Pyrazine control of the supramolecular chemistry of iron(ii) and cobalt(ii) phthalocyanines

Three supramolecular complexes of FePc and CoPc with pyrazine in crystalline form have been obtained. In the case of FePc the biaxial ligation by pyrazine with the formation of FePc(pyz)2 (I) has been observed, whereas in the case of CoPc, depending on the thermal conditions, mono- and biaxial ligation by pyrazine are observed. At temperature 140 °C the recrystallisation process yields the formation of monoaxially ligated T-shaped and H-shaped complexes, CoPc(pyz) and (CoPc)2(pyz), which cocrystallise with pyrazine as solvent molecules forming {[2CoPc(pyz)][(CoPc)2(pyz)]·3pyz} (II) crystals. At higher temperature (180 °C) recrystallisation of CoPc in pyrazine leads to mono- and biaxial ligation of the central Co(II) of CoPc forming two different types of complexes: (CoPc)2(pyz) and CoPc(pyz)2, which, at used condition, cocrystallise forming [CoPc(pyz)2(CoPc)2(pyz)] (III) crystals. The solubility of compounds I, II and III in pyridine and related N-donating solvents are greater than that of the parent FePc and CoPc complexes. The UV-Vis spectra of I, II and III show that the Pc π-system is not significantly perturbed by the axial ligand.