Anion templating from a silver(i) dithiophosphate 1D polymer forming discrete cationic and neutral octa- and decanuclear silver(i) clusters.

We report on a Ag5 coordination polymer and discrete Ag8 and Ag10 dithiophosphate clusters. The cluster formation and structures were affected by the stoichiometric control of the M : L molar ratios used. The cluster [Ag5{S2P(O(i)Pr)2}4]n(PF6)n, , is a monomeric unit within a coordination polymer formed through the reaction between [Ag(CH3CN)4]PF6 and the dithiophosphate ligand, [S2P(O(i)Pr)2](-), used in a M : L molar ratio of 5 : 4. All other clusters formed in the study are discrete units with encapsulated anions within the metal framework. The clusters [Ag8(X){S2P(O(i)Pr)2}6](PF6) (X = F, , Cl, , Br, ) are all cationic and contain monoanionic halogens. The related cluster [Ag8(H/D){S2P(O(i)Pr)2}6](PF6) contains either a hydride or a deuteride ion, and , respectively. The cluster [Ag8(S){S2P(O(i)Pr)2}6], , is neutral due to the di-anionic nature of the encapsulated sulfide anion. Clusters were all formed by reacting [Ag(CH3CN)4]PF6 and [S2P(O(i)Pr)2](-) in a M : L molar ratio of 8 : 6 and stirring for 1 h in THF; thereafter the respective anions (one equiv.) were added in situ. The cluster [Ag10(I)4{S2P(O(i)Pr)2}6], , is also neutral due to the charge balancing of the additional metal and halogen. In this case the M : L : X molar ratio was 10 : 6 : 4. All new clusters were characterized by (1)H and (31)P NMR, and elemental analysis, and , , were characterized by single crystal X-ray diffraction.

Reversible phase transitions within self-assembled fibrillar networks of (R)-18-(n-alkylamino)octadecan-7-ols in their carbon tetrachloride gels.

The CCl(4) gel phases of a series of low-molecular-mass organogelators, (R)-18-(n-alkylamino)octadecan-7-ols (HSN-n, where n = 0-5, 18 is the alkyl chain length), appear to be unprecedented in that the fibrillar networks of some of the homologues undergo thermally reversible, gel-to-gel phase transitions, and some of those transitions are evident as opaque-transparent changes in the appearance of the samples. The gels have been examined at different concentrations and temperatures by a wide variety of spectroscopic, diffraction, thermal, and rheological techniques. Analyses of those data and data from the neat gelators have led to an understanding of the source of the gel-to-gel transitions. IR and SANS data implicate the expulsion (on heating the lower-temperature gel) or the inclusion (on cooling the higher-temperature gel) of molecules of CCl(4) that are interspersed between fibers in bundles. However, the root cause of the transitions is a consequence of changes in the molecular packing of the HSN-n within the fibers. This study offers opportunities to design new gelators that are capable of behaving in multiple fashions without entering the sol/solution phase, and it identifies a heretofore unknown transformation of organogels.

Reduction-sensitive, robust vesicles with a non-covalently modifiable surface as a multifunctional drug-delivery platform.

The design and synthesis of a novel reduction-sensitive, robust, and biocompatible vesicle (SSCB[6]VC) are reported, which is self-assembled from an amphiphilic cucurbit[6]uril (CB[6]) derivative that contains disulfide bonds between hexaethylene glycol units and a CB[6] core. The remarkable features of SSCB[6]VC include: 1) facile, non-destructive, non-covalent, and modular surface modification using exceptionally strong host-guest chemistry; 2) high structural stability; 3) facile internalization into targeted cells by receptor-mediated endocytosis, and 4) efficient triggered release of entrapped drugs in a reducing environment such as cytoplasm. Furthermore, a significantly increased cytotoxicity of the anticancer drug doxorubicin to cancer cells is demonstrated using doxorubicin-loaded SSCB[6]VC, the surface of which is decorated with functional moieties such as a folate-spermidine conjugate and fluorescein isothiocyanate-spermidine conjugate as targeting ligand and fluorescence imaging probe, respectively. SSCB[6]VC with such unique features can be used as a highly versatile multifunctional platform for targeted drug delivery, which may find useful applications in cancer therapy. This novel strategy based on supramolecular chemistry and the unique properties of CB[6] can be extended to design smart multifunctional materials for biomedical applications including gene delivery.

Anion-templated syntheses of octanuclear silver clusters from a silver dithiophosphate chain.

Extended chain polymers [Ag(5){S(2)P(OEt)(2)}(4)(PF(6))](n), (1) could be converted to clusters of the type, [Ag(8)(X){S(2)P(OEt)(2)}(6)](PF(6)) [X = F (2); Cl (3); H (4)], by the addition of appropriate anions, of which [Ag(8)(H){S(2)P(OEt)(2)}(6)](+) showed a unique tetracapped-tetrahedral Ag(8) core and contained Ag-mu-H-Ag linkages.

Synthesis and characterization of [Pb{Se2P(OiPr)2}2]n pseudo polymorphs: polymeric, single source precursor enabling preparation of shape-controlled lead selenide structures.

Novel lead pseudo polymorphs supported by diselenophosphate (dsep) ligands, [Pb{Se(2)P(O(i)Pr)(2)}(2)](n) (1alpha and 1beta), were synthesized and structurally characterized. The two structures differed in the binding modes of the dsep ligand. Each repeating unit in 1alpha was composed of a lead atom coordinated by two dsep ligands, one in a chelating mode and the other in a bridging-dangling mode. By contrast, the dsep ligands in 1beta adopted a bimetallic-biconnective (mu(1)-S, mu(1)-S) binding pattern. The bridging-dangling mode observed in 1alpha is the first example of this mode for the dsep ligand. [Pb{Se(2)P(O(i)Pr)(2)}(2)](n) could be successfully utilized as a single source precursor (SSP) for growing lead selenide (PbSe) nanostructures with different shapes via the solvothermal process. The morphologies of the as-grown PbSe structures were controlled by capping agents, poly(vinyl pyrrolidone) (PVP) and ethylenediamine, both bind on the {200} plane and enhance the growth rate of the <111> direction of the PbSe crystals, resulting in the formation of cubes and eight-horned rod dendrites, respectively. Raman spectroscopy was utilized to investigate the phonon vibration behaviour of the as-grown eight-horned rod dendrites. All peaks in the Raman spectra can be attributed to longitudinal (LO) and transverse (TO) optical phonon modes of the PbSe rod dendrites.

Stable silver(I) hydride complexes supported by diselenophosphate ligands.

The first stable structure of silver(I) cluster cations [Ag(8)(mu(4)-H){Se(2)P(OR)(2)}(6)](+) [R = (i)Pr, 1; Et, 2] containing Ag(I)-hydride bridges (Ag-mu-H-Ag) in T symmetry was reported. The clusters having an interstitial hydride were composed of an octanuclear silver core in tetracapped tetrahedral geometry, which was inscribed within a Se(12) icosahedron represented by six dialkyl diselenophosphate ligands in a tetrametallic-tetraconnective (mu(2), mu(2)) bonding mode. The presence of hydride was unequivocally corroborated by both (1)H and (109)Ag NMR spectroscopies of which a nonet in the (1)H NMR spectrum for the hydride resonance coupled with a doublet peak observed in the (109)Ag NMR spectrum clearly suggests that eight silver nuclei are equivalent in the NMR time scale and a fast exchange of the positions between the vertex and capping silver atoms in solution must occur. The hypothesis was also supported by a density functional theory (DFT) investigation on a simplified model [Ag(8)(H)(Se(2)PH(2))(6)](+), which confirmed that the Ag(8)H cubic core of T(h) symmetry may not be formed as it is energetically highly unfavorable (0.67 eV less stable than the T structure).

Octanuclear copper(I) clusters inscribed in a Se(12) icosahedron: anion-induced modulation of the core size and symmetry.

Synthesis and structural characterization of an octanuclear Cu(I) cluster [Cu(8){Se(2)P(O(i)Pr)(2)}(6)](PF(6))(2) (1) with an empty Cu(8) cubic core involving diisopropyl diselenophosphate (dsep) ligand has been demonstrated despite its high tendency to abstract anions even from the traces of impurities in the solvent. Reaction of 1 with anion sources (Bu(4)NF for F(-); NaBH(4) for H(-), and NaSH for S(2-)) in a 1:1 ratio produced anion-centered Cu(8) clusters with a formula [Cu(8)(X){Se(2)P(O(i)Pr)(2)}(6)](PF(6)) (X = F, 2a; H, 3a; D, 3a') and [Cu(8)(S){Se(2)P(O(i)Pr)(2)}(6)] (4) in high yields. In addition, fluoride- and hydride-centered Cu(8)(I) clusters [Cu(8)(X){Se(2)P(OEt)(2)}(6)](PF(6)) (X = F, 2b; H, 3b) could be generated in approximately 80% yield by direct reaction of [Cu(CH(3)CN)(4)](PF(6)), NH(4)Se(2)P(OEt)(2), and the anion sources (Bu(4)NF for F(-); NaBH(4) for H(-)) in 8:6:1 ratio. Whereas the structural elucidation of complexes 2 and 4 revealed an anion-centered cubic Cu(8) core surrounded by six dsep ligands, it was a tetracapped tetrahedral copper framework with a hydride in the center in compounds 3. All Cu...Cu distances along either the edge of the cube in 2 and 4 or the tetracapped tetrahedron in 3 are shorter than those identified in 1. Although the cubic (or spherical) contraction of the copper framework that was identified in a series of closed-shell anion-centered (except a hydride) Cu(8) cube having T(h) symmetry could be explained by the existence of strong anion-cation attractions, it was definitely a surprise that the hydride, which is the smallest closed-shell anion and spherical too, induced a tetrahedral contraction of four out of the eight Cu atoms in the empty cube 1, resulting in a tetracapped-tetrahedral geometry and reducing the symmetry to T from T(h). Furthermore the fact that the encapsulated anion induced modulation of the copper core size and symmetry was fully reproduced by DFT calculations on model compounds. To the best of our knowledge, this demonstrated the first example of the reduction of molecular symmetry (from T(h) to T) simply by changing the encapsulated species without altering the general bonding pattern of the surrounding ligands. We also demonstrated that the hydride can easily replace other anions (Cl(-), Br(-), F(-), S(2-), Se(2-)) in a very facile manner to produce hydride-centered species. Eventually, compounds 3 were stable in the presence of other anions, and hydride/deuteride exchange could not be achieved.

Conjugate base of a secondary phosphine selenide [P(Se)(O(i)Pr)2]- as the bridging unit for the construction of heterometallic Fe(II)-Hg(II)/Cd(II) complexes.

Reactions of perchlorate salts of Hg(II)/Cd(II) with [CpFe(CO)(2)P(Se)(O(i)Pr)(2)] (denoted as L) produced dicationic clusters [HgL(2)](ClO(4))(2), 1; [HgL(3)](ClO(4))(2), 2; and [CdL(3)(H(2)O)](ClO(4))(2), 11. However, the reactions of L with Hg(II)/Cd(II) halides yielded neutral complexes. For instance, HgI(2) produced [Hg(3)I(6)L(2)], 3, or [HgI(2)L(2)], 4, depending on the metal-to-ligand ratio used. Reaction of L with any of the Hg(II)/Cd(II) halides in a 1:1 ratio produced neutral clusters [HgX(mu-X)L](2) (M = Hg; X = Cl, 5; Br, 6; I, 7; M = Cd; X = Cl, 8; Br, 9; I, 10). Thus, variation of the M-to-L ratio made it possible for the formation of compounds with different metal/ligand stoichiometries only when ClO(4)(-) and I(-) salts of Hg(II) were used. Single-crystal X-ray crystallography revealed that two and three L units were connected to a Hg(II) via its Se atom in 1 and 2, respectively, whereas Hg(II) in 4 was connected to two "I" and two "L" units. An L (through its Se) and a terminal halogen were attached to each of the Hg(II)'s of the Hg(2)X(2) parallelogram core in 5 and 6. The cadmium complex 8, with a Cd(2)Cl(2) parallelogram core, was isostructural with the mercury complex 5. Although bonding and connectivity in 8 were similar to those in 9 and 10, the conformation of the bulky L ligands was unusually syn in 9 and 10, unlike the anti orientation in 5, 6, and 8. The syn conformation of L was also observed in compounds 1 and 2. Secondary interactions, namely, Se...Se interaction, the X...H-C type of H-bonding (X = halogen or Se), and pi-stacking, revealed in the structures played a role in determining the ligand conformation. The [P(Se)(O(i)Pr)(2)](-), the conjugate base of secondary phosphine selenide [HP(Se)(O(i)Pr)(2)], acted as a bridge with P bonded to Fe and Se bonded to Hg (or Cd) in these heterometallic clusters. Compound 5 further demonstrated a longer P-Se bond in the secondary phosphine selenide compared to that in isostructural, tertiary phosphine selenide metal complexes.

Facile entrapment of a hydride inside the tetracapped tetrahedral Cu(I)8 cage inscribed in a S12 icosahedral framework.

Reaction of [Cu(CH(3)CN)(4)](PF(6)) and NH(4)[S(2)P(OR)(2)] in a 4:3 ratio in acetone at room temperature produces octanuclear dicationic copper complexes [Cu(8){S(2)P(OR)(2)}(6)](PF(6))(2) (R = (i)Pr, 1; Et, 3) in 81 and 83% yields, respectively. On the other hand, reaction of [Cu(CH(3)CN)(4)](PF(6)), NH(4)[S(2)P(OR)(2)], and NaBH(4) in an 8:6:1 molar ratio in THF for 1 h yields [Cu(4)(H)(mu(3)-Cu)(4){S(2)P(OR)(2)}(6)](PF(6)) (R = (i)Pr, 2a; Et, 4a) in 87 and 82% yields, respectively. In a similar reaction when NaBD(4) is used instead of NaBH(4), [Cu(4)(D)(mu(3)-Cu)(4){S(2)P(OR)(2)}(6)](PF(6)) (R = (i)Pr, 2b; Et, 4b) are obtained in 83 and 78% yields, respectively. Structural elucidations of 2a and 4a reveal the tetracapped tetrahedral Cu(8) cage with an interstitial hydride. Each of the Cu(I) centers is trigonally coordinated by three S atoms, and each of the six dithiophosphate ligands is connected to a Cu(4) butterfly, where the hinge positions are occupied by two copper atoms situated at the vertex of the central tetrahedron and the wingtips are two capping Cu atoms. The 12 S atoms out of the six ligands constitute an icosahedron around the hydride-centered tetracapped tetrahedral Cu(8) framework. Surprisingly, empty Cu(8) clusters 1 and 3 can abstract hydride (or deuteride) from NaBH(4) (or NaBD(4)) in THF to form 2a and 4a (or 2b and 4b), respectively. Apparently the cubic Cu(8) core, which is known to be formed in the reaction of Cu(I) salt and dichalcogenophosph(in)ate ligands, undergoes a tetrahedral contraction due to the strong Cu...H interactions. Interestingly, the chloride can also be replaced from the chloride-centered Cu(8) complex of [Cu(8)(Cl){S(2)P(OEt)(2)}(6)](PF(6)) by hydride (or deuteride) to form 2a and 4a (or 2b and 4b). However, the hydride- and deuteride-centered compounds 2a,b and 4a,b do not allow the guest exchange.

The coordination chemistry of selenophosphite ligands. Synthesis and characterization of heterometallic tetranuclear clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)) (M = Cu, Ag; R = (n)Pr, (i)Pr) and [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, Br).

A neutral selenium donor ligand, [CpFe(CO)(2)P(Se)(OR)(2)] is used for the construction of Cu(I) and Ag(I) complexes with a well-defined coordination environment. Four clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)), (where M = Cu, R = (n)Pr, ; R = (i)Pr, and M = Ag, R = (n)Pr, ; R = (i)Pr, ) are isolated from the reaction of [M(CH(3)CN)(4)(PF(6))] (where M = Cu or Ag) and [CpFe(CO)(2)P(Se)(OR)(2)] in a molar ratio of 1 : 3 in acetonitrile at 0 degrees C. The reaction of [CpFe(CO)(2)P(Se)(O(i)Pr)(2)] with cuprous halides in acetone produce two mixed-metal, Cu(I)(2)Fe(II)(2) clusters, [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, ; Br, ). All six clusters have been fully characterized spectroscopically ((1)H, (13)C, (31)P, and (77)Se NMR, IR), and by elemental analyses. X-Ray crystal structures of and consist of discrete cationic clusters in which three iron-selenophosphito fragments are linked to the central copper or silver atom via selenium atoms. Both clusters and crystallize in the noncentrosymmetric, hexagonal space group P6[combining macron]2c. The coordination geometry around the copper or silver atom is perfect trigonal-planar with Cu-Se and Ag-Se distances, 2.3505(7) and 2.5581(7) A, respectively. X-Ray crystallography also reveals that each copper center in neutral heterometallic clusters and is trigonally coordinated to two halide ions and a selenium atom from the selenophosphito-iron moiety. The structures can also be delineated as a dimeric unit which is generated by an inversion center and has a Cu(2)X(2) parallelogram core. The dihedral angle between the Cu(2)X(2) plane and the plane composed of Cp ring is found to be 24.62 and 84.58 degrees for compound and , respectively. Hence the faces of two opposite Cp rings are oriented almost perpendicular to the Cu(2)X(2) plane in , but are close to be parallel in . This is the first report of the coordination chemistry of the anionic selenophosphito moiety [(RO)(2)PSe](-), the conjugated base of a secondary phosphine selenide, which acts as a bridging ligand with P-coordination on iron and Se-coordination to copper or silver.

Phosphonate- and ester-substituted 2-cyanoethylene-1,1-dithiolate clusters of zinc: aerial CO2 fixation and unusual binding patterns.

Treatment of [Zn(tmeda)Cl2] (tmeda = N, N, N', N'-tetramethylethylenediamine) with a phosphonate-substituted 2-cyanoethylene-1,1-dithiolato ligand in air yields a tetranuclear zinc-carbonate complex 1 having the formula of [Zn4(tmeda)3(mu3-CO3){S2CC(CN)P(O)(OEt)2}3] in which four zinc atoms form a trigonal pyramid with the apical zinc atom in a hitherto unknown S3O3 coordination sphere. It is the first example of aerial CO2 fixation to afford a metal-carbonato compound incorporating 1,1-ethenedithiolate ligands. In sharp contrast, reaction with an isobutyl ester-substituted 2-cyanoethylene-1,1-dithiolate forms a trimeric zinc complex [Zn(tmeda){S2CC(CN)(CO2(i)Bu)}]3, 2, which does not contain the metal-bound carbonate. Compound 2 is the first example of a trinuclear zinc complex composed of four-, five-, and six-coordinated Zn atoms. The unsymmetrical ligand orientation around three zinc centers in 2 suggests that the other structural isomer, which would have an idealized C3 axis, may exist. The reaction of the ethyl ester derivative of 2-cyanoethylene-1,1-dithiolate with [Zn(tmeda)Cl2] affords [{Zn(tmeda)Cl}2{S2CC(CN)(CO2Et)}], 3. The ester-functionalized 1,1-dithiolate ligands in compounds 2 and 3 display a bimetallic, triconnective coordination mode, which is rare for these types of ligands. Some probable intermediates generated from the formation of compound 1 have also been proposed.

Metal binding characteristics of a laterally nonsymmetric aza cryptand upon functionalization with a pi-acceptor group.

The laterally nonsymmetric aza cryptand synthesized by condensing tris(2-aminoethyl)amine (tren) with tris[[2-(3-(oxomethyl)phenyl)oxy]ethyl]amine readily forms mononuclear inclusion complexes with both transition and main-group metal ions. In these complexes, the metal ion occupies the tren-end of the cavity making bonds with the three secondary amino and the bridgehead N atoms. When a strong pi-acceptor group such as 2,4-dinitrobenzene is attached to one of the secondary amines, the binding property of the cryptand changes drastically. When perchlorate or tetrafluoroborate salts of Ni(II), Cu(II), Zn(II), or Cd(II) are used, the metal ion enters the cavity which can be monitored by the hypsochromic shift of the intramolecular charge-transfer transition from the donor amino N atom to the acceptor dinitrobenzene. However, in the presence of coordinating ions such as Cl(-), N(3)(-), and SCN(-), the metal ion comes out of the cavity and binds the cryptand outside the cavity at a site away from the dinitrobenzene moiety. Four such complexes are characterized by X-ray crystallography. Thus, a metal ion can translocate between inside and outside of the cryptand cavity depending upon the nature of the counter anion.