Synthesis and X-ray Powder Structures of Two Lamellar Copper Arylenebis(phosphonates)

Reaction of copper salts with 1,4-phenylenebis(phosphonic acid) yielded a conventional layered compound, Cu(2)[(O(3)PC(6)H(4)PO(3))(H(2)O)(2)], while a similar reaction with 4,4'-biphenylenebis(phosphonic acid) resulted in a new lamellar structure with composition Cu[HO(3)P(C(6)H(4))(2)PO(3)H]. The structures of these compounds were solved ab initio by using X-ray powder diffraction data. The crystals of the phenylenebis(phosphonate) compound are monoclinic, space group C2/c, with a = 18.8892(4) ?, b = 7.6222(2) ?, c = 7.4641(2) ?, beta = 90.402(2) degrees, and Z = 4. The layer structure in this case is similar to that in copper phenylphosphonate, Cu[O(3)PC(6)H(5)]. The metal atoms display a distorted square pyramidal geometry where four of the coordination sites are occupied by the phosphonate oxygens. The remaining site is filled by an oxygen atom of the water molecule. Adjacent metal-O(3)PC layers are covalently pillared by the phenyl group of the phosphonates to create a 3-dimensional structure. Cu[HO(3)P(C(6)H(4))(2)PO(3)H] is triclinic, space group P&onemacr;, with a = 4.856(2) ?, b = 14.225(5) ?, c = 4.788(2) ?, alpha = 97.85(1) degrees, beta = 110.14(1) degrees, gamma = 89.38(1) degrees, and Z = 1. The structure in this case, ideally consists of linear chains of copper atoms. The copper atoms are bridged by centrosymmetrically related phosphonate groups utilizing two of their oxygen atoms. This binding mode leads to square planar geometry for the copper atoms. The third oxygen atom of the phosphonate is protonated and is involved in linking adjacent linear chains through hydrogen bonds. At the same time, these hydroxyl oxygens interact weakly (Cu-O = 3.14 ?) with the copper atoms of the adjacent chain. Considering these long Cu-O interactions, the geometry of the copper atom may be described as distorted square bipyramidal. As in the phenylphosphonate structure, the biphenyl groups covalently link the Cu-O(3)PC networks in the perpendicular direction.     

Synthesis, characterization, and crystal structures of three new divalent metal carboxylate-sulfonates with a layered and one-dimensional structure

Hydrothermal reactions of 5-sulfoisophthalic acid (HO(3)SC(6)H(3)-1,3-(CO(2)H)(2), H(3)L) with M(II) carbonate (or oxide) and 4,4'-bipyridine (4,4'-bipy) (or 2,2'-bipyridine, 2,2'-bipy) resulted in three new metal carboxylate-sulfonate hybrids, namely, [CdL(H-4,4'-bipy)] (1) and [Cd(3)L(2)(2,2-bipy)(4)(H(2)O)(2)].2H(2)O (2) with layered structures and [ZnL(H-4,4'-bipy)(H(2)O)].2H(2)O (3), whose structure features a one-dimensional double chain. The cadmium(II) ion in complex 1 is seven-coordinated by five carboxylate oxygen atoms and one sulfonate oxygen atom from four ligands and a unidentate 4,4'-bipyridine. The interconnection of the cadmium(II) ions through bridging carboxylate-sulfonate ligands resulted in the formation of a <002> double layer with the bipyridyl rings orientated toward the interlayer space. Complex 2 has a different layered structure. Cd(1) is seven-coordinated by two bidentate chelating carboxylate groups from two ligands, a bidentate chelating 2,2'-bipy and an aqua ligand, and Cd(2) is octahedrally coordinated by two bidentate chelating 2,2'-bipy's, a sulfonate oxygen, and an aqua ligand. The coordination geometry around Cd(3) is similar to that of Cd(1) with the aqua ligand being replaced by an oxygen atom from the sulfonate group. The carboxylate-sulfonate ligand acts as pentadentate ligand, bridging with three cadmium(II) ions. The bridging of cadmium(II) ions through the carboxylate-sulfonate ligands resulted in the formation of <006> and <003> layers; the 2,2'-bipy molecules and [Cd(2)(2,2'-bipy)(2)(H(2)O)] cations are orientated to the interlayer space. Complex 3 features a 1D metal carboxylate-sulfonate double chain along the diagonal of the a- and b-axes. The zinc(II) ion is octahedrally coordinated by four carboxylate O atoms from three ligands, a unidentate 4,4'-bipy, and an aqua ligand. Each pair of zinc(II) ions is bridged by two carboxylate groups from two ligands to form a dimer, and such dimeric units are interconnected by bridging ligands to form a double chain. The sulfonate group of the carboxylate sulfonate ligand remains noncoordinated and forms a number of hydrogen bonds with aqua ligands as well as lattice water molecules.     

Conformational analysis—IV: A lanthanide induced shift (LIS) NMR investigation of the conformation and relative conformer energies of trans and cis 2-decalone

The solution conformation of trans-2-decalone and the conformational population of cis-2-decalone has been determined by LIS analysis. The angle of pucker (α) of the ketone ring in trans-2-decalone is 51 ± 2°, identical to that of cyclohexanone, but different from that determined for substituted decalones in the solid state, in which significant flattening of the ring occurs.The steroidal conformer of cis-2-decalone, when the latter is complexed to Yb(fod)₃ in CDCl₃, found to be preferred over the non-steroidal conformer by a ratio of 55:45, in contrast to the preference reported from the low temperature ¹³C NMR spectrum for the non complexed ketone in CH₂Cl₂. The two determinations can be combined to give the enthalpy difference in favor of the non-steroidal conformer of ca 0.8 kcal mole^?1.     

Revealing the bonding of solvated Ru complexes with valence-to-core resonant inelastic X-ray scattering

Ru-complexes are widely studied because of their use in biological applications and photoconversion technologies. We reveal novel insights into the chemical bonding of a series of Ru(ii)- and Ru(iii)-complexes by leveraging recent advances in high-energy-resolution tender X-ray spectroscopy and theoretical calculations. We perform Ru 2p4d resonant inelastic X-ray scattering (RIXS) to probe the valence excitations in dilute solvated Ru-complexes. Combining these experiments with a newly developed theoretical approach based on time-dependent density functional theory, we assign the spectral features and quantify the metal–ligand bonding interactions. The valence-to-core RIXS features uniquely identify the metal-centered and charge transfer states and allow extracting the ligand-field splitting for all the complexes. The combined experimental and theoretical approach described here is shown to reliably characterize the ground and excited valence states of Ru complexes, and serve as a basis for future investigations of ruthenium, or other 4d metals active sites, in biological and chemical applications.

Combined experimental and theoretical Ru 2p4d resonant inelastic X-ray scattering study probes the chemical bonding and the valence excited states of solvated Ru complexes.     

Hydrothermal synthesis and crystal structures of new uranyl oxalate hydroxides: α- and β-[(UO2)2(C2O4)(OH)2(H2O)2] and [(UO2)2(C2O4)(OH)2(H2O)2]·H2O

Two modifications of the new uranyl oxalate hydroxide dihydrate [UO₂)₂(C₂O₄)(OH)₂(H₂O)₂] (1 and 2) and one form of the new uranyl oxalate hydroxide trihydrate [(UO₂)₂(C₂O₄)(OH)₂(H₂O)₂]·H₂O (3) were synthesized by hydrothermal methods and their structures determined from single-crystal X-ray diffraction data. The crystal structures were refined by full-matrix least-squares methods to agreement indices R(wR)=0.0372(0.0842) and 0.0267(0.0671) calculated for 1096 and 1167 unique observed reflections (I>2σ(I)), for α (1) and β (2) forms, respectively and to R(wR)=0.0301(0.0737) calculated for 2471 unique observed reflections (I>2σ(I)), for 3. The α-form of the dihydrate is triclinic, space group , Z=1, a=6.097(2), b=5.548(2), , α=89.353(5), β=94.387(5), γ=97.646(5)°, , β-form is monoclinic, space group C2/c, Z=4, a=12.180(3), b=8.223(2), , β=95.817(4), . The trihydrate is monoclinic, space group P2₁/c, Z=4, a=5.5095(12), b=15.195(3), , β=93.927(3), . In the three structures, the coordination of uranium atom is a pentagonal bipyramid composed of dioxo UO₂²⁺ cation perpendicular to five equatorial oxygen atoms belonging to one bidentate oxalate ion, one water molecule and two hydroxyl ions in trans configuration in 2 and in cis configuration in 1 and 3. The UO₇ polyhedra are linked through hydroxyl oxygen atoms to form different structural building units, dimers [U₂O₁₀] obtained by edge-sharing in 1, chains [UO₆]_∞ and tetramers [U₄O₂₆] built by corner-sharing in 2 and 3, respectively. These units are further connected by oxalate entities that act as bis-bidentate to form one-dimensional chains in 1 and bi-dimensional network in 2 and 3. These chains or layers are connected in frameworks by hydrogen-bond arrays.     

Steroid derivatives of purine-6(1H)-thione (1a-c)

The products obtained as a result of the alkylation of purine-6(1H)-thione, and 6-alkylthiopurines with steroidal-21-(p-bromobenzenesullonates) (H) and 3-methoxy-16α-bromoestra-1,3,5 (10)-tricne-17-one (IV) is reported. The ratio of 9-alkylated to 7-alkylated purine in the alkylation of 6-methylthiopurine (VI) is presented. The use of the S-diphenylmethylprotecling group in the syntheses of sensitive 9-steroidal-9H-purine-6(1H)-thiones is discussed.     

Controlled release of 4-hydroperoxycyclophosphamide from the fatty acid dimer-sebacic acid copolymer

Controlled polymeric release of chemotherapeutic agents has shown promise in the management of malignant gliomas. 4-Hydroperoxycyclophosphamide (4HC), loaded on the fatty acid dimer–sebacic acid copolymer (FAD:SA, 1:1), significantly prolonged survival in rats implanted with F98 and 9L gliomas. Here, we studied the in vitro and in vivo release kinetics in phosphate-buffered saline and rat brain of 20% 4HC/FAD:SA (wt:wt), the optimal dose for treatment of rat gliomas. In vitro release under infinite sink conditions was steady over the initial 12 hr to a peak of 20–35% of impregnated drug, consistent with early phase control via surface erosion. Release over the next 3 weeks was minimal, consistent with barrier formation around the polymer by an oily fatty acid dimer degradation product and consequent slowing of release. However, the polymer started to disintegrate by day 4, and there were minimal visible remnants by 3 weeks. Thus, a considerable amount of polymer-carried drug was probably lost in the disintegrating fragments. Also, drug loss is expected from its inherent hydrolytic instability. In vivo release into brain revealed two peak levels of drug at 0–1 hr and 5–20 days. With loaded polymer implanted intraperitoneally or cyclophosphamide injected systemically, peak brain drug levels were measured in 2–8 hr, with substantial decrease by 48 hr without a second peak. Brain levels were substantially higher than blood levels at all time periods. We conclude that FAD:SA (1:1) adequately protects the otherwise labile 4HC, allowing effective and substained drug release in vivo. Furthermore, it should be possible to modify the polymer to adjust the time of peak release for more beneficial therapeutic effects.