Structure and thermal stability of phosphorus-iodonium ylids.

Hypervalent iodine(III) reagents have become indispensable tools in organic synthesis, but gaps remain in the functionalities they can transfer. In this study, a fundamental understanding of the thermal stability of phosphorus-iodonium ylids is obtained through X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Insights into the structural factors affecting thermal stability and potential decomposition pathways will enable the future design and development of new reagents.

Ligand solid-solution tuning of magnetic and mechanical properties of the van der Waals metal-organic magnet NiCl(btd)(bod).

Van der Waals (vdW) magnets offer unique opportunities for exploring magnetism in the 2D limit. Metal-organic magnets (MOM) are of particular interest as the functionalisation of organic ligands can control their physical properties. Here, we demonstrate tuning of mechanical and magnetic function of a noncollinear vdW ferromagnet, NiCl(btd) (btd = 2,1,3-benzothiadiazole), through creating solid-solutions with the oxygen-substituted analogue ligand 2,1,3-benzoxadiazole (bod).

Synthesis of the Bulky Phosphanide [P(SiPr)] and Its Stabilization of Low-Coordinate Group 12 Complexes.

Here, we report an improved synthesis of the bulky phosphanide anion [P(SiPr)] in synthetically useful yields and its complexation to group 12 metals. The ligand is obtained as the sodium salt NaP(SiPr) in a 42% isolated yield and a single step from red phosphorus and sodium. This is a significantly higher-yielding and safer preparation compared to the previously reported synthesis of this ligand, and we have thus applied to the synthesis of the two-coordinate complexes M[P(SiPr)] (M = Zn, Cd, Hg).

Structural Transformations of Metal-Organic Cages through Tetrazine-Alkene Reactivity.

The assembly of metal-organic cages is governed by metal ion coordination preferences and the geometries of the typically rigid and planar precursor ligands. PdL cages are among the most structurally diverse, with subtle differences in the metal-ligand coordination vectors resulting in drastically different assemblies, however almost all rely on rigid aromatic linkers to avoid the formation of intractable mixtures. Here we exploit the inverse electron-demand Diels-Alder (IEDDA) reaction between tetrazine linker groups and alkene reagents to trigger structural changes induced by post-assembly modification.

Organofunctionalized borotungstate polyoxometalates as tunable photocatalysts for oxidative dimerization of amines.

Organofunctionalized borotungstate Keggin polyoxometalates, ( BuN)H[HBWO(P(O)Ph)] (PBW), ( BuN)H[HBWO(As(O)Ph)] (AsBW), and ( BuN)[HBWO(PhSiOSiPh)] (SiBW), were synthesized and structurally characterized. Cyclic voltammetry showed that the electronic properties of the clusters are dependent on the nature of the appended main group atoms (P, As, or Si). The first reduction potentials were found to shift positively with respect to that of the unmodified parent species ( BuN)[BWO], with PBW showing the largest shift at +100 mV.

Benzene-1,2,4,5-tetrol.

The crystal structure of the title compound was determined at 120 K. It crystallizes in the triclinic space group with four independent mol-ecules in the asymmetric unit. In the crystal, each symmetry-unique mol-ecule forms π-π stacks on itself, giving four unique π-π stacking inter-actions.

Controlling Noncollinear Ferromagnetism in van der Waals Metal-Organic Magnets.

Van der Waals (vdW) magnets both allow exploration of fundamental 2D physics and offer a route toward exploiting magnetism in next generation information technology, but vdW magnets with complex, noncollinear spin textures are currently rare. We report here the syntheses, crystal structures, magnetic properties and magnetic ground states of four bulk vdW metal-organic magnets (MOMs): FeCl(pym), FeCl(btd), NiCl(pym), and NiCl(btd), pym = pyrimidine and btd = 2,1,3-benzothiadiazole. Using a combination of neutron diffraction and bulk magnetometry we show that these materials are noncollinear magnets.

Mechanistic investigations of the Fe(ii) mediated synthesis of squaraines.

The scission and homologation of CO is a fundamental process in the Fischer-Tropsch reaction. However, given the heterogeneous nature of the catalyst and forcing reaction conditions, it is difficult to determine the intermediates of this reaction. Here we report detailed mechanistic insight into the scission/homologation of CO by two-coordinate iron terphenyl complexes.

2,2-Difluoroethylation of Heteroatom Nucleophiles via a Hypervalent Iodine Strategy.

The 2,2-difluoroethyl group is an important lipophilic hydrogen bond donor in medicinal chemistry, but its incorporation into small molecules is often challenging. Herein, we demonstrate electrophilic 2,2-difluoroethylation of thiol, amine and alcohol nucleophiles with a hypervalent iodine reagent, (2,2-difluoro-ethyl)(aryl)iodonium triflate, via a proposed ligand coupling mechanism. This transformation offers a complementary strategy to existing 2,2-difluoroethylation methods and allows access to a wide range of 2,2-difluoroethylated nucleophiles, including the drugs Captopril, Normorphine and Mefloquine.

Modular synthesis of cyclic β-difluoroamines.

Fluorine-containing saturated nitrogen heterocycles are very attractive structures in medicinal and biological chemistry because fluorine can be used to tune conformation as well as key properties such as basicity and bioavailability. At present cyclic fluorinated amines are accessed using hazardous reagents such as DAST or by lengthy synthesis routes. Here we report a modular two-step synthesis of cyclic β-fluoroalkyl amines using a photoredox-catalysed cyclisation/hydrogen atom transfer reaction of bromodifluoroethylamines.

Enantioselective synthesis of 14-hydroxy-6-oxomorphinans.

The enantioselective synthesis of pharmacologically important 14-hydroxy-6-oxomorphinans is described. 4,5-Desoxynaltrexone and 4,5-desoxynaloxone were prepared using this route and their biological activities against the opioid receptors were measured.

Porous isoreticular non-metal organic frameworks.

Metal-organic frameworks (MOFs) are useful synthetic materials that are built by the programmed assembly of metal nodes and organic linkers. The success of MOFs results from the isoreticular principle, which allows families of structurally analogous frameworks to be built in a predictable way. This relies on directional coordinate covalent bonding to define the framework geometry.

Iodoetherification as a strategy towards sp-rich scaffolds for drug discovery.

Functionalised tetrahydropyran and spirooxepane scaffolds were prepared utilising an iodoetherification strategy and elaborated to demonstrate their potential use in library synthesis. The iodoetherification products could be readily transformed to the corresponding azides that could be further functionalised via copper-catalysed azide-alkyne cycloaddition or reduction to the amine. The lead-likeness and three-dimensionality of the scaffolds were examined and compared to commercial libraries.

Probing the Mechanism of Action of Bis(phenolato) Amine (ONO Donor Set) Titanium(IV) Anticancer Agents.

The need for anticancer therapies that overcome metallodrug resistance while minimizing adverse toxicities is targeted, herein, using titanium coordination complexes. Octahedral titanium(IV) ,-[Ti{RN(CH-2-MeO-4-R-CH)}] [R = Et, allyl, -Pr, CHO, F, CH(morpholino), the latter from the formyl derivative; R = Me, Et; not all combinations] are attained from Mannich reactions of commercial 2-methoxyphenols (27-74% overall yield, 2 steps). These crystalline (four X-ray structures) Ti(IV)-complexes are active against MCF-7, HCT-116, HT-29, PANC-1, and MDA-MB-468 cancer cell lines (GI = 0.

Selective electrochemical CO conversion with a hybrid polyoxometalate.

A multi-component coordination compound, in which ruthenium antenna complexes are connected to a polyoxotungstate core is presented. This hybrid cluster effectively promotes the electrochemical conversion of CO to C1 feedstocks, the selectivity of which can be controlled by the acidity of the media.

Silver(I)-Catalyzed Synthesis of Cuneanes from Cubanes and their Investigation as Isosteres.

Bridged or caged polycyclic hydrocarbons have rigid structures that project substituents into precise regions of 3D space, making them attractive as linking groups in materials science and as building blocks for medicinal chemistry. The efficient synthesis of new or underexplored classes of such compounds is, therefore, an important objective. Herein, we describe the silver(I)-catalyzed rearrangement of 1,4-disubstituted cubanes to cuneanes, which are strained hydrocarbons that have not received much attention since they were first described in 1970.

A Domino Radical Amidation/Semipinacol Approach to All-Carbon Quaternary Centers Bearing an Aminomethyl Group.

A photoredox-mediated radical amidation ring-expansion sequence that enables the generation of all-carbon quaternary centers bearing a protected aminomethyl substituent is described. The methodology can be applied to both styrene and unactivated alkene substrates generating structurally diverse sp -rich amine derivatives in a concise manner.

Diphosphoryl-functionalized Polyoxometalates: Structurally and Electronically Tunable Hybrid Molecular Materials.

Herein, we report the synthesis and characterization of a new class of hybrid Wells-Dawson polyoxometalate (POM) containing a diphosphoryl group (P O X) of the general formula [P W O (P O X)] (X=O, NH, or CR R ). Modifying the bridging unit X was found to impact the redox potentials of the POM. The ease with which a range of α-functionalized diphosphonic acids (X=CR R ) can be prepared provides possibilities to access diverse functionalized hybrid POMs.

Electronic Structure and Photoactivity of Organoarsenic Hybrid Polyoxometalates.

Organofunctionalization of polyoxometalates (POMs) allows the preparation of hybrid molecular systems with tunable electronic properties. Currently, there are only a handful of approaches that allow for the fine-tuning of POM frontier molecular orbitals in a predictable manner. Herein, we demonstrate a new functionalization method for the Wells-Dawson polyoxotungstate [PWO] using arylarsonic acids which enables modulation of the redox and photochemical properties.

Highly electron deficient diketopyrrolopyrroles.

The synthesis, spectroelectrochemical and structural characteristics of highly electron-accepting diketopyrrrolopyrrole (DPP) molecules with adjoining pyridinium rings is reported, along with an assessment of their toxicity, which is apparently low. The compounds show reversible electrochemistry and in one subfamily a massive increase in molar extinction coefficient upon electrochemical reduction.

Catalysis enabled synthesis, structures, and reactivities of fluorinated S-corona[]arenes ( = 8-12).

Previously inaccessible large S-corona[]arene macrocycles ( = 8-12) with alternating aryl and 1,4-CF subunits are easily prepared on up to gram scales, without the need for chromatography (up to 45% yield, 10 different examples) through new high acceleration SAr substitution protocols (catalytic NRF in pyridine, R = H, Me, Bu). Macrocycle size and functionality are tunable by precursor and catalyst selection. Equivalent simple NRF catalysis allows facile late-stage SAr difunctionalisation of the ring CF units with thiols (8 derivatives, typically 95+% yields) providing two-step access to highly functionalised fluoromacrocycle libraries.

Reactions of polyaromatic molecules in crystals under electron beam of the transmission electron microscope.

Reactivity of a series of related molecules under the 80 keV electron beam have been investigated and correlated with their structures and chemical composition. Hydrogenated and halogenated derivatives of hexaazatrinaphthylene, coronene, and phthalocyanine were prepared by sublimation in vacuum to form solventless crystals then deposited onto transmission electron microscopy (TEM) grids. The transformation of the molecules in the microcrystals were triggered by an 80 keV electron beam in the TEM and studied using correlated selected area electron diffraction, conventional bright field imaging, and energy dispersive X-ray spectroscopy.

Slow magnetic relaxation in Fe(II) -terphenyl complexes.

Two-coordinate transition metal complexes are exciting candidates for single-molecule magnets (SMMs) because their highly axial coordination environments lead to sizeable magnetic anisotropy. We report a series of five structurally related two-coordinate Fe(II) -terphenyl complexes (4-R-2,6-XylCH)Fe [R = Bu (1), SiMe (2), H (3), Cl (4), CF (5)] where, by changing the functionalisation of the -substituent (R), we alter their magnetic function. All five complexes are field-induced single-molecule magnets, with relaxation rates that are well-described by a combination of direct and Raman mechanisms.