A Dual Threat: Redox-Activity and Electronic Structures of Well-Defined Donor–Acceptor Fulleretic Covalent-Organic Materials

The effect of donor (D)–acceptor (A) alignment on the materials electronic structure was probed for the first time using novel purely organic porous crystalline materials with covalently bound two- and three-dimensional acceptors. The first studies towards estimation of charge transfer rates as a function of acceptor stacking are in line with the experimentally observed drastic, eight-fold conductivity enhancement. The first evaluation of redox behavior of buckyball- or tetracyanoquinodimethane-integrated crystalline was conducted. In parallel with tailoring the D-A alignment responsible for “static” changes in materials properties, an external stimulus was applied for “dynamic” control of the electronic profiles. Overall, the presented D–A strategic design, with stimuli-controlled electronic behavior, redox activity, and modularity could be used as a blueprint for the development of electroactive and conductive multidimensional and multifunctional crystalline porous materials.     

Confinement-Driven Photophysics in Hydrazone-Based Hierarchical Materials

Confinement-imposed photophysics was probed for novel stimuli-responsive hydrazone-based compounds demonstrating a conceptual difference in their behavior within 2D versus 3D porous matrices for the first time. The challenges associated with photoswitch isomerization arising from host interactions with photochromic compounds in 2D scaffolds could be overcome in 3D materials. Solution-like photoisomerization rate constants were realized for sterically demanding hydrazone derivatives in the solid state through their coordinative immobilization in 3D scaffolds. According to steady-state and time-resolved photophysical measurements and theoretical modeling, this approach provides access to hydrazone-based materials with fast photoisomerization kinetics in the solid state. Fast isomerization of integrated hydrazone derivatives allows for probing and tailoring resonance energy transfer (ET) processes as a function of excitation wavelength, providing a novel pathway for ET modulation.     

Synthesis of cananodine by intramolecular epoxide opening

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.     

Stack the Bowls: Tailoring the Electronic Structure of Corannulene‐Integrated Crystalline Materials

We report the first examples of purely organic donor–acceptor materials with integrated π‐bowls (πBs) that combine not only crystallinity and high surface areas but also exhibit tunable electronic properties, resulting in a four‐orders‐of‐magnitude conductivity enhancement in comparison with the parent framework. In addition to the first report of alkyne–azide cycloaddition utilized for corannulene immobilization in the solid state, we also probed the charge transfer rate within the Marcus theory as a function of mutual πB orientation for the first time, as well as shed light on the density of states near the Fermi edge. These studies could foreshadow new avenues for πB utilization for the development of optoelectronic devices or a route for highly efficient porous electrodes.     

New integer representations as the sum of three cubes

We describe a new algorithm for finding integer solutions to for specific values of . We use this to find representations for values of for which no solution was previously known, including and .

     

Structure-activity relationships for reactivity of carbonyl-containing compounds with glutathione

For toxicological-based structure-activity relationships to advance, will require a better understanding of molecular reactivity. A rapid and inexpensive spectrophotometric assay for determining the reactive to glutathione (GSH) was developed and used to determine GSH reactivity (reactGSH) data for 21 aliphatic derivatives of esters, ketones and aldehydes. From these data, a series of structure-activity relationships were evaluated. The structure feature associated with reactGSH was an acetylenic or olefinic moiety conjugated to a carbonyl group (i.e. polarized alpha,beta-unsaturation). This structure conveys the capacity to undergo a covalent interaction with the thiol group of cysteine (i.e. Michael- addition). Quantitatively reactGSH of the alpha,beta-unsaturated carbonyl compounds is reliant upon the specific molecular structure with several tendencies observed. Specifically, it was noted that for alpha,beta-unsaturated carbonyl compounds: (1) the acetylenic-substituted derivatives were more reactive than the corresponding olefinic-substituted ones; (2) terminal vinyl-substituted derivatives was more reactive than the internal vinylene-substituted ones; (3) methyl substitution on the vinyl carbon atoms diminishes reactivity and methyl-substitution on the carbon atom farthest from the carbonyl group causes a larger reduction; (4) derivatives with carbon-carbon double bond on the end of the molecule (i.e. vinyl ketone) were more reactive than one with the carbon-oxygen bond at the end of the molecule (i.e. aldehyde) and (5) the ester with an additional unsaturated vinyl groups were more reactive than the derivative having an unsaturated ethyl group.     

Characterization of AMPylation on Threonine,Serine, and Tyrosine Using Mass Spectrometry

Recent studies have suggested that adenosine 5'-monophosphate (AMP) post-translational modification of proteins could represent a novel molecular signaling pathway. Mass spectrometric fragmentation characteristics of this modification have not previously been described and studied systematically. In this work, we therefore examined the fragmentation pattern of chemically synthesized peptides containing AMPylated Thr, Ser, and Tyr. The formation of characteristic ions and the influence of collision energy (CE) on the detection of characteristic ions and their relative peak intensity are reported. When peptide with AMPylated Ser/Thr underwent collision induced dissociation (CID), peaks at m/z 348.1, 136.1, and 250.1, fragments with AMP group attached, and fragments consistent with neutral loss of 347 Da were major characteristic ions; fragments consistent with neutral loss of 135 Da or 249 Da were weaker and not always detectable. The observations for Tyr AMPylation followed the same general patterns as those for Ser/Thr modification, with the exception that the ions detected for Tyr AMPylation did not include either the peak at m/z 348.1, or fragments with a mass shift of –347 Da. The results described in this paper highlight a series of diagnostic ions, which can be used not only to confidently identify the AMPylation site based on MS and MS/MS data, but also to selectively scan AMPylated peptides in complex protein mixtures.     

Structure of chlorohydroxonitrosyl(terpyridine)ruthenium(II) hexafluorophosphate

The title complex has the NO grouptrans to the hydroxyl ligand and the chloride ion in the plane of the tripyridyl ligand. The Ru?O and Ru?N(O) distances are 1.939(5) Å and 1.764(6) Å, respectively; the Ru?N?O bond angle is 171.7(6)⁰. These values are consistent with previously reported shortening of Ru?O distances whentrans to a linear NO ligand. The space group of the structure isP2₁/c, witha=9.7213(9) Å,b=13.9318(11) Å,c=14.523(4) Å, and β=105.820(13)⁰.     

Synthesis and structural characterization of double metal cyanides of iron and zinc: catalyst precursors for the copolymerization of carbon dioxide and epoxides

Several synthetic approaches for the preparation of double metal cyanide (DMC) derivatives of iron(II) and zinc(II) are described. These include (1) metathesis reactions of ZnCl(2) or ZnI(2) with KCpFe(CN)(2)CO in aqueous solution, (2) reactions of KCpFe(CN)(2)CO and its phosphine-substituted analogues with Zn(CH(3)CN)(4)(BF(4))(2) and subsequent displacement of acetonitrile at the zinc centers by the addition of a neutral (phosphine) or anionic (phenoxide) ligand, and (3) reactions of the protonated HCpFe(CN)(2)(phosphine) complexes with Zn(N(SiMe(3))(2))(2), followed by the addition of phenols. All structures are based on a diamond-shaped planar arrangement of the Fe(2)(CN)(4)Zn(2) core with various appended ligands at the metal sites. Although attempts to replace the iodide ligands in [CpFe(mu-CN)(2)PPh(3)ZnI(THF)](2) with acetate using silver acetate failed, two novel cationic mixed-metal cyanide salts based on the [CpFe(PPh(3))(mu-CN)(2)Zn(NC(5)H(5))](2)(2+) framework were isolated from pyridine solution and their structures were defined by X-ray crystallography. The anionic ligand bound to zinc in these derivatives, which serve as an anionic polymerization initiator, was shown to be central to the catalytic copolymerization reaction of CO(2)/epoxide to provide polycarbonates and cyclic carbonates. The structurally stabilized phosphine-strapped complexes [CpFe(mu-CN)(2)Zn(X)THF](2)(mu-dppp), where X = I or phenolate, were shown to be thermally stable under the conditions (80 degrees C) of the copolymerization reaction by in situ infrared spectroscopy. Both of these derivatives were proposed to serve as mimics for the heterogeneous DMC catalysts in the patent literature, with the derivative where the initiator is a phenolate being more active for the production of polycarbonates.     

Solution and solid-state structural studies of epoxide adducts of cadmium phenoxides. Chemistry relevant to epoxide activation for ring-opening reactions

The reaction of Cd[N(SiMe(3))(2)](2) with 2 equiv of the corresponding phenol in toluene has led to the isolation of [Cd(O-2,6-R(2)C(6)H(3))(2)](2) derivatives, where R represents the sterically bulky (t)Bu and Ph substituents. The dimeric nature of these complexes in the solid state has been established via X-ray crystallography, i.e., trigonal geometry around cadmium is observed in 1 (R = (t)Bu) where the two cadmium centers are bridged by two phenoxides with each metal containing a terminal phenoxide. Complex 2 (R = Ph) contains an additional interaction of the metal centers with carbon atoms of the aromatic substituents on the phenoxide ligands. These dimeric structures are maintained in weakly coordinating solvents as revealed by (113)Cd NMR in d(2)-methylene chloride, which displays (111)Cd-(113)Cd coupling. Nevertheless, because of the excessive steric requirements of these phenoxide ligands, these dimers are easily disrupted in solution by weak donor ligands such as epoxides. Three bisepoxide adducts have been isolated as crystalline solids and characterized by X-ray crystallography. As previously observed in other Cd(O-2,6-(t)Bu(2)C(6)H(3))(2) x L(2) complexes, these epoxide adducts adopt a crystallographically imposed square-planar geometry about the cadmium centers, with the exception of the exo-2,3-epoxynorbornane derivative, which displays a distorted tetrahedral geometry. Temperature-dependent (113)Cd NMR studies have established that there is little difference in the binding abilities of these epoxides with either complex 1 or complex 2. Importantly, it is concluded from these studies that the lack of reactivity of alpha-pinene oxide and exo-2,3-epoxynorbornane toward copolymerization reactions with carbon dioxide, in the presence of zinc bisphenoxide catalysts, is not due to differences in epoxide metal binding. This is further affirmed by the isolation and crystallographic characterization of the very stable Zn(O-2,6-(t)Bu(2)C(6)H(3))(2) x (exo-2,3-epoxynorbornane)(2) derivative.