Encapsulation of ruthenium(ii) with macrobicyclic dioxime-functionalized ligands: on the way to new types of DNA-cleaving agents and probes

Voloshin, Yan Z.; Varzatskii, Оleg А.; Крон, Т. Е.; Belsky, V. K.; Zavodnik, V. E.; Strizhakova, Nataly G.; Надточенко, В. А.; Smirnov, V. N.

doi:10.1039/b107172f

Cited by 50 publications

(28 citation statements)

References 31 publications

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“…[4,5] The Co 2+ ion is, however, a less efficient template, and the yields of the cobalt(II) precursors turned out to be significantly lower than those for the iron(II) ion. The reason is the values of the physical ionic (Shannon) radii of the template cobalt(II) ion (electronic configuration d 7 , r i = 0.79 and 0.885 Å for the lowand high-spin states of this ion in the octahedral environment, respectively) that are appreciably greater than that of the low-spin iron(II) ion (electronic configuration d 6 , r i = 0.75 Å). The six d electrons of the Fe 2+ ion in a strong field of the clathrochelate ligand fully occupy three bonding d orbitals (t 2g 6 Ǟ e g 4 + a 1 2 ).…”

Section: Synthesis Of Complexesmentioning

confidence: 97%

“…The treatment of the hexachlorine-containing cobalt(II) precursors with aliphatic amines afforded unexpected clathrochelate products. It was shown earlier [7,8] that hexachlorine-containing iron(II) and ruthenium(II) precursors in most solvents (DMF, benzene, CH 2 Cl 2 , 1,4-dioxane, and the corresponding amine) reacted with sterically unhindered primary aliphatic amines (n-butylamine and cyclohexylamine) to yield tetraamine clathrochelates with functionalizing substituents in two of the three dioximate fragments, but only trisubstituted complexes have been isolated in chloroform media. [7,8] With sterically hindered tert-butylamine and secondary amines (in particular, diethylamine) in solvents with a high donor number, the formation of trifunctionalized iron(II) complexes monosubstituted in all three dioximate fragments was predominant, whereas only disubstituted products were formed in chloroform media.…”

Section: Synthesis Of Complexesmentioning

confidence: 98%

“…The same effect was observed in the case of their iron and ruthenium(II)-containing analogues. [4,7] The reduction of an encapsulated cobalt ion is responsible for the change in the color of the corresponding clathrochelate complexes from dark-brown to navy blue. The same blue color has been observed for the previously reported cobalt(I) complexes with nitrogen-containing ligands, [9] and it is determined by two highly intensive bands at approximately 15000 (ε ≈ 5-8 ϫ 10 3 mol -1 L cm -1 ) and 18500 (ε ≈ 4-7 ϫ 10 3 mol -1 L cm -1 ) cm -1 .…”

Section: Uv/vis Spectramentioning

confidence: 99%

“…[4,7] In the latter case, the synthesis of the hexaaryl-and hexaalkylsulfide clathrochelates was performed both with alkaline metal thiolates (RSH/MOR and RSH/M 2 CO 3 systems) in solvents with a high donor number (e.g., DMF and 1,4-dioxane) and with a RSH/triethylamine system in the aprotonic solvents with a low donor number (e.g., CH 2 C1 2 and CHCl 3 ). In the case of hexachlorine-containing cobalt(II) precursors, our attempts to use alkaline metal thiolates (C 6 H 5 SH/K 2 CO 3 and n-C 4 H 9 SH/K 2 CO 3 systems in 1,4-dioxane and DMF) as nucleophilic agents gave no target clathrochelates: their clathrochelate frameworks easily underwent a destruction with detachment of one of the three dioximate fragments to produce square-planar cobalt(II) dioximates.…”

Section: Synthesis Of Complexesmentioning

confidence: 99%

“…taneous impact of the following factors: (i) a high stability of the electronic configurations d 6 , d 7 , and d 8 in a strong macrobicyclic ligand field, (ii) a high affinity of these ions to the nitrogen donor atoms of the cage ligands [according to the Pearson hard soft acid base (HSAB) principle], and (iii) the fact that the cavity size of these ligands in different conformations [from a trigonal prism (TP) for the cobalt(I) and cobalt(II) ions to a trigonal antiprism (TAP) for the cobalt(III) ion] fits that of the high-spin Co + , the low-and high-spin Co 2+ , and the low-spin Co 3+ ions. In contrast, the iron and ruthenium ions form stable complexes of this type exclusively in the (2+) oxidation low-spin state.…”

Section: Introductionmentioning

confidence: 99%

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Tris‐Dioximate Cobalt(I,II,III) Clathrochelates: Stabilization of Different Oxidation and Spin States of an Encapsulated Metal Ion by Ribbed Functionalization

et al. 2010

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Boron-capped hexachlorine-containing cobalt(II) clathrochelates were prepared by means of template condensation of dichloroglyoxime (Cl 2 GmH 2 ) with boron-containing Lewis acids on a cobalt(II) ion matrix. The nucleophilic substitution of the reactive chlorine atoms of these macrobicyclic tris-dioximates with thiolate anions gave the hexasulfide cobalt(II) and dodecasulfide Co III Co II Co III mono-and bis-clathrochelates. The treatment of the hexachlorine-containing cobalt(II) precursors with primary aliphatic amines afforded hexaamine cobalt(III) clathrochelates. The reduction of these precursors led to the clathrochelate [Co(Cl 2 Gm) 3 (BR) 2 ] -anions, which were isolated as the salts with bulky organic cations. The relative stability of these cobalt(I) complexes accounted for a strong electronic effect of six electron-withdrawing ribbed chlorine substituents. Superconducting quantum interference device (SQUID) magnetometry, EPR, and multi-

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Section: Synthesis Of Complexesmentioning

confidence: 97%

Section: Synthesis Of Complexesmentioning

confidence: 98%

Section: Uv/vis Spectramentioning

confidence: 99%

Section: Synthesis Of Complexesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Tris‐Dioximate Cobalt(I,II,III) Clathrochelates: Stabilization of Different Oxidation and Spin States of an Encapsulated Metal Ion by Ribbed Functionalization

et al. 2010

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Tuning a Metal's Oxidation State: The Potential of Clathrochelate Systems

et al. 2005

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"Oxidation state" is one of most fundamental concepts in chemistry. The stabilization of previously unknown or unusual oxidation states of metal ions allows us to obtain results that are important both for theoretical inorganic chemistry and for the design of new molecular electronic devices, electrochromic materials, and electron-storage systems.Complexes with a metal ion encapsulated in a threedimensional macropolycyclic ligand cavity have undoubted promise in stabilizing unusual oxidation states of such caged ions. This is due to the fact that an encapsulated and coordinatively saturated metal ion is completely isolated from environmental factors (in particular, effects of solvation and additional coordination that exclude occurrence of redox processes by bridge mechanisms). The size of a three-dimensional ligand cavity may be controlled by changing the nature of the capping and chelating fragments of the macropolycyclic framework, and donor atoms (groups) that are optimal for stabilization of a desired electronic configuration of this ion may be chosen. [1] Varying the substituents on a clathrochelate framework is thought to be a new and unique opportunity to stabilize unusual oxidation states of an encapsulated metal ion: although the apical substituents in the capping fragments of the same type affect the electronic characteristics of ligand donor atoms (and, therefore, the encapsulated metal ion) to a very minor extent, [2] the influence of electron-donating (electron-withdrawing) substituents in chelate (ribbed) fragments with a system of conjugated p-bonds may prove to be crucial. [3] We suppose that the electron-withdrawing substituents in such fragments of a clathrochelate ligand stabilize the lowest oxidation states of an encapsulated metal ion. A new approach to the synthesis of cobalt(i) complexes uses a macrobicyclic hexachloride ligand with six strongly electronwithdrawing substituents in chelating p-conjugated a-dioximate fragments. The template condensation of dichloroglyoxime with the corresponding boron-containing Lewis acid on a Co 2+ ion matrix leads to formation of the brown n-butylborane-capped hexachloride cobalt(ii) clathrochelate [Co-{(Cl 2 Gm) 3 (Bn-C 4 H 9 ) 2 }] (1) in high yield (Gm = glyoxime).We were unable to oxidize, either chemically or electrochemically, the clathrochelate 1 to the corresponding cobalt-(iii) complex (the process is irreversible and is accompanied by destruction of the clathrochelate structure), but 1 easily undergoes a chemical reduction in acetonitrile solution with silver in the presence of tetraalkylammonium or tetra(dimethylamido)phosphonium halides to produce the dark-blue complex 1 À in high yield (Scheme 1). Analogous reductions were also carried out for phenylboronic and fluoroboronic hexachloride cobalt(ii) clathrochelates. The resulting tetraalkylammonium and tetra(dimethylamido)phosphonium salts of clathrochelate anions with an encapsulated Co + ion proved to be air-stable as solid for several months.The X-ray crystallography data for 1 and [(NMe 2 ...

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