Publications by authors named "Allan J Jacobson"

Assembling macroscopic helices with controllable chirality and understanding their formation mechanism are highly desirable but challenging tasks for artificial systems, especially coordination polymers. Here, we utilize solvents as an effective tool to induce the formation of macroscopic helices of chiral coordination polymers (CPs) and manipulate their helical sense. We chose the Ni/-,-BrpempH system with a one-dimensional tubular structure, where -,-BrpempH stands for -,-(1-(4-bromophenyl)ethylaminomethylphosphonic acid).

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Nanotubular materials have garnered considerable attention since the discovery of carbon nanotubes. Although the layer-to-tube rolling up mechanism has been well recognized in explaining the formation of many inorganic nanotubes, it has not been generally applied to coordination polymers (CPs). To uncover the key factors that determine the rolling-up of layered CPs, we have chosen the Co/-, -Xpemp [Xpemp = (4-X-1-phenylethylamino)methylphosphonic acid, X = H, F, Cl, Br] systems and study how the weak interactions influence the formation of layered or tubular structures.

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Materials with two-dimensional, geometrically frustrated, spin-/ lattices provide a fertile playground for the study of intriguing magnetic phenomena such as quantum spin liquid (QSL) behavior, but their preparation has been a challenge. In particular, the long-sought, exotic spin-/ star structure has not been experimentally realized to date. Here we report the synthesis of [(CH)(NH)][Cu(μ-OH)(μ-SO)(μ-SO)]·0.

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The geometrically frustrated diamond spin chain system has yielded materials with a diversity of interesting magnetic properties but is predominantly limited to compounds with single-spin components. Here, we report the compound [(CH)NH][FeFe(μ-O)(μ-OH)(μ-SO)] (), which features the mixed-valent iron(II/III) diamond chain: [Fe-(Fe)-Fe-(Fe)]. Fe Mössbauer spectroscopy shows that two-thirds of the total spins in the [FeFe] diamond chain are spin5/2 (high-spin Fe), while the remaining one-third are spin2 (high-spin Fe).

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Two new amine-templated transition metal-based sulfates, [(CH)NH] [SO] [M(μ-OH)(μ-SO)] where M = Cr and Fe, have been synthesized via mild solvothermal synthesis. The compounds are isostructural and were refined in the monoclinic space group 2/. They feature the rare sulfate-bridged inorganic molecular wheels [Cr(OH)(SO)] and [Fe(OH)(SO)].

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A large spin, magnetically anisotropic, octanuclear vanadium(iii) wheel-like cluster has been synthesized. The coupling between adjacent VIII ions is ferromagnetic giving a ground state of St = 8, the largest known for a vanadium-based complex.

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Porous molecular crystals are an emerging class of porous materials that is unique in being built from discrete molecules rather than being polymeric in nature. In this study, we examined the effects of molecular structure of the precursors on the formation of porous solid-state structures with a series of 16 rigid aromatics. The majority of these precursors possess pyrazole groups capable of hydrogen bonding, as well as electron-rich aromatics and electron-poor tetrafluorobenzene rings.

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The complex phase transitions of vanadium dioxide (VO) have drawn continual attention for more than five decades. Dynamically, ultrafast electron diffraction (UED) with atomic-scale spatiotemporal resolution has been employed to study the reaction pathway in the photoinduced transition of VO, using bulk and strain-free specimens. Here, we report the UED results from 10-nm-thick crystalline VO supported on AlO(0001) and examine the influence of surface stress on the photoinduced structural transformation.

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A custom-designed semifluorinated phosphonic acid, (9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-heptadecafluorohexadecyl)phosphonic acid (F8H8PA), and a normal hexadecylphosphonic acid (H16PA) were synthesized and used to generate self-assembled monolayers (SAMs) on commercially available yttrium barium copper oxide (YBCO) tapes. In this study, we wished to evaluate the effectiveness of these monolayer films as coatings for selectively etching YBCO. Initial films formed by solution deposition and manual stamping using a non-patterned polydimethylsiloxane stamp allowed for a comparison of the film-formation characteristics.

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Cyanide-catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square-shaped macrocycle ornamented with four α-hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.

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Two mesoporous fluorinated metal-organic frameworks (MOFs) were synthesized from extensively fluorinated tritopic carboxylate- and tetrazolate-based ligands. The tetrazolate-based framework MOFF-5 has an accessible surface area of 2445 m(2) g(-1), the highest among fluorinated MOFs. Crystals of MOFF-5 adsorb hydrocarbons, fluorocarbons, and chlorofluorocarbons (CFCs)-the latter two being ozone-depleting substances and potent greenhouse species-with weight capacities of up to 225%.

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Commonly used inhalation anesthetics-enflurane, isoflurane, sevoflurane, halothane, and methoxyflurane-are adsorbed within the pores of a porous fluorinated molecular crystal to the tune of up to 73.4(±0.2)% by weight.

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One of the enticing features of metal-organic frameworks (MOFs) is the potential to control the chemical and physical nature of the pores through postsynthetic modification. The incorporation of redox active guest molecules inside the pores of the framework represents one strategy toward improving the charge transport properties of MOFs. Herein, we report the vapor-phase redox intercalation of an electroactive organic compound, hydroquinone (H2Q) or benzene-1,4-diol, into the channels of the host [V(IV)O(bdc)], (bdc =1,4-benzenedicarboxylate) conventionally denoted as MIL-47.

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Metal-organic and covalent organic frameworks are porous materials characterized by outstanding thermal stability, high porosities and modular synthesis. Their repeating structures offer a great degree of control over pore sizes, dimensions and surface properties. Similarly precise engineering at the nanoscale is difficult to achieve with discrete molecules, since they rarely crystallize as porous structures.

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A series of layered divalent metal formate compounds, [M(HCOO)2(HCONH2)2] (M = Mn (1Mn), Ni (2Ni), Cu(3Cu), Zn(4Zn), Mg(5Mg)), have been prepared by solvothermal synthesis and their room temperature (RT) and low-temperature (LT) crystal structures, and thermal and magnetic properties determined. All the compounds contain octahedral metal ions connected by four anti-anti formato ligands to form (4,4) nets with the composition of M(HCOO)2. The oxygen atoms from two coordinating formamide ligands above and below the layer complete the MO6 distorted octahedral coordination.

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A chiral precursor K2Sb2(L-tartrate)2 was used for the assembly of three homochiral heterometallic antimony(III)-tartrate transition-metal-oxo clusters: Mn(H2O)6[Fe4Mn4Sb6(μ4-O)6(μ3-O)2(l-tartrate)6(H2O)8]·10.5H2O (1), [V4Mn5Sb6(μ4-O)6(μ3-O)2(L-tartrate)6(H2O)13]·9.5H2O (2), and (H3O)[Ni(H2O)6]2[NiCrSb12(μ3-O)8(μ4-O)3(l-tartrate)6]·6H2O (3).

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This manuscript describes the synthesis of uniform monodisperse SnO2-coated gold nanoparticles and examines their colloidal stability as function of pH, with direct comparison to better known and widely used SiO2-coated gold nanoparticles. Aqueous acidic and basic colloidal SnO2-coated and SiO2-coated Au nanoparticle solutions were prepared, and their stability was monitored visually and by UV-vis spectroscopy. Notably, the SnO2-coated Au nanoparticle solutions were stable up to pH 12.

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Ferromagnetic thin films of the A-site nano-ordered double perovskite LaBaCo(2)O(5.5+δ) (LBCO) were grown on (001) MgO, and their structural and magnetic properties were characterized. The as-grown films have an excellent epitaxial behavior with atomically sharp interfaces, with the c-axis of the LBCO structure lying in the film plane and the interface relationship given by (100)(LBCO)//(001)(MgO) and [001](LBCO)//[100](MgO) or [010](MgO).

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A homochiral diamond framework was obtained by using a secondary building unit (SBU) comprising an oxo-cluster containing 4Fe(III) and 3Mn(II) ions supported by Sb(3)O tartrate scaffolds. A fully protonated tetratopic cation, tetrakis(4-pyridyloxymethylene)methane (TPOM), acts as a template to arrange the clusters on a diamond lattice.

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The hydrothermal reaction of fumaric acid, benzylamine, and metal salts yielded M[(rac-N-benzyl-Asp)(H(2)O)] (M = Co, Ni), 1 and 2, and Ni[(rac-N-benzyl-Asp)(H(2)O)(3)]·H(2)O 3. Under mild hydrothermal conditions, Michael addition of benzylamine to fumaric acid led to the formation of a racemic mixture of N-benzyl aspartic acid enantiomers. The noncentrosymmetric structures of 1 and 2 consist of one-dimensional polymeric chains in which metal cations are bridged by d- and l-N-benzyl aspartate anions alternating along the chain.

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A chiral cluster compound, dipotassium bis(μ-tartrato)diantimony(III), K(2)Sb(2)L(2) (H(4)L = L-tartaric acid), was used as a secondary building unit to react with lanthanide ions. Three series of homochiral coordination compounds were obtained: 0D [La(H(2)L)(H(2)O)(4)](2)[Sb(2)L(2)]·7H(2)O (0D-La), 1D Ln(Sb(2)L(2))(H(2)O)(5)(NO(3))·H(2)O (1D-Ln) (Ln = La-Lu or Y, expect Pm), 2D(I) [(Ln(H(2)O)(5))(2)(Sb(2)L(2))(3)]·5H(2)O (2D(I)-Ln) (Ln = La, Ce, Pr), and 2D(II) [(La(H(2)O)(5))(2)(Sb(2)L(2))(3)]·6H(2)O (2D(II)-La). Single-crystal X-ray diffraction studies indicated that 0D-La crystallizes in space group P1, and the structure contains isolated Sb(2)L(2)(2-) units located between chains of composition La(H(2)L)(H(2)O)(4).

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The structural details of the compounds vanadium benzenedicarboxylate VO(bdc)·Guest, where the Guests are the absorbed six-ring molecules: benzene, 1,4-cyclohexadiene, 1,3-cyclohexadiene, cyclohexene and cyclohexane, have been determined from single crystal X-ray data. All of the six-ring guest molecules show a high degree of ordering inside the channels of VO(bdc). The interactions between the guests and the host framework are dominated by van der Waals bonding.

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AlF(bdc), bdc = 1,4-benzenedicarboxylate, a new member of the family of MX(bdc) compounds has been synthesized under solvothermal conditions. It is formed without H(2)bdc in the channels and substantial absorption capacity is observed in its as-synthesized form. AlF(bdc) does not absorb water at ambient temperatures and shows absorption properties similar to VO(bdc).

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The synthesis of gold, palladium, and gold-palladium alloy nanoshells (approximately 15-20 nm thickness) was accomplished by the reduction of gold and palladium ions onto dielectric silica core particles (approximately 100 nm in diameter) seeded with small gold nanoparticles (approximately 2-3 nm in diameter). The size, morphology, elemental composition, and optical properties of the nanoshells were characterized using field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The results demonstrate the successful growth of gold, palladium, and gold-palladium alloy nanoshells, where the optical properties systematically vary with the relative content of gold and palladium.

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A new ammonium vanadium tellurate, (NH(4))(2)[VO(2)](2)[TeO(4)(OH)(2)] (1), was hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, and TG analysis. Compound 1 crystallizes in the monoclinic system, space group P2(1)/n: a = 8.9112(18) A, b = 15.

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