August A. Gallo

Bio: August A. Gallo is an academic researcher from University of Louisiana at Lafayette. The author has contributed to research in topics: Aryl & Square pyramidal molecular geometry. The author has an hindex of 14, co-authored 35 publications receiving 579 citations.

Dinuclear and Polynuclear Bridged Azido–Nickel(II) Complexes: Synthesis, Structure Determination, and Magnetic Properties

Abstract: Azido–NiII complexes of dinuclear, [Ni2(trpn)2(μ1,3-N3)2](ClO4)2 (1), and monodimensional structures cis-[Ni(abap)(μ1,3-N3)]n(ClO4)n (2) and cis-[Ni(Me6trien)(μ1,3-N3)]n(ClO4)n·nH2O (3a) as well as the monomer [Ni(Me6trien)(N3)]ClO4 (3b) {trpn = tris(3-aminopropyl)amine; abap = N-(2-aminoethyl)-N,N-bis(3-aminopropyl)amine; Me6trien = 1,1,4,7,10,10-hexamethyltriethylene tetramine} were synthesized and structurally characterized by spectroscopic techniques, X-ray crystallography, and variable-temperature magnetic measurements. In the complexes 1–3a, the ClO4– groups are counterions and the Ni2+ centers are bridged by the azido ligands in an end-to-end bonding fashion. The coordination geometry around the NiII ions is six-coordinate with a distorted octahedral environment achieved by the four N atoms of the tetradentate amines and two terminal N atoms of the azide groups. Complex 1 consists of dinuclear units with doubly bridged azido groups whereas in 2 and 3a, a polymeric 1D chain is formed in which the adjacent azido groups link the NiII centers in a cis arrangement. In complex 2, the structural parameters of the two adjacent azido bridging ligands are different and an alternating 1D system with two different end-to-end azido bridges is produced. Complex 3a is a uniform 1D system where the strong steric hindrance imposed by the methyl groups of the Me6trien ligand [diagonal N(azide)–Ni–N(amine) bond angles] causes pronounced deviation from the ideal octahedral geometry. Complex 3b exhibits a distorted square pyramidal geometry. The complexes 1–3a show antiferromagnetic coupling. In complex 1, the exchange coupling constant was J = –64(1) cm–1, whereas in the polynuclear species 2 and 3a, the calculated values were J1 = –63.7(2) (α = 0.52) and J = –26.8(1) cm–1, respectively. The magnetic parameters have been correlated to the structural data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Gold-Catalyzed Synthesis of 3-Arylindoles via Annulation of Nitrosoarenes and Alkynes

Abstract: We have successfully developed a Au-catalyzed annulation method to produce substituted 3-arylindoles from the reaction of nitrosoarenes with arylsubstituted acetylenes under reductive conditions using sodium borohydride. Terminal alkynes reacted better than non-terminal ones with various substituted nitrosoarenes to afford regioselective 3-substituted indoles. This method is simple and straightforward and can be applied successfully to the synthesis of highly substituted indoles.

Thiocyanato-copper(II) complexes derived from a tridentate amine ligand and from alanine

Abstract: Two thiocyanato-Cu(II) complexes including mononuclear dithiocyanato Cu(Me3dpt)(NCS)2 (1) and the polymeric 1D [Cu(d,l-Ala)(μN,S–NCS)(H2O)] n (2) were synthesized and structurally characterized (Me3dpt = bis(N-methyl-3-propyl)methylamine, Ala = alaninate anion). The IR spectrum of complex 1 confirmed the N-bonding coordination mode of the thiocyanate groups, and its visible spectrum revealed the square pyramidal geometry around the central Cu2+ ion. Single X-ray crystallography of 1 showed that the Cu(II) center displays square pyramidal geometry with severe distortion toward trigonal bipyramidal environment. Complex 2 forms a 1-D polymeric chain with the NCS− acting as a μN,S-ligand. A distorted SP geometry around the Cu2+ centers was achieved by the O and N atoms of alaninato anion, the aqua ligand and by the N and S atoms of the bridging thiocyanate groups. Hydrogen bonds of the type N–H···O, N–H···S and O–H···O are formed in this complex leading to the extension of the 1D chain to a supramolecular network.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Recent Advances in Gold-Catalyzed N- and O-Functionalizations of Alkynes with Nitrones, Nitroso, Nitro and Nitroxy Species

Abstract: Nitrone and nitroso species are versatile compounds to react with alkenes or butadienes to access five- and six-membered nitroxy (NO) containing heterocycles, to offer further access to acyclic 1,3- and 1,4-amino alcohols after facile cleavage of the NO bonds. The N- and O-functionalizations of alkynes with nitrones or nitroso species have been explored less well than the corresponding alkene reactions. In recent decades, gold catalysts have enabled the electrophilic activation of alkynes with weak nucleophiles. This review summarizes recent progress to implement N- and O-functionalizations of alkynes with common NO containing species including nitrone, nitroso, nitro and other nitroxy derivatives. Reported reactions include the following three topics: (i) 1,2-difunctionalizations, (ii) cyclizations and (iii) cycloaddition or annulation reactions. The review is organized according to the types of nucleophiles, followed by reactions of the mentioned types. Enantioselective functionalizations of alkynes with these nitroxy nucleophiles are also included.