LADDER SUPERSTRUCTURE-DIRECTED SYNTHESIS OF A WELL-DEFINED m-PHENELENEDIIMINO-BRIDGED LADDER POLYMETHYLSILOXANE

A well-defined m-phenylenediimino-bridged ladder polymethylsiloxane(LP) was first synthesized through a welldefined ladder superstructure(LS) acting as synthetic template,which was self-assembled by concerted interaction of hydrogen bonding and aromaticπ-πstacking of the monomer(M),N,N'-bis(phenyldichlorosilyl)-m-phenylenediamine.Some key characterization data of LP and,in particular,the extremely vulnerable LS with very unstable Si-Cl and Si-N groups were given.The molecular weights(M_n) of LS and LP ar...     

光固化聚氨酯丙烯酸酯杂化材料的核磁共振谱

光固化聚氨酯丙烯酸酯杂化材料的核磁共振谱;SiO2;溶胶-凝胶法     

STUDIES ON REGULARITY OF POLY PHENYLSILSESQUIOXANE CHAINS

IR and ~(29)Si NMR were used to determine the structures of ladderlike polymer polyphenylsilsesquioxanes (PPS). It was found that PPS with lots of defects had a wide and strong absorption band in 1000—1400 cm~(-1) with only one sharp peak at 1137 cm~(-1) while two peaks (1130 and 1045 cm~(-1) were observed for PPS with perfect ladderlike structure. Branching and crosslinking of PPS lead to the reduction of 1045 cm~(-1) peak. ~(29)Si NMR spectra, however, showed two peaks (δ=-78 ppm and -87 ppm when δ_(HMDS)=0 ppm) for defective or branched PPS. The -87 ppm peak is related to the ladderlikely constructed Si atoms and -78 ppm corresponds to defective Si atoms. PPS with defects less than 0.1% chain units was obtained by azeotropic polycondensations.     

A synthetic breakthrough into an unanticipated stability regime: a series of isolable complexes in which C6, C8, C10, C12, C16, C20, C24, and C28 polyynediyl chains span two platinum atoms

The reaction of trans-[PtCl(p-tol){P(p-tol)3}2] (PtCl) and H(C[triple chemical bond]C)2H (cat. CuI, HNEt2) gives PtC4H (82 %), which can be cross-coupled with excess HC[triple chemical bond]CSiEt3 (acetone, O2, CuCl/TMEDA; Hay conditions) to yield PtC6Si (77 %). The addition of nBu4N+F- in wet acetone gives PtC6H (84 %), and further addition of ClSiMe3 (F- scavenger) and excess HC[triple chemical bond]CSiEt3 (Hay conditions) yields PtC(8)Si (23 %). Similar cross-coupling reactions of PtCxH (generated in situ for x>6) and excess H(C[triple chemical bond]C)2SiEt3 give a) x=4, PtC8Si (29 %), PtC12Si (30 %), and PtC16Si (1 %); b) x=6, PtC10Si (59 %) and PtC14Si (7 %); c) x=8, PtC12Si (42 %); and d) x=10, PtC14Si (20 %). Hay homocoupling reactions of PtC4H, PtC6H, PtC8H, and PtC10H give PtC8Pt, PtC12Pt, PtC16Pt, and PtC20Pt (88-70 %), but PtC12H decomposes too rapidly. However, when PtC12Si and PtC14Si are subjected to Hay conditions, protodesilylation occurs in the presence of the oxidizing agent and PtC24Pt (36 %) and PtC28Pt (51 %) are isolated. Reactions of PtC6H and PtC10H with PtCl (CuI, HNEt2) give PtC6Pt (56 %) and PtC10Pt (84 %). The effect of the chain lengths in PtCxPt upon thermal stabilities (>200 degrees C for x< or =20), IR nu(C[triple chemical bond]C) patterns (progressively more bands), colors (yellow to orange to deep red), UV/Vis spectra (progressively red-shifted and more intense bands with epsilon>400,000 M(-1) cm(-1)), redox properties (progressively more difficult oxidations), and NMR spectra (many monotonic trends) are analyzed, including implications for the sp carbon allotrope carbyne. Whereas all other dodecaynes and tetradecaynes rapidly decompose at room temperature, PtC24Pt and PtC28Pt remain stable at >140 degrees C. Crystal structures of PtCxSi (x=6, 8, 10) and PtCxPt (x=6, 8, 10, 12) have been determined.     

Differential effects of Mg(ii) and N(alpha)-4-tosyl-l-arginine methyl ester hydrochloride on the recognition and catalysis in ATP hydrolysis

The supramolecular interactions of Mg(ii) and N(alpha)-4-tosyl-l-arginine methyl ester hydrochloride (TAME) with ATP have been investigated using (1)H and (31)P NMR spectra. Furthermore, the hydrolysis of ATP catalyzed by Mg(ii) and TAME has been studied at 60 degrees C and pH 7 using (31)P NMR spectra. In the Mg(ii)-ATP-TAME ternary system, the binding interaction of Mg(2+) with ATP involves not only N1 and N7 in the adenine ring but also beta- and gamma-phosphate of ATP. The binding forces are mainly electrostatic interaction and cation (Mg(2+))-pi interaction. The guanidinium group and the aromatic ring of TAME interacts with ATP by beta and gamma phosphate and the adenine ring of ATP. The binding forces are mainly electrostatic interactions and pi-pi stacking. A significant difference between the binary and the ternary system indicates that TAME is essential to the stablization of the intermediate. Kinetic studies show that the hydrolysis rate constant of ATP is 2.16 x 10(-2) h(-1) at pH 7 in the Mg(ii)-TAME-ATP ternary system. The Mg(ii) ion and TAME can accelerate the ATP hydrolysis process. A possible mechanism has been proposed that the hydrolysis occurs through an addition-elimination, in which the phosphoramidate intermediate was observed at 3.21 ppm in the (31)P NMR of the ternary system. These results provide further information concerning the effect of the key amino acid residue and metal ions as cofactors of ATPase on ATP synthesis/hydrolysis at the molecular level.     

Functionalization of multiwalled carbon nanotubes by pyrene-labeled hydroxypropyl cellulose

Pyrene-labeled hydroxypropyl cellulose (HPC-Py) was synthesized through a condensation reaction between hydroxypropyl cellulose (HPC) and 1-pyrenebutyric acid (Py). A hybrid (HPC/MWNTs) of the HPC-Py and multiwalled carbon nanotubes (MWNTs) was prepared through a noncovalent method. Temperature-variable UV-vis spectra indicated that the HPC-Py had a lower critical solution temperature of about 44 degrees C in water. (1)H NMR, UV-vis, Raman, and fluorescence spectra were used to systematically investigate the pi-pi stacking interaction between the HPC-Py and MWNTs. Dispersion experiments showed the HPC/MWNTs hybrids could be well dispersed in water and many organic solvents.     

CONCERTED H-BONDING TEMPLATE SYNTHESIS OF AN ORDERED LADDER POLYSILSESQUIOXANE

A novel soluble regular ladder poly（benzoyl-3-aminopropyl） silsesquioxane （LPBAS） was facilely prepared under effective assistance of concerted H-bonding self-assembly of amido groups of side chains and silanol groups, respectively, of a new template monomer [1,3-bis（benzoyl-3-aminopropyl）-1,1,3,3-tetraethoxydisiloxane] （M）. The ordered ladder structure of LPBAS is manifested in： （1） the presence of two Bragg peaks representing the ladder width （d） and ladder thickness （t） in X-ray diffraction （XRD） pattern; （2） narrow base-line width （w = 6） of resonance absorption for -CH2SiO3/2 moiety in 29Si-NMR and （3） high glass transition temperature Tg = 1 12℃ in differential scanning calorimetry （DSC） analysis.     

TS-1分子筛的合成Ⅰ.29Si和1H NMR研究正硅酸乙酯的水解

利用29Si和1H NMR方法研究了TS-1分子筛合成过程中正硅酸乙酯(TEOS)的水解行为.1H NMR结果表明,TEOS在四丙基氢氧化铵(TPAOH)溶液中的水解速度快于在四乙基氢氧化铵(TEAOH)中的水解速度.TEOS水解后的29Si NMR谱显示,TEOS在TPAOH中水解产生的聚合硅酸根物种的分布与在TEAOH中的类似,都存在着单体、二聚、三聚及环聚等硅酸根物种的平衡,但TEOS-TEAOH体系中低聚硅酸根物种的浓度明显大于TEOS-TPAOH中的浓度.向水解后的样品中添加水,可促使多聚硅酸根物种转化为低聚物种.大量异丙醇的加入将导致单聚和二聚硅酸根物种的高聚.钛酸四丁酯加入到TEOS-TPAOH水解体系中得到的29Si NMR结果明显不同于TEOS-TEAOH水解体系.     

Characterization of silica-pillared derivatives from aluminum-containing kanemite

A series of aluminum-containing kanemite (Al-kanemite) samples with several Si/Al molar ratios were synthesized. The Al-kanemite samples were pillared with silica. X-ray diffractograms showed that the layered structure of the Al-kanemite samples was maintained at Si/Al= infinity approximately 10 but was broken at Si/Al = 5, 2.5, and 1. 29Si MAS NMR spectra of the Al-kanemite samples, except for that of Si/Al = 1, mainly showed peaks of Q(3) sites, which were attributed to Si(OSi)(3)(OH) groups, although peaks assigned to Si(OAl)(OSi)(2)(OH) were also seen. The 27Al MAS NMR spectra indicated that the Al-kanemite samples had only four-coordinate aluminum atoms. The FTIR spectra of pyridine adsorbed on the pillared Al-kanemite derivatives revealed Lewis acid sites on the surface. The nitrogen adsorption isotherms of the derivatives were classified as type I (Langmuir) absorption isotherms. Using the alpha(s) method, the specific surface areas of the derivatives were 572-756 m(2)g(-1), and the pore sizes were calculated as 1.25-1.83 nm. The pillared Al-kanemite derivatives had slit-shaped micropore structures.     

Effect of molecular oxygen on the variable-temperature 29Si MAS NMR spectra of zeolite-sorbate complexes

Structure determinations of siliceous zeolite-sorbate host-guest complexes by solid-state NMR require highly resolved 29Si MAS NMR spectra. As the temperature is lowered, the 29Si MAS NMR spectra of many zeolite-sorbate complexes become broadened such that the resolution of the individual 29Si peaks is lost, limiting the application of solid-state NMR for structure determination. It is shown that the 29Si peak widths are related to the 29Si T2 relaxation times and that the source of the 29Si relaxation and the line broadening is paramagnetic molecular oxygen in the channels of the zeolite. Removal of the oxygen by purging the sample with nitrogen gas leads to a dramatic increase in the resolution of the 29Si MAS NMR spectrum of the p-dibromobenzene/ZSM-5 complex. An analysis of the individual 29Si T1 relaxation times reveals that the oxygen molecules are localized mainly in the zigzag channels of ZSM-5, suggesting that the p-dibromobenzene molecules are located in the channel intersections.     

29Si NMR study of structural ordering in aluminosilicate geopolymer gels

A systematic series of aluminosilicate geopolymer gels was synthesized and then analyzed using 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) in combination with Gaussian peak deconvolution to characterize the short-range ordering in terms of T-O-T bonds (where T is Al or Si). The effect of nominal Na2O/(Na2O + K2O) and Si/Al ratios on short-range network ordering was quantified by deconvolution of the 29Si MAS NMR spectra into individual Gaussian peaks representing different Q4(mAl) silicon centers. The deconvolution procedure developed in this work is applicable to other aluminosilicate gel systems. The short-range ordering observed here indicates that Loewenstein's Rule of perfect aluminum avoidance may not apply strictly to geopolymeric gels, although further analyses are required to quantify the degree of aluminum avoidance. Potassium geopolymers appeared to exhibit a more random Si/Al distribution compared to that of mixed-alkali and sodium systems. This work provides a quantitative account of the silicon and aluminum ordering in geopolymers, which is essential for extending our understanding of the mechanical strength, chemical and thermal stability, and fundamental structure of these systems.     

Synthesis of functionalized porphyrins as oxygen ligand receptors

Oxophilic synthetic receptors were designed and synthesized using a porphyrin scaffold, with the aim of constructing a preorganized complementary binding site for phenols and carbohydrates. We pursued three strategies for phenol recognition: (1) Lewis acid/Lewis base combinations serving as a hydrogen bond donor and acceptor for the OH group, (2) Lewis base/pi-pi stacking, targeting both the OH group and the aromatic moiety of phenols, and (3) exchange of the axial hydroxyl ligand on a trivalent and oxophilic metal center of aluminum porphyrin. For the recognition of acidic phenols, the most promising recognition motif was Lewis base/pi-pi stacking, which can bind to phenols with a hydrogen bond and pi-pi stacking interactions. [5-(8-Quinolyl)-10,15,20-triphenylporphyrinato]zinc binds to p-nitrophenol with a binding constant of 540 M(-)(1) in CHCl(3) at 25 degrees C. For carbohydrate recognition, we designed the metalloporphyrin receptor having 8-quinolyl groups and o-carbomethoxymethoxyphenyl groups, where these Lewis basic parts serve as the cooperative hydrogen bonding sites for the hydroxyl groups of glucoside. The receptor binds to beta-octyl glucoside with a binding constant of 7.35 x 10(4) M(-)(1) in CHCl(3) at 15 degrees C, demonstrating importance of formation of a highly ordered hydrogen bonding network between the receptor and the guest. These binding features have significant implications for the rational design of oxophilic artificial receptors.     

高硅FAU沸石与甲胺吸附物的相互作用

合成高硅沸石中所用的模板剂胺类分子与沸石骨架 Si—O基团间的相互作用机理尚不清楚 .迄今为止 ,沸石与吸附胺之间的相互作用的研究还只限于测定沸石酸性质 [1,2 ]、表面羟基活性位或了解模板分子在沸石骨架中的位置和状态 [3,4 ] .甲胺、乙胺在骨架完美的高硅 FAU(Y型 )沸石上的亲和性指数 AT 值 ,即被吸附有机物脱附峰温与该有机物的沸点之差分别高达 1 60与 1 5 0℃[5] .而在高硅 MFI(Silicalite-1 )沸石上为 1 60与 1 2 7℃ [6 ] .与大多数有机物不同 ,被吸附的胺类脱附时的吸热效应十分明显 .上述现象表明胺与高硅沸石骨架 O2 -…     

Structures and properties of ruthenium(II) complexes of pyridylamine ligands with oxygen-bound amide moieties: regulation of structures and proton-coupled electron transfer

Tris(2-pyridylemthyl)amine (TPA) derivatives having two amide moieties at the 6-positions of the two pyridine rings of TPA and their Ru(II) complexes were synthesized and characterized by spectroscopic methods, X-ray crystallography, and electrochemical measurements. The complexes prepared were [RuCl(L)]PF(6) (L = N,N-bis(6-(1-naphthoylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (1), N,N-bis(6-(2-naphthoylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (2), N,N-bis(6-(isobutyrylamide)-2-pyridylmethyl)-N-(2-pyridylmethyl)amine (3)); the crystal structures of the three compounds were established by X-ray crystallography. In variable-temperature (1)H NMR spectra of 1 and 2 in CD(3)CN solutions, the pi-pi stacking in 1 was too rigid to exhibit any fluxional motions in NMR measurements; however, the pi-pi stacking of 2 was weaker and showed fluxional behavior in nearly T-shaped pi-pi interaction for the 2-naphthly groups (DeltaH degrees = -2.3 kJ mol(-1); DeltaG degrees = -0.9 kJ mol(-1) and DeltaS degrees = -7.7 J mol(-1) K(-1) at 233 K in CD(3)CN). For each of these three complexes, one of the amide moieties coordinated to the Ru(II) center through an amide oxygen. The other uncoordinated amide N-H formed intramolecular hydrogen bonding which remained intact even in aqueous media, indicating the intramolecular hydrogen bonding was geometrically compelled to form. The amide coordination is also stabilized and strengthened by the hydrogen bonding, so that the structure of each compound is maintained in solution. It is suggested that this hydrogen bonding lowers the redox potentials of the Ru(II) centers due to polarization of the coordinated amide C=O bond, in which the oxygen atom becomes more electrostatically negative and its electron-donating ability is strengthened. The N-H protons in the coordinated amide moieties were found to undergo a reversible deprotonation-protonation process, and the redox potentials of the Ru(II) centers could be regulated in the range of 500 mV in CH(3)CN solutions. The Pourbaix diagram for 1 clearly showed that this proton-coupled redox behavior is a one-electron/one-proton process, and the pK(a) value was estimated to be approximately 6.     

甲胺与MFI、FAU 及FER型高硅沸石的相互作用

The adsorption of methylamine on highly siliceous MFI, FAU and FER-type zeolites was investigated withXRD, FT-IR, Raman, ^13C and ^29Si MAS NMR, and compared with the adsorption of methanol. As the adsorption of the amine, the relative intensity of XRD peaks of the zeolites has been changed significantly, the high-resolution ^29Si MAS NMR peaks have been broadened and shifted to low field, and the resonance of Si-OH groups has appeared. The vibration of N-H has been shifted to low frequency and C-N vibration moved to high frequency in the IR spectra, and the ^13C resonance peak broadened and shifted to high field for the adsorbed amine. The facts reveal an associating interaction between the perfect framework of the zeolites and the adsorbed methylamine with hydrogen bonds, leading to the formation of Si-OH groups and the high desorption temperature of the methylamine from the zeolites.     

Extremely long axial Cu-N bonds in chiral one-dimensional zigzag cyanide-bridged Cu(II)(-)Ni(II) and Cu(II)(-)Pt(II) bimetallic assemblies

Preparations, crystal structures, and spectral and magnetic properties of two new chiral one-dimensional cyano-bridged coordination polymers, [Cu(II)L2]M(II)(CN)].2H2O (M(II) = Ni(II) (1) and Pt(II) (2), L = trans-cyclohexane-(1R,2R)-diamine) have been presented. Complex 1 crystallizes in the monoclinic P2(1) space group with a = 9.864(4) A, b = 15.393(8) A, c = 7.995(4) A, beta = 110.32(3) degrees , V = 1138.4(10) A3, and Z = 2, while 2 crystallizes in the monoclinic P2(1) space group with a = 9.899(3) A, b = 15.541(4) A, c = 8.102(2) A, beta = 111.02(2) degrees , V = 1163.6(5) A3, and Z = 2. The unique zigzag cyano-bridged chains along the crystallographic b axis consist of alternate chiral [CuL(2)]2+ cations and square-planar [M(CN)4]2- anions. One side of the axial Cu-N(triple bond C) bond distances are 2.324(6) and 2.34(1) A with Cu-N[triple bond]C angles of 137.8(6) degrees and 138.2(9) degrees for 1 and 2, respectively. On the other hand, the opposite side of the axial Cu-N(triple bond C) bond distances are 3.120(8) and 3.09(1) A with significantly large bent Cu-N[triple bond]C angles of 97.9(5) degrees and 96.8(7) degrees for 1 and 2, respectively. The novel axial bonding features of extremely long semi-coordination Cu-N bonds are attributed to coexistence of pseudo-Jahn-Teller elongation and electrostatic interaction in the unique zigzag cyano-bridged chains. The characteristic bonding features with overlap between small 3d (Ni(II)) or large 5d (Pt(II)) and 3d (Cu(II)) orbitals results in larger shifts in XPS peaks of not only Cu2p(1/2) and Cu2p(3/2) but also Ni2p(1/2) and Ni2p(3/2) for 1 than those of 2, which is also consistent with weak antiferromagnetic interactions with Weiss constants of -5.31 and -5.94 K for 1 and 2, respectively. The d-d, pi-pi*, and CT bands in the electronic, CD, and MCD spectra for 1 and 2 in the solid state at room temperature are discussed from the viewpoint of magneto-optical properties.     

Reversible photoswitching of the coordination numbers of silicon in organosilicon compounds bearing a 2-(phenylazo)phenyl group

Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by (1)H, (13)C, (19)F, and (29)Si NMR spectra, UV-vis spectra, and X-ray crystallographic analyses. In the UV-vis spectra, silyl groups caused red shifts of both the n-pi and pi-pi transitions of the azo group compared with the transitions of the unsubstituted azobenzene. The E-isomers of the fluorosilanes showed an intramolecular interaction between a nitrogen atom of the azo group and the silicon atom, leading their intermediate structures between a distorted trigonal bipyramidal structure and a tetrahedral structure around the silicon atoms, which were revealed by the X-ray crystallographic analyses and the NMR spectra. On the other hand, silanes without fluorine atoms showed tetrahedral structures in the absence of such an interaction. The photoirradiation of the E-isomers of the fluorosilanes afforded reversibly the corresponding Z-isomers in good yields. The silicon atoms of the Z-isomers were found to be tetracoordinate in the absence of Si-N interactions by the (29)Si NMR spectra. The coordination numbers of the silicon atom of the fluorosilanes were reversibly switched between four and five by photoirradiation. These properties were compared to those of a tetrafluoro[2-(phenylazo)phenyl]silicate.