Syntheses, structures and properties of a phthalocyanine peripherally introduced with bis(3,5-trifluoromethyl)phenyl substituents and its zinc(II) and cobalt(II) complexes

A phthalocyanine bearing eight bis(3,5-trifluoromethyl)phenyl substituents at the peripheral β positions, H 2 Pc{β-Ph-3,5-(CF 3 ) 2 } 8 , along with its zinc(II) and cobalt(II) complexes, [ZnPc{β-Ph-3,5-(CF 3 ) 2 } 8 ] and [CoPc{β-Ph-3,5-(CF 3 ) 2 } 8 ], were synthesized and characterized using elemental analysis, MALDI-TOF mass spectrometry, and 1 H NMR spectroscopy. X-ray crystallography was performed for [ZnPc{β-Ph-3,5-(CF 3 ) 2 } 8 (H 2 O)]·2(acetone) and [CoPc{β-Ph-3,5-(CF 3 ) 2 } 8 (py) 2 ]·2py. An axial water molecule coordinates the zinc(II) ion in addition to the pyrrole nitrogen atoms of the Pc ring, which is slightly curved toward the opposite side of the axial water molecule. The cobalt(II) ion is axially coordinated by two pyridine molecules along with the equatorial pyrrole nitrogen atoms of the Pc ring, with the Pc ring remaining nearly planar. The zinc(II) and cobalt(II) complexes displayed the Q-band peaks at 690 and 680 nm, respectively, while the metal-free ligand exhibited split Q-band peaks at 670 and 709 nm. These spectral features suggest they exist as monomeric species in solutions in CH2Cl2 at a molar concentration of 1.0 10 -5 M. Cyclic voltammetry in CH 2 Cl 2 revealed Pc ligand-centered first oxidation and reduction waves at E 1/2 = 0.45 and -0.51 V (vs SCE) for H 2 Pc{β-Ph-3,5-(CF 3 ) 2 } 8 , E 1/2 = 0.43 and -0.85 V (vs SCE) for [ZnPc(β-Ph-3,5-(CF 3 ) 2 ) 8 ], and E 1/2 = 0.91 and -1.23 V (vs SCE) for [CoPc{β-Ph-3,5-(CF 3 ) 2 } 8 ].