Selective adsorption of SO2 is realized in a porous metal–organic framework material, and in‐depth structural and spectroscopic investigations using X‐rays, infrared, and neutrons define the ...underlying interactions that cause SO2 to bind more strongly than CO2 and N2.
The bis-bidentate bridging ligand L {α,α′-bis3-(2-pyridyl)pyrazol-1-yl-1,4-dimethylbenzene}, which contains two chelating pyrazolyl-pyridine units connected to a 1,4-phenylene spacer via flexible ...methylene units, reacts with transition metal dications to form a range of polyhedral coordination cages based on a 2M:3 L ratio in which a metal ion occupies each vertex of a polyhedron, a bridging ligand lies along every edge, and all metal ions are octahedrally coordinated. Whereas the Ni(II) complex Ni8L12(BF4)12(SiF6)2 is an octanuclear cubic cage of a type we have seen before, the Cu(II), Zn(II), and Cd(II) complexes form new structural types. Cu6L9(BF4)12 is an unusual example of a trigonal prismatic cage, and both Zn(II) and Cd(II) form unprecedented hexadecanuclear cages M16L24X32(X = ClO4 or BF4) whose core is a skewed tetracapped truncated tetrahedron. Both Cu6L9 and M16L24 cages are based on a cyclic helical M3L3 subunit that can be considered as a triangular “panel”, with the cages being constructed by interconnection of these (homochiral) panels with additional bridging ligands in different ways. Whereas Cu6L9(BF4)12 is stable in solution (by electrospray mass spectrometry, ES-MS) and is rapidly formed by combination of Cu(BF4)2 and L in the correct proportions in solution, the hexadecanuclear cage Cd16L24(BF4)32 formed on crystallization slowly rearranges in solution over a period of several weeks to the trigonal prism Cd6L9(BF4)12, which was unequivocally identified on the basis of its 1H NMR spectrum. Similarly, combination of Cd(BF4)2 and L in a 2:3 ratio generates a mixture whose main component is the trigonal prism Cd6L9(BF4)12. Thus the hexanuclear trigonal prism is the thermodynamic product arising from combination of Cd(II) and L in a 2:3 ratio in solution, and arises from both assembly of metal and ligand (minutes) and rearrangement of the Cd16 cage (weeks); the large cage Cd16L24(BF4)32 is present as a minor component of a mixture of species in solution but crystallizes preferentially.
Highly electron deficient diketopyrrolopyrroles Humphreys, Joshua; Malagreca, Ferdinando; Hume, Paul A ...
Chemical communications (Cambridge, England),
02/2023, Letnik:
59, Številka:
12
Journal Article
Recenzirano
Odprti dostop
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.
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.
Previously inaccessible large S8-coronanarene macrocycles (n = 8–12) with alternating aryl and 1,4-C6F4 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 SNAr substitution protocols (catalytic NR4F in pyridine, R = H, Me, Bu). Macrocycle size and functionality are tunable by precursor and catalyst selection. Equivalent simple NR4F catalysis allows facile late-stage SNAr difunctionalisation of the ring C6F4 units with thiols (8 derivatives, typically 95+% yields) providing two-step access to highly functionalised fluoromacrocycle libraries. Macrocycle host binding supports fluoroaryl catalytic activation through contact ion pair binding of NR4F and solvent inclusion. In the solid-state, solvent inclusion also intimately controls macrocycle conformation and fluorine–fluorine interactions leading to spontaneous self-assembly into infinite columns with honeycomb-like lattices.
Two new types of coordination cage have been prepared and structurally characterized: M16(μ-L)24X32 are based on a tetra-capped truncated tetrahedral core and have a bridging ligand L1 along each of ...the 24 edges; M12(μ-L1)12(μ3-L)4X24 are based on a cuboctahedral core which is supported by a combination of face-capping ligands L2 and edge-bridging ligands L1. The difference between the two illustrates how combinations of ligands with different coordination modes can generate coordination cages which are not available using one ligand type on its own.
Reaction of a tris-bidentate ligand L1 (which can cap one triangular face of a metal polyhedron), a bis-bidentate ligand L2 (which can span one edge of a metal polyhedron), and a range of M2+ ions (M ...= Co, Cu, Cd), which all have a preference for six coordination geometry, results in assembly of the mixed-ligand polyhedral cages M12(μ3-L1)4(μ-L2)1224+. When the components are combined in the correct proportions M2+:L1:L2 = 3:1:3 in MeNO2, this is the sole product. The array of 12 M2+ cations has a cuboctahedral geometry, containing six square and eight triangular faces around a substantial central cavity; four of the eight M3 triangular faces (every alternate one) are capped by a ligand L1, with the remaining four M3 faces having a bridging ligand L2 along each edge in a cyclic helical array. Thus, four homochiral triangular {M3(L2)3}6+ helical units are connected by four additional L1 ligands to give the mixed-ligand cuboctahedral array, a topology which could not be formed in any homoleptic complex of this type but requires the cooperation of two different types of ligand. The complex Cd3(L2)3(ClO4)4(MeCN)2(H2O)2(ClO4)2, a trinuclear triple helicate in which two sites at each Cd(II) are occupied by monodentate ligands (solvent or counterions), was also characterized and constitutes an incomplete fragment of the dodecanuclear cage comprising one triangular {M3(L2)3}6+ face which has not yet reacted with the ligands L1. 1H NMR and electrospray mass spectrometric studies show that the dodecanuclear cages remain intact in solution; the NMR studies show that the Cd12 cage has four-fold (D 2) symmetry, such that there are three independent Cd(II) environments, as confirmed by a 113Cd NMR spectrum. These mixed-ligand cuboctahedral complexes reveal the potential of using combinations of face-capping and edge-bridging ligands to extend the range of accessible topologies of polyhedral coordination cages.
The tetradentate ligand Lnaph contains two N-donor bidentate pyrazolyl−pyridine units connected to a 1,8-naphthyl core via methylene spacers; L*45 and L*56 are chiral ligands with a structure similar ...to that of Lnaph but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes Cu(Lnaph)(OTf) and Ag(Lnaph)(BF4) have unremarkable mononuclear structures, with CuI being four-coordinate and AgI being two-coordinate with two additional weak interactions (i.e., “2 + 2” coordinate). In contrast, Cu4(Lnaph)4BF44 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with Cu(L*45)(BF4) and Ag(L*45)(ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, Ag4(L*56)4(BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, Ag(L*45)(ClO4) and Ag4(L*56)4(BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications CoII, CuII, and CdII, Lnaph generates a series of unusual dodecanuclear coordination cages M12(Lnaph)18X24 (X- = ClO4 - or BF4 -) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L*45 forms the simpler tetranuclear, tetrahedral coordination cage Zn4(L*45)6(ClO4)8, with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of Zn12(L*45)18(ClO4)24 can be detected in solution by ESMS. Formation of Zn4(L*45)6(ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.
Emissions of SO
from flue gas and marine transport have detrimental impacts on the environment and human health, but SO
is also an important industrial feedstock if it can be recovered, stored and ...transported efficiently. Here we report the exceptional adsorption and separation of SO
in a porous material, Cu
(L) (H
L = 4',4‴-(pyridine-3,5-diyl)bis(1,1'-biphenyl-3,5-dicarboxylic acid)), MFM-170. MFM-170 exhibits fully reversible SO
uptake of 17.5 mmol g
at 298 K and 1.0 bar, and the SO
binding domains for trapped molecules within MFM-170 have been determined. We report the reversible coordination of SO
to open Cu(II) sites, which contributes to excellent adsorption thermodynamics and selectivities for SO
binding and facile regeneration of MFM-170 after desorption. MFM-170 is stable to water, acid and base and shows great promise for the dynamic separation of SO
from simulated flue gas mixtures, as confirmed by breakthrough experiments.
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. The synthesis of 2,6-disubstituted or 1,3-disubstituted cuneanes can be achieved with high regioselectivities, with the regioselectivity being dependent on the electronic character of the cubane substituents. A preliminary assessment of cuneanes as scaffolds for medicinal chemistry suggests cuneanes could serve as isosteric replacements of trans-1,4-disubstituted cyclohexanes and 1,3-disubstituted benzenes. An analogue of the anticancer drug sonidegib was synthesized, in which the 1,2,3-trisubstituted benzene was replaced with a 1,3-disubstituted cuneane.
The need for anticancer therapies that overcome metallodrug resistance while minimizing adverse toxicities is targeted, herein, using titanium coordination complexes. Octahedral titanium(IV) ...trans,mer-Ti{R1N(CH2–2-MeO-4-R1-C6H2)2}2 R1 = Et, allyl, n-Pr, CHO, F, CH2(morpholino), the latter from the formyl derivative; R2 = 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 (GI50 = 0.5–38 μM). Their activity and cancer selectivity (vs nontumor MRC-5 cells) typically exceeds that of cisplatin (up to 16-fold). Proteomic analysis (in MCF-7) supported by other studies (G2/M cell cycle arrest, ROS generation, γH2AX production, caspase activation, annexin positivity, western blot, and kinase screens in MCF-7 and HCT-116) suggest apoptosis elicited by more than one mechanism of action. Comparison of these data to the modes of action proposed for salan Ti(IV) complexes is made.
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