Synthesis and magnetic properties of a porphine-based photosynthesizer with magnetic nano-carriers

The coupling of benzyl protected dopamine with meso-tetra(4-carboxyphenyl)porphine (m-TCPP) and a simple deprotection by hydrogenation under catalyst (Pd/C) to remove the benzyl groups afforded the meso-tetra(4-carboxyphenyl)porphine-dopamine conjugate, m-TCPPD (1). Previously prepared superparamagnetic iron oxide nanoparticles (SPIONs) were coated with m-TCPPD by sonication in methanol, and then the m-TCPPD coated SPIONs (2) were separated with a permanent magnet. The microstructure and magnetic properties of the m-TCPPD coated SPIONs were characterized by UV, ¹H NMR, MALDI MS, XRD, TEM, FT-IR, TGA and VSM. The crystallite size obtained from X-ray line profile fitting is comparable with the particle size obtained from TEM. Magnetization measurements reveal that m-TCPPD coated SPIONs do not reach saturation even at high fields. The absence of remanance and weak magnetization, which are characteristic features of superparamagnetics, has been observed. The average particle size has been determined, by fitting the Langevin function to the experimental M−H hysteresis curves, as approximately 8 nm.