The title novel iron cage complex was obtained using the direct template condensation of the three dichloroglyoximate ligand synthons with methylboronic acid as a Lewis-acidic cross-linking agent on the iron(II) ion as a matrix. This coordination-driven reaction proceeded under the vigorous reaction conditions. Charge density distribution in two solvent-free crystal polymorphs grown from a benzene – iso-octane mixture was experimentally studied using the precise single-crystal XRD experiment. The asymmetric unit of the polymorph P (space group P21/c, a = 8.4499(1), b = 24.2386(4), c = 9.7489(2)Å, β = 108.667(1)°) contains one independent macrobicyclic iron(II)-centered molecule. This molecule in the polymorph C (space group C2/c, a = 15.159(2), b = 8.0971(11), c = 15.366(3)Å, β = 93.850(8)°) lies on the crystallographic axis C2; only half of such molecule is symmetrically independent. The polymorph P is isostructural to the earlier-studied cobalt(II)-centered derivative of the same encapsulating ligand. QTAIM analysis of a charge density distribution and the k-Φ analysis of the non-covalent interactions for all these three cage metallocomplexes were performed. Peculiarities of an electron population of 3d-orbitals in them and an effect of the trigonal prismatic – trigonal antiprismatic distortion of their MN6-coordination polyhedra were analyzed. Differences in their molecular conformations and electrostatic potential distributions, as well as in the intermolecular interactions in their crystals, were observed and explained.

Template condensation of 4-acetylthiazoloxime as a chelating ligand synthon and phenylboronic acid as a Lewis-acidic cross-linking agent on the nickel(II) ion using its perchlorate salt gave the ionic associate of phenylboronmonocapped nickel(II)-centered tris-thiazoloximate cation with ClO4- counter-anion. That with metal(II) chlorides (M2+ = Fe2+, Co2+, Ni2+, Mn2+ and Zn2+) as the sources of M2+ ions afforded the corresponding chloride-H-bonded pseudomacrobicyclic intracomplexes. As follows from the single-crystal X-ray diffraction data, their pseudomacrobicyclic structures are formed by C-H...Cl- contacts with three N,S-heterocyclic groups of thiazoloximate synthons. Fe(II), Co(II) and Zn(II) ions are located in the centers of their trigonal-prismatic MN6-coordination polyhedra, while geometry of NiN6-polyhedra is intermediate between a trigonal prism and trigonal antiprism. All the prepared metal(II) pseudoclathrochelates were also characterized using elemental analysis, PXRD, MALDI-TOF MS, UV-vis and NMR methods. According to the magnetometry and X-ray diffraction data, their metal(II) ions are in high-spin states. The ac and dc magnetic studies, supported by the SA-CASSCF/NEVPT2 quantum chemical calculations, revealed that a given cobalt(II) pseudoclathrochelate exhibits the strong uniaxial magnetic anisotropy due to the unquenched angular orbital momentum. It also demonstrates a zero-field single-molecule magnet behavior with quantum tunneling of the magnetization as the only one magnetically sensitive relaxation mechanism.

The titled compound was prepared by carrying out template condensation of chelating and capping ligand synthons on cobalt(II) ion as a matrix. Its three-dimensional molecule has a trigonal-prismatic geometry favorable for appearance of slow magnetic relaxation. Magnetism measurements, supported by ab initio calculations, revealed its strong uniaxial magnetic anisotropy and zero-field SIM behaviour.

New olefinboron-monocapped iron, nickel, and cobalt(II) pseudoclathrochelates were prepared by the template condensation of 2-acetylpyridineoxime as a chelating ligand synthon with 4-vinylphenylboronic acid as a Lewis-acidic capping agent on the corresponding metal(II) ion as a matrix. Thus, obtained reactive cage-like 3d-metal complexes were characterized using elemental analysis, MALDI-TOF mass, 1H and 13C{1H} NMR, and UV-vis spectra, and by the single-crystal X-ray diffraction experiments. Their copolymerization as the monomers with N-phenylmaleimide and styrene afforded the first magnetically active metalloclathrochelate-containing copolymeric products. Degrees of a conversion of these monomers in a course of copolymerization reactions were controlled using the solution 1H NMR spectra. Molecular masses and molecular weight distributions in their products were obtained using the Gel Permeation Chromatography method. Mass fractions of the corresponding metallocomplex units in them were studied using the three independent methods, such as the energy-dispersive X-ray and solution UV-vis spectroscopies and magnetometry (in the case of the paramagnetic cobalt- and nickel-containing copolymers) and were found to be approximately 10%.

Novel monoribbed-functionalized iron(II) cage complexes with optically active and/or terminal biorelevant group(s) were designed and prepared by two-step nucleophilic substitution of their mono- and dichloroclathrochelate precursors. The single-crystal XRD structures of all of them and those of known leader iron(II)-centered cage bioeffector and of its reactive monochloroclathrochelate precursor were solved. These experimental data were used for theoretical quantum chemical calculations of electrostatic potentials for their 3D-shaped molecules. This allowed to localize the peripheral (exterior) biorelevant group(s), which are responsible for supramolecular binding of thus designed clathrochelate guests to globular proteins as the hosts. Host-guest binding in aqueous solutions between the unfolded protein macromolecules and all the aforementioned iron(II) complexes was studied by the circular dichroism method. An inherent chirality of the metalloclathrochelates with optically active ribbed substituent and a metal-centered chirality of all the prepared macrobicyclic compounds, induced by their supramolecular clathrochelate-to-protein binding, were observed.

A series of monocapped cobalt(II) tris-pyrazoloximates was obtained through the template condensation of the corresponding pyrazoloxime, phenylboronic acid and a suitable cobalt(II) halogenide. Comparing 3-acetylpyrazoloxime versus its methine-containing homolog, the former produced cobalt(II) clathrochelates in substantially higher yields due to the electron donating effect of the methyl substituent, increasing the N-donor ability of its oxime group. Their less N-donor analog with the electron acceptor trifluoromethyl group did not form cobalt(II) complexes of this type. In all their solvent-free and solvent-containing crystals, the encapsulated cobalt(II) ion adopted a high-spin state, as gauged by the Co-N bond lengths of 2.112(4)-2.188(9) Å, and was located almost in the center of its CoN6-coordination polyhedron. Their CoN6-polyhedra had an almost ideal trigonal-prismatic (TP) geometry with distortion angles φ below 4°. This TP-like geometry was assisted by hydrogen bonding between their NH groups and the apical counterion. The absence of methyl groups makes them close to an ideal TP. In contrast, stronger N-H⋯Cl hydrogen bonds occurred in the methyl-containing complex, while the Co-N bond lengths stayed the same at 2.144(2) Å on average. In its solvates with benzene, chloroform and acetone, there is a clear tendency for φ to decrease from 2.7(3)° to 0.47(13)°. The comparable effects of the ribbed methyl substituents, the cross-linking counterion and the lattice solvent on their molecular geometry were observed; the larger the distortions from an ideal TP geometry, the stronger the hydrogen bonds to the corresponding apical halogenide anion. The analysis of the experimental AC- and DC-magnetometry data for their fine-crystalline samples suggests that the passing from the derivative of the methyl-substituted synthon to that of its methine-containing homolog caused a substantial decrease in the magnetic susceptibility value χT and an increase in the QTM contribution to the magnetic relaxation. The effect of a cross-linking halogenide counteranion on the Orbach remagnetization barrier is greater than that of the solvatomorphism of their crystals.

Title hybrid iron(ii)- and cobalt(iii)-centered complexes were prepared in moderate yields using the template reactions of 3-acetylpyrazoloxime as a chelating ligand synthon with a Lewis-acidic zirconium or hafnium(iv) phthalocyaninate on the corresponding 3d-metal ion as a matrix. Formation of the cobalt(iii)-centered complexes is observed due to the oxidation of Co2+ cations of the initial cobalt(ii) salt. Thus obtained binuclear chloride H-bonded iron(ii) and cobalt(iii) compounds were characterized using elemental analysis, H-1 and C-13 {H-1} NMR, MALDI-TOF mass, Fe-57 M & ouml;ssbauer (for iron compounds) and UV-vis spectra, and by single-crystal X-ray diffraction (XRD). Their redox properties were studied by cyclic (CV) and differential pulse voltammetry methods, and using spectroelectrochemical experiments. Their encapsulated 3d-metal ions with the electronic d(6) configuration are located almost in the center of MN6-coordination polyhedra, the geometry of which is more closer to a trigonal antiprism (TAP, the distortion angle phi = 60 degrees) than to a trigonal prism (TP, phi = 0 degrees) with phi similar to 40 degrees. Fe-II-N distances fall in the range 1.913(6)-1.965(7) & Aring;, while the CoIII-N bond lengths are from 1.890(8) to 1.935(8) & Aring;. The geometry of (MO3N4)-O-IV-coordination polyhedra of their capping metal(iv) ions is intermediate between a capped TAP and a capped TP. In the molecules of (ZrMMMZrIV)-M-IV-M-III-M-II-Zr-II-pentanuclear intracomplexes, (HS)Fe-III-N and (LS)Co-III-N distances in their two semiclathrochelate fragments fall in the ranges 1.915(10)-1.980(12) & Aring; and 1.886(13)-1.930(13) & Aring;, respectively, and the geometry of MN6-coordination polyhedra is closer to a TAP (values of phi are higher than 30 degrees). The geometry of MN6-polyhedra of the HS cross-linking metal(ii) ions between them is close to a TAP (values of phi are higher than 50 degrees). All the obtained binuclear hybrid complexes exhibit very similar electrochemical patterns. Their CVs contain quasi-reversible or irreversible three reduction and three oxidation waves. The potentials of electrochemical reductions, assigned to the Pc-localized redox processes, are close to each other. The first of them is a quasi-reversible process attributed to the Pc-based one-electron reduction, while the first oxidation wave was assigned to the metal-centered M2+/3+ redox couples. The spectroelectrochemical data confirmed an assignment of the aforementioned electrochemical processes.

Template condensation of 2-acetylpyridineoxime with butyl ester of 1,3-propanediboronic acid in the presence of iron(II) affords a poorly separable mixture of complex products. Similar results were observed when Fe3+ ions were used for cross-linking in place of the diboronic acid. Prolonged crystallization of these mixtures gave crystals of perchlorate salts of a (FeFeFeII)-Fe-II-Fe-III-trinuclear hexapyridineoximate cation and of an analogous (FeFeFeII)-Fe-II-Fe-II-intracomplex that crystallize with chloroform and dichloromethane solvent molecules, respectively. Both complexes were characterized by synchrotron single-crystal X-ray diffraction (XRD) experiments. The Fe-N distances of the two 'terminal' iron cations are virtually the same between these trinuclear complexes and unambiguously support assignments of oxidation number +2 and low-spin state (S = 0). The centers of the FeN6-coordination polyhedra adopt geometries resembling trigonal antiprisms with distortion angles phi of approximately 40 degrees. The FeO6-coordination polyhedra possess an almost ideal O-h geometry with phi close to 60 degrees. Each of these iron(II) or iron(III) mu(3)-metallocenters acts as a bifunctional Lewis acid that cross-links two pseudoclathrochelate entities, formed by the 'terminal' iron(II) ions, to give an almost linear (the corresponding intramolecular Fe(2)center dot center dot center dot Fe(1)center dot center dot center dot Fe(3) angles are close to 180 degrees) helical cation or intracomplex.

Fast crystallization of the monoclathrochelate cobalt(II) intracomplex [Co(Cl2Gm)3(BAd)2] (where Cl2Gm2- is a dichloroglyoxime dianion and BAd is an adamantylboron capping group, 1), initially obtained by the direct template condensation of the corresponding chelating α-dioximate and cross-linking ligand synthons on the Co2+ ion as a matrix, from benzene or dichloromethane afforded its structural triclinic and hexagonal polymorphs. Its prolonged recrystallization from dichloromethane under air atmosphere and sunlight irradiation unexpectedly gave the crystals of the CoIIICoIICoIII-trinuclear dodecachloro-bis-clathrochelate intracomplex [[CoIII(Cl2Gm)3(BAd)]2CoII] (2), the molecule of which consists of two macrobicyclic frameworks with encapsulated low-spin (LS) Co3+ ions, which are cross-linked by a μ3-bridging Co2+ ion as a bifunctional Lewis-acidic center. The most plausible pathway of such a 1 → 2 transformation is based on the photoinitiated radical oxidation of dichloromethane with air oxygen giving the reactive species. Cobalt(II) monoclathrochelate 1 was found to undergo a temperature-induced spin crossover (SCO) both in its solutions and in the solid state. In spite of the conformational rigidity of the corresponding quasiaromatic diboron-capped tris-α-dioximate framework, the main parameters of this SCO transition (i.e., its completeness and gradual character) are strongly affected by the nature of the used solvent (in the case of its solutions) and by the structural polymorphism of its crystals (in the solid state). In the latter case, the LS state (S = 1/2) of this complex is more thermally stable and, therefore, the cobalt(II)-centered 1/2 → 3/2 SCO is more gradual than that in solutions.

The title cobalt(II) pseudoclathrochelate complexes possess an intermediate trigonal prismatic-trigonal antiprismatic geometry. As follows from PPMS data, they exhibit an SMM behaviour with Orbach relaxation barriers of approximately 90 K. Paramagnetic NMR experiments confirmed a persistence of these magnetic characteristics in solution. Therefore, a straightforward apical functionalization of this 3D molecular platform for its targeted delivery to a given biosystem can be performed without substantial changes.

Reaction of the template synthesis of the methylboron-capped iron(II) tris-heptoximate clathrochelate on Fe2+ ion as a matrix was found to proceed in the quantitative yield in diluted aqueous-organic solutions. This complex is intensively colored in the visible range, whereas the initial ligand synthons are optically silent, thus allowing to photometric study the kinetics of its synthesis and acidic decomposition reactions. Template condensation of the corresponding chelating and capping ligand synthons gave a solid form of this macrobicyclic complex, which was characterized using modern spectral methods and by the single-crystal X-ray diffraction (XRD) experiment. Kinetic schemes and parameters of the aforementioned reactions for the methylboron-capped clathrochelates, the derivatives of six- (H(2)Nx), seven-(H(2)Gx) and eight(H(2)Ox)-membered alicyclic alpha-dioximes, are dramatically affected by their alicyclic ring size. If the general schemes of their formation persist, those for H(2)Nx and H(2)Gx contain a rate-determining stage, whereas that for H(2)Ox has three initial consecutive stages with close rates. Passing from H(2)Nx to H(2)Gx caused a decrease in the synthesis reaction rates of their macrobicyclic derivatives by approximately three orders of magnitude. These kinetic effects were explained using the XRD data for the initial alpha-dioximes and for their methylboron-capped macrobicyclic derivatives.

Kinetics and thermodynamics of the template synthesis and of the acidic decomposition of the methylboron-capped iron(II) tris-1,2-dioximates-the clathrochelate derivatives of six (nioxime)- and eight (octoxime)-membered alicyclic ligand synthons-were compared. In the case of a macrobicyclic iron(II) tris-nioximate, the plausible pathway of its formation contains a rate-determining stage and includes a reversible formation of an almost trigonal-antiprismatic (TAP) protonated tris-complex, followed by its monodeprotonation and addition of CH3B(OH)(2). Thus, the formed TAP intermediate undergoes a multistep rate-determining stage of double cyclization with the elimination of two water molecules accompanied by a structural rearrangement, thus giving an almost trigonal-prismatic (TP) iron(FII) semiclathrochelate. It easily undergoes a cross-linking with CH3B(OH)(2), resulting in the elimination of H+ ion and in the formation of a macrobicyclic structure. In contrast, the analogous scheme for its macrobicyclic tris-octoximate analog was found to contain up to three initial stages affecting the overall synthesis reaction rate. The rates of acidic decomposition of the above clathrochelates were found to be also affected by the nature of their ribbed substituents. Therefore, the single crystal XRD experiments were performed in order to explain these results. The difference in the kinetic schemes of a formation of the boron-capped iron(II) tris-nioximates and tris-octoximates is explained by necessity of the substantial changes in a geometry of the latter ligand synthon, caused by its coordination to the iron(II) ion, due to both the higher distortion of the FeN6-coordination polyhedra, and the intramolecular sterical clashes in the molecules of the macrobicyclic iron(II) tris-octoximates.

Hydrogen-evolving cathodes were prepared using a series of iron(ii) clathrochelates bearing various number of terminal phenanthrenyl groups via physisorption on carbon paper and employed in the polymer electrolyte membrane water electrolysis cells instead of typically used platinum. In situ electrochemical activation of the cathodes was carried out, after that the cells performance and durability were evaluated. These clathrochelate complexes represent a promising alternative to platinum as hydrogen-evolving cathode electrocatalysts.

Hexaphenanthrene iron, cobalt and ruthenium(II) macrobicyclic complexes, the molecules of which have been designed for their efficient immobilization on carbon materials, such as activated carbon (AC), reduced graphene oxide (RGO) and carbon paper (CP), were tested as the cathode electro(pre)catalysts for hydrogen production in a PEM MEA water electrolysis cell. They were found to possess the good performances of hydrogen production. The use of the suitable carbon materials of a high surface area, AC and RGO, as the substrates for their efficient immobilization, as well as the addition of Nafion (R) as a polymer electrolyte, allowed to substantially increase an electrocatalytic activity of the corresponding clathrochelate-containing CP-based cathodes. Chemical design of the above metal-encapsulating cage molecules allowed a substantial decrease in a consumption of these metals by using their adsorbed monolayers. The high adsorptive capacities of the suitable carbon materials resulted in a substantial increase in a surface concentration of their electrocatalytically active centers, and, therefore, in that of an electrocatalytic activity of the obtained hybrid clathrochelate-containing carbon-based cathode materials. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Boron-cross-linked cobalt(II) pseudoclathrochelate was obtained by the template reaction of 2-acetylpyrazoloxime, phenylboronic acid, and a new DMF cobalt(II) solvato complex with a decachloro-closo-decaborate dianion. As confirmed by single-crystal X-ray diffraction, this complex crystallizes with two symmetry-independent cobalt(II) pseudoclathrochelate cations, one decachloro-closo-decaborate dianion, one benzene, one dichloromethane solvent molecule, and two molecules of DMF. The latter act as pseudocapping fragments to the monocapped tris-pyrazoloximate ligands by forming N-H···O hydrogen bonds with their pyrazole groups. The CoIIN6-coordination polyhedra adopt a nearly ideal TP geometry with distortion angles φ equal to 1.22(16) and 2.58(17)° for two symmetry-independent pseudoclathrochelate cations, both containing the encapsulated cobalt(II) ion in its high-spin state (Co-N 2.115(4)-2.198(3) Å). Magnetic properties of this complex were studied both by dc-magnetometry and by solution-state NMR spectroscopy to reveal a high magnetic anisotropy, thus suggesting a large magnetic susceptibility tensor anisotropy (25.8 × 10-32 m3 at 298 K) and a large negative zero-field splitting energy (-85 cm-1). The results of magnetometry studies in the ac magnetic field suggest a single molecule magnet behavior of this TP complex with an effective magnetization reversal barrier of approximately 130 cm-1. Its pseudocapping DMF molecules that form H-bonds with tris-pyrazoloximate fragments are easy to substitute by strong H-bond acceptors, such as chloride ions and di- and tetramethylureas, thus affecting the magnetic properties of a whole pseudomacrobicyclic paramagnetic system.

First pseudomacrobicyclic phthalocyaninate-capped cobalt(III) tris-pyridineoximates were obtained in moderate yields (40-49 %) by the direct template condensation of 2-acetylpyridineoxime with zirconium(N) and hafnium(IV) phthalocvaninates on the cobalt ion as a matrix. These complexes were thoroughly characterized using elemental analysis, MALDI-TOF mass-spectrometty, NAIR and UV-Vis spectroscopies and by the single-crystal X-ray dyfraction. Their electrochemical behaviour was studied byusing the cyclic and differential pulse voltammetries.

Transition metal clathrochelates are promising electrocatalysts of the hydrogen evolution reaction, for example at the cathodes of water electrolysers. Their electrochemical activity can be maximized by forming monolayers on a surface of electrode materials of large specific area, such as carbon powders or fibers. Surface functionalization via physisorption is the easiest way to implement these electrocatalysts. This process can be improved by increasing the number of polyaromatic groups per a cage molecule of these complexes. We performed the synthesis and characterization of three novel iron, ruthenium and cobalt(II) clathrochelates, containing six terminal polyaromatic groups each. Their chemical composition and macrobicyclic structure were determined using MALDI-TOF MS, UV-Vis, H-1 and C-13{H-1} NMR spectra. The cyclic voltammograms of these three complexes and of their hexachloromacrobicyclic precursors were recorded in dichloromethane solutions, using glassy carbon and platinum as working electrodes, over the 10-100 mV.s(-1) range of potential scan rate. The physisorption isotherms of these three complexes, on three different carbon materials of practical interest for their application at the cathodes of water electrolysers (activated carbon, reduced graphene oxide and carbon paper) were measured in dichloromethane - acetonitrile solutions using UV-vis spectrophotometry. The thermodynamic parameters of the sorption processes were calculated. (C) 2019 The Electrochemical Society.

Herein, we report a new trigonal prismatic cobalt(II) complex that behaves as a single molecule magnet. The obtained zero-field splitting, which is also directly accessed by THz-EPR spectroscopy (-102.5 cm-1 ), results in a large magnetization reversal barrier U of 205 cm-1 . Its effective value, however, is much lower (101 cm-1 ), even though there is practically no contribution from quantum tunneling to magnetization relaxation.