Synthesis, crystal structures and spectroscopic characterization of Co(II) bis(4,4'-bipyridine) with mesoporphyrins a,b,a,b-tetrakis(o-pivalamidophenyl) porphyrin (a,b,a,b-TpivPP) and tetraphenylporphyrin (TPP)

摘要

The reaction of the starting materials [CoII(Porph)] (Porph = a,a,a,a-tetrakis(opivalamidophenyl) porphyrin (TpivPP) and the meso-tetraphenylporphyrin (TPP)) with an excess of 4,4'-bipyridine in chlorobenzene leads to the creation of two cobalt(II) derivatives: [Co~(II)(a,b,a,b-TpivPP)(4,4'-bpy)_2]·C_6H_5Cl·C6H_(14) (1) and [Co~(II)(TPP)(4,4'-bpy)_2]·2bpy (2). These compounds have been characterized by UV-vis, IR, ~1H NMR and MALDI-TOF spectroscopy. The proton NMR spectra of (1) and (2) clearly indicated that these derivatives are paramagnetic while the UV-vis data confirmed creation of a new six-coordinated or penta-coordinated Co(II)-meso-porphyrin complexes by displaying red shifted Soret bands. The determined X-ray structures of (1) and (2) show that in the solid state these species are considered as coordination polymers which consist of 1D chains of alternating [CoII(Porph)] and 4,4'-bipyridine molecules located at the axial positions of the cobalt(II) coordination sphere. The coordination geometry of Co(II) in (1) and (2) is octahedral; the porphyrin (TpivPP or TPP) acts as a tetradentate chelating ligand with four nitrogen atoms from the pyrrole moieties occupying the equatorial positions along the porphyrin core. The N-donor atoms of the 4,4'-bipyridine create the axial ligands. It is noteworthy that for complex (1) the starting porphyrin is the a,a,a,a-TpivPP atropisomer but the final coordination polymer contains the a,b,a,b-TpivPP conformer.