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A density functional theory investigation on a series of S-shaped or cyclic (B(sub n)E(sub m)Si)2H2 molecules (E = B, C, Si; n = 3-6; m = 1, 2) containing double planar tetra-, penta-, and hexacoordinate silicons is presented. Theoretical evidence is provided to support the earlier proposed structural pattern to host planar hypercoordinate silicons in small aromatic molecules.

Geometrical optimizations and electronic structural analyses of the -O(sub 2)B(sub 2)- bridged hydrometal complexes (M4H3C)(sub 2)B(sub 2)O(sub 2) and (M4H3N)(sub 2)B(sub 2)O(sub 2)(super 2+) (M=Ni, Mg) containing double tetracoordinate planar nonmetals (TPN) are performed using the density functional theory at the B3LYP/6-311+G(d,p) level. Theoretical evidence of the possibility of double TPN centers coexisting in one planar molecule is presented.

The presentation of density functional theory evidence of hexacoordinate planar main group atoms centered in hexagonal hydrocopper complexes is given. The bonding capacity of silicon, phosphorous, and arsenic to planar hexacoordination in hydrocopper complexes is extended.

Tetradecker transition metal complexes containing double planar hexacoordinate carbons and double planar heptacooridnate borons are examined by using density functional theory. The results have provided a new method for synthesizing planar hyper-coordinate carbons and borons in transition metal complexes.

A density functional theory investigation on M5H5X hydrometal pentagons (M=Ag, Au, Pd Pt) with D5h planar pentacoordinate nonmetal centers (X = Si, Ge, P, S) is presented. The introduction of the nonmetal centers X introduces p aromaticity to M5H5X complexes.

A universal structural pattern is presented at density functional theory level to incorporate planar tetra-, penta-, hexa-, hepta-, and octacoordinate silicons in C2vBnE2Si series. The structural pattern could be applied to form other planar coordinate nonmetals including Ge, P, As, Al, and Ga, which needs to be confirmed in experiments to open a new branch of chemistry on planar coordinate main group elements.

Amorfrutins with a 2-hydroxybenzoic acid core structure are promising natural PPARγ agonists with potent antidiabetic activity. Owing to the complex matrix and low concentration in botanical material, the identification of unknown amorfrutins remains a challenge. In the present study, a combined application of UPLC-Q-TOF-MS and UPLC-QqQ-MS was developed to discover unknown amorfrutins from fruits of Amorpha fruticosa. First, reference compounds of amorfrutin A (AA), amorfrutin B (AB), and 2-carboxy-3,5-dihydroxy-4-geranylbibenzyl (AC) were analyzed using UPLC-Q-TOF-MS to reveal the characteristic fragment ions and the possible neutral loss. Second, the extract of A. fruticosa was separated and screened by UPLC-QqQ-MS using neutral loss scan to find out suspect compounds associated with the specified neutral fragment Δm/z 44. Third, the extract was re-analyzed by UPLC-Q-TOF-MS to obtain the exact mass of quasi-molecular ion and fragment ions of each suspect compound, and to subsequently calculate their corresponding molecular formulas. Finally, according to the molecular formula of suspect compound and its fragment ions and comparing with literature data, structure elucidation of four unidentified amorfrutins was achieved. The results indicated that the combination of QqQ-MS neutral loss scan and Q-TOF-MS molecular formula calculation was proven to be a powerful tool for unknown natural product identification, and this strategy provides an effective solution to discover natural products or metabolites of trace content.ᅟ [ABSTRACT FROM AUTHOR]