Isomerization And Chemical Modifications Of Borospherene B₃₉^-

Today,for chemists,quantum chemical theoretical calculation has been one main method to study the application of new materials and to predict the physical and chemical properties of novel nano structures.Since the discovery of C60,carbon fullerenes with different dimensions have been synthesized in macroquantities as well as practical application,motivated by this,attempts have been made to seek alternative freestanding fullerene structures constructed by other atoms.The observation of all-boron fullerene B40 and B₃₉^-tremendously stretch the inorganic fullerene architecture.Based on density functional theory,a systemic theoretical investigation has been performed on the isomerization and chemical modify of B₃₉^-borospherenes,the main contents are as follows:1."W-X-M" Transformation in Isomerization of B₃₉^-BorospherenesThe first axially chiral all-boron fullerenes C3/C2 B₃₉^-are as the second experimentally observed borospherene after D2d B40-/0,first-principles molecular dynamics simulations demonstrated that B₃₉^-fullerenes hop between the two C3 and C2 lowest-energy isomers.The Stone-Wales transformation plays an important role in the isomerization of fullerenes and graphenic systems.However,the isomerization mechanism of the recently discovered borospherenes（all-boron fullerenes）still remains unknown.Extensive first-principles molecular dynamics simulations and quadratic synchronous transit transition-state searches indicate that,via three transition states（TS1,TS2,TS3）and two intermediate species（Ml and M2）,the C3 B₃₉^-global minimum structure convert into its C2 isomer.In the first axially chiral borospherenes C3 B₃₉^-and C2 B₃₉^-,we identify three active boron atoms which are located at the center of three alternative sites involving five boron atoms denoted as "W","X",and "M",respectively.The concerted movements of these active boron atoms and their close neighbors on the boron double chains between neighboring hexagonal and heptagonal holes define the "W-X-M" transformation of borospherenes.The maximum barriers are only 3.89 kcal/mol from C3 to C2 B₃₉^-and 2.1 kcal/mol from C2 to C3 B₃₉^-,rendering dynamic fluxionalities to these borospherenes.The new "W-X-M"transformation mechanism not only explain the interchange of hexagon and heptagon in the interwoven boron double-chains structures,but also as the grow mechanism of borospheren.Just as the Stone-Wales transformation play an important role in isomerization of carbon materials and the grow mechanism of C20+2n,the "W-X-M" transformation can be easily extended to other borospherenes and borospherene-based nanostructures.2.Theory investigation of metalloborospherenes MB39Based on global minimum structural searches and first-principles theory calculations,we report herein a systematic theoretical investigation on their alkali metal neutral salts,present by lithium in this article:the exohedral C1 Li&B39（1）and C1 Li&B39（2）which are the global minima and the second lowest-lying isomer of the system obtained by capping a Li atom on a heptagon on the cage surface of C2 B₃₉^-and C3 B₃₉^-,respectively.These metalloborospherenes turn out to be charge-transfer complex Li+B₃₉^-in nature,with the huge HOMO-LUMO energy gaps 2.72 eV and 2.84 eV and formation energy of-83.1 and-78.2 kcal/mol,respectively,their unique electronic structures and physical properties have made them as attractive candidates for especial electronic nanomaterials.Detailed molecular orbital analyses indicate that Li&B39（1/2）possessσplusπdouble delocalization bonding patterns similar to their C2/C3 B₃₉^-parents and B40.Extensive molecular dynamics simulations reveal that those metalloborospherenes fluctuate between low-lying isomers above room temperature.The simulative photoelectron spectroscopy（PES）and UV,IR,and Raman spectra of Li&B39（1/2）,preparing for the production and detection,will positively stimulate future experimental studies of metalloborospherenes.Such neutral borospherene salts may be produced in macro-quantities in future experiments,serve as building blocks to form borospherene-based nanomaterials.Those theoretical searches have made them as attractive candidates for especial nanomaterials,such as molecule device and field-emission materials,and they may constitute a new class of nanostructures complementary to the carbon nanometer materials.