Titanium/yttrium mixed metal nitride clusterfullerene TiY _2N@C _(80): Synthesis, isolation, and effect of the group-III metal

摘要

Titanium/yttrium mixed metal nitride clusterfullerene (MMNCF) TiY _2N@C _(80) has been successfully synthesized, representing the first Ti-containing non-scandium MMNCF. TiY _2N@C _(80) has been isolated by multistep HPLC and characterized by various spectroscopies in combination with DFT computations. The electronic absorption property of TiY _2N@C _(80) was characterized by UV-vis-NIR spectroscopy, indicating the resemblance to that of TiSc _2N@C _(80) with broad shoulder absorptions. The optical band gap of TiY _2N@C _(80) (1.39 eV) is very close to that of TiSc _2N@C _(80) (1.43 eV) but much smaller than that of Y _3N@C _(80)(I h, 1.58 eV). Such a resemblance of the overall absorption feature of TiY 2N@C 80 to TiSc 2N@C 80 suggests that TiY _2N@C _(80) has a similar electronic configuration to that of TiSc _2N@C _(80), that is, (TiY _2N) ~(6+)@C 80 ~(6-). FTIR spectroscopic study and DFT calculations accomplish the assignment of the C _(80):I _h isomer to the cage structure of TiY _2N@C _(80), with the C _1 conformer being the lowest energy structure, which is different from the C _s conformer assigned to TiSc _2N@C _(80). The electrochemical properties of TiY _2N@C _(80) were investigated by cyclic voltammetry, revealing the reversible first oxidation and first reduction step with E _(1/2) at 0.00 and -1.13 V, respectively, both of which are more negative than those of TiSc _2N@C _(80), while the electrochemical energy gap of TiY _2N@C _(80) (1.11 V) is almost the same as that of TiSc _2N@C _(80) (1.10 V). Contrary to the reversible first reduction step, the second and third reduction steps of TiY _2N@C _(80) are irreversible, and this redox behavior is dramatically different from that of TiSc _2N@C _(80), which shows three reversible reduction steps, indicating the strong influence of the encaged group-III metal (Y or Sc) on the electronic properties of TiM _2N@C _(80) (M = Y, Sc).