A bimetallic pentadecanuclear cyanido-bridged {Fe9[W(CN)8]6 (MeOH)24}·xMeOH cluster of an Fe(II/III)-W(IV/V) mixed valence nature, reveals a reversible single-crystal-to-single-crystal transformation, concomitant with metal-to-metal charge transfer between Fe and W ions. The dominance of (HS)Fe(II)-NC-W(V) units at a high temperature, and (HS)Fe(III)-NC-W(IV) units at a low temperature, leads to an unprecedented reversed thermal hysteresis loop in magnetic measurements.

Precisely controlled stoichiometric mixtures of Co(2+) and Fe(2+) metal ions were combined with the [W(V)(CN)8](3-) metalloligand in a methanolic solution to produce a series of trimetallic cyanido-bridged {Fe(9-x)Co(x)[W(CN)8]6(MeOH)24}·12MeOH (x = 0, 1, ..., 8, 9; compounds 0, 1, ..., 8, 9) clusters. All the compounds, 0-9, are isostructural, and consist of pentadecanuclear clusters of a six-capped body-centered cube topology, capped by methanol molecules which are coordinated to 3d metal centers. Thus, they can be considered as a unique type of a cluster-based molecular solid solution in which different Co/Fe metal ratios can be introduced while preserving the coordination skeleton and the overall molecular architecture. Depending on the Co/Fe ratio, 0-9 exhibit an unprecedented tuning of magnetic functionalities which relate to charge transfer assisted phase transition effects and slow magnetic relaxation effects. The iron rich 0-5 phases exhibit thermally induced reversible structural phase transitions in the 180-220 K range with the critical temperatures being linearly dependent on the value of x. The phase transition in 0 is accompanied by (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) charge transfer (CT) and the additional minor contribution of a Fe-based spin crossover (SCO) effect. The Co-containing 1-5 phases reveal two simultaneous electron transfer processes which explore (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) CT and the more complex (HS)Co(II) W(V) ↔ (LS)Co(III) W(IV) charge transfer induced spin transition (CTIST). Detailed structural, spectroscopic, and magnetic studies help explain the specific role of both types of CN(-)-bridged moieties: the Fe-NC-W linkages activate the molecular network toward a phase transition, while the subsequent Co-W CTIST enhances structural changes and enlarges thermal hysteresis of the magnetic susceptibility. On the second side of the 0-9 series, the vanishing phase transition in the cobalt rich 6-9 phases results in the high-spin ground state, and in the occurrence of a slow magnetic relaxation process at low temperatures. The energy barrier of the magnetic relaxation gradually increases with the increasing value of x, reaching up to ΔE/kB = 22.3(3) K for compound 9.

A low-waste, time-economical, and scalable semiheterogeneous purification protocol for the removal of ruthenium residues from olefin metathesis (OM) reactions has been developed. It is based on the non-covalent immobilization of the commercially available isocyanide 1,4-bis­(3-isocyanopropyl)­piperazine (QA) on unmodified silica gel. The use of the heterogeneous scavenger QA@SiO 2 synthesized in situ during the purification process was shown to yield OM products with metal contamination usually below 5 ppm. Furthermore, the new purification protocol was effective on a gram scale in the ring-closing OM of an intermediate in the synthesis of cathepsin K inhibitors, leading to a product containing only 0.29 ppm Ru. Finally, QA was used in an aqueous medium and reduced the metal contamination from 9977 to 21 ppm.

The synthesized chiral (R)- and (S)-2-(1-hydroxyethyl)­pyridine ligands (R/S-mpm) were introduced to self-assembled CoII-[WV(CN)8] and NiII-[WV(CN)8] magnetic systems giving a remarkable series of four enantiopure cyanido-bridged clusters, {MII[MII(R/S-mpm)­(MeOH)]8­[WV(CN)8]6}­·14MeOH (M = Co, 1-R and 1-S; M = Ni, 2-R and 2-S). They consist of 15 metal centers, 9 CoII or NiII ions, and 6 [WV(CN)8]3– ions, embedded in a 6-capped body-centered cube topology. Bidentate enantiopure mpm ligands coordinated to eight external CoII or NiII sites induce their chiral character, which results in the strong natural optical activity in the broad UV–vis range of 200–700 nm. All (1-R/S) and (2-R/S) clusters reveal cyanido-mediated ferromagnetic exchange interaction giving high-spin ground states of 15/2 (1-R/S) and 12 (2-R/S). For (2-R/S) forms of {Ni9W6}, the exchange constant J = +16.1 cm–1 was obtained using exact diagonalization of the exchange Hamiltonian. Because of the significant magnetic anisotropy, (1-R/S) forms of {Co9W6} cluster reveal the low temperature onset of the slow magnetic relaxation characteristic of single-molecule magnets (SMMs). Thus, they can be considered as a rare example of chiral SMM molecules.

The unique enantiopure {[Λ-Co(II)((R)-mpm)2]3[W(V)(CN)8]2}·9H2O [(R)-1] and {[Δ-Co(II)((S)-mpm)2]3[W(V)(CN)8]2}·9H2O [(S)-1], where mpm = α-methylpyridinemethanol, magnetic spongelike materials, crystallizing in the chiral P21 space group, are constructed of cyanido-bridged {Co3W2} trigonal bipyramids with three cis-[Co(II)(mpm)2(μ-NC)2] moieties in equatorial sites and two [W(V)(CN)8](3-) units in apical positions. The arrangement of {Co3W2} clusters in the crystal lattice is controlled by interactions with crystallization H2O molecules, resulting in two independent hydrogen-bonding systems: the first weaving along open channels in the a direction (weakly bonded H2O) and the second closed in the cages formed by the surrounding [W(CN)8](3-) and mpm fragments (strongly bonded H2O). The strong optical activity of (R)- and (S)-1 together with continuous chirality measure (CCM) analysis confirms the chirality transfer from enantiopure (R)- and (S)-mpm to [Co(mpm)2(μ-NC)2] units, a cyanido-bridged skeleton, and to the whole crystal lattice. Magnetic properties confronted with ab initio calculations prove the ferromagnetic couplings within Co(II)-NC-W(V) linkages inside {Co3W2} molecules, accompanied by weak antiferromagnetic intermolecular interactions. The reversible removal of weakly bonded H2O above 50 °C induces the structural phase transition 1 ⇄ 1deh and strongly affects the magnetic characteristics. The observed changes can be interpreted in terms of the combined effects of the decreasing strength of ferromagnetic Co(II)-W(V) coupling and the increasing role of antiferromagnetic intermolecular correlation, both connected with dehydration-induced structural modifications in the clusters' core and supramolecular network of 1.

Transition metal catalysts play a prominent role in modern organic and polymer chemistry, enabling many transformations of academic and industrial significance. However, the use of organometallic catalysts often requires the removal of their residues from reaction products, which is particularly important in the pharmaceutical industry. Therefore, the development of efficient and economical methods for the removal of metal contamination is of critical importance. Herein, we demonstrate that commercially available 1,4-bis(3-isocyanopropyl)piperazine can be used as a highly efficient quenching agent (QA) and copper scavenger in Cu/TEMPO alcohol aerobic oxidation (Stahl oxidation) and atom transfer radical polymerization (ATRP). The addition of QA immediately terminates Cu-mediated reactions under various conditions, forming a copper complex that can be easily separated from both small molecules and macromolecules. The purification protocol for aldehydes is based on the addition of a small amount of silica gel followed by QA and filtration. The use of QA@SiO 2 synthesized in situ results in products with Cu content usually below 5 ppm. Purification of polymers involves only the addition of QA in THF followed by filtration, leading to polymers with very low Cu content, even after ATRP with high catalyst loading. Furthermore, the addition of QA completely prevents oxidative alkyne-alkyne (Glaser) coupling.Although isocyanide QA shows moderate toxicity, it can be easily converted into a non-toxic compound by acid hydrolysis. Scheme 1 (A) Mechanism of Cu/TEMPO alcohol aerobic oxidation (Stahl oxidation). (B) Mechanism of Cu-catalyzed normal ATRP and low-ppm ATRP in the presence of excess reducing agents. 4252 | Chem. Sci., 2020, 11, 4251-4262 This journal isFig. 3 QA reactivity towards the [Cu II (TPMA)Br] + . (A) UV-vis spectra of [Cu II Br 2 ] ¼ 2.5 mM; [TPMA] ¼ 2.5 mM in DMSO at 22 C in air. (B) UV-vis spectra of copper complex after addition of QA (4 equiv.). (C) UV-vis spectra of copper complex after addition of QA (4 equiv.) and AA (10 equiv.). This journal is a Reaction conditions: [monomer]/[EBiB]/[Cu II Br 2 ]/[Me 6 TREN] ¼ 200/1/0.05/0.25 in MeCN, ([MA] ¼ 7.4 M, [nBA] ¼ 4.7 M, [tBA] ¼ 4.6 M, [MMA] ¼ 6.2 M) at 22 C. b Monomer conversion was determined by using 1 H NMR spectroscopy. c Theoretical molecular weight was calculated using the equation M n,th ¼ [M] Â MW M Â a + MW EBiB , where [M], MW M , a, and MW EBiB correspond to initial monomer concentration, molar mass of monomer, conversion, and molar mass of EBiB initiator, respectively. d Molecular weight and dispersity (Đ) were determined by GPC analysis (THF as eluent) calibrated to poly(methyl methacrylate) standards. e Equivalents of QA with respect to Cu II Br 2 . f Copper content was determined by ICP-MS. g ARGET ATRP: ascorbic acid (5 equiv. with respect to Cu II Br 2 ), under anaerobic conditions. h SARA ATRP: 4 cm Cu(0) wire (d ¼ 1 mm, S ¼ 1.27 cm 2 ), under anaerobic conditions. i pATRP: UV irradiation (l ¼ 365 nm), under anaerobic conditions. j pAT...

Promoted by homogeneous Ru-benzylidene complexes, the olefin metathesis reaction is a powerful methodology for C-C double bonds formation that can find a number of applications in green chemical production. A set of heterogeneous olefin metathesis pre-catalysts composed of ammonium-tagged Ru-benzylidene complexes 4 (commercial FixCat™ catalyst) and 6 (in-house made) immobilized on solid supports such as 13X zeolite, metal-organic framework (MOF), and SBA-15 silica were obtained and tested in catalysis. These hybrid materials were doped with various amounts of ammonium-tagged styrene derivative 5—a precursor of a spare benzylidene ligand—in order to enhance pre-catalyst regeneration via the so-called release-return “boomerang effect”. Although this effect was for the first time observed inside the solid support, we discovered that non-doped systems gave better results in terms of the resulting turnover number (TON) values, and the most productive were hybrid catalysts composed of 4@MOF, 4@SBA-15, and 6@SBA-15.

We propose an outline of plausibly deniable chemical encryption algorithm, a technique aimed at increasing the cost of a small organic molecule identification in a sample by means of chemical analysis through mixing it with a rationally designed randomized mixture of analytical interferents, in a remote analogy to other domains of cryptography. The algorithm is then applied in a proof-of-concept demonstration example.