Endohedral C3 Ca@B39+ and C2 Ca@B39+: axially chiral metalloborospherenes based on B39−
Using the newly discovered borospherenes C3 B39− and C2 B39− as molecular devices and based on extensive global-minimum searches and first-principles calculations, we present herein the possibility of the first axially chiral metalloborospherenes C3 Ca@B39+ (1, 1A) and C2 Ca@B39+ (2, 1A), which are the global minimum and the second lowest-lying isomer of CaB39+, respectively. These metalloborospherene species turn out to be charge-transfer complexes Ca2+@B39− in nature, with the Ca centre on the C3 or C2 molecular axis donating one electron to the B39 cage which behaves like a superhalogen. Molecular orbital analyses indicate that C3/C2 Ca2+@B39− possess the universal bonding pattern of σ plus π double delocalization, similar to their C3/C2 B39− parents. Molecular dynamics simulations show that both C3 Ca@B39+ (1) and C2 Ca@B39+ (2) are dynamically stable at 200 K, with the former starting to fluctuate structurally at 300 K and the latter at 400 K, again similar to C3/C2 B39−. The infrared and Raman spectra of C3/C2 Ca@B39+ (1/2) are simulated and compared with those of C3/C2 B39− to facilitate their forthcoming experimental characterization.