Space hybrids

The theory of defining localized functions as simultaneous eigenfunctions of commuting matrices representing the variables x, y, and z is developed further to include r, the radial variable. The appropriate complete basis set for use when the weight function in the scalar product is an exponential is described. Hybrid functions that are each strongly localized around a center are defined as eigenfunctions and can be used to describe the electron density of an atom. The hybrid centers lie at the vertices of regular polyhedra centered on the nucleus. The hybrids have the important property of vanishing at the centers of all the other hybrids. Two simple examples are given to illustrate the theory and the methods of calculation. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Spherical hybrids

A general solution is presented to the problem of finding hybrid functions which point from the center toward the vertices of a regular solid. Results are given for the examples of 6, 8, 12, and 24 vertices. By taking linear combinations with suitable alias functions, the hybrids have been given nodes passing through all vertices except their own. This allows them to be used for interpolation and quadrature. The various functions required are defined as solid harmonics and group theoretical methods of generating these are discussed fully. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 197–214, 1997     

Localized planar atomic hybrids

The derivation of localized atomic hybrids in the plane is discussed using their definition as simultaneous eigenfunctions of the x and y position operators, when these are represented by commuting matrices in a finite basis. The use of alias functions, as introduced in the preceding paper, to produce commuting matrices is described and illustrated. Full results are obtained for any regular polygon. The extension to three dimensions allows the sp² trigonal, sp²d square, and sp²d² pentagonal hybrids to be derived. The theory also allows the radial factors to differ so that several shells of hybrids can be found at once. The double trigonal configuration is described as an example. The implications for any calculation of a molecular dipole moment are discussed. © 1995 John Wiley & Sons, Inc.     

Synthesis of isochrysohermidin-distamycin hybrids

The synthesis of the alkylating subunit of the DNA cross-linking agent, isochrysohermidin (2), and its subsequent incorporation into conjugates with distamycin A (1) are described. The DNA binding properties of these agents were compared to that of distamycin A, using a fluorescence intercalator displacement (FID) assay.     

Semiconductor quantum dot-inorganic nanotube hybrids

A synthetic route for preparation of inorganic WS(2) nanotube (INT)-colloidal semiconductor quantum dot (QD) hybrid structures is developed, and transient carrier dynamics on these hybrids are studied via transient photoluminescence spectroscopy utilizing several different types of QDs. Measurements reveal efficient resonant energy transfer from the QDs to the INT upon photoexcitation, provided that the QD emission is at a higher energy than the INT direct gap. Charge transfer in the hybrid system, characterized using QDs with band gaps below the INT direct gap, is found to be absent. This is attributed to the presence of an organic barrier layer due to the relatively long-chain organic ligands of the QDs under study. This system, analogous to carbon nanotube-QD hybrids, holds potential for a variety of applications, including photovoltaics, luminescence tagging and optoelectronics.     

Organic and inorganic nanoparticle hybrids

Viruses are exemplary models in nanoassembly for their regular geometries, well characterized surface properties, and nanoscale dimensions. Armed with versatile tools aimed at site-directed mutagenesis to modify the virion's surface, conjugation chemistry for capsid coupling, and manipulation of nanoparticles, we have demonstrated nanoscale assembly of inorganic carbon nanotubes and quantum dots with engineered viruses to produce an intimate array of hybrid structures.     

Spin-frustrated organic-inorganic hybrids of lindgrenite

We report the syntheses and magnetic properties of hybrid organic-inorganic materials that represent layer-expanded versions of the rare mineral lindgrenite (Cu3(OH)2(MoO4)2). The structures of these compounds feature one-dimensional chains of alternating corner- and edge-sharing Cu(II) triangles. By expanding the inorganic layers of lindgrenite with 4,4'-bipyridine, spin-frustrated antiferromagnetism is revealed by a change of the spin frustration parameter f from 1.2 in lindgrenite to 19.4 in (4,4'-bpy)Cu3(OH)2(MoO4)2.     

Mixed cyclisations giving phthalocyanine-naphthalocyanine hybrids

Mixed cyclisations have been performed to give phthalocyanine-naphthalocyanine hybrids bearing solubilising substituents. Reactivity differences between the two phthalonitrile precursors result in inefficient mixed-macrocyclisation under standard, non-templating conditions leading to predominant formation of symmetrical phthalocyanine. Templated mixed-macrocyclisation leads to the hybrids. However, the reaction proceeds with unexpected selectivity with only one of the possible 2:2 products observed.     

A theoretical study of fullerene-ferrocene hybrids

Using density functional theory within the generalized gradient approximation, I analyzed the electronic structure of a C(60)-ferrocene hybrid [= C(60) (*) FeCp] around HOMO in comparison with that of ferrocene, where C(60) (*) and Cp denote C(60)(CH(3))(5) and a cyclopentadienyl ring. HOMO-LUMO gap is significantly smaller than that of ferrocene because of the intervention of pi(C(60) (*)) states below LUMO. In addition, geometrical and electronic structures of N@C(60) (*) FeCp are also investigated. I find that there are two isomers with the energy difference of 0.13 eV. In one of the two, the encased nitrogen atom is located at the center of the fullerene cage. The Fe atom is eta(5)-coordinated to both Cp and R*, where R* is a five-membered ring of C(60) (*) cage. On the other hand, the atom is coordinated to R* with eta(4)-hapticity, and the nitrogen atom is bonded to a carbon atom of the R* ring in the other isomer. Upon the isomerization between the two isomers, there occurs a partial transfer of spin density between the nitrogen and Fe atoms as well as the creation and breaking of a C-N bond.     

A theoretical study on fullerene-dizincocene hybrids

Using the density functional theory, we investigated the possible formation of fullerene-dizincocene hybrids, specifically C(60)*-Zn-Zn-Cp*, C(60)*-Zn-Zn-C(60)*, C(70)*-Zn-Zn-Cp*, and C(70)*-Zn-Zn-C(70)*, where C(60)*, Cp*, and C(70)* represent C(60)(CH(3))(5), C(5)(CH(3))(5), and C(70)(CH(3))(5) radicals. Our calculation shows that these hybrids have HOMO-LUMO gaps which are larger than has been experimentally identified for C(60)*-Fe-Cp. In addition, the strength of the Zn--Zn bonds is similar to that in Cp*-Zn-Zn-Cp* which was also synthesized recently. Furthermore, heterohybrids, C(60)*-Zn-Zn-Cp* and C(70)*-Zn-Zn-Cp* are expected to exist in equilibria with homohybrids, C(60)*-Zn-Zn-C(60)* and C(70)*-Zn-Zn-C(70)*, in which heterohybrids are much more favored. On the other hand, another hybrid involving Sc(3)N@C(68) as a fullerene unit is not highly probable.     

Processing of polypropylene - clay hybrids

Polypropylene compounds containing organophilic layered silicates were prepared by means of melt extrusion at 180°C. We have studied the effect of the coupling agent on morphology development and mechanical properties. We are convinced of the importance of both the chemistry and the process conditions to elaborate nanocomposites with optimized properties.     

Layered double hydroxide hybrids with dicetylphosphate

Dicetyl phosphate (DCP) ions incorporated into layered double hydroxide (LDH) clays to form a DCP/LDH hybrid were prepared and structurally characterized by X-ray diffraction analysis, scanning electron microscopy, thermogravimetry, and differential thermal analyses. DCP was concluded not only to form well-aligned bilayer structures along the vertical axis of the LDH layers but also to be arranged in a distorted hexagonal packing orientation in the lateral planes within the DCP/LDH hybrid interlayers.     

Solid-phase synthesis of cyclic peptide-DNA hybrids

[reaction: see text] A methodology for preparing cyclic peptide-DNA hybrids on controlled pore glass in high yield is reported. This methodology employs Fmoc/Alloc-protected amino acid and nucleoside phosphoramidites on an omega-hydroxylauric acid-derivatized support and is suitable for library synthesis. A cyclic hybrid of the sequence Glu-Leu-TT-DP-Lys, where Glu and Lys are linked and T denotes a 5'-amino-5'-deoxynucleotide, exhibited high resistance to exo- and endonucleases.     

Formation of chiral mesostructured porphyrin-silica hybrids

Formation of a chiral mesostructured porphyrin-silica hybrid with cylindrical helical stacking of anionic porphyrins was achieved by the aid of cationic organosilane. The enantiopurity of the hybrid was dramatically enhanced by a small amount of (R)-1,1'-bi-2-naphthol or its enantiomer.     

Quantum well/columnar discotic hybrids

Theory predicts that the deposition of a nanostructured dielectric film on the surface of a semiconductor quantum well will modulate its optical properties due to interactions between the quantum well exciton and the dielectric structure. We have chosen a columnar discotic triphenylene as dielectric medium since the columnar structure is able to provide spatial, and thus dielectric, modulations both on a 2 or a 0.4 nm scale, depending on the columnar orientation within the film. Film deposition on quantum well structures and model substrates by spincoating and via the vapour phase, in combination with annealing steps, gave rise to a rich spectrum of textural modifications and columnar orientations in the dielectric films. The investigations revealed significant modulations of the optical properties of the quantum well as a function of the textures and the columnar orientational order.     

Epoxy-silica hybrids as stone restoration materials

Hybrid organic-inorganic systems based on two epoxy-resins, the aromatic DGEBA and the aliphatic Eurostac 2101, and the amine ATS were developed for stone conservation. Their efficacy, explored through some preliminary tests such as water absorption, mercury porosimetry and appearance, was evaluated on two selected lithic typologies, Mistretta quartzite (MIS) and Comiso calcarenite (COM). The experiments carried out on MIS showed that none of the employed mixtures is able to significantly affect its porosimetric properties, while only DGEBA/ATS solutions reduce its water absorption, but cause not negligible alterations in appearance. The treatment of COM with DGEBA/ATS solutions does not alter significantly the porosimetric features while preventing the water migration inside the stone. On the contrary EP/ATS mixtures perform better in porosimetric terms, while water absorption tests are not promising.