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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. [ABSTRACT FROM AUTHOR]

A multistep general synthetic strategy towards polytopic carboranyl-containing (semi)clathrochelate metal complexes, based on the template synthesis, transmetallation, amide condensation and 1,3-dipolar cycloaddition reactions, is developed. Their mono(semi)clathrochelate precursors with a single reactive group were obtained using a transmetallation of the triethylantimony-capped macrobicyclic precursor. The thus obtained carboxyl-terminated iron(II) semiclathrochelate underwent a macrobicyclization with zirconium(IV) phthalocyaninate to form the corresponding phthalocyaninatoclathrochelate. The direct one-pot template condensation of the suitable chelating and cross-linking ligand synthons on the Fe2+ ion as a matrix was also used for its preparation. Further amide condensation of the aforementioned semiclathrochelate and hybrid complexes with propargylamine in the presence of carbonyldiimidazole gave the (pseudo)cage derivatives with a terminal C≡C bond. Their "click" reaction with an appropriate carboranylmethyl azide afforded the ditopic carboranosemiclathrochelates and the tritopic carboranyl-containing phthalocyaninatoclathrochelates with a flexible spacer fragment between their polyhedral entities. The obtained new complexes were characterized using elemental analysis, MALDI-TOF mass spectrometry, multinuclear NMR, and UV-vis spectroscopy, and by single crystal X-ray diffraction experiments. Their FeN6-coordination polyhedra show a truncated trigonal-pyramidal geometry, while the cross-linking heptacoordinate Zr4+ or Hf4+ cations in the hybrid compounds form the MIVN4O3-coordination polyhedra with the geometry of a capped trigonal prism. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Solution behaviour in DMSO using 1D and 2D NMR spectroscopy was performed for lanthanide complexes Ln(L)(HL) and Ln(HL)2Cl, containing non-macrocyclic 2-(tosylamino)-benzylidene-N-benzoylhydrazone (H2L), and the structure of [Yb(L)]+ cation in solution was determined. Based on the NMR data, the possibility to obtain novel complexes containing [Ln(L)2]− was predicted, which was successfully synthesized, and the crystal structure of K(C2H5OH)3[Yb(L)2] was determined. Thanks to its high quantum yield of NIR luminescence (1.3 ± 0.2%), high absorption, low toxicity, and the stability of its anion against dissociation in DMSO, K(H2O)3[Yb(L)2] was successfully used for bioimaging. [ABSTRACT FROM AUTHOR]

Thirteen new metallacarborane complexes of rhodium and iridium with covalently bound cage carbon atoms were synthesized and their thermal stability was investigated. Two iridium complexes undergo a polyhedral rearrangement with the formation of more than one isomer. The structures of the new isomers were determined by a single crystal X-ray diffraction analysis and 11B{1H}–11B{1H} COSY NMR. A full isomerization scheme of the less thermally stable complex was proposed based on DFT calculations. According to this mechanism sequential downhill and uphill bifurcations arise in the reaction pathway. Each bifurcation is responsible for a new product formation. [ABSTRACT FROM AUTHOR]