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Metalloporphyrins with paramagnetism are becoming research focus because their potential use in biomedical field as fluorescence probes and the magnetic resonance imaging (MRI) contrast agents. Divalent manganese metal ion (Mn2+) has a half-filled 3d shell with a strong paramagnetic effect. To investigate whether porphyrins coordinated to Mn2+ can serve as multiple functional probes, hematoporphyrin monomethyl ether coordinated to Mn2+ (Mn-HMME) was synthesized and its characterization, MRI enhancement property, luminescence property and photosensitivity were studied. Mn-HMME was characterized by UV-visible spectrum and Fourier transform infrared spectrum. It was found that the number of Q bands in the absorption spectrum of Mn-HMME reduced to two compared to free HMME. From the Fourier transform infrared spectrum of Mn-HMME, the characteristic infrared absorption peak of N-H bond in HMME at 970 cm-1 disappears, but the nitrogen-metal characteristic absorption peaks (1114 cm-1 and 1093 cm-1) were observed. The MRI of Mn-HMME indicates that Mn-HMME has relatively strong MRI enhancement effect. From luminescence spectroscopic analysis, the fluorescence emission of Mn-HMME was weaker than that of free HMME but still detectable. This may be caused by the energy transfer from free HMME to Mn2+. The test of photosensitivity of Mn- HMME denotes that the photosensitivity of Mn-HMME disappears. Our results indicate that Mn-HMME has the potential as a multiple functional probe in both fluorescence imaging and MRI.
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