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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]

Bismuth germanate Bi4Ge3O12 single crystals doped with 0.1 and 1.0 wt% Dy2O3 have been successfully grown by the Czochralski method. The actual compositions of the Dy3+-doped Bi4Ge3O12 crystals have been refined for the first time using single-crystal and synchrotron powder X-ray diffraction. Different local structural behavior of the Dy3+ and Bi3+ ions in the Bi4Ge3O12 crystal matrix depending on the initial Dy3+ content has been revealed by X-ray absorption spectroscopy. In the crystal with the refined composition (Bi3.996(11)Dy0.004)Ge3O12 (0.1 wt% Dy2O3), the octahedron Dy3+O7 with a split vertex and vacancy octahedron Bi3+O5 are formed in adjacent octahedra. In the crystal with the refined composition (Bi3.952(47)Dy0.048)Ge3O12 (1.0 wt% Dy2O3), the semi-octahedron Dy3+O5 and distorted octahedron Bi3+O6 are realized. A character of distribution of the residual electron density showed a probable decrease in the symmetry of Dy3+-doped Bi4Ge3O12 crystals that limits the possible maximum Dy3+ content in the Bi4Ge3O12 crystal matrix. Noticeable fluctuations were not revealed in the absorption and luminescence spectra of Dy3+-doped Bi4Ge3O12 crystals. [ABSTRACT FROM AUTHOR]