Novel paramagnetic-luminescent building blocks containing manganese(II) and anthracene-based curcuminoids

In an effort to study innovative multifunctional molecular materials, two new coordination compounds have been designed containing Mn^II as a metallic source and a specific curcuminoid called 9Accm as a chelating ligand. Synthetic reactions were carried out between Mn(O₂CMe) ₂·4H₂O and 1,7-di-9-anthracene-1,6-heptadiene-3,5- dione (9Accm), leading to [Mn(9Accm)₂(py)₂] (1) and [Mn(9Accm)₂(4,4′-bpy)]_n (2), respectively. In particular, compound 1 was characterized by analytical, spectroscopic techniques (UV-Vis, fluorescence in the solid state and in solution and EPR), magnetic susceptibility measurements and X-ray crystallography. Compound 2 was characterized by a number of techniques as elemental analysis, UV-Vis, fluorescence (in the solid state and in solution), SQUID magnetic susceptibility studies and EPR. The structure of 1 reveals mononuclear octahedral Mn ^II species incorporating 9Accm and pyridine while analyses of 2 implies the formation of 1D chain in which Mn^II centers bound to 9Accm and link with each other by 4,4-bipyridine molecules. Compound 1 is a mononuclear compound that can act as a potential building block for the design of novel Mn^II-curcuminoid species (e.g. compound 2). Both systems exhibit magnetic properties due to the nature of the metallic source and display fluorescence in the visible region in the solid state and in solution due to the nature of the ligand 9Accm. Therefore, 1 and 2 are excellent examples of multifunctional systems at the molecular scale. Even though both systems are very similar this work depicts the magnetic/fluorescent differences between each other.