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[Background] A deeper knowledge on the effects of the degradation of magnetic nanoparticles on their magnetic properties is required to develop tools for the identification and quantification of magnetic nanoparticles in biological media by magnetic means., [Methods] Citric acid and phosphonoacetic acid-coated magnetic nanoparticles have been degraded in a medium that mimics lysosomal conditions. Magnetic measurements and transmission electron microscopy have been used to follow up the degradation process., [Results] Particle size is reduced significantly in 24 h at pH 4.5 and body temperature. These transformations affect the magnetic properties of the compounds. A reduction of the interparticle interactions is observed just 4 h after the beginning of the degradation process. A strong paramagnetic contribution coming from the degradation products appears with time., [Conclusions] A model for the in vivo degradation of magnetic nanoparticles has been followed to gain insight on the changes of the magnetic properties of iron oxides during their degradation. The degradation kinetics is affected by the particle coating, in our case being the phosphonoacetic acid-coated particles degraded faster than the citric acid-coated ones.

peer-reviewed, In this work, we report the synthesis and structural characterisation of the ligand 2(pyridin-3-yl)-benzo [de]isoquinoline-1,3(2H)-dione, 5, its isostructural Werner complexes ML4(NCS)2 (L = 5; M = Co(II) and Ni (II)), and five clathrates with three aromatic guests, ML4(NCS)2·2G (M = Co(II) and Ni(II), G = nitrobenzene (NB); M = Co, G = 1,2 dichlorobenzene (1,2-DCB); M = Co(II) and Ni(II), G = o-xylene (OX)). 5 was pre-pared in high yield by condensation in the solid-state (C3S3, Cocrystal Controlled Solid-State Synthesis). The Werner complexes ML4(NCS)2 (M = Co(II) and Ni(II)) (apohosts) were prepared by reacting M(NCS)2 (M = Co(II) and Ni(II)) and 5 in 1-butanol at 60 °C for 24 h. The Werner clathrates were prepared by reacting M(NCS)2 (M = Co(II) and Ni(II)), G and 5 in 1-butanol at 60 °C for 48–96 h. The clathrates were observed to transform to the apohost ML4(NCS)2 upon heating. CoL4(NCS)2·2NB was subsequently regenerated by exposing CoL4(NCS)2 to liquid NB at 60 °C for 48 h. This phase change occurred as a single-crystal to single-crystal phase transformation and was studied by single crystal X-ray diffraction, powder X-ray diffraction and thermal analyses. Structural analyses of the apohost CoL4(NCS)2 and its Werner clathrate CoL4(NCS)2·2NB indicated that rotational freedom of the Co-N bonds together with torsional flexibility of the ligand between the imide bond and the pyridine moiety are key to enabling the structural switching induced by exposure to NB or its removal