D. G. Samsonenko

Cucurbituril as a New Macrocyclic Ligand for Complexation of Lanthanide Cations in Aqueous Solutions

(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Highly Efficient, Regioselective, and Stereospecific Oxidation of Aliphatic C–H Groups with H2O2, Catalyzed by Aminopyridine Manganese Complexes

Aminopyridine manganese complexes [LMn(II)(OTf)(2)] having a similar coordination topology catalyze the oxidation of unactivated aliphatic C-H groups with H(2)O(2), demonstrating excellent efficiency (up to TON = 970), site selectivity, and stereospecificity (up to >99%).

Synthesis, crystal structures, luminescent and thermal properties of two new metal–organic coordination polymers based on zinc(II) carboxylates

Two new metal–organic coordination polymers, [NH2(CH3)2]2[Zn3(bdc)4]·DMF·H2O (1) (H2bdc = 1,4-benzenedicarboxylic acid) and [NH2(CH3)2]2[Zn3(bpdc)4]·5DMF (2) (H2bpdc = 4,4′-biphenyldicarboxylic acid), were synthesized by heating a DMF solution of Zn(NO3)2·6H2O, [NH2(CH3)2]Cl and organic carboxylic acids. Single-crystal X-ray structure analysis reveals that these compounds have 3D anionic framework structures built from zinc(II) carboxylate layers linked by carboxylate anions. Compounds 1 and 2 were characterized by IR, TGA and XRPD, and their luminescent properties were also investigated.

Synthesis and crystal structure of the nanosized supramolecular SmIII complex with macrocyclic cavitand cucurbituril {[Sm(H2O)4]2(C36H36N24O12)3}Br6.44H2O

The supramolecular compound {[Sm(H2O)4]2(Cuc)3}Br6·44H2O (Cuc = C36H36N24O12) was synthesized. Its crystal and molecular structure was established by X-ray diffraction analysis. The binuclear complex cation {(Cuc)[Sm(H2O)4](Cuc)[Sm(H2O)4](Cuc)}6+ built from the alternating cucurbituril molecules (C36H36N24O12) and the [Sm(H2O)4]3+ aqua ions is a triple-decker nanosized (33 Å) sandwich.

Synthesis and crystal structures of sumpramolecular compounds of cucurbit[n]urils (n = 6, 8) with polynuclear strontium aqua complexes

Crystals of the {[Sr4(H2O)12(NO3)4](C36H36N24O12)}(NO3)4·3H2O and {[Sr2(H2O)12][Sr(H2O)3(NO3)2]2(C48H48N32O16)}(NO3)4·8H2O were prepared by slow concentration of aqueous solutions containing strontium nitrate and macrocyclic cavitands, viz., cucurbit[6]uril and cucurbit[8]uril ([C6H6N4O2]n, n = 6 and 8), respectively. According to the results of X-ray diffraction analysis, the crystal structures of these supramolecular compounds are built from polymeric chains, which consist of the alternating cucurbit[n]uril molecules and Sr2+ cations linked through the bridging aqua ligands and nitrate anions. The supramolecular compound of cucurbit[8]uril provides the first example of compounds in which this macrocycle is bound to metal aqua complexes.

Titanium salan catalysts for the asymmetric epoxidation of alkenes: steric and electronic factors governing the activity and enantioselectivity.

A new insight into the highly enantioselective (up to >99.5 % ee) epoxidation of olefins in the presence of chiral titanium(IV) salan complexes is reported. A series of 14 chiral ligands with varying steric and electronic properties have been designed, and it was found that electronic effects modulate the catalytic activity (without affecting the enantioselectivity), whereas the steric properties account for the enantioselectivity of the epoxidation. Competitive oxidations of p-substituted styrenes reveal the electrophilic nature of the oxygen-transferring active species, with a Hammett ρ value of -0.51; the enantioselectivity is unaffected by the electron-donating (or withdrawing) ability of the p-substituents. Mechanistic studies provide evidence in favor of a stepwise reaction mechanism: in the first (rate-determining) stage, olefin most probably coordinates to the active species, followed by intramolecular enantioselective oxygen transfer. The enantioselectivity increases with decreasing temperature. The modified Eyring plots for the epoxidation of styrene and (Z)-β-methylstyrene are linear, indicating a single, enthalpy-controlled mechanism of stereoselectivity, with ΔΔH(≠) =-6.6 kJ mol(-1) and -5.4 kJ mol(-1) , respectively.

Synthesis and crystal structure of supramolecular adduct of tetranuclear uranyl chloride aquacomplex with macrocyclic cavitand cucurbituril

Crystals of supramolecular compound {[(UO2)4O2Cl4(H2O)6](H2O⊂C36H36N24O12)}·4H2O were obtained under conditions of hydrothermal synthesis from solutions of uranyl(vi) nitrate and cucurbituril in the presence of rubidium chloride. The crystal and molecular structure were determined by X-ray diffraction analysis.

DISTORTION OF THE CUCURBITURIL MOLECULE BY AN INCLUDED 4-METHYLPYRIDINUM CATION

The crystal and molecular structures of a “guest–host” complex of cucurbituril with 4‐methylpyridinium, {(4‐MePyH) ⊂ (C36H36N24O12)}(NO3) · 4H2O, were determined by X‐ray structural analysis. The crystals are monoclinic with a = 26.276(3) Å, b = 25.861(2) Å, c = 17.375(2) Å, β = 124.17(1)°, Vcell =9768.6(18) Å3, space group Cc, and Z = 8. The structure contains two crystallographically independent supramolecular complexes. They are arranged in pillars oriented along the a axis. In each pillar, the complexes are parallel to each other. The pillars are shifted with respect to each other by one‐half of the crystallographic translation. The centers of the supermolecules are arranged according to a pseudo‐body‐centered motif. Distortions of the cucurbituril molecule depending on the guest type have been analyzed with the use of results obtained in the present and previous studies.

Crystal Structure of the Ca2+ Supramolecular Complex with Cucurbituryl {[Ca(H2O)3(HSO4)(CH3OH)]2(C36N24O12H36)}(HSO4)2 · 4H2O

AbstractThe calcium(II) supramolecular complex with cucurbituryl of composition {[Ca(H2O)3(HSO4)(CH3OH)]2(C36N24O12H36)}(HSO4)2 · 4H2O is obtained by slow diffusion of methanol into a calcium(II) solution in 2 M H2SO4; its crystal structure is determined by X-ray diffraction analysis. The crystals are triclinic, a = 10.4030(9) Å, b = 11.936(1) Å, c = 15.119(1) Å, α = 69.829(6)°, β = 72.019(5)°, γ = 70.171(7)°, V = 1618.1(2) Å3, space group P