Synthesis of a Neutral Mixed-Valence Diferrocenyl Carborane for Molecular Quantum-Dot Cellular Automata Applications.

The preparation of 7-Fc(+) -8-Fc-7,8-nido-[C2 B9 H10 ](-) (Fc(+) FcC2 B9 (-) ) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed-valence Fe(II) /Fe(III) complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis-NIR spectroscopic and TD-DFT computational studies indicate that electron transfer within Fc(+) FcC2 B9 (-) is achieved through a bridge-mediated mechanism.

Hydrogen-bonded clusters of 1, 1'-ferrocenedicarboxylic acid on Au(111) are initially formed in solution.

Low-temperature scanning tunneling microscopy is used to observe self-assembled structures of ferrocenedicarboxylic acid (Fc(COOH)2) on the Au(111) surface. The surface is prepared by pulse-deposition of Fc(COOH)2 dissolved in methanol, and the solvent is evaporated before imaging. While the rows of hydrogen-bonded dimers that are common for carboxylic acid species are observed, the majority of adsorbed Fc(COOH)2 is instead found in six-molecule clusters with a well-defined and chiral geometry.

Hydrogen-bonded clusters of ferrocenecarboxylic acid on Au(111).

Self-assembled monolayers of ferrocenecarboxylic acid (FcCOOH) contain two fundamental units, both stabilized by intermolecular hydrogen bonding: dimers and cyclic five-membered catemers. At surface coverages below a full monolayer, however, there is a significantly more varied structure that includes double-row clusters containing two to twelve FcCOOH molecules. Statistical analysis shows a distribution of cluster sizes that is sharply peaked compared to a binomial distribution.

Self-assembly of hydrogen-bonded two-dimensional quasicrystals.

The process of molecular self-assembly on solid surfaces is essentially one of crystallization in two dimensions, and the structures that result depend on the interplay between intermolecular forces and the interaction between adsorbates and the underlying substrate. Because a single hydrogen bond typically has an energy between 15 and 35 kilojoules per mole, hydrogen bonding can be a strong driver of molecular assembly; this is apparent from the dominant role of hydrogen bonding in nucleic-acid base pairing, as well as in the secondary structure of proteins. Carboxylic acid functional groups, which provide two hydrogen bonds, are particularly promising and reliable in creating and maintaining surface order, and self-assembled monolayers of benzoic acids produce structure that depends on the number and relative placement of carboxylic acid groups.

Adsorption of diferrocenylacetylene on Au(111) studied by scanning tunneling microscopy.

Scanning tunneling microscopy images of diferrocenylacetylene (DFA) coadsorbed with benzene on Au(111) show individual and close-packed DFA molecules, either adsorbed alongside benzene or on top of a benzene monolayer. Images acquired over a range of positive and negative tip-sample bias voltages show a shift in contrast, with the acetylene linker appearing brighter than the ferrocenes at positive sample bias (where unoccupied states primarily contribute) and the reverse contrast at negative bias. Density functional theory was used to calculate the electronic structure of the gas-phase DFA molecule, and simulated images produced through two-dimensional projections of these calculations approximate the experimental images.

catena-Poly[[penta-μ-benzoato-μ-chlorido-dioxanedineodymium(III)] dioxane 2.5-solvate].

The asymmetric unit of the title compound, [Nd(2)(C(6)H(5)COO)(5)Cl(C(4)H(8)O(2))]·2.5C(4)H(8)O(2), consists of two Nd(III) ions bridged by one Cl(-) ion, five benzoate ions and one coordinating 1,4-dioxane mol-ecule. One Nd(III) ion is nine-coordinate, with a very distorted monocapped square-anti-prismatic geometry.

Effects of the alkali-metal cation size on molecular and extended structures: formation of coordination polymers and hybrid materials in the homologous series [(4-Et-C6H4OM)·(diox)n], M = Li, Na, K, Rb, Cs.

The complete series of group 1 metal 4-ethylphenoxide (4-Et-C(6)H(4)O(-)) networks have been synthesized using 1,4-dioxane (diox) as a neutral linker. [{(4-Et-C(6)H(4)OLi)(4)·(diox)(2.5)}·diox](∞) (1) and [{(4-Et-C(6)H(4)ONa)(6)·(diox)(3)}(∞)] (2) form 2D and 3D networks, respectively, composed of discrete aggregates linked by diox.

Dramatic effect of aggregation on rates and thermodynamics of stereoisomerization of magnesium enolates.

Thermodynamic stereocontrol of the (hexamethyldisilazide)magnesium enolates of propiophenone in THF is reported. The overall stereoselectivity proves to be very sensitive to concentration, since dimeric species with bridging enolates show no stereoselectivity while monomeric enolates show a very strong thermodynamic preference for the Z enolate. Kinetically, interconversion among aggregates is remarkably slow, whereas stereoisomerization of the monomer, even in the absence of a proton source such as ketone or amine, is remarkably fast.

Synchrotron study of poly[[di-μ-aqua-(μ-2,2'-bipyridyl-5,5'-dicarboxyl-ato)di-potassium] dihydrate].

The title compound, {[K(2)(C(12)H(6)N(2)O(4))(H(2)O)(2)]·2H(2)O}(n), forms a three-dimensional coordination polymer in the solid state. The asymmetric unit consists of one K(+) ion, half of a 2,2'-bipyridyl-5,5'-dicarboxyl-ate ligand, one coordinated water mol-ecule and one solvent water mol-ecule. The K(+) ion is 7-coordinated by the oxygen atoms of two water mol-ecules and by five oxygen atoms of four carboxyl-ate groups, one of which is chelating.

High-connectivity networks and hybrid inorganic rod materials built from potassium and rubidium p-halide-substituted aryloxides.

A series of complex networks have been synthesized from the association of potassium and rubidium p-halide-substituted aryloxides using 1,4-dioxane molecules as neutral linkers. The crystalline polymers [(4-F-C6H4OK)6 x (dioxane)4]infinity (1), [(4-I-C6H4OK)6 x (dioxane)6]infinity (2), and [(4-I-C6H4ORb)6 x (dioxane)6]infinity (3) are built from discreet, hexameric M6O6 aggregates. Compound 1 forms an unusual 16-connected framework involving both K-F and K-O(diox) interactions.

Manipulation of molecular aggregation and supramolecular structure using self-assembled lithium mixed-anion complexes.

A set of zero-, one-, two-, and three-dimensional materials have been synthesized by systematically varying the stoichiometry of the two components 2,4,6-Me3-C6H2OLi (ArOLi) and Me2N(CH2)(2)OLi (ROLi) within single aggregates, while using 1,4-dioxane (diox) as a ditopic linker. The homoleptic complex [{(ArOLi)4 x (diox)2} superset3(diox)](infinity) 1 forms a 3D diamondoid extended structure, where Li4O4 cubanes act as tetrahedral nodes. Attempts to rationally alter the dimensionality of the network through the sequential replacement of ArOLi vertices by potentially chelating ROLi units have succeeded.

Homo- and heterodimetallic geminal dianions derived from the bis(phosphinimine) {Ph2P(NSiMe3)}2CH2 and the alkali metals Li, Na, and K.

The geminal organodimetallic complexes [({Ph2P(NSiMe3)}2C)2M4], where M4=Na4, 3; Li2Na2, 4; LiNa3, 5; Li2K2, 6; Na2K2, 7, and Na3K, 8, have been prepared through a variety of methods including direct or sequential deprotonation of the neutral ligand with strong bases (tBuLi, nBuNa, (Me3Si)2NNa, PhCH2K or (Me3Si)2NK), transmetalation of the homometallic derivatives (M4=Li4, 2 or Na4, 3) with tBuONa or tBuOK, and by cation exchange upon mixing the homometallic complexes in an arene solution. Complexes 3-8 have been characterized by single-crystal X-ray diffraction and are found to form a homologous series of dimeric structures in the solid-state, in accord with the previously reported structure of 2. Each complex is composed of a plane of four metals, M4, in which the ligands adopt capping positions to form distorted M4C2 octahedral cores.

High-connectivity networks: characterization of the first uninodal 9-connected net and two topologically novel 7-connected nets.

Ring and cage aggregates containing the large alkali metals potassium or rubidium have proven to be excellent building blocks for the creation of high-connectivity nets, as demonstrated by their use as septahedral and nonahedral nodes in synthesis of two new types of 7-connected nets and the first ever example of a 9-connected net.

X-ray and neutron diffraction studies of water-encapsulated inside potassium aryloxide aggregates: complementary host-guest stabilization of mono- and dihydrated cages.

The controlled hydrolysis of potassium 2-tert-butylphenoxide or 2-isopropylphenoxide leads to the unexpected encapsulation of the water inside K6O6 hexameric drum aggregates. Encapsulation of the neutral molecules is enabled in these instances through the formation of strong hydrogen bonds and dative interactions between the host and guest.

Assembly of a homochiral, body-centered cubic network composed of vertex-shared Mg12 cages: use of electrospray ionization mass spectrometry to monitor metal carboxylate nucleation.

Reaction of Mg(NO3)2.6H2O with (+)-camphoric acid (H2cam) in acetonitrile results in the immediate formation of soluble, dimetallic [Mg2(Hcam)3]+ cations. The formation of these stable cations in solution was determined by electrospray ionization mass spectrometry (ESI-MS).

Synthesis, structure, and computational studies of the tetrameric magnesium imides [2,4,6-Cl3C6H2NMg.S]4 (S=1,4-dioxane and tetrahydrofuran).

The magnesium imide complexes [(ArNMg.diox)4.3(diox)] (4) and [(ArNMg.

Organometallic polymers assembled from cation-pi interactions: use of ferrocene as a ditopic linker within the homologous series [{(Me3Si)2NM}2.(Cp2Fe)]infinity (M=Na, K, Rb, Cs; Cp=cyclopentadienyl).

Addition of ferrocene to solutions of alkali metal hexamethyldisilazides M(HMDS) in arenes (in which M=Na, K, Rb, Cs) allows the subsequent crystallization of the homologous series of compounds [{(Me(3)Si)(2)NM}(2) (Cp(2)Fe)](infinity) (1-4). Similar reactions using LiHMDS led to the recrystallization of the starting materials. The crystal structures of 1-4 reveal the formation of one-dimensional chains composed of dimeric [{M(HMDS)}(2)] aggregates, which are bridged through neutral ferrocene molecules by eta(5)-cation-pi interactions.

Direct and efficient one-pot preparation of ketones from aldehydes using N-tert-butylphenylsulfinimidoyl chloride.

A general, one-pot process has been established to prepare ketones from aldehydes using N-tert-butylphenylsulfinimidoyl chloride. By employing the developed protocol, a range of unsymmetrical ketones has been prepared in good yields from aldehydes in one simple synthetic operation. [reaction: see text]

Kinetics and mechanism of ketone enolization mediated by magnesium bis(hexamethyldisilazide).

Magnesium bis(hexamethyldisilazide), Mg(HMDS)(2), reacts with substoichiometric amounts of propiophenone in toluene solution at ambient temperature to form a 74:26 mixture of the enolates (E)- and (Z)-[(HMDS)(2)Mg(2)(mu-HMDS){mu-OC(Ph)=CHCH(3)}], (E)-1 and (Z)-1, which contain a pair of three-coordinate metal centers bridged by an amide and an enolate group. The compositions of (E)-1 and (Z)-1 were confirmed by solution NMR studies and also by crystallographic characterization in the solid state. Rate studies using UV-vis spectroscopy reveal the rapid and complete formation of a reaction intermediate, 2, between the ketone and magnesium, which undergoes first-order decay with rate constants independent of the concentration of excess Mg(HMDS)(2) (DeltaH++ = 17.

Synthesis, structural characterization, gas sorption and guest-exchange studies of the lightweight, porous metal-organic framework alpha-[Mg3(O2CH)6].

Unsolvated magnesium formate crystallizes upon reaction of the metal nitrate with formic acid in DMF at elevated temperatures. Single-crystal XRD studies reveal the formation of [Mg3(O2CH)6 [symbol: see text] DMF], 1, a metal-organic framework with DMF molecules filling the channels of an extended diamondoid lattice. The DMF molecules in 1 can be entirely removed without disruption to the framework, giving the guest-free material alpha-[Mg3(O2CH)6], 2.

4-Methoxy- and 4-cyano-substituted lithium aryloxides: electronic effects of substituents on aggregation.

The para-substituted lithium aryloxides [{4-NC-C6H4OLi.(Pyr)2}2.Pyr] 1a, [{4-NC-C6H4OLi.

Synthesis of mono- and geminal dimetalated carbanions of bis(phenylsulfonyl)methane using alkali metal bases and structural comparisons with lithiated bis(phenylsulfonyl)imides.

The alpha,alpha'-stabilized carbanion complexes [(PhSO2)2CHLi.THF]1, [(PhSO2)2CHNa.THF]2 and [(PhSO2)2CHK]3 were prepared by the direct deprotonation of bis(phenylsulfonyl)methane I in THF with one molar equivalent of MeLi, BuNa and BnK respectively.

Stereoselective enolizations mediated by magnesium and calcium bisamides: contrasting aggregation behavior in solution and in the solid state.

The reactions of magnesium and calcium bis(hexamethyldisilazide) with propiophenone have been studied with a view to determine the utility of these bases in the stereoselective enolization of ketones and to uncover the nature of the metal enolate intermediates produced. Both base systems are highly Z-selective when the reactions are conducted in the presence of polar solvents. However, in situ monitoring of the magnesium system in arene solution revealed a preference for E-enolate formation, which was confirmed by silyl enol ether trapping studies.

Rational assembly of primitive cubic networks using hexameric stacks of sodium aryloxides as nodes.

The two sodium aryloxide complexes [{(4-R-C6H4ONa)6 x (dioxane)3}infinity], where R = Et (1) or F (2), have been prepared and found to form three-dimensional cubic networks in the solid state. Each structure is similarly composed of dioxane-connected Na6O6 aggregates that act as octahedral nodes in directing the assembly process. Although the localized metrical parameters within the hexameric cages are similar to each other, as well as to those of the molecular analogue [(4-F-C6H4ONa)6 x (THF)8] (3), the gross architectures show significant variations.

Use of tetrameric cubane aggregates of lithium aryloxides as secondary building units in controlling network assembly.

Pre-aggregation of lithium aryloxides into tetrahedral arrangements followed by crystallization with the divergent Lewis base dioxane results in the preparation of three types of coordination polymers: zig-zag chains, (6,3) sheets, and diamondoid lattices.