RESUMO
The geometrical and electronic structures of the electron-deficient dialuminum aurides Al2Aun(0/-) and hybrid boron-aluminum aurides BAlAun(0/-) (n = 1-3) are systematically investigated based on the density and wave function theories. Ab initio theoretical evidence strongly suggests that bridging gold atoms exist in the ground states of C2v Al2Au(-) ((3)B1), C2v Al2Au ((2)B1), C2v Al2Au2(-) ((2)A1), C2v Al2Au2 ((1)A1), Cs Al2Au3(-) ((1)A'), and D3h Al2Au3 ((2)A1), which prove to possess an Al-Au-Al τ bond. For BAlAun(0/-) (n = 1-3) mixed clusters, bridging B-Au-Al units only exist in Cs BAlAu3(-) ((1)A') and Cs BAlAu3 ((2)A'), whereas Cs BAlAu(-) ((3)A''), Cs BAlAu ((2)A''), Cs BAlAu2(-) ((2)A'), and Cs BAlAu2 ((1)A') do not possess a bridging gold, as demonstrated by the fact that B-Al and B-Au exhibit significantly stronger electronic interaction than Al-Au in the same clusters. Orbital analyses indicate that Au 6s contributes approximately 98%-99% to the Au-based orbital in these Al-Au-Al/B-Au-Al interactions, whereas Au 5d contributes 1%-2%. The adiabatic and vertical detachment energies of Al2Aun(-) (n = 1-3) are calculated to facilitate future experimental characterizations. The results obtained in this work establish an interesting τ bonding model (Al-Au-Al/B-Au-Al) for electron-deficient systems in which Au 6s plays a major factor.
RESUMO
A systematic density functional theory and wave function theory investigation on the geometrical and electronic structures of the electron-deficient diboron aurides B(2) Au n-/0 (n = 1, 3, 5) and their mixed analogues B(2) H(m) Au n- (m + n = 3, 5) has been performed in this work. Ab initio theoretical evidences strongly suggest that bridging gold atoms exist in the ground states of C(2v) B(2) Au(-) ((1) A(1) ), C(2) B(2) Au 3-((1) A), C(2v) B(2) Au(3) ((2) B(1) ), C(2v) B(2) Au 5-((1) A(1) ), and C(s) B(2) Au(5) ((2) Aâ³), which all prove to possess a B-Au-B three-center-two-electron (3c-2e) bond. For B(2) H(m) Au n- (m + n = 3, 5) mixed anions, bridging B-Au-B units appear to be favored in energy over bridging B-H-B, as demonstrated by the fact that the Au-bridged C(2v) B(2) H(2) Au(-) ((1) A(1) ), C(s) B(2) HAu 2- ((1) A'), and C(1) B(2) HAu 4- ((1) A) lie clearly lower than their H-bridged counterparts C(s) B(2) H(2) Au(-) ((1) A'), C(2) B(2) HAu 2- ((1) A), and C(2v) B(2) HAu 4- ((1) A(1) ), respectively. Orbital analyses indicate that Au 6s makes about 92-96% contribution to the Au-based orbitals in these B-Au-B 3c-2e interactions, whereas Au 5d contributes 8-4%. The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations. The results obtained in this work establish an interesting 3c-2e bonding model (B-Au-B) for electron-deficient systems in which Au 6s plays a major role with non-negligible contribution from Au 5d.
RESUMO
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.
