Metal nitride cluster as a template to tune the electronic and magnetic properties of rare-earth metal containing endohedral fullerenes
In this thesis, Ce-, Pr-, Ho-based and Sc-, Lu- and Y-involved mixed metal nitride clusterfullerenes were synthesized by “reactive gas atmosphere” or “selective organic solid” route. Metal nitride cluster template provides a convenient platform for the construction of rare-earth containing endohedral fullerenes in the form of mixed metal nitride cluster fullerenes (LnxM3-xN@C2n; Ln=lanthanide metal). Different metals and carbon cages can be regarded as the infinite building blocks for the endohedral fullerenes family. Sc, Lu and Y are employed as the second metal (M) to tune: (a) the size and the geometry of entrapped mixed metal nitride cluster; (b) the inherent strain between encaged species and carbon cage; (c) the paramagnetic contribution from Ln3+ (LnxM3-xN@C80) to 13C and 45Sc NMR chemical shifts; (d) the electrochemical oxidation potential of CexY3-xN@C2n. The isolation of (a) C80-based MMNCFs which including HoxM3-xN@C80 (I, II; M=Sc, Lu, Y; x= 1, 2), CeY2N@C80 (I), CeSc2N@C80 (II) and PrSc2N@C80 (I, II) was accomplished by multi-step HPLC. Moreover, Ce-based MMNCFs with cage size larger than C80 were isolated which include CeY2N@C84, CeY2N@C86, Ce2YN@C86, Ce2YN@C88 and CeY2N@C88. The purity of above-mentioned MMNCFs was confirmed by LDI-TOF mass spectroscopy. FTIR spectra own advantages for the analyzing the antisymmetric metal-nitrogen stretching vibrational modes (νM-N) of LnxM3-xN@C80 (I, II; x= 0-3). Raman spectra provide critical information on the interaction between the entrapped metal nitride cluster and the C80 cage. The 4f electron(s) located on the encaged lanthanide metals (e.g. 4f1-Ce3+, 4f2-Pr3+ and 4f10-Ho3+) results in remarkable 13C NMR paramagnetic chemical shifts. The convincing proofs of the strain-driven endohedral redox couple CeIV/CeIII in mixed metal nitride clusterfullerenes CeM2N@C80 (M= Sc, Lu, Y) were presented by the characterization of cyclic voltammtry and 13C NMR spectroscopy.