Heptacoordinate transition-metal-decorated metallo-borospherenes and multiple-helix metallo-boronanotubes

The recent discovery of lanthanide-metal-decorated metallo-borospherenes LM3B18- (LM = La, Tb) marks the onset of a new class of boron-metal binary nanomaterials. Using the experimentally observed or theoretically predicted borospherenes as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel chiral metallo-borospherenes C-2 Ni-6 is an element of B-39(-) (1), C-1 Ni-6 is an element of B-41(+) (3), C-2 Ni-6 is an element of B-42(2+) (4), C-2 Ni-6 is an element of B-42 (5), and C-2 Ni-8 is an element of B-56 (6) as the global minima of the systems decorated with quasi-planar heptacoordinate Ni (phNi) centers in eta(7)-B-7 heptagons on the cage surfaces, which are found to be obviously better favoured in coordination energies than hexacoordinate Ni centers in previously reported D-2d Ni-6 is an element of B-40 (2). Detailed bonding analyses indicate that these phNi-decorated metallo-borospherenes follow the sigma + pi double delocalization bonding pattern, with two effective (d-p)sigma coordination bonds formed between each phNi and its eta(7)-B-7 ligand, rendering spherical aromaticity and extra stability to the systems. The structural motif in elongated axially chiral Ni-6 is an element of B-42(2+) (4), Ni-6 is an element of B-42 (5), and Ni-8 is an element of B-56 (6) can be extended to form the metallic phNi-decorated boron double chain (BDC) double-helix Ni-4 is an element of B-28 (2, 0) (P4m2) (8), triple-helix Ni-6 is an element of B-42 (3, 0) (P3m1) (9), and quadruple-helix Ni-8 is an element of B-56 (4, 0) (P4mm) (10) metallo-boronanotubes, which can be viewed as quasi-multiple-helix DNAs composed of interconnected BDCs decorated with phNi centers in eta(7)-B-7 heptagons on the tube surfaces in the atomic ratio of Ni : B = 1 : 7.

Automated summary

Using theoretical calculations and experimental observations, we have predicted a series of novel metallo-borospherenes and metallo-boronanotubes with good coordination energy and stability, which show promising potential for various applications.