Efficient electrosorption of uranium(VI) by B,N, and P co-doped porous carbon materials containing phosphate functional groups

Journal of Solid State Electrochemistry - In this paper, polyphosphazene was synthesized as precursors using benzene-1,4-diboronic acid and hexachlorocyclotriphosphazene (HCCP) by a simple one-step...     

Poly(β-pinenes) carrying one,two, and three functional end groups. II. Syntheses and characterization

Conditions for the convenient synthesis of linear poly(β-pinenes) that carry one or two tert-chloro end groups (～Cl^t) and three-arm star poly(β-pinenes) that carry three termini have been worked out. Specifically, the polymer with one ～Cl^t end group was prepared by the H₂O/BCl₃ system, whereas those with two and three ～Cl^t termini were prepared by the use of p-dicumyl chloride and sym-tricumyl chloride/BCl₃ inifer combinations. The ～Cl^t-terminated polymers were dehydro-chlorinated to yield the corresponding olefins. The molecular weights of the products were low enough to permit infrared (IR) and quantitative ¹H-NMR investigations. Poly(β-pinene-b-tetrahydrofuran) diblock copolymers have been synthesized by inducing the polymerization of tetrahydrofuran (THF) by the Pβ? Cl^t/AgCF₃SO₃ initiating system.     

Protonation of Chloro-, Bromo- and Iodo-pentacyanocobaltate(III) Complexes

The reactions between Fe(Phen)₃²⁺[phen = tris-(1,10) phenanthroline] and Co(CN)₅X³⁻ (X = Cl, Br or I) have been studied in aqueous acidic solutions at 25 °C and ionic strength in the range I = 0.001–0.02 mol dm⁻³ (NaCl/HCl). Plots of k₂ versus √I, applying Debye–Huckel Theory, gave the values −1.79 ± 0.18, −1.65 ± 0.18 and 1.81 ± 0.10 as the product of charges (Z_AZ_B) for the reactions of Fe(Phen)₃²⁺ with the chloro-, bromo- and iodo- complexes respectively. Z_AZ_B of ≈ −2 suggests that the charge on these Co^III complexes cannot be −3 but is −1. This suggests the possibility of protonation of these Co^III complexes. Protonation was investigated over the range [H⁺] = 0.0001 −0.06 mol dm⁻³ and the protonation constants K_a obtained are 1.22 × 10³, 7.31 × 10³ and 9.90 × 10² dm⁶ mol⁻³ for X = Cl, Br and I, respectively.     

Reactions of the tetrahedral clusters [MCo(3)(CO)(12)](-) (M = Ru, Fe) with functional mono- and diynes

The tetrahedral cluster [RuCo(3)(CO)(12)](-) reacts with various alkynes, including the new PhCtbd1;CC(O)NHCH(2)Ctbd1;CH (L(1)()), to afford the butterfly clusters [RuCo(3)(CO)(10)(micro(4)-eta(2)-RC(2)R')](-) (1, R = R' = C(O)OMe; 2, R = H, R' = Ph; 3, R = H, R' = MeC=CH(2); 4, R = H, R' = CH(2)OCH(2)Ctbd1;CH; 5, R = H, R' = CH(2)NHC(O)Ctbd1;CPh), in which the ruthenium atom occupies a hinge position and the alkyne is coordinated in a micro(4)-eta(2) fashion. Reaction of the anions 1-3 with [Cu(NCMe)(4)]BF(4) led to selective loss of the 12e fragment Co(CO)(-) to form [RuCo(2)(CO)(9)(micro(3)-eta(2)-RC(2)R')] (6, R = R' = C(O)OMe; 7, R = H, R' = Ph; 8, R = H, R' = MeC=CH(2)). To prepare functionalized RuCo(3) or FeCo(3) clusters that could be subsequently condensed with a silica matrix via the sol-gel method, we reacted [MCo(3)(CO)(12)](-) (M = Ru, Fe) with the alkyne PhCtbd1;CC(O)NH(CH(2))(3)Si(OMe)(3)(L(2)()) and obtained the butterfly clusters [MCo(3)(CO)(10)(micro(4)-eta(2)-PhC(2)C(O)NH(CH(2))(3)Si(OMe)(3))](-) 9 and 10, respectively. Air-stable [RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))](-) (11) was obtained from 1,4-bis(trimethylsilyl)butadiyne and reacted with [Cu(NCMe)(4)]BF(4) to give [RuCo(2)(CO)(9)(micro(3)-eta(2)-HC(2)Ctbd1;CSiMe(3))] (12), owing to partial ligand proto-desilylation, and not the expected [RuCo(2)(CO)(9)(micro(3)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))]. Reaction of 11 with [NO]BF(4) afforded, in addition to 12, [RuCo(3)(CO)(9)(NO)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))] (13) owing to selective CO substitution on a wing-tip cobalt atom with NO. The thermal reaction of 11 with [AuCl(PPh(3))] led to replacement of a CO on Ru by the PPh(3) originating from [AuCl(PPh(3))] and afforded [RuCo(3)(CO)(9)(PPh(3))(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CSiMe(3))](-) (14), also obtained directly by reaction of 11 with one equivalent of PPh(3). Proto-desilylation of 11 using TBAF/THF-H(2)O afforded [RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;CH)](-) (15) which, by Sonogashira coupling with 1,4-diiodobenzene, yielded the dicluster complex [[RuCo(3)(CO)(10)(micro(4)-eta(2)-Me(3)SiC(2)Ctbd1;C)]](2)C(6)H(4)](2)(-) (16). The crystal structures of NEt(4).3a, NEt(4).4a, 6, NEt(4).11b, NEt(4).14, and [N(n-Bu)(4)].15a have been determined by X-ray diffraction. Preliminary results indicate the potential of silica-tethered alkyne mixed-metal clusters, obtained by the sol-gel method, as precursors to bimetallic particles.     

Protonation equilibria of nitrilotris(methylenephosphonato)-and ethylenediamine-tetrakis(methylenephosphonato)-complexes of scandium,yttrium, and lanthanoids

The protonation equilibria of nitrilotris(methylenephosphonic acid) (NTMP, H₆L) and ethylenediaminetetrakis(methylenephosphonic acid) (EDTMP, H₈L) complexes of scandium, yttrium, and lanthanoids have been studied potentiometrically at 25°C and at an ionic strength of 0.1 mol-dm^–3 KNO₃. The first protonation constants of NTMP complexes of lanthanoids, K _MHL , decrease with decreasing of the ionic radius of the lanthanoid [log K _MHL =7.82 (La³⁺) –6.90 (Lu³⁺)] and show a so-called Tetrad effect. The second protonation constants, K _{MH 2}L, change very little with the lanthanoid metal ions (logK _{MH 2}L=5.3–5.7). These results suggest that, in the first protonation process in ML, the proton attacks the nitrogen of NTMP rupturing the M-N of M(ntmp)^3–. The pattern of the change in the protonation constants of the EDTMP complexes with the atomic number of the lanthanoid is quite different from that of the NTMP complexes. This fact indicates that the manner of protonation of the EDTMP complexes differs from that of NTMP complexes. The protonation constants of yttrium complexes of NTMP and EDTMP agree with those of lanthanoid complexes, whereas those of scandium complexes deviate from the values predicted from its ionic radius.     

Easily grafted polyurethanes with reactive main chain functional groups. Synthesis,characterization, and antithrombogenicity of poly(ethylene glycol)-grafted poly(urethanes)

A novel synthesis of poly(ethylene glycol) (PEG)-grafted poly(urethanes) (PURs) is described based on a precursor PUR containing free amino groups in the main chain. Three different poly(urethane) backbones were prepared: a homopoly(urethane) comprised of N-Bocdiethanolamine (BDA) and 4,4′-methylenebis(phenyl isocyanate) (MDI), a copoly(urethane) (COPUR) consisting of BDA, N-benzyldiethanolamine and MDI, and a poly(urethane urea) (PUU) that was prepared from BDA, MDI, and ethylenediamine as the chain extender. The M_n of these poly(urethanes) ranged from 32,000 to 72,000 g/mol. PEG (750, 1,900, and 5,000 g/mol) was grafted onto the boc-deprotected poly(urethanes) via the chloroformate. Films of the polymers were spin cast from dilute solutions, annealed, and the surfaces analyzed by goniometry. Water contact angle data indicates increasing PEG surface coverage of the poly(urethanes) with increasing PEG molecular weight. Reorientation of the polymer films is evidenced by contact angle hysteresis. Polymer thrombogenicity, which was studied using blood perfusion experiments, shows that COPUR-g-PEG5000 and PUU-g-PEG5000 exhibit very little platelet adhesion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3441–3448, 1999     

Syntheses,characterization, and functionalization of poly(ester amide)s with pendant amine functional groups

Poly(ester amide)s (PEAs) comprising α‐amino acids, diols, and diacids are promising materials for biomedical applications such as tissue engineering and drug delivery because of their tunability and potential for either hydrolytic or enzymatic degradation. Although a number of PEAs of different compositions have been reported, there is a significant need for the incorporation of amino acids with functional side chains. This will allow for the conjugation of drugs or cell signaling molecules in tissue engineering scaffolds, thus expanding the potential applications of these materials. The objective of this work was the incorporation of l ‐lysine into PEAs to provide functionalizable pendant amine groups. Thus, varying percentages of lysine were incorporated into PEAs comprised of l ‐phenylalanine, 1,4‐butanediol, and succinic acid by tuning the ratio of ε‐protected‐l ‐lysine and l ‐phenylalanine derived monomers. The polymers were characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, and differential scanning calorimetry. The lysine ε‐protecting group was removed, then the reactivity of the pendant amines was demonstrated by reaction with amino acid and tri(ethylene glycol) derivatives. The degradation of thin films of polymers were studied using scanning electron microscopy and the incorporation of lysine was found to significantly accelerate both the hydrolytic and enzymatic degradation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6376–6392, 2008     

Synthesis and characterization of poly(N-acyl or N-aroyl ethylenimines) containing various pendant functional groups. I. Copolymers with pendant olefin groups

Decenyl (D) and heptyl (H) oxazolines were copolymerized in o-dichlorobenzene solvent using methyl 4-nitrobenzenesulfonate as an initiator. A series of decenyl/heptyl oxazolines random copolymers (or DH copolymers) with a total degree of polymerization of 100 and narrow molecular weight distribution were obtained. These copolymers are considered as the poly(N-acylethylenimine)s with allyl pendant groups randomly attached to the far end of their polymethylene, (SINGLE BOND)(CH₂)₇(SINGLE BOND), side chains. The polymers were characterized by NMR, FT–IR. Both DSC and x-ray diffractometer demonstrated that the polymers are highly crystalline. © 1996 John Wiley & Sons, Inc.     

Spectral characteristics, DNA-binding and cytotoxicity of two functional Ru(II) mixed-ligand complexes

Two functional Ru(II) mixed-ligand complexes, [Ru(phen)(2)(ttbd)](2+) (1) (ttbd = 4-(6-propenyl-pyrido[3,2-a]phenzain-10-yl-benzene-1,2-diamine, phen = 1,10-phenanthroline) and [Ru(bpy)(2)(ttbd)](2+) (2) (bpy = 2,2'-bipyridine), have been synthesized and characterized. The spectral characteristics of complexes 1 and 2 were investigated using fluorescence spectroscopy and revealed that both complexes were very sensitive to solvent polarity and oxygen molecules in nonaqueous solvents. The binding properties of the two complexes towards calf thymus DNA (CT-DNA) were investigated with different spectrophotometric methods, viscosity measurements and quantum chemistry calculations, indicating that both complexes could enantioselectively bind to CT-DNA by means of intercalation, but with different binding strengths and discrimination. On the other hand, the cytotoxicity of both complexes have been evaluated by MTT assays and Giemsa staining experiments. The main results reveal that the hydrophobicity and surface area of the ancillary ligands have a significant effect on their DNA binding behavior and both complexes are likely to be useful for optically probing nonaqueous and oxygen-free environments.     

Protonation and Zn(II) coordination by dipyridine-containing macrocycles with different molecular architecture. A case of pH-controlled metal jumping outside-inside the macrocyclic cavity

The synthesis of the macrocyclic ligand 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridylophane (L3), which contains a pentaamine chain linking the 4,4'-positions of a 2,2'-dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6'-positions of 2,2'-dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens.     

Mechanisms of nucleophilic substitution reactions of methylated hydroxylamines with bis(2,4-dinitrophenyl)phosphate. Mass spectrometric identification of key intermediates

Mono- and dimethylation of hydroxylamine on nitrogen does not significantly affect rates of initial attack of NHMeOH and NMe(2)OH on bis(2,4-dinitrophenyl)phosphate (BDNPP), which is largely by oxygen phosphorylation. O-Methylation, however, blocks this reaction and NH(2)OMe then slowly reacts with BDNPP via N-attack at phosphorus and at the aryl group. With NHMeOH, the initial product of O-attack at phosphorus reacts further, either by reaction with a second NHMeOH or by a spontaneous shift of NHMe to the aryl group via a transient cyclic intermediate. There is a minor N-attack of NHMeOH on BDNPP in an S(N)2(Ar) reaction. Reactions occurring via N-attack are blocked by N-dimethylation, and reaction of NMe(2)OH with BDNPP occurs via O-attack, generating a long-lived product. Reaction mechanisms have been probed, and intermediates identified, by using both NMR and MS spectroscopy, with the novel interception of key reaction intermediates in the course of reaction by electrospray ionization mass and tandem mass spectrometry.     

Synthesis, X-ray crystal structures, and phosphate ester cleavage properties of bis(2-pyridylmethyl)amine copper(II) complexes with guanidinium pendant groups

Three new derivatives of bis(2-pyridylmethyl)amine (DPA) featuring ethylguanidinium (L (1)), propylguanidinium (L (2)), or butylguanidinium (L (3)) pendant groups have been prepared by the reaction of N, N- bis(2-pyridylmethyl)alkane-alpha,omega-diamines with 1 H-pyrazole-1-carboxamidine hydrochloride. The corresponding mononuclear copper(II) complexes were prepared by reacting the ligands with copper(II) nitrate and were isolated as [Cu(LH (+))(OH 2)](ClO 4) 3. xNaClO 4. yH 2O ( C1: L = L (1), x = 2, y = 3; C2: L = L (2), x = 2, y = 4; C3: L = L (3), x = 1, y = 0) following cation exchange purification. Recrystallization yielded crystals of composition [Cu(LH (+))(X)](ClO 4) 3.X ( C1': L = L (1), X = MeOH; C2': L = L (2), X = H 2O; C3': L = L (3), X = H 2O), which were suitable for X-ray crystallography. The crystal structures of C1', C2', and C3' indicate that the DPA moieties of the ligands coordinate to the copper(II) centers in a meridional fashion, with a water or methanol molecule occupying the fourth basal position. Weakly bound perchlorate anions located in the axial positions complete the distorted octahedral coordination spheres. The noncoordinating, monoprotonated guanidinium groups project away from the Cu(II)-DPA units and are involved in extensive charge-assisted hydrogen-bonding interactions with cocrystallized water/methanol molecules and perchlorate anions within the crystal lattices. The copper(II) complexes were tested for their ability to promote the cleavage of two model phosphodiesters, bis( p-nitrophenyl)phosphate (BNPP) and uridine-3'- p-nitrophenylphosphate (UpNP), as well as supercoiled plasmid DNA (pBR 322). While the presence of the guanidine pendants was found to be detrimental to BNPP cleavage efficiency, the functionalized complexes were found to cleave plasmid DNA and, in some cases, the model ribose phosphate diester, UpNP, at a faster rate than the parent copper(II) complex of DPA.     

Polymerization of monomers containing functional silyl groups. 12. Anionic polymerization of styrene derivatives para-substituted with pentamethyldisilyl (Si-Si), heptamethyltrisilyl (Si-Si-Si), and nonamethyltetrasilyl (Si-Si-Si-Si) groups

Three styrene derivatives, para-substituted pentamethyldisilyl (Si-Si), heptamethyltrisilyl (Si-Si-Si), and nonamethyltetrasilyl (Si-Si-Si-Si) groups 1 - 3 were synthesized and polymerized in tetrahydrofuran (THF) at −78°C and in benzene at 40°C. The polymerizations of 1 and 2 in THF were found to proceed without transfer and termination reactions to afford stable living polymers. The Si-Si and Si-Si-Si bonds are found to be completely stable under the conditions. Under the same conditions, novel block copolymers with well-defined structures were synthesized by sequential addition of 1 or 2 and styrene. By contrast, side reactions occurred during the polymerizations of 1 and 2 in benzene at 40°C, although polymer yields were quantitative. More seriously, polymer was not obtained in the polymerization of 3 both in THF and in benzene. Thus, the effect of chain length of the oligosilyl group is found to be critical in the anionic polymerization of 1 - 3 .     

Synthesis and properties of azobenzene‐containing poly(1‐alkyne)s with different functional pendant groups

1‐Alkynes containing azobenzene mesogenic moieties [HC?C(CH₂)₉? O? ph? N?N? ph? O? R; R = ethyl ( 1 ), octyl ( 2 ), decyl ( 3 ), (S)‐2‐methylbutyl ( 4 ), or (S)‐1‐ethoxy‐1‐oxopropan‐2‐yl ( 5 ); ph = 1,4‐phenyl] were synthesized and polymerized in the presence of a Rh catalyst {(nbd)Rh⁺[B(C₆H5)₄]^?; nbd = 2,5‐norbornadiene} to yield a series of liquid‐crystalline polymers in high yields (e.g., >75%). These polymers had moderate molecular weights (number‐average molecular weight ≥ 12,000), high cis contents in the main chain (up to 83%), good thermal stability, and good solubility in common organic solvents, such as tetrahydrofuran, chloroform, and dichloromethane. These polymers were thoroughly characterized by a combination of infrared, nuclear magnetic resonance, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy, and two‐dimensional wide‐angle X‐ray diffraction techniques. The liquid‐crystalline behavior of these polymers was dependent on the tail group attached to the azobenzene structure. Poly‐ 1 , which had the shortest tail group, that is, an ethyl group, showed a smectic A mesophase, whereas poly‐ 2 , poly‐ 3 , and poly‐ 5 , which had longer or chiral tail groups, formed smectic C mesophases, and poly‐ 4 , which had another chiral group attached to the azobenzene structure, showed a chiral smectic C mesophase in both the heating and cooling processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4532–4545, 2006     

Preparation, structure, and properties of tetranuclear vanadium(III) and (IV) complexes bridged by diphenyl phosphate or phosphate

Three novel tetranuclear vanadium(III) or (IV) complexes bridged by diphenyl phosphate or phosphate were prepared and their structures characterized by X-ray crystallography. The novel complexes are [{V(III)(2)(μ-hpnbpda)}(2){μ-(C(6)H(5)O)(2)PO(2)}(2)(μ-O)(2)]·6CH(3)OH (1), [{V(III)(2)(μ-tphpn)(μ-η(3)-HPO(4))}(2)(μ-η(4)-PO(4))](ClO(4))(3)·4.5H(2)O (2), and [{(V(IV)O)(2)(μ-tphpn)}(2)(μ-η(4)-PO(4))](ClO(4))(3)·H(2)O (3), where hpnbpda and tphpn are alkoxo-bridging dinucleating ligands. H(3)hpnbpda represents 2-hydroxypropane-1,3-diamino-N,N'-bis(2-pyridylmethyl)-N,N'-diacetic acid, and Htphpn represents N,N,N',N'-tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine. A dinuclear vanadium(IV) complex without a phosphate bridge, [(VO)(2)(μ-tphpn)(H(2)O)(2)](ClO(4))(3)·2H(2)O (4), was also prepared and structurally characterized for comparison. The vanadium(III) center in 1 adopts a hexacoordinate structure while that in 2 adopts a heptacoordinate structure. In 1, the two dinuclear vanadium(III) units bridged by the alkoxo group of hpnbpda are further linked by two diphenylphosphato and two oxo groups, resulting in a dimer-of-dimers. In 2, the two vanadium(III) units bridged by tphpn are further bridged by three phosphate ions with two different coordination modes. Complex 2 is oxidized in aerobic solution to yield complex 3, in which two of the three phosphate groups in 2 are substituted by oxo groups.     

Poly(β-pinenes) carrying one,two, or three functional end groups. I. The effect of reaction conditions on the polymerization of β-pinene

β-Pinene was polymerized with H₂O/BCl₃ (protic) and p-dicumyl chloride and sym-tricumyl chloride (nonprotic) inifer systems in CH₂Cl₂ or CH₂Cl₂/n-C₆H₁₄ solvents from ?10 to ?70°C. The effect of solvent polarity, temperature, and monomer and inifer concentration on conversions and molecular weights was investigated. Low conversions and molecular weights, M?_n = 1300–2500, obtained under these conditions suggest rapid termination.     

Design, formation and properties of tetrahedral M(4)L(4) and M(4)L(6) supramolecular clusters

The rigid tris- and bis(catecholamide) ligands H(6)A, H(4)B and H(4)C form tetrahedral clusters of the type M(4)L(4) and M(4)L(6) through self-assembly reactions with tri- and tetravalent metal ions such as Ga(III), Fe(III), Ti(IV) and Sn(IV). General design principles for the synthesis of such clusters are presented with an emphasis on geometric requirements and kinetic and thermodynamic considerations. The solution and solid-state characterization of these complexes is presented, and their dynamic solution behavior is described. The tris-catecholamide H(6)A forms M(4)L(4) tetrahedra with Ga(III), Ti(IV), and Sn(IV); (Et(3)N)(8)[Ti(4)A(4)] crystallizes in R3(-)c (No. 167), with a = 22.6143(5) A, c = 106.038(2) A. The cluster is a racemic mixture of homoconfigurational tetrahedra (all Delta or all Lambda at the metal centers within a given cluster). Though the synthetic procedure for synthesis of the cluster is markedly metal-dependent, extensive electrospray mass spectrometry investigations show that the M(4)A(4) (M = Ga(III), Ti(IV), and Sn(IV)) clusters are remarkably stable once formed. Two approaches are presented for the formation of M(4)L(6) tetrahedral clusters. Of the bis(catecholamide) ligands, H(4)B forms an M(4)L(6) tetrahedron (M = Ga(III)) based on an "edge-on" design, while H(4)C forms an M(4)L(6) tetrahedron (M = Ga(III), Fe(III)) based on a "face-on" strategy. K(5)[Et(4)N](7)[Fe(4)C(6)] crystallizes in I43(-)d (No. 220) with a = 43.706(8) A. This M(4)L(6) tetrahedral cluster is also a racemic mixture of homoconfigurational tetrahedra and has a cavity large enough to encapsulate a molecule of Et(4)N(+). This host-guest interaction is maintained in solution as revealed by NMR investigations of the Ga(III) complex.