Impact of dihydrogen bonding on lattice energies and sublimation enthalpies of crystalline [HGaNH], [HBNH] and [HGeCH].

The lattice energies of [HGaNH], [HBNH] and [HGeCH] in their experimentally determined space groups, 2/, 2 and , respectively, were calculated using density functional methods for periodic structures with the periodic code CRYSTAL17. Using the basis set pob-TZVP for all calculations, B3LYP including Grimme's D3 dispersion correction was found to reproduce experimental bond distances and angles most accurately. CRYSTAL17 was also used to optimize geometries and calculate energies of the molecular structures in the gas phase.

Computational Thermochemistry of Mono- and Dinuclear Tin Alkyls Used in Vapor Deposition Processes.

Hexamethylditin has been reported to be a more effective precursor compared to monotin analogs in hybrid molecular beam epitaxy depositions of perovskite oxides. To understand the differences, a library of 68 monotin- and ditin-containing molecules bearing hydrido and/or carbon-based ligands was generated, and their structures were optimized using density functional theory. On the basis of a modified W1-F12 composite thermochemical method, thermochemical data (enthalpy of formation, entropy, and heat capacity) were calculated for each structure over a range of temperatures (298-5000 K).

Effects of a phosphonate anchoring group on the excited state electron transfer rates from a terthiophene chromophore to a ZnO nanocrystal.

Terthiophene dyes were synthesized having a carboxylate or a phosphonate moiety at the 2-position which serves as an anchoring group to zinc oxide nanocrystals (ZnO NCs). Electronic absorption and fluorescence measurements, combined with reduction potentials, provided estimates of -1.81 and -1.

Poly(cyclohexylethylene)-block-Poly(lactide) Oligomers for Ultrasmall Nanopatterning Using Atomic Layer Deposition.

Poly(cyclohexylethylene)-block-poly(lactide) (PCHE-PLA) block polymers were synthesized through a combination of anionic polymerization, heterogeneous catalytic hydrogenation and controlled ring-opening polymerization. Ordered thin films of PCHE-PLA with ultrasmall hexagonally packed cylinders oriented perpendicularly to the substrate surface were prepared by spin-coating and subsequent solvent vapor annealing for use in two distinct templating strategies. In one approach, selective hydrolytic degradation of the PLA domains generated nanoporous PCHE templates with an average pore diameter of 5 ± 1 nm corroborated by atomic force microscopy and grazing incidence small-angle X-ray scattering.

Zinc oxide nanocrystal quenching of emission from electron-rich ruthenium-bipyridine complexes.

A series of heteroleptic bipyridine ruthenium complexes were prepared using known synthetic methods. Each compound incorporated one electron withdrawing 4,4'-dicarboxylic acid-2,2'-bipyridine and two bipyridines each of which had electron donating dialkylamine substituents in the 4 and 4' positions. The electronic absorption spectra exhibited absorptions that moved to lower energy as the donor ability of the amine substituent increased.

Size-tuned ZnO nanocrucible arrays for magnetic nanodot synthesis via atomic layer deposition-assisted block polymer lithography.

Low-temperature atomic layer deposition of conformal ZnO on a self-assembled block polymer lithographic template comprising well-ordered, vertically aligned cylindrical pores within a poly(styrene) (PS) matrix was used to produce nanocrucible templates with pore diameters tunable via ZnO thickness. Starting from a PS template with a hexagonal array of 30 nm diameter pores on a 45 nm pitch, the ZnO thickness was progressively increased to narrow the pore diameter to as low as 14 nm. Upon removal of the PS by heat treatment in air at 500 °C to form an array of size-tunable ZnO nanocrucibles, permalloy (Ni80Fe20) was evaporated at normal incidence, filling the pores and creating an overlayer.

Combined plasma gas-phase synthesis and colloidal processing of InP/ZnS core/shell nanocrystals.

Indium phosphide nanocrystals (InP NCs) with diameters ranging from 2 to 5 nm were synthesized with a scalable, flow-through, nonthermal plasma process at a rate ranging from 10 to 40 mg/h. The NC size is controlled through the plasma operating parameters, with the residence time of the gas in the plasma region strongly influencing the NC size. The NC size distribution is narrow with the standard deviation being less than 20% of the mean NC size.

Tuning electron transfer rates via systematic shifts in the acceptor state density using size-selected ZnO colloids.

We report direct measurements of the influence of the available density of acceptor states on the rate of near-barrierless electron transfer between a dye sensitizer and an oxide semiconductor. The electron donor was the excited state of a zinc porphyrin, and the acceptors were a series of size-selected ZnO nanocrystals. The available density of states was tuned by controlling the relative position of the ZnO band edge using quantum confinement.

Thermally degradable ligands for nanocrystals.

We exchanged the oleate ligands on as-prepared PbSe/CdSe core/shell nanocrystals with octyldithiocarbamate to enable the removal of insulating ligands by gentle heating. The octyldithiocarbamate ligand could readily be stripped from the surface by heating briefly to temperatures from 140 to 205 degrees C, which is substantially lower than the temperature (330 degrees C) required to remove oleate from the nanocrystal surface. X-ray diffraction and transmission electron microscopy reveal that the nanocrystals sinter around 250 degrees C, resulting in a loss of quantum confinement.

Zinc oxide nanocrystals stabilized by alkylammonium alkylcarbamates.

Nearly monodispersed, spherical ZnO nanocrystals were synthesized from the reaction of an amide precursor, [Zn(N(i)Bu(2))(2)](2), with hexylamine followed by reactions of the as-formed solution in a moist air flow. Extensive experiments were conducted to optimize the synthesis and to characterize the nanocrystals. The room temperature reactions led to 3.

Hydrido and chloro gallium and aluminium complexes with the tridentate bis(2-dimethylaminoethyl)amide ligand.

Five-coordinate gallium and aluminium dihydrides, H2Ga[N(CH2CH2NMe2)2] () and H2Al[N(CH2CH2NMe2)2] (), were synthesized and found to be volatile and thermally stable. and reacted with H3Ga(NMe3) and H3Al(NMe3), respectively, to form H2Ga[N(CH2CH2NMe2)2]GaH3 () and H2Al[N(CH2CH2NMe2)2]AlH3 (), in which the amido nitrogen bridged between the MH2 and MH3 groups (M=Ga or Al). A mixed metal complex, H2Al[N(CH2CH2NMe2)2]GaH3 () was obtained from the reaction of with H3Al(NMe3) or with H3Ga(NMe3), and a crystal consisting of a mixture of and was structurally characterized.

Pseudo-two-dimensional structures (HXYH)3n2H6n (XY = GaN, SiC, GeC, SiSi, or GeGe; n = 1-3): density functional characterization of structures and energetics.

Hybrid density functional calculations with effective core potential basis sets are performed for monomeric group 13/15 and group 14/14 analogues of cyclohexane, as well as for three different pseudo-two-dimensional structures that can be formed from expanding one and two concentric rings around the central one (trans-fused chairs, a rolling combination of trans- and cis-fused chairs, and cis-fused boats). Varying contributions from torsional strain, angle strain, electrostatics, and nontraditional H-H hydrogen bonding lead to different orderings and magnitudes of motif energies in the various systems: Homoatomic SiSi and GeGe systems prefer the trans-fused chair alternative and heteroatomic systems GaN, SiC, and GeC prefer the rolling chair. Decomposition of structure energies into characteristic fragment contributions indicates that pseudo-one-dimensional rods of poly(imidogallane) are thermodynamically more stable than any of the pseudo-two-dimensional structures.

Mono- and digallane complexes of a tridentate amido-diamine ligand.

Bis(2-dimethylaminoethyl)amido gallane, H2GaN(CH2CH2NMe2)2, that melts at 27 degrees C and remains stable upon heating at 55 degrees C for two days, was synthesized either from the reaction of the quinuclidine adduct of monochlorogallane with the lithium salt of the corresponding amine, or from the reaction of trimethylamine gallane and the amine; the latter affords an unusual co-product with both GaH2 and GaH3 bonded to the same amido nitrogen.

Oligomeric rods of alkyl- and hydridogallium imides.

Reaction of [RGa(NMe(2))(2)](2), where R = Me, Et, Bu, and Hx, with ammonia at 150 degrees C in an autoclave produced insoluble white powders formulated as oligomers of [RGaNH](n). The analogous reaction between NH(3) and MeGa[N(SiMe(3))(2)](2) at low temperature (<25 degrees C) formed an isolable intermediate, [MeGa(mu-NH(2))N(SiMe(3))(2)](2), that was characterized using single-crystal X-ray diffraction. Infrared spectroscopy and X-ray diffraction of the oligomers were consistent with a rodlike structure comprised of six-membered, [RGaNH](3) rings stacked perpendicular to the long axis of the rod.

Gallium and indium hydrazides. Molecular and electronic structure of In[N(SiMe3)NMe2]3 and related compounds.

Gallium and indium hydrazides, Ga[N(SiMe(3))NMe(2)](3) (1) and In[N(SiMe(3))NMe(2)](3) (2), were synthesized from the reactions of metal chlorides and Li[N(SiMe(3))NMe(2)]. Single crystal X-ray crystallographic analysis revealed that compound 2 was monomeric with trigonal planar geometries on the indium and the indium-bonded nitrogen atoms. The average In[bond]N distance of 2.

Synthesis and structures of gallium amido imido phenyl clusters (PhGa)(4)(NH(i)Bu)(4)(N(i)Bu)(2) and (PhGa)(7)(NHMe)(4)(NMe)(5).

The phenylgallium-containing clusters constructed with bridging imido and amido ligands, (PhGa)(4)(NH(i)Bu)(4)(N(i)Bu)(2) (1) (51% yield) and (PhGa)(7)(NHMe)(4)(NMe)(5) (2) (31% yield), were synthesized from the room-temperature reactions of bis(dimethylamido)phenylgallium, [PhGa(NMe(2))(2)](2), with isobutylamine and methylamine, respectively. The reaction of [PhGa(NMe(2))(2)](2) in refluxing isobutylamine (85 degrees C) afforded (Ph(2)GaNH(i)Bu)(2) as one of the products, while the reaction of [PhGa(NMe(2))(2)](2) with methylamine at 150 degrees C afforded compound 2 in only 9% yield. Compound 1 possessed an admantane-like Ga(4)N(6) core, whereas compound 2 had a novel Ga(7)N(9) core constructed with both chair- and boat-shaped Ga(3)N(3) rings.

Synthesis and thermolysis of alkyl- and phenylamido diphenylgallium, [Ph(2)GaN(H)R](2). isolation and structural characterization of (PhGaNMe)(7) and (PhGaNPh)(4).

Alkyl- and phenylamido diphenylgallium compounds, [Ph(2)GaN(H)R](2) (R = Me, 1; Et, 2; (n)Pr, 3; (i)Bu, 4; Ph, 5), were prepared from the reactions of Ph(3)Ga with the corresponding primary amines and aniline at elevated temperatures and were characterized by elemental analysis, mass spectroscopy, and (1)H NMR and IR spectroscopy. These dimeric compounds contained bridging amido groups and exhibited both trans and cis isomers in solution. Thermolysis of compounds 1 and 5 was carried out either without solvent or in dodecane solutions, and two clusters, (PhGaNMe)(7) 6 and (PhGaNPh)(4) 7, were isolated in 24% and 55% yields and characterized.