Noble gas encapsulated B40 cage.

The efficacy of B40 borospherene to act as a host for noble gas atoms is explored via density functional theory based computations. Although the Ng@B40 complexes are thermochemically unstable with respect to dissociation into free Ng and B40, it does not rule out their viability as all the systems possess a high activation free energy barrier (84.7-206.3 kcal mol-1). Therefore, once they are formed, it is hard to take out the Ng atom. Two Ng atoms can also be incorporated within B40 for the lighter Ng atoms (He and Ne). In fact, the destabilization offered by the encapsulation of one and two He atoms and one Ne atom inside B40 is significantly less than that in experimentally synthesized He@C20H20, highlighting their greater possibility for synthesis. Although Ar2 and Kr2 encapsulated B40 systems are very much destabilized by the repulsive interaction between Ng2 and B40, an inspection of the bonding situation reveals that the confinement can even induce some degree of covalent interaction between two otherwise non-bonded Ng atoms. Ng atoms transfer electrons towards B40 which is smaller for lighter Ng atoms and gradually increases along He to Rn. Even if the electrostatic interaction between Ng and B40 is the most predominant term in these systems, the extent of the orbital interaction is also considerable. However, the very large Pauli repulsion counterbalances the attractive interaction, eventually turning the interaction repulsive in nature. Ng@B40 also shows dynamical behaviour involving continuous exchange between hexagonal and heptagonal holes, similar to the host cage, as understood from the very little variation in the activation barrier because of the Ng encapsulation. Furthermore, sandwich complexes like [(η5-C5Me5)Fe(η6-B40)]+ and [(η5-C5Me5)Fe(η7-B40)]+ are noted to be viable with the latter being slightly more stable than the former. The encapsulation of Xe slightly improves the dissociation energy associated with the decomposition into Xe@B40 and [Fe(η5-C5Me5)]+ compared to that in the bare one.

[1]  R. Bader.  Atoms in molecules : a quantum theory , 1990 .

[2]  H. Stoll,et al.  Systematically convergent basis sets with relativistic pseudopotentials. II. Small-core pseudopotentials and correlation consistent basis sets for the post-d group 16–18 elements , 2003 .

[3]  E. Jemmis,et al.  Exohedral Complexation of B40 , C60 and Arenes with Transition Metals: A Comparative DFT Study. , 2016, Chemistry, an Asian journal.

[4]  M. Head‐Gordon,et al.  Long-range corrected hybrid density functionals with damped atom-atom dispersion corrections. , 2008, Physical chemistry chemical physics : PCCP.

[5]  R. Haddon.  Organometallic chemistry of fullerenes: η2‐ and η5‐(π)complexes , 1998 .

[6]  Martin Saunders,et al.  Incorporation of helium, neon, argon, krypton, and xenon into fullerenes using high pressure , 1994 .

[7]  Pratim K. Chattaraj,et al.  Dynamical behavior of Borospherene: A Nanobubble , 2015, Scientific Reports.

[8]  Mariusz Klobukowski,et al.  Well-tempered Gaussian basis sets for the calculation of matrix Hartree-Fock wavefunctions , 1993 .

[9]  S. F. Boys,et al.  The calculation of small molecular interactions by the differences of separate total energies. Some procedures with reduced errors , 1970 .

[10]  Kelling J. Donald,et al.  Influence of endohedral confinement on the electronic interaction between He atoms: a He2@C20H20 case study. , 2009, Chemistry.

[11]  Lei Liu,et al.  Structure and bonding of IrB12−: converting a rigid boron B12 platelet to a Wankel motor , 2016 .

[12]  P. Chattaraj,et al.  Encapsulation of small gas molecules and rare gas atoms inside the octa acid cavitand , 2016, Theoretical Chemistry Accounts.

[13]  Hua‐Jin Zhai,et al.  Cage-like B40+: a perfect borospherene monocation , 2016, Journal of Molecular Modeling.

[14]  F. Matthias Bickelhaupt,et al.  Chemistry with ADF , 2001, J. Comput. Chem..

[15]  Pratim K. Chattaraj,et al.  Confinement induced binding in noble gas atoms within a BN-doped carbon nanotube , 2015 .

[16]  S. Kennel,et al.  Metallofullerene drug design , 1999 .

[17]  Gabriel Merino,et al.  Coaxial Triple-Layered versus Helical Be6 B11- Clusters: Dual Structural Fluxionality and Multifold Aromaticity. , 2017, Angewandte Chemie.

[18]  S. Mirzadeh,et al.  TOWARD FULLERENE-BASED RADIOPHARMACEUTICALS : HIGH-YIELD NEUTRON ACTIVATION OF ENDOHEDRAL 165HO METALLOFULLERENES , 1999 .

[19]  Frank Weinhold,et al.  Natural bond orbital analysis of near‐Hartree–Fock water dimer , 1983 .

[20]  H. Prinzbach,et al.  Putting Helium Inside Dodecahedrane , 1999 .

[21]  Pratim K Chattaraj,et al.  Confinement induced binding of noble gas atoms. , 2014, The Journal of chemical physics.

[22]  Yang Liu,et al.  He@Mo(6)Cl(8)F(6): a stable complex of helium. , 2010, Journal of Physical Chemistry A.

[23]  Artur Michalak,et al.  Donor–Acceptor Properties of Ligands from the Natural Orbitals for Chemical Valence , 2007 .

[24]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[25]  B28: the smallest all-boron cage from an ab initio global search. , 2015, Nanoscale.

[26]  A. Haaland,et al.  Topological analysis of electron densities: is the presence of an atomic interaction line in an equilibrium geometry a sufficient condition for the existence of a chemical bond? , 2004, Chemistry.

[27]  Jun Li,et al.  Experimental and theoretical evidence of an axially chiral borospherene. , 2015, ACS nano.

[28]  Clark R. Landis,et al.  NBO 6.0: Natural bond orbital analysis program , 2013, J. Comput. Chem..

[29]  J L Bada,et al.  Extraterrestrial Helium Trapped in Fullerenes in the Sudbury Impact Structure , 1996, Science.

[30]  Keiji Morokuma,et al.  Why do molecules interact? The origin of electron donor-acceptor complexes, hydrogen bonding and proton affinity , 1977 .

[31]  Pratim K Chattaraj,et al.  B18(2-): a quasi-planar bowl member of the Wankel motor family. , 2014, Chemical communications.

[32]  Martin Saunders,et al.  129Xe NMR spectrum of xenon inside C(60). , 2002, Journal of the American Chemical Society.

[33]  J. Oscar C. Jiménez-Halla,et al.  B19-: an aromatic Wankel motor. , 2010, Angewandte Chemie.

[34]  R. Bader,et al.  A Bond Path: A Universal Indicator of Bonded Interactions , 1998 .

[35]  M. Saunders,et al.  Using cyanide to put noble gases inside C60. , 2003, The Journal of organic chemistry.

[36]  Alberto Vela,et al.  The implications of symmetry of the external potential on bond paths. , 2008, Chemistry.

[37]  Thomas Heine,et al.  Unravelling phenomenon of internal rotation in B13+ through chemical bonding analysis. , 2011, Chemical communications.

[38]  Evert Jan Baerends,et al.  Relativistic regular two-component Hamiltonians. , 1996 .

[39]  Artur Michalak,et al.  A Combined Charge and Energy Decomposition Scheme for Bond Analysis. , 2009, Journal of chemical theory and computation.

[40]  Ranajit Saha,et al.  How Far Can One Push the Noble Gases Towards Bonding?: A Personal Account , 2019, Molecules.

[41]  Evert Jan Baerends,et al.  Relativistic total energy using regular approximations , 1994 .

[42]  Hua‐Jin Zhai,et al.  Cage-Like B41 (+) and B42 (2+) : New Chiral Members of the Borospherene Family. , 2015, Angewandte Chemie.

[43]  Shuijie Qin,et al.  Structures, stabilities and spectral properties of borospherene B44− and metalloborospherenes MB440/− (M = Li, Na, and K) , 2017, Scientific reports.

[44]  P. Chattaraj,et al.  Noble‐Noble Strong Union: Gold at Its Best to Make a Bond with a Noble Gas Atom , 2019, ChemistryOpen.

[45]  Artur Michalak,et al.  Applications of natural orbitals for chemical valence in a description of bonding in conjugated molecules , 2008, Journal of molecular modeling.

[46]  D. Marynick,et al.  Theoretical estimates of the η6 bonding capability of buckminsterfullerene in transition metal complexes , 1993 .

[47]  Arvi Rauk,et al.  On the calculation of multiplet energies by the hartree-fock-slater method , 1977 .

[48]  Lai‐Sheng Wang,et al.  Competition between quasi-planar and cage-like structures in the B29- cluster: photoelectron spectroscopy and ab initio calculations. , 2016, Physical chemistry chemical physics : PCCP.

[49]  R. Bader,et al.  Spatial localization of the electronic pair and number distributions in molecules , 1975 .

[50]  Walter Thiel,et al.  Interaction energies and NMR chemical shifts of noble gases in C60 , 1997 .

[51]  Michal Straka,et al.  Density functional calculations of 3He chemical shift in endohedral helium fullerenes: Neutral, anionic, and di-helium species. , 2006, The journal of physical chemistry. A.

[52]  Martin Saunders,et al.  Stable Compounds of Helium and Neon: He@C60 and Ne@C60 , 1993, Science.

[53]  G. Frenking,et al.  Breaking the Isolated Pentagon Rule by Encapsulating Xe2 in C60: The Guest Defines the Shape of the Host , 2016 .

[54]  Takeshi Akasaka,et al.  Endohedral dimetallofullerenes Sc2@C84 and La2@C80. Are the metal atoms still inside the fullerence cages? , 1996 .

[55]  Evert Jan Baerends,et al.  The zero order regular approximation for relativistic effects: the effect of spin-orbit coupling in closed shell molecules. , 1996 .

[56]  Hua‐Jin Zhai,et al.  Saturn-like charge-transfer complexes Li₄&B₃₆, Li₅&B₃₆⁺, and Li₆&B₃₆²⁺: exohedral metalloborospherenes with a perfect cage-like B₃₆⁴⁻ core. , 2016, Physical chemistry chemical physics : PCCP.

[57]  Pratim K. Chattaraj,et al.  Movement of Ng2 molecules confined in a C60 cage: An ab initio molecular dynamics study , 2014 .

[58]  Ranajit Saha,et al.  A Spinning Umbrella: Carbon Monoxide and Dinitrogen Bound MB12- Clusters (M = Co, Rh, Ir). , 2017, The journal of physical chemistry. A.

[59]  Truong Ba Tai,et al.  A new chiral boron cluster B44 containing nonagonal holes. , 2016, Chemical communications.

[60]  Yanming Ma,et al.  B38: an all-boron fullerene analogue. , 2014, Nanoscale.

[61]  Gernot Frenking,et al.  Energy decomposition analysis , 2020, Catalysis from A to Z.

[62]  Lon J. Wilson,et al.  Synthesis, Characterization, and Neutron Activation of Holmium Metallofullerenes , 1996 .

[63]  S. Grimme,et al.  A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. , 2010, The Journal of chemical physics.

[64]  Si‐Dian Li,et al.  Cage-like B39+ clusters with the bonding pattern of σ + π double delocalization: new members of the borospherene family. , 2017, Physical chemistry chemical physics : PCCP.

[65]  Martin Saunders,et al.  AN NMR STUDY OF HE2 INSIDE C70 , 1998 .

[66]  Gernot Frenking,et al.  Is this a chemical bond? A theoretical study of Ng2@C60 (Ng=He, Ne, Ar, Kr, Xe). , 2007, Chemistry.

[67]  M. G. Evans,et al.  Some applications of the transition state method to the calculation of reaction velocities, especially in solution , 1935 .

[68]  Lai‐Sheng Wang,et al.  Planar B38- and B37- clusters with a double-hexagonal vacancy: molecular motifs for borophenes. , 2017, Nanoscale.

[69]  M. S. de Vries,et al.  Atoms in carbon cages: the structure and properties of endohedral fullerenes , 1993, Nature.

[70]  H. Schwarz,et al.  Injection of helium atoms into doubly and triply charged carbon (C60) cations , 1991 .

[71]  Evert Jan Baerends,et al.  Relativistic regular two‐component Hamiltonians , 1993 .

[72]  S. C. O'brien,et al.  Lanthanum complexes of spheroidal carbon shells , 1985 .

[73]  Hugo A. Jiménez-Vázquez,et al.  Binding Energy in and Equilibrium Constant of Formation for the Dodecahedrane Compounds He@C20H20 and Ne@C20H20 , 2001 .

[74]  Aromatic cage-like B46: existence of the largest decagonal holes in stable atomic clusters , 2017 .

[75]  Hua‐Jin Zhai,et al.  B11(-): a moving subnanoscale tank tread. , 2015, Nanoscale.

[76]  Keiji Morokuma,et al.  Molecular Orbital Studies of Hydrogen Bonds. III. C=O···H–O Hydrogen Bond in H2CO···H2O and H2CO···2H2O , 1971 .

[77]  Elfi Kraka,et al.  Chemical Bonds without Bonding Electron Density — Does the Difference Electron‐Density Analysis Suffice for a Description of the Chemical Bond? , 1984 .

[78]  P. Chattaraj,et al.  Confinement of (HF)2 in Cn (n = 60, 70, 80, 90) cages , 2014 .

[79]  J. Cioslowski,et al.  Endohedral fullerites: A new class of ferroelectric materials. , 1992, Physical review letters.

[80]  P. Chattaraj,et al.  Cucurbit[6]uril: A Possible Host for Noble Gas Atoms. , 2015, The journal of physical chemistry. B.

[81]  Jun Li,et al.  Observation of an all-boron fullerene. , 2014, Nature chemistry.

[82]  Gustavo E. Scuseria,et al.  Noble Gas Endohedral Complexes of C60 Buckminsterfullerene , 1997 .

[83]  K. Peterson.  Systematically convergent basis sets with relativistic pseudopotentials. I. Correlation consistent basis sets for the post-d group 13–15 elements , 2003 .

[84]  R. Bader,et al.  Bond paths are not chemical bonds. , 2009, The journal of physical chemistry. A.

[85]  Kenneth B. Wiberg,et al.  Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane , 1968 .

[86]  F. Weinhold,et al.  Natural population analysis , 1985 .

[87]  F. Weigend,et al.  Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. , 2005, Physical chemistry chemical physics : PCCP.

[88]  Lei Liu,et al.  Dynamical behavior of boron clusters. , 2016, Nanoscale.

[89]  Tian Lu,et al.  Multiwfn: A multifunctional wavefunction analyzer , 2012, J. Comput. Chem..

[90]  Fernando Cortés-Guzmán,et al.  Complementarity of QTAIM and MO theory in the study of bonding in donor–acceptor complexes , 2005 .

[91]  Helmut Schwarz,et al.  Endohedral Cluster Compounds: Inclusion of Helium within C 60•⊕ and C 70•⊕ through Collision Experiments , 1991 .

[92]  Evert Jan Baerends,et al.  Geometry optimizations in the zero order regular approximation for relativistic effects. , 1999 .

[93]  Walter Thiel,et al.  How Does Helium Get into Buckminsterfullerene , 1996 .

[94]  Arvi Rauk,et al.  Carbon monoxide, carbon monosulfide, molecular nitrogen, phosphorus trifluoride, and methyl isocyanide as .sigma. donors and .pi. acceptors. A theoretical study by the Hartree-Fock-Slater transition-state method , 1979 .

[95]  Tapan K. Ghanty,et al.  Noble Gas Encapsulated Endohedral Zintl Ions Ng@Pb122– and Ng@Sn122– (Ng = He, Ne, Ar, and Kr): A Theoretical Investigation , 2017 .

[96]  K. Burke,et al.  Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)] , 1997 .