Ya. Z. Voloshin

Cage complexes of transition metals in biochemistry and medicine

The review presents the following main trends and the perspectives of application of the transition metal clathrochelates in medicine and biochemistry: encapsulation of radioactive metal ion for diagnostics and therapy; imaging agents for MRI; antidotes and prolonged pharmaceuticals; pharmaceuticals for boron neutron capture therapy; antihelminthic and antiparasitic detergents; antioxidants; membrane transport of the metal ions; interaction of the cage metal complexes with nucleic acids and the potential of their self-assembling reactions in immunology and molecular biology (recognition of antibodies, antigens and DNA sites); design of HIV inhibitors for the therapy.

Template synthesis and structures of apically functionalized iron(ii) clathrochelates

Template condensation of three nioxime or dichloroglyoxime molecules with monosubstituted boronic acids on an iron(ii) ion matrix afforded apically functionalized tris-nioximate clathrochelates and hexachloride precursors of apically-ribbed functionalized clathratochelates, respectively. The macrobicyclic tris-nioximates containing apical o-dimethoxyphenyl, p-bromophenyl, phenylethynyl, biphenylyl, 6-pyrimidinyl, or tert-butyl substituents and the dibenzothienyl-containing hexachloroglyoximate clathrochelate thus obtained were characterized by elemental analysis and IR, UV-Vis, 1H and 13C NMR, 57Fe Mössbauer and PD mass spectroscopies. The structures of o-dimethoxyphenyl- and phenylethynyl-containing iron(ii) tris-nioximates and the dibenzothienyl precursor were established by X-ray diffraction analysis.

Structural peculiarities of a homologous series of iron(II) cage complexes with ribbed glyoximate, methylglyoximate, and dimethylglyoximate chelate fragments

The crystal and molecular structures of four representatives of the homologous series of iron(ii) clathrochelates FeBd2Gm(BF)2·1.5CHCl3, FeBd2Mm(BF)2·CH2Cl2, FeBd2Dm(BF)2·CH2Cl2, and FeBd2Dm(BF)2·0.5C6H6·0.5iso-C8H18 whose frameworks contain two α-benzyldioximate (Bd) chelate rings and one acyclic α-dioximate fragment (Gm2−, Mm2−, and Dm2− are glyoxime, methylglyoxime, and dimethylglyoxime dianions, respectively) were studied by X-ray diffraction. Two types, A and B, of independent macrobicycles were observed in the unit cell of the crystal FeBd2Gm(BF)2·1.5CHCl3. The geometry of the FeN6 coordination polyhedra of encapsulated iron(ii) ions is intermediate between a trigonal prism (TP) and a trigonal antiprism (TAP). The encapsulated iron(ii) ions occupy centers of the TP-TAP polyhedra. For the macrobicyclic derivatives of dimethylglyoxime, the distortion angles φ(average values 24.0 and 24.7°) are larger than for the glyoximate and methylglyoximate analogs (average values 20.7, 22.6, and 23.2°). The larger trigonal-prismatic distortion of the coordination polyhedron in type-B FeBd2Gm(BF)2 molecules as compared to type-A FeBd2Gm(BF)2 can be explained by a difference in their intermolecular interactions. The carbon-carbon distances in the glyoximate and methylglyoximate ribbed fragments of the clathrochelates FeBd2Gm(BF)2 and FeBd2Mm(BF)2 (average values 1.414 shorter than in the α-benzyldioximate chelate rings (about 1.45 FeBd2Gm(BF)2·1.5CHCl3 and FeBd2Dm(BF)2·CH2Cl2 have laminated structures in which chains of the clathrochelate molecules are differently oriented relative to the axes of the unit cells. The crystals FeBd2Mm(BF)2·CH2Cl2 and FeBd2Dm(BF)2·0.5C6H6·0.5 iso-C8H18 have framework structures and their solvate molecules occupy voids between the dimeric associates and the macrobicyclic molecules, respectively.

Free-radical polymerization of methyl methacrylate in the presence of a ferrocenyl-containing iron(II) clathrochelate complex and initiators of various natures

Benzoyl peroxide-, lauryl peroxide-, and AIBN-initiated free-radical polymerization of methyl methacrylate has been studied in bulk and solution in the presence of macrobicyclic iron(II) bis(ferrocenyl borate) tris(nioximate). It has been found that the ferrocenyl-containing iron(II) clathrochelate forms efficient initiating systems with peroxides, whereas, in the case of AIBN, its presence has no effect on the kinetic parameters of the process and the properties of the resulting polymer. The use of clathrochelate complex-peroxide initiator systems accelerates the polymerization of methyl methacrylate and decreases the molecular mass of the polymer. The kinetic parameters of the process have been determined.

Structural chemistry of complexes with an encapsulated metal ion. α-Dioximate, oximehydrazonate, and dihydrazonate clathrochelates

The review surveys the main trends in the structural chemistry of clathrochelates: the determination of the crystal and molecular structures of various types of new complexes, their symmetry and functionality; the supramolecular organization and phase transitions of clathrochelate crystals; the structure—spectral parameter relationships and the deduction of the molecular structures; the use of X-ray diffraction data for explanation of the kinetic and thermodynamic parameters of the synthesis and decomposition of clathrochelates.

Ribbed-monofunctionalized iron(II) clathrochelate with tert-butyl sulfide substituents: Synthesis, structure, and thermochemical transformations

A ribbed-monofunctionalized macrobicyclic iron(II) complex with tert-butyl sulfide substituents has been prepared via nucleophilic substitution of its dichloroclathrochelate precursor with tert-butylthiolate ion. This new complex has been characterized using elemental analysis, IR and multinuclear NMR spectroscopy, and the single crystal X-ray diffraction. Its thermal destruction occurs with release of isobutylene and polyunsaturated hydrocarbons giving iron borate, iron fluoropolyborate, and iron nitride as follows from combined thermal analysis and X-ray powder diffraction data.

Supramolecular organization of the crystals of allylsulfide clathrochelate: influence of the nature of solvate molecules

The influence of the nature of solvate molecules on the supramolecular organization of the crystals of α-benzyldioximate FeBd2((AllylS)2Gm)(BF)2 clathrochelate containing the allylsulfide substituents was studied by X-ray diffraction analysis.

Preparation of poly(methyl methacrylate) in the presence of ferrocenyl-containing Fe(II) semi- and clathrochelates

The effect of ferrocenyl-containing semi- and clathrochelates on radical polymerization of methyl methacrylate, initiated by benzoyl peroxide, and on molecular characteristics of the polymer formed was examined.

Two alternative approaches to modification of a cage complex: nucleophilic substitution and electrophilic addition for the synthesis of an iron(II) clathrochelate with an annulated imidazole fragment

A rib-functionalized iron(II) tris-dioximate clathrochelate bearing an annulated phenylimidazole fragment was prepared using nucleophilic substitution and electrophilic addition at the chelating α-dioximate fragment of the macrobicyclic framework. The resultant cage complex was identified with single crystal XRD, analytical data, 1H, 13C, 19F, 11B NMR spectroscopy, and examined with UV–vis spectroscopy and CVA. Two approaches to modification of the clathrochelate framework are compared. Graphical abstract

Cobalt(II) clathrochelates as components of initiating systems for radical polymerization of methyl methacrylate

200 The use of metal complex compounds in radical polymerization of vinyl monomers is one of the most successful and promising ways of development of tai lor made synthesis of polymers on their basis [1, 2]. It has been shown [3–6] that iron(II) semi and clathro chelates in combination with traditional initiators of radical polymerization (in particular, diacyl perox ides) form high performance initiating systems. Such systems have a favorable effect on both the kinetic parameters of the process (increase the initiation rate; under certain conditions, mitigate the detrimental gel effect; reduce the effective activation energy of poly merization; etc.) and the physicochemical character istics of the resulting polymers (variation of the molec ular weight from 300 thousand daltons to 4 million daltons, the increase in stereoregularity and thermal stability). In this context, the use of new types of clath rochelates, in particular, macrobicyclic cobalt(II) tris(α dioximate)s (Scheme 1, compounds 1–3), as modifying additives in the radical polymerization of methyl methacrylate (MMA) initiated by benzoyl per oxide seems to be promising. All these compounds dif fer from the previously studied cage iron(II) com plexes [3–6] in the nature of both the encapsulated metal ion and the apical and edge substituents.