring atom of 3-CNpy in II or 4-CNpy in III. Interaction of the central Be(II) ion of the BePc with axial O or N donating ligands leads to the saucer-shape form of Pc macrocycle and deviates the Be(II) from the N4-isoindole plane by 0.308(2) Å in I, and 0.297(2) and 0.281(2) Å in II and III, respectively. Thus π–π interaction between the π-clouds of Pc aromatic macrorings in I, II and III is the force responsible for the stabilisation of the molecular arrangement in the crystals. Thermogravimetric analyses confirm the compositions of the complexes. The UV–Vis spectra of I, II and III show that Pc π-system is not significantly perturbed by the axial ligands.