Building-up novel coordination polymer with magnesium porphyrin: Synthesis, molecular structure, photophysical properties and spectroscopic characterization. Potential application as antibacterial agent

Abstract

The new meso-tetraphenylporphyrin magnesium(II) polymer compound with the formula {[MgII(TPP)(4,4′-bpy)]}n.n[MgII(TPP)(4,4′-bpy)2] (I), (TPP) = meso-tetraphenylporphyrinato and 4,4′-bipy = 4,4′-bipyridine) was synthetized and characterized by IR, UV–visible, photoluminescence and 1H NMR spectroscopy studies, single-crystal XRD analyses and cyclic voltammetry. From the X-ray data, it was established that the central metal Mg2+ is located on an inversion center, being octahedrally coordinated to four pyrrole nitrogen atoms of the porphyrin ring and the nitrogen atoms of the two 4,4′-bipyridine axial ligand situated in trans positions with respect to the metal center. The crystal of (I) is made by [MgII(TPP)(4,4′-bipy)2] monomer complexes and {[MgII(TPP)(4,4′-bpy)]}n polymers linked together via CH…π type intermolecular interactions leading to a three-dimensional network. The UV–visible spectrum of (I) shows that the Soret band value (432 nm) is redshifted compared to the free base H2TPP while the λmax values of the Q bands are in the range 570–610 nm. The optical gap of (I) was estimated at 2.00 eV and the cyclic voltammogram of the title compound presents two reversible oxidation waves and one reversible reduction wave. The HOMO and LUMO energy values were deduced from the voltammogram which are −4.94 and −3.06 eV respectively. The use of [MgII(TPP)(DMF)] starting material compound, {[MgII(TPP)(4,4′-bpy)]}n.n[MgII(TPP)(4,4′-bpy)2] (I) and the [MgII(TPP)(HTMA)2] (HTMA = hexamethylenetetramine) (II) as novel significant antibacterial agents was also tested.