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ABSTRACT: Calculations performed at the ab initio level using the recently reported planar concentric π-aromatic B(18)H(6) (2+)(1) [Chen Q et al. (2011) Phys Chem Chem Phys 13:20620] as a building block suggest the possible existence of a new class of B(3n )H( m ) polycyclic aromatic hydroboron (PAHB) clusters-B(30)H(8)(2), B(39)H(9) (2-)(3), B(42)H(10)(4/5), B(48)H(10)(6), and B(72)H(12)(7)-which appear to be the inorganic analogs of the corresponding C( n )H( m ) polycyclic aromatic hydrocarbon (PAHC) molecules naphthalene C(10)H(8), phenalenyl anion C(13)H(9) (-), phenanthrene/anthracene C(14)H(10), pyrene C(16)H(10), and coronene C(24)H(12), respectively, in a universal atomic ratio of B:C = 3:1. Detailed canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), and electron localization function (ELF) analyses indicate that, as they are hydrogenated fragments of a boron snub sheet [Zope RR, Baruah T (2010) Chem Phys Lett 501:193], these PAHB clusters are aromatic in nature, and exhibit the formation of islands of both σ- and π-aromaticity. The predicted ionization potentials of PAHB neutrals and electron detachment energies of small PAHB monoanions should permit them to be characterized experimentally in the future. The results obtained in this work expand the domain of planar boron-based clusters to a region well beyond B(20), and experimental syntheses of these snub B(3n )H( m ) clusters through partial hydrogenation of the corresponding bare B(3n ) may open up a new area of boron chemistry parallel to that of PAHCs in carbon chemistry.
Journal of Molecular Modeling 11/2012; · 1.80 Impact Factor
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ABSTRACT: Searches for planar hexacoordinate carbon (phC) species comprised of only seven atoms uncovered good CX(3)M(3) prototypes, D(3h) CN(3)Be(3)(+) and CO(3)Li(3)(+). The latter is the global minimum. It might also be possible to detect the deep-lying kinetically-viable D(3h) CN(3)Be(3)(+) local minimum, based on its robustness toward molecular dynamic simulations and its very high isomerization barrier.
Physical Chemistry Chemical Physics 07/2012; 14(43):14760-3. · 3.57 Impact Factor
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ABSTRACT: Based upon comprehensive theoretical investigations and known experimental observations, we predict the existence of the double-chain planar D(2h) B(4)H(2)(1), C(2h) B(8)H(2)(3), and C(2h) B(12)H(2)(5) which appear to be the lowest-lying isomers of the systems at the density functional theory level. These conjugated aromatic borenes turn out to be the boron hydride analogues of the conjugated ethylene D(2h) C(2)H(4)(2), 1,3-butadiene C(2h) C(4)H(6)(4), and 1,3,5-hexatriene C(2h) C(6)H(8)(6), respectively, indicating that a B(4) rhombus in B(2n)H(2) borenes (n = 2, 4, 6) is equivalent to a C[double bond, length as m-dash]C double bond unit in the corresponding C(n)H(n+2) hydrocarbons. Detailed canonical molecular orbital (CMO), adaptive natural density partitioning (AdNDP), and electron localization function (ELF) analyses unravel the bonding patterns of these novel borene clusters and indicate that they are all overall aromatic in nature with the formation of islands of both σ- and π- aromaticity. The double-chain planar or quasi-planar C(2v) B(3)H(2)(-)(7), C(2) B(5)H(2)(-)(8), and C(2h) B(6)H(2)(9) with one delocalized π orbital, C(2v) B(7)H(2)(-)(10), C(2) B(9)H(2)(-)(11), and C(2h) B(10)H(2)(12) with two delocalized π orbitals, and C(2v) B(11)H(2)(-)(13) with three delocalized π orbitals are found to be analogous in π-bonding to D(2h) B(4)H(2)(1), C(2h) B(8)H(2)(3), and C(2h) B(12)H(2)(5), respectively. We also calculated the electron affinities and ionization potentials of the neutrals and simulated the photoelectron spectroscopic spectra of the monoanions to facilitate their future experimental characterization. The results obtained in this work enrich the analogous relationship between hydroborons and their hydrocarbon counterparts and help to understand the high stability of the theoretically predicted all-boron nanostructures which favor the formation of double-chain substructures.
Physical Chemistry Chemical Physics 06/2012; 14(43):14769-74. · 3.57 Impact Factor
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ABSTRACT: Following the isoelectronic relationship in global minima planar pentacoordinate carbon (ppC) species (cationic CAl(5)(+), neutral CAl(4)Be, and monoanionic CAl(3)Be(2)(-)), we designed a dianionic ppC species C(2v) CAl(2)Be(3)(2-) (1a) and its salt complex C(2v) LiCAl(2)Be(3)(-) (2a) in this work. In combination with DFT and high-level ab initio calculations (CCSD(T)), the extensive exploration on their potential energy surfaces indicates that they are the global minima. Their kinetic stability was proved by two sets of 100 ps ab initio Born-Oppenheimer molecular dynamic simulations at the B3LYP/6-31+G(d) level. The detailed analyses indicate that the introduction of Li(+) into 1a only influences the electrovalent bonding (through changing of the charge distribution) and the σ aromaticity (through changing of the in-plane ring current), while the structures, the bonding properties, the π aromaticity, and so forth are almost unchanged. Nevertheless, the MO energy levels, the HOMO-LUMO gaps, and the values of vertical detachment energies (VDEs) all verify that the lithiation significantly improves the stability. We think the ppC dianion 1a is possible to detect directly in the gas-phase experiments, but it can be detected as its salt complex 2a more easily.
The Journal of Physical Chemistry A 03/2012; 116(12):3290-4. · 2.95 Impact Factor
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ABSTRACT: Based upon extensive density functional theory and wave function theory calculations performed in this work, we predict the existence of the perfectly planar triangle C(3h) B(6)H(3)(+) (1, (1)A') and the double-chain stripe C(2h) B(8)H(2) (9, (1)A(g)) which are the ground states of the systems and the inorganic analogues of cyclopropene cation D(3h) C(3)H (3) (+) and cyclobutadiene D(2h) C(4)H(4), respectively. Detailed adaptive natural density partitioning (AdNDP) analyses indicate that C(3h) B(6)H (3) (+) is π plus σ doubly aromatic with two delocalized π-electrons and six delocalized σ-electrons formally conforming to the 4n + 2 aromatic rule, while C(2h) B(8)H(2) is π antiaromatic and σ aromatic with four delocalized π-electrons and ten delocalized σ-electrons. The perfectly planar C(2h) B(8)H(4) (5, (1)A(g)) also proves to be π antiaromatic analogous to D(2h) C(4)H(4), but it appears to be a local minimum about 50 kJ mol(-1) less stable than the three dimensional C(s) B(8)H(4)(6, (1)A'). AdNDP, nucleus independent chemical shifts (NICS) and electron localization function (ELF) analyses indicate that these boron hydride clusters form islands of both σ- and π-aromaticities and are overall aromatic in nature in ELF aromatic criteria.
Journal of Molecular Modeling 01/2012; 18(7):3161-7. · 1.80 Impact Factor
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ABSTRACT: Boron could be the next element after carbon capable of forming 2D-materials similar to graphene. Theoretical calculations predict that the most stable planar all-boron structure is the so-called α-sheet. The mysterious structure of the α-sheet with peculiar distribution of filled and empty hexagons is rationalized in terms of chemical bonding. We show that the hexagon holes serve as scavengers of extra electrons from the filled hexagons. This work could advance rational design of all-boron nanomaterials.
Physical Chemistry Chemical Physics 06/2011; 13(24):11575-8. · 3.57 Impact Factor
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ABSTRACT: Is it possible to achieve molecules with starlike structures by replacing the H atoms in (CH)(n)(q) aromatic hydrocarbons with aluminum atoms in bridging positions? Although D(4h) C(4)Al(4)(2-) and D(2) C(6)Al(6) are not good prospects for experimental realization, a very extensive computational survey of fifty C(5)Al(5)(-) isomers identified the starlike D(5h) global minimum with five planar tetracoordinate carbon atoms to be a promising candidate for detection by photoelectron detachment spectroscopy. BOMD (Born-Oppenheimer molecular dynamics) simulations and high-level theoretical computations verified this conclusion. The combination of favorable electronic and geometric structural features (including aromaticity and optimum C-Al-C bridge bonding) stabilizes the C(5)Al(5)(-) star preferentially.
Chemistry 01/2011; 17(2):714-9. · 5.93 Impact Factor
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ABSTRACT: A density functional theory investigation on the geometrical and electronic properties of B4S (B2(BS)) and B5S (B(BS)) clusters has been performed in this work. Both the doublet B2(BS) ([SBBBBS]−) (D∞h, 2Πu) and the singlet B2(BS) ([SBBBBS]2−) (D∞h, 1Σ) proved to have perfect linear ground-state structures containing a multiply bonded BB core (BB or BB) terminated with two BS groups, while Td B(BS) turned out to possess a perfect B− tetrahedral center directly corrected to four BS groups, similar to the corresponding boron hydride molecules of D∞h B2H, D∞h B2H, and Td BH, respectively. B4S2 and B5S4 neutrals, however, appeared to be much different: they favor a planar fan-shaped C2v B4S2 (a di-S-bridged B4 rhombus) and a planar kite-like C2v B5S4 (a di-S-bridged B3 triangle bonded to two BS groups), respectively. One-electron detachment energies and symmetrical stretching vibrational frequencies are calculated for D∞h B2(BS) and Td B(BS) monoanions to facilitate their future characterizations. Neutral salts of B2(BS)2Li2 with an elusive BB triple bond and B(BS)4Li containing a tetrahedral B− center are predicted possible to be targeted in experiments. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
International Journal of Quantum Chemistry 11/2009; 110(14):2689 - 2696. · 1.36 Impact Factor
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ABSTRACT: Ab initio and DFT calculations have been carried out to search for the simplest neutral singlet species with double planar tetracoordinate carbons (dptCs) [the "simplest" means the species containing the least number (six) and types (two) of atoms]. Under the restrictions to the possible models (M1-M4) with dptCs and to the singlet electronic states, the B3LYP/6-31+G* scanning on the candidates, C(2)E(4) (E = the second- and third-row main group elements), only led to two minima (D(2h) C(2)Al(4) and C(2h) C(2)Be(4)) with stable DFT wave functions. The extensions to the heavier elements after the fourth row in the IIA and IIIA groups revealed that the D(2h) C(2)E(4) (E = Ga, In, and Tl) are also minima with dptCs but C(2)Ca(4) (C(2h)) is a first-order saddle point. Extensive explorations at the DFT level on their potential energy surfaces (PESs) further confirmed that the D(2h) C(2)E(4) (E = Al, Ga, In, and Tl) are the global minima, but the C(2h) C(2)Be(4) is a local minimum. The optimizations at the MP2 level distorted the D(2h) C(2)E(4) (E = Ga, In, and Tl) slightly and the distortion energies are less than 0.02 kcal/mol. The C(2)E(4) (E = Al, Ga, In, and Tl) with dptCs are 18.0, 18.3, 13.4, and 12.2 kcal/mol energetically more favorable than their nearest isomers, respectively, at the CCSD(T)//MP2 level with aug-cc-pVTZ for C and Al and aug-cc-pVTZ-PP for Ga, In, and Tl basis set. The substantial energy differences suggest their promise to be experimentally realized. The strong peak on the C(2)Al(4)(-) component in the time-of-flight mass spectrum from laser vaporization of a mixed graphite/aluminum may relate to the D(2h) C(2)Al(4) global minimum. The analyses of the electronic structures of C(2)Al(4) (D(2h)), CAl(4)(2-) (D(4h)) and CAl(5)(+)(D(5h)) indicates that the C(2) moiety in C(2)Al(4) is the equivalence of carbon centers in CAl(4)(2-) and CAl(5)(+) and unveils the reasons for their stability. The electronic structures of C(2)Al(4) and ethene are compared. On the one hand, an Al atom functions like an H atom because the eight more valence electrons of C(2)Al(4) than C(2)H(4) occupy four nonbonding orbitals and are not effectively utilized for bonding. On the other hand, an Al atom is different from an H atom because an Al atom has p electrons available for peripheral bonding around the C(2) moieties in C(2)Al(4), which further rationalize the origins for C(2)E(4) to achieve double ptCs.
The Journal of Physical Chemistry A 05/2009; 113(14):3395-402. · 2.95 Impact Factor
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ABSTRACT: A density functional theory and wave function theory investigation on the geometrical and electronic structures of B5O4(0/-) clusters has been performed in this work. B5O4(-) anion proves to possess a perfect tetrahedral ground state of T(d) B(BO)4(-) ((1)A1) analogous to BH4(-) with four equivalent -BO terminals around the B center, while B5O4 neutral favors a slightly off-planed C(s) B(BO)4 ((2)A') which contains three -BO terminals and one -O- bridge. An intramolecular BO radical transfer occurs from T(d) B(BO)4(-) to C(s) B(BO)4 when one electron is detached from the anion. The one-electron detachment energies of the anion and characteristic stretching vibrational frequencies of -B=O groups at about 2000 cm(-1) have been calculated to facilitate future experimental characterization of these clusters.
The Journal of Physical Chemistry A 03/2009; 113(11):2561-4. · 2.95 Impact Factor
