Thermal decomposition studies of the polyhedral oligomeric silsesquioxane, POSSh, and when it is impregnated with the metallocene bis(eta5-cyclopentadienyl)zirconium (IV) dichloride or immobilized on silica

Thermal decomposition studies of the free polyhedral oligomeric silsesquioxane, POSSh, and when this compound has been impregnated with Cp2ZrCl2 (Cp = eta5-C5H5) or immobilized on SiO2 were conducted using infrared emission spectroscopy (IES) over a 100-1000 degrees C temperature range and by thermogravimetric analysis (TGA). The organic groups in POSS(h) apparently decompose thermally into Si-CH3, Si-H and other fragments. Upon impregnation with Cp2ZrCl2, however, a different thermal decomposition pathway was followed and new infrared emission bands appeared in the 1000-900 cm(-1) region suggesting the formation of Si-O-Zr moieties. When immobilized on SiO2 and subjected to thermal decomposition, the POSSh compound lost its organic groups and the inorganic structure remaining was incorporated into the SiO2 framework.

Synthesis of erbium hydroxide microflowers and nanostructures in subcritical water

The effects of temperature, pressure, pH, residence time and reactant concentrations, as well as the presence or absence of CO(2), on the size and morphology of erbium hydroxide particles synthesized in a hydrothermal batch reactor and a diamond-anvil cell (DAC) reactor have been investigated. Several new erbium-based microstructures and nanostructures were obtained that encompass different phases and shapes, including crystalline microflowers, hexagonal microlayers, microsticks and microspheres made from nanoparticles, as well as nanofibers, nanorods and nanolayers. The Er(2)OCO(3)(OH)(2) microflowers are pure, structurally uniform, and mostly free from dislocations. Their crystallinity, morphology, optical properties and structural features have been examined and compared with those of the other phases by field-emission scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy-dispersive x-ray (EDX) analysis, and by Raman, infrared, UV-visible and fluorescence spectroscopy.

Vibrational spectra of silsesquioxanes impregnated with the metallocene catalyst bis(eta(5)-cyclopentadienyl)zirconium(IV) dichloride

FT-IR photoacoustic and Raman spectroscopy have been used to study the interactions between the metallocene catalyst, Cp(2)ZrCl(2) (Cp=eta(5)-C(5)H(5)), and two polyhedral oligomeric silsesquioxanes (POSS) supports. The first silsesquioxane support, POSS(h), contains (beta-hydroxyl)-tertiary amine groups, while in the second one, POSS(u), these -OH groups have been converted into N-(p-toluyl) urethane groups. The vibrational spectra of the Cp(2)ZrCl(2):POSS(h) and Cp(2)ZrCl(2):POSS(u) samples show that the Cp(2)ZrCl(2) catalyst reacts with the C-OH groups of POSS(h) and also interacts with N-H and >CO groups of POSS(u). Furthermore, Cp(2)ZrCl(2) can react with the Si-OH groups of the POSS supports and also interact with the O atoms that are bonded to the benzene rings and the N atoms of the tertiary amines in both silsesquioxanes. As a result of the interactions between Cp(2)ZrCl(2) and the POSS supports, acidic species are generated. The Cp(2)ZrCl(2):POSS(h) mass ratio seems to be an important parameter in the formation of Zr-O bonds and the acidic species.

[Infrared and raman spectra studies of DL-homocysteic acid (DLH) and its lanthanum complex at high external pressure]

DL-Homocysteic acid (DLH, (NH3 )-CH(COOH)-(CH2 )2-SO3-) is extensively in existence as free amino-acid in the central nervous system of mammal. The infrared (IR) and Raman spectra of DL-Homocysteic acid (DLH) and its La complex [La (DLH)2Cl3 . H2O = LaL2] were measured at high external pressure. The DLH has two pressure-induced phase transitions (near 17 kbar and 37 kbar) and three pressure-phase areas below 50 kbar for there are ten intermolecular hydrogen bonds between the DLH molecules. But there is only one pressure-induced phase transition (near 27 kbar) to be observed in the complex LaL2. These show that the ten intermolecular hydrogen bonds of the DLH molecules changed due to the formation of complex LaL2. In infrared spectra, the changing trend of the pressure sensitivities (dv/dp) of symmetry stretching of SO3- in DLH and asymmetry stretching of SO3- in LaL2 are very different from the other vibrational modes when both compounds undergo high external pressure. In infrared spectra, the average pressure sensitivities of symmetry stretching of SO3- are: low-pressure phase area (0.30 cm(-1) x (kbar)(-1)) < middle-pressure phase area (0.32 cmn(-1) (kbar) (-1)) < high-pressure phase area (0.41 cm(-1) x (kbar)(-1)), but 0.86 cm(-1) x (kbar)(-1) (low-pressure phase area) >0.64 cm(-1) x (kbar)(-1) (middle-pressure phase area) >0.26 cm(-1) x (kbar)(-1) (high-pressure phase area) to other vibrational modes in DLH. The average pressure sensitivities of asymmetry stretching of SO3- in LaL2 are lower in low-pressure phase area than in high-pressure phase area, but the average pressure sensitivities of other modes are higher in low-pressure phase area than in high-pressure phase area.

X-ray diffraction, Raman spectroscopic, and solid-state NMR studies of the group 14 metal-(tetracarbonyl)cobalt complexes Ph3MCo(CO)4 (M = Si, Sn, Pb)

Single-crystal X-ray diffraction studies illustrate that the three title compounds are isomorphous, belonging to the triclinic space group P[Formula: see text], with slightly distorted trigonal bipyramidal geometry about cobalt. The solid-state 29Si, 119Sn, and 207Pb cross-polarization magic angle spinning (CP MAS) NMR spectra are presented. The indirect spin–spin coupling constant (J), quadrupolar–dipolar shift (d), direct dipolar coupling constant (D' ), anisotropy in spin–spin coupling (ΔJ), and the chemical shift tensor were extracted. A plot of the reduced coupling constant vs. s-electron densities at the nucleus indicates that the Fermi contact term may be dominant for the tin and lead complexes; however, the large ΔJ for all complexes indicate that there are also significant anisotropic terms. Trends in the Raman scattering spectra are also discussed.Key words: 29Si, 119Sn, and 207Pb CP MAS NMR, tetracarbonyl cobalt, spin–spin coupling, chemical shift tensor, quadrupole coupling, Fermi contact, cobalt–group 14.

Practical tethering of vitamin B1 on a silica surface via its phosphate group and evaluation of its activity

A convenient immobilization of thiamine pyrophosphate molecules on a silica surface through the phosphate group is developed, leading to a very active heterogenized biocatalyst for pyruvate decarboxylation.

[Raman and infrared spectral studies of tungsten organometallic carbyne complex at high external pressure]

The Raman and infrared spectra of complex: [Cl(CO)2 (DPPE) W identical to CC6H4C identical to CC6H4NC]2 Re Cl(CO)3 (DPPE = bis (diphenylphosphino) ethane, (Ph)2PCH2CH2P(Ph)2) were measured at high external pressure (up to about 50 kbar). The pressure induced phase transition was observed near 30 kbar. The pressure dependence d nu/dp of nu (W identical to C) at the low-pressure phase is a little high (0.59 cm-1.(kbar)-1) and is very low (0.04 cm-1.(kbar)-1) at the high-pressure phase. It shows that the pi-backbonding from W to pi*--orbital of CO is strengthened at the high external pressure in fragment Cl(CO)2 (DPPE) W identical to C; The bond intensity and the force constant of W identical to C and nu (W identical to C) are decreasing; This effect compete with the normal increasing nu (W identical to C) on compression.

Pressure-tuning infrared and Raman spectroscopy of group 14 tetraphenyl compounds

The effect of high external pressures on the vibrational spectra of the tetraphenyl Group 14 compounds, Ph4M (M = Si, Ge, Sn, Pb), were examined between ambient pressure and 40 kbar with the aid of a diamond-anvil cell. The four compounds displayed similar behaviour as the pressure was increased and a structural transition at approximately 15 kbar, most probably associated with a phenyl ring rotation, was identified in each case. The pressure dependencies of selected vibrational modes were obtained.

Microperoxidase-11: molecular dynamics and Q-band excited resonance Raman of the oxidized, reduced and carbonyl forms

Resonance Raman spectra with Q-band excitation are reported for microperoxidase-11, the cytochrome c analog. Spectra were acquired in the mid-frequency range for the oxidized, and reduced forms of the undecapeptide, as well as for the imidazole and carbonyl complexes. Oxidation and spin state marker bands of the undecapeptides are consistent with a six-coordinate, low spin iron in both oxidation states. Porphyrin core size correlations yield a porphyrin-centre to pyrrole-nitrogen distance of 2.00 A for MP11, suggestive of a six-coordinate species in a distorted heme environment. Molecular dynamics results show that the non-planarity of the heme of the parent cytochrome is conserved in the microperoxidase and its carbonmonoxy analog.

Quadrupole-dipole effects in solid-state, CP-MAS, tin-119 NMR spectra of para-substituted Triaryltin(pentacarbonyl)manganese(I) complexes

Solid-state, CP-MAS, 119Sn NMR spectra were measured for a series of para-substituted triaryltin(pentacarbonyl)manganese(I) complexes. All the spectra show an asymmetric sextet due to spin-spin coupling and second-order quadrupolar effects, transmitted by dipolar coupling between the 119Sn and 55Mn nuclei, which are not suppressed by magic-angle rotation. The solid-state 1JMn-Sn spin-spin and nuclear quadrupole coupling constants range from 130 to 250 Hz and -8 to 21 MHz, respectively, and show an inverse linear correlation, which is attributed to the dominance of the Fermi contact contribution to the 1JMn-Sn coupling. The tris(p-methylthiophenyl)tin derivative is an exception, attributed to a difference in crystal structure from the other complexes. The magnitudes of the principal elements of the 119Sn chemical shift tensors were determined and appear to be strongly influenced by the ring torsion angles and the para-substituents of the phenyl rings. Solid-state 119Sn NMR spectroscopy provides a useful method of probing the electronic environment around the tin and manganese nuclei in transition metal complexes. Copyright 1998 Academic Press.

High-pressure infrared and FT-Raman investigation of a dental composite

Composite resins are often used as filling materials on load-bearing surfaces of teeth. As masticatory stresses can be high, here, we study the effect of pressure on the behaviour of a dental composite. Using a polymerized wafer, the IR and FT-Raman spectra of a zirconia-containing proprietary composite (Z100, 3M, Minneapolis, MN, USA) were recorded. The high-pressure IR spectra were also recorded. Band assignments were made for the main peaks of both organic and inorganic components. Breaks in the pressure dependences (dv/dP) of the organic components were found at 22 kbar. Different pressure dependences for different vibrational modes of inorganic components were also observed. These data suggest that the network structure of the composite is compacted under high pressure and that both the atomic distance and bonding angles in the network are altered.

An FT-Raman spectroscopic investigation of dentin and collagen surfaces modified by 2-hydroxyethylmethacrylate

Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its role in promoting adhesion is not completely understood. Here, we use FT-Raman spectroscopy to elucidate further the nature of the interaction of HEMA with dentin. Ground dentin was exposed to 2.5% (w/w) nitric acid, washed, dried in air, and treated with HEMA. The samples were then sequentially washed with distilled water, with FT-Raman spectra being obtained after different wash times. Hydroxyapatite and bovine type I collagen were similarly treated with HEMA except for the acid exposure. The FT-Raman spectra of these samples were also recorded. The spectra of HEMA-treated water-washed dentin and collagen revealed the following changes: (1) The band intensities of HEMA absorbed on dentin and collagen decreased with increasing wash times (2) the nu(C=O) and nu(CCO) modes of HEMA at 1718 and 607 cm-1, respectively, either disappeared or decreased after extensive washing; (3) the nu (C=C) (1640 cm-1) and delta (=CH2), (1403 cm-1) bands exhibited minor variations in band position and relative intensity. These results demonstrate that HEMA interacts with dentin both physically and chemically. The chemical interaction can be interpreted by either hydrogen bonding or the formation of a new bond to the ester group of HEMA.

Effect of high external pressures on the vibrational spectra of biomedical materials: calcium hydroxyapatite and calcium fluoroapatite

Infrared and Raman spectra of the principal mineral component of human hard tissue, calcium hydroxyapatite, Ca10(PO4)6(OH)2, or HAP, and the analogous calcium fluoroapatite, Ca10(PO4)6F2, or FAP, have been recorded, using a diamond-anvil cell, at pressures ranging from ambient to 30 kbar. For FAP, the absence of any discontinuities in the slopes of the nu (cm-1) versus P (kbar) plots for the observed bands indicates that no pressure-induced structural transition occurs in this material throughout the pressure range investigated. For the internal vibrational modes of HAP, however, there are distinct breaks at approximately 20 kbar in the nu versus P plots, suggesting the occurrence of a structural change at this pressure. The OH stretching mode of HAP shifts to higher wave numbers with increasing pressure while the associated OH librational mode shifts in the opposite direction. The pressure-induced structural transition in HAP is reversible and occurs at approximately 22 kbar upon decompression. Further evidence for a structural change taking place at approximately 20 kbar was provided by a parallel pressure-tuning Raman study. Hydrogen bonding does not occur, or is very weak, in HAP.

Carbonylmetalloimmunoassay (CMIA) a new type of non-radioisotopic immunoassay. Principles and application to phenobarbital assay

A new non-radioisotopic immunoassay procedure, which we have termed carbonylmetalloimmunoassay (CMIA), is described. The tracers used in this approach are organometallic carbonyl complexes that can be detected at femtomole levels (300-700 fmol) by Fourier transform infrared (FT-IR) spectroscopy. The validity of the technique has been tested in a phenobarbital assay using as the marker a cyclopentadienylmanganese (I) tricarbonyl (cymantrene) moiety, ethyl acetate extraction to separate the free and bound organometallic fractions, and FT-IR spectroscopy to detect the CO stretching modes of the organometallic label. Typical dilution and standard curves obtained with this CMIA procedure are presented. The method was of comparable sensitivity to a [14C] radioimmunoassay (RIA) for the detection of phenobarbital. A comparison of the results for phenobarbital assays by both CMIA and RIA showed that higher titres were obtained using the CMIA method. The standard curves suggest that CMIA is a reliable and reproducible immunoassay procedure for phenobarbital.

Crystal and molecular structures of 1,4-dibromo- and 1,4-diiodocubane

The crystal structure of 1,4-dibromocubane has been determined by X-ray diffraction. The crystal is monoclinic, P21/n, a = 6.878(1), b = 6.960(7), c = 8.793(2) Å, β = 113.08(2)°, Z = 2, R = 0.055. The C—Br bond length, at 1.926 Å, is shorter than usual and the carbon framework is probably distorted by longer bonds along the edges. The direct dipole coupling constants between protons, obtained from the partially oriented NMR spectrum, show that a distortion of the proton positions from the ideal cube occurs in the bromo compound but not in diiodocubane, presumably because of the higher strain energy in the former. Keywords: halocubanes, crystal structures, NMR spectroscopy, molecular modelling calculations.

Fourier transform infrared spectroscopic method for the quantitative trace analysis of transition-metal carbonyl-labeled bioligands

A quantitative FT-IR spectroscopic method has been developed for the trace analysis in chlorinated organic solvents of transition-metal carbonyl-labeled bioligands. In order to illustrate the widespread analytical potential of the method, three derivatives of the female hormonal steroid 17 beta-estradiol, containing Cr(CO)3, Cp2Mo2(CO)4 (Cp = eta 5-C5H5), and Co2(CO)6 as labels, and the anticonvulsant drug phenobarbital, labeled with (eta 5-C5H4)Mn(CO)3, were examined. The cobalt carbonyl marker proved to be the best sulted for quantitative analysis purposes, and the minimum tracer quantity detectable for this particular marker (64 scans, 4-cm-1 resolution, 3.5 min) was optimized in CCl4 solution at about 300 fmol (or 0.3 pmol, 180 pg) by using an ultralow volume (23.0 microL), gold light-pipe IR solution cell and a liquid nitrogen cooled, InSb (indium antimonide) IR detector. The repeatability of this radically different analytical procedure over the concentration range 1.0 x 10(-6) to 5.0 x 10(-8) M was good (coefficient of variance less than or equal to 6%) and the method provides the basis for a new immunological test--carbonylmetalloimmunoassay (CMIA).

(N-succinimidyl 4-pentynoate)hexacarbonyldicobalt: a transition-metal carbonyl complex having similar uses to the Bolton-Hunter reagent

The synthesis of the transition-metal carbonyl complex (N-succinimidyl 4-pentynoate)hexacarbonyldicobalt [[(C4H4O2N)O(CO)CH2CH2C identical to CH]Co2(CO)6] is described. This cobalt carbonyl complex is structurally similar to the Bolton-Hunter conjugation reagent and has been successfully employed as a nonradioactive tracer for labeling the drug carbamazepine. The metal carbonyl tracer can be detected at extremely low concentrations (ca. 1 pmol) by FT-IR spectroscopy in the v(CO) region (2150-1800 cm-1). The cobalt carbonyl labeled carbamazepine retains good recognition for anti-carbamazepine antibodies. This novel labeling procedure, which can be broadly termed carbonylmetalloimmunoassay (CMIA), has considerable potential for assaying a wide range of biological materials.

Organometallic estrogens: synthesis, interaction with lamb uterine estrogen receptor, and detection by infrared spectroscopy

As an integral part of the development of a new technique using organometallic markers for the detection of hormone receptors by FT-IR spectroscopy, a series of estradiol derivatives labeled with Cr(CO)3 or Cr(CO)2CS fragments on the A ring has been synthesized. The stereochemistry of one of these steroids, alpha-[3-(dimethyl-tert-butylsiloxy)-17 beta-estradiol]dicarbonyl(thiocarbonyl)chromium(0), has been established by X-ray diffraction. The organochromium-labeled steroids are stable in aqueous methanol solution, and their relative binding affinities to estrogen receptor have been determined; these values vary from 0.4 to 28%. The complex exhibiting the strongest affinity, [3-O-(3-hydroxypropyl)-17 beta-estradiol]-chromium tricarbonyl complex, has been prepared in a tritiated form with a high specific activity (4.1 Ci/mmol). This tritiated hormone binds reversibly to the estradiol receptor in lamb uterine cytosol with an affinity (Kd = 0.85 nM) and number of binding sites (n = 770 fmol/mg of protein) close to the values observed for estradiol itself. The level of nonspecific binding is low, and the hormone is not bound significantly to other nontarget tissues. The observation that the binding affinity of the steroid depends on which side of the steroidal A ring the organometallic label is bound demonstrates the nonequivalence of the two sides of the A ring with respect to the receptor site. The FT-IR spectra of the organochromium markers in the v(CO) region can be used for the detection of the estradiol receptor in lamb uterine cytosol.

Synthesis of some 6 beta-acetylthio hydroxysteroids

The reactions of 3 beta-hydroxy-20-oxo-5-pregnene-16 alpha-carbonitrile, 3 beta-hydroxy-5-androsten-17-one, 3 beta-hydroxy-5-pregnen-20-one, and 5-cholesten-3 beta-ol with thioacetic acid in dioxane afford mainly 6 beta-acetylthio derivatives which were characterized by IR, NMR (1H, 13C), and mass spectroscopy. A similar reaction of 17 beta-hydroxy-1,4-androstadien-3-one yields chiefly the known 1 alpha-SCOCH3 derivative.

Barriers to rotation of the cyclopentadienyl ligand: spin-lattice relaxation time measurements and atom–atom potential calculations on cyclopentadienyl manganese and rhenium tricarbonyl and vanadium tetracarbonyl complexes

The barriers to cyclopentadienyl ring rotation in the solid phase have been measured by spin-lattice relaxation time methods for the organometallic complexes CpMn(CO)3 (7.24 kJ mol−1), CpRe(CO)3 (7.15 kJ mol−1), and CpV(CO)4 (7.07 kJ mol−1), where Cp = η5-C5H5. Nonbonded atom–atom potential calculations of the barriers in these complexes and in BzCr(CO)3 (Bz = η6-C6H6) show that the molecular conformation of the Mn and Re compounds is determined by crystal packing forces and that concerted ring motions are possible for the cyclopentadienyl complexes, but not for the benzene chromium tricarbonyl.

Reactions of metal carbonyl complexes. VIII. Kinetics and mechanisms of the substitution reactions of cis-Mn(CO)4LBr (L = PPh3, AsPh3, SbPh3) with group VA bidentate ligands

The substitution reactions of cis-Mn(CO)4LBr (L = PPh3, AsPh3, SbPh3) with diphos, diarsine, and dipy (A—A) take place with the loss of one CO group and L to form fac-Mn(CO)3(A—A)Br. The observed reaction rates in CHCl3 solution are first order in substrate but depend on the nature of L and A—A, and in some cases the concentration of A—A as well. When L = PPh3 and A—A = diphos, and when L = AsPh3 and A—A = diphos, diarsine, or dipy, the rates are independent of [A—A]. For these reactions, an SN1 dissociative mechanism involving the rupture of one of the Mn—CO bonds as the rate-determining step is proposed. The observed positive entropies of activation (∼10 e.u.) for these reactions are supportive of the proposed mechanism. The reactions of cis-Mn(CO)4(SbPh3)Br with A—A are essentially independent of both the nature and the concentration of A—A. However, for these reactions, an SN1 dissociative mechanism involving the rupture of the Mn—SbPh3 bond as the rate-determining step is proposed; the observed positive ΔS≠ values (∼12 e.u.) are in accord with such a mechanism. The rates when L = PPh3 and A—A = diarsine or dipy are dependent on both the nature and the concentration of A—A. A mechanism involving rapid pre-equilibrium steps between the parent molecule and the intermediates, Mn(CO)3(PPh3)Br and Mn(CO)4Br, is proposed to account for the complex kinetic behaviour found for these reactions. These results are particularly noteworthy because octahedral first-row transition metal complexes generally undergo substitution reactions which are independent of the concentrations of the entering nucleophiles.

Vibrational spectra of η5-cyclopentadienyldicarbonyl(thiocarbonyl)-manganese(I) and η5-cyclopentadienylcarbonyl(dithiocarbonyl)-manganese(I)

The ir and laser Raman spectra of η5-C5H5Mn(CO)2(CS) and η5-C5H5Mn(CO)(CS)2 have been investigated. In the case of the monothiocarbonyl complex, vapor phase, solution, and solid-state measurements were made, while for the dithiocarbonyl, only solid-state data were obtained. The vibrational spectra of both complexes have been assigned satisfactorily in terms of the C5v and Cs local symmetries of the η5-C5H5—Mn and Mn(CO)2(CS) (or Mn(CO)(CS)2) moieties, respectively. The effect of change of state on the spectra of the monothiocarbonyl complex is discussed.

π-Cyclopentadienylmanganese Thiocarbonyl Complexes

The complete series of thiocarbonyl complexes, π-C5H5Mn(CO)3−x(CS)x(x = 1, 2, 3), have been prepared by reaction of the appropriate cis-cyclooctene derivative, π-C5H5Mn(CO)3−x(CS)x−1(C8H14), with CS2 in the presence of triphenylphosphine.

Vibrational spectra of halopentacarbonylmanganese(I) derivatives

The solid-state infrared (i.r.) and laser Raman spectra of the halopentacarbonylmanganese(I) derivatives, Mn(CO)5X (X = Cl, Br,and I), have been recorded in the C—O stretching and the low frequency (700–33 cm−1) regions. The i.r. overtone and combination spectra recorded in the regions 2800–2250 and 1350–700 cm−1 have been used to help in the assignment of some of the low frequency fundamentals. The solid-state i.r. and laser Raman spectra of the dimeric halotetracarbonylmanganese(I) derivatives, [Mn(CO)4X]2 (X = Br and I), have been recorded in the C—O stretching and the low frequency regions for comparative purposes and shown to be consistent with the expected D2h symmetry of the molecules.