Silver(I) salts with penicillin anions

Silver(I) salts with benzylpenicillin (Bzp^–), ampicillin (Amp^–), and oxacillin (Oxa^–) anions with compositions of AgBzp, AgAmp, and AgOxa are isolated from an aqueous solution in the solid state and characterized by IR spectroscopy and thermal analysis (TG/DSC). IR spectroscopy data lead to the conclusion that Ag(I) coordinates the Oxa^– ion through carbonyl oxygen atoms of the ß-lactam and amide groups. No coordination is observed for the Bzp^– and Amp^– anions.     

A thermal oxidative degradation study of triallyl isocyanurate crosslinking moiety in fluorinated rubber by two-dimensional infrared correlation spectroscopy

Thermal degradation of crosslinking moiety in fluorinated rubbers was studied with a new method using spatial-dependent infrared (IR) microscopy and two-dimensional (2D) IR correlation spectroscopy. Upon heating the fluorinated rubber, initially the amount of crosslinker decreased followed by generating another chemical species with carbonyl substituent with IR absorption at around 1730 cm^–1, implying generation of carboxylic acids forming intermolecular hydrogen bonding. Furthermore, projection 2D IR correlation analysis revealed that another chemical species with IR absorption at around 1755 cm^–1 generates, indicating that further degradation progresses upon heating and intermolecular hydrogen bonding were broken. As a result, the multi-step degradation process of the crosslinker in the fluorinated rubber could be detected by combination of spatial-dependent IR microscopy and projection 2D IR correlation spectroscopy.     

Bridge‐Localized HOMO‐Binding Character of Divinylanthracene‐Bridged Dinuclear Ruthenium Carbonyl Complexes: Spectroscopic,Spectroelectrochemical, and Computational Studies

The electronic properties of four divinylanthracene‐bridged diruthenium carbonyl complexes [{RuCl(CO)(PMe₃)₃}₂(μ? CH?CHArCH?CH)] (Ar=9,10‐anthracene ( 1 ), 1,5‐anthracene ( 2 ), 2,6‐anthracene ( 3 ), 1,8‐anthracene ( 4 )) obtained by molecular spectroscopic methods (IR, UV/Vis/near‐IR, and EPR spectroscopy) and DFT calculations are reported. IR spectroelectrochemical studies have revealed that these complexes are first oxidized at the noninnocent bridging ligand, which is in line with the very small ν(C?O) wavenumber shift that accompanies this process and also supported by DFT calculations. Because of poor conjugation in complex 1 , except oxidized 1⁺ , the electronic absorption spectra of complexes 2⁺ , 3⁺ , and 4⁺ all display the characteristic near‐IR band envelopes that have been deconvoluted into three Gaussian sub‐bands. Two of the sub‐bands belong mainly to metal‐to‐ligand charge‐transfer (MLCT) transitions according to results from time‐dependent DFT calculations. EPR spectroscopy of chemically generated 1⁺ – 4⁺ proves largely ligand‐centered spin density, again in accordance with IR spectra and DFT calculations results.     

Quantitative Determination of Fluconazole by Infrared Spectrophotometry

Abstract

The purpose of the study was the quantitative determination of fluconazole by IR spectrophotometry which was realized by the application of the KBr disc technique. In this study dehydrocholic acid was used as internal standard.

The absorption bands at 960 and 675 cm^?1 were chosen for fluconazole and 1705 cm^?1 for dehydrocholic acid. The concentration range between 0.4–1.6% w/w in KBr disc showed compliance with Beer's law.

Besides IR spectroscopy, UV spectroscopy and HPLC methods were also used In the quantitative determinations. In the UV spectroscopy method the absorbance value at 261 nm in MeOH was used for fluconazole. In quantitative determinations which were performed by using HPLC, ketoconazole was the internal standard. Different regression equations were applied for each method in order to complete the quantitative determination. In UV spectroscopy and HPLC methods, relative standards were found as 0.74, 1.04% and in IR spectroscopy (675, 960 cm^?1) relative standards were found as 1.1 and 1.51%, respectively.     

Synthesis and structure of nitroethylpyrrolidone carboxylates

3-Methoxycarbonyl-4-phenyl- and 4-(3-pyridyl)-2-pyrrolidones react with 2-aryl(heteryl)-1-nitroethenes to form C³-adducts as one or two diastereomers. Their structure was characterized by the IR, ¹H, and ¹³C NMR spectroscopy, using the two-dimensional correlation spectroscopy.     

Polysiloxane-Modified Mesoporous Materials

We report the preparation of polysiloxane-modified mesoporous silica gels derived from the acid catalysed hydrolysis of tetraethoxysilane (TEOS) and oligomeric silanol terminated polydimethylsiloxane (PDMS) in the presence of the non-ionic surfactant, octaethylene glycol monohexadecyl ether. The gels were characterised using thermal gravimetric analysis (TGA), infra-red (IR) spectroscopy, X-ray diffraction (XRD) and ²⁹Si solid state cross-polarisation (CP) magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. TGA and IR spectroscopy showed the loss of surfactant after calcination and a decrease in the Si–OH band at 950 cm^–1 indicated further condensation had occurred. This was confirmed by the increase in Q⁴ at –110 ppm, in ²⁹Si MAS NMR spectroscopy, which also showed that calcination had led to the redistribution of PDMS forming a T species. XRD data showed ordering within the structure, with an initial d-spacing of 45 Å, decreasing to 35 Å after calcination.     

Rhodium and iridium complexes containing nitrosoarene ligands

A number of new nitrosoarene complexes of rhodium(I) and iridium(I) have been prepared, and characterized by elemental analysis, IR spectroscopy and ¹H NMR spectroscopy. Some reactions of the complexes have been studied.     

Preparation and Characterization of Polyborosiloxanesand Their Blends with Phenolic Resin as ShapeableCeramic Precursors简

Two polyborosiloxanes(PBSis) with char yield up to 74.13% at 800 °C were synthesized by the direct polycondensation of boric acid with phenyltrimethoxysilane in diglyme. The PBSis were characterized by gel permeation chromatography, IR spectroscopy as well as1H-,29Si- and11B-NMR. PBSi modified phenol-formaldehyde resins(PBSi/PFs) were prepared at different PBSi/PF mass ratios and were cured at 150 °C. The PBSi/PFs were characterized by IR spectroscopy, scanning electron microscopy, thermogravimetric analysis and tensile test. The results revealed that the cured PBSi/PFs had sea-island morphology and higher char yield than the common PF. PBSi/PF blend with PBSi/PF mass ratio of 0.4:1 had char yield up to 70.83% at 800 °C. The PBSi/PFs had tensile strength similar to PF. The ceramization of PBSi/PFs was also studied. The silicon boron oxycarbide(SiBOC) ceramics formed were characterized by IR spectroscopy and elemental analysis. This method provided a valuable way to prepare easily shapeable polymer blends as ceramic precursors.     

Product analyses and crosslink mechanism of plasma-polymerized methyl methacrylate

Plasma-polymerized methyl methacrylate (PPMMA) film was produced by a radio-frequency glow discharge of methyl methacrylate (MMA) gas with argon. PPMMA deposited under a plasma of mild energy was separated into a soluble fraction (sol-PPMMA) and an insoluble matrix (insol-PPMMA), which is highly crosslinked, by solvent-extraction and filtration. The chemical structure of the sol-PPMMA was determined by pyrolysis/gas chromatography, IR spectroscopy, ¹H-NMR, ¹³C-NMR, and elemental analysis techniques. On the other hand, the structure of the insol-PPMMA was examined with IR spectroscopy, ¹³C-NMR with CP/MAS method, and elemental analysis. The crosslinking mechanism in the plasma polymerization of MMA is discussed on the basis of product analyses of the sol-PPMMA and the insol-PPMMA.     

Pyridine induced disproportionation reaction of Co2(CO)8 in THF: Homonuclear ion pairs and dihydrogen activation

The IR spectra of the Co²⁺/Py/Co(CO)₄⁻, system in THF reveal complex associative phenomena. Three kinds of homonuclear ion pairs were distinguished by means of variable temperature IR spectroscopy. Under the conditions in which these associative equilibria exist cobalt(II) is reduced by dihydrogen to cobalt( −I) under 1 atm of syngas at room temperature.     

Synthesis,characterization, and antimicrobial activity of heterobimetallic complexes of Sn(IV) and Zn(II) with 4-aminophenylacetic acid

A series of new heterobimetallic complexes of zinc and tin with 4-aminophenylacetic acid has been prepared. Their composition and structure in solid state and in solution have been elucidated by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopy. IR spectroscopy results have confirmed the bidentate nature of the ligand, its molecules being arranged in planar square [Zn(II)] and trigonal bipyramid [Sn(IV)] around the metal ions. NMR studies have revealed four-coordinated geometry in the solution. The complexes containing both Sn(IV) and Zn(II) are better antimicrobial agents as compared to the Zn-only analog.     

Synthesis of O,O‐Diphenyl N‐trichlorogermanylpropiono‐α‐aminophosphonates

A variety of novel O,O‐Diphenyl N‐(trichlorogermanyl)propiono‐α‐aminophosphonates were synthesized by the reaction of β‐(trichlorogermanyl) propionyl chloride with diphenyl α‐aminophosphonates in the presence of triethylamine. The structures of all of the products were confirmed by ¹H‐NMR spectroscopy, elemental analyses, and IR spectroscopy. Data of ¹H‐NMR and IR spectroscopic determinations indicated the title compounds to be pentacoordinated organogermanium compounds. The results of bioassay showed that some of the title compounds possess potential anticancer activity. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 5–8, 1999     

One‐Step Synthesis of Multiphase Block Copolymers via Simultaneus Free Radical and Ring Opening Polymerization Using Poly(ethylene oxide) Possessing Azo Group

Multiphase block copolymers having the structure of poly(?‐caprolacton‐b‐etyhlene glycol‐b‐styrene‐b‐ethylene glycol‐b‐?‐caprolacton) were synthesized from poly(ethylene oxide) possesing azo group in the main chain by the combination of free radical polymerization (FRP) of styrene (S) and ring opening polymerization (ROP) of ?‐caprolacton (?‐CL) in one‐step. The block copolymers were characterized ¹H‐NMR and FT‐IR spectroscopy and gel permeation chromatography (GPC). ¹H‐NMR and FT‐IR spectroscopy and GPC studies of the obtained polymers indicate that multiphase block copolymers easily formed as a result of combination FRP and ROP in one‐step.     

Phosphate Derivatives of Natural Lactones. II. Synthesis of Novel Dialkylphosphonates of Arteannuin B

Novel dialkylphosphonates of arteannuin B were synthesized in 45-47% yields by reaction of this cadinanolide with dialkylphosphites. Their structures were established using IR, PMR, ¹³C and ³¹P NMR spectroscopy, and two-dimensional ¹H-¹H NMR (COSY) spectroscopy. The reaction of arteannuin B and dialkylphosphites is highly stereoselective.     

Spectroscopic Studies on the Interaction of Asiatic Acid with Bovine Serum Albumin

Fluorescence spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, circular dichroism (CD) and FT‐Raman spectroscopy were employed to analyze the binding of the asiatic acid (AA) to bovine serum albumin (BSA) under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by AA was the result of the formation of BSA‐AA complex. The fluorescence quenching mechanism of BSA by AA was a static quenching procedure. According to the Van′t Hoff equation, the thermodynamic parameters enthalpy change (ΔH⁰) and entropy change (ΔS⁰) for the reaction were evaluated to be ?12.55 kJ·mol^?1 and 67.08 kJ·mol^?1, respectively, indicating that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The influence of AA on the conformation of BSA has also been analyzed on the basis of FT‐IR, CD and FT‐Raman spectra.     

New metallocene-bridged cyclodextrin dimer: A stable derivative of the antitumor drug titanocene dichloride and its potent cytotoxity against human breast cancer (MCF-7) cells

A novel cyclodextrin dimer bridged with titanocene moiety, titanocene di[mono[6-deoxy-6-(2-(thio-1,2-dicyane ethylenylthio)ethyl thio-1,2-dicyane ethylenylthio)]-β-cyclodextrin] (6), has been synthesized and characterized by IR spectroscopy, UV spectroscopy, thermogravimetry, MALDI-TOF MS spectrum, ¹H and ¹³C NMR spectroscopy. Especially, its potent cytotoxity against Human Breast Cancer (MCF-7) has also been studied.     

Gas‐Phase Peptide Structures Unraveled by Far‐IR Spectroscopy: Combining IR‐UV Ion‐Dip Experiments with Born–Oppenheimer Molecular Dynamics Simulations

Vibrational spectroscopy provides an important probe of the three‐dimensional structures of peptides. With increasing size, these IR spectra become very complex and to extract structural information, comparison with theoretical spectra is essential. Harmonic DFT calculations have become a common workhorse for predicting vibrational frequencies of small neutral and ionized gaseous peptides. ¹ Although the far‐IR region (<500 cm^?1) may contain a wealth of structural information, as recognized in condensed phase studies, ² DFT often performs poorly in predicting the far‐IR spectra of peptides. Here, Born–Oppenheimer molecular dynamics (BOMD) is applied to predict the far‐IR signatures of two γ‐turn peptides. Combining experiments and simulations, far‐IR spectra can provide structural information on gas‐phase peptides superior to that extracted from mid‐IR and amide A features.     

Aggregation Behaviors of Tricarbocyanine Dye in Water and in AOT Reverse Micelles

The photophysical property of the tricarbocyanine dye IR144 has been extensively studied in non‐aqueous solvents. However, as a potential near‐infrared biomedical imaging probe, the photophysical property of IR144 in water is still little known. So, the aggregation behaviors of IR144 in water with steady‐state absorption spectroscopy and integrated polarization dependent femtosecond pump‐probe spectroscopy were investigated. Through comparing the absorption spectral bandshape of IR144 in water and in water pool of AOT reverse micelles, It is found that IR144 form dimer aggregates in water even at very low concentration (<1.0×10^?7 mol·L^?1). And the absorption spectrum of the IR144 aggregates always displays a bimodal feature, which is independent of the dye concentration ranging from 1.0×10^?7 to 1.0×10^?4 mol·L^?1. For better understanding the aggregation behaviors of IR144 in water, we measured the ground state recovery kinetics and the reorientation kinetics of IR144 in water and in water pool of AOT reverse micelles (W₀=[H₂O]/[AOT], W₀=40). It is found that the fluorescence quantum yield of IR144 in water is lower than that in water pool of AOT reverse micelles, and the reorientation time of IR144 in water is slower than that in water pool of AOT reverse micelles. Those kinetic measurements also verify that IR144 exists as dimer aggregates in water.     

Solvent Migration in Microhydrated Aromatic Aggregates: Ionization‐Induced Site Switching in the 4‐Aminobenzonitrile–Water Cluster

The dependence of the preferred microhydration sites of 4‐aminobenzonitrile (4ABN) on electronic excitation and ionization is determined through IR spectroscopy of its clusters with water (W) in a supersonic expansion and through quantum chemical calculations. IR spectra of neutral 4ABN and two isomers of its hydrogen‐bonded (H‐bonded) 4ABN–W complexes are obtained in the ground and first excited singlet states (S₀, S₁) through IR depletion spectroscopy associated with resonance‐enhanced multiphoton ionization. Spectral analysis reveals that electronic excitation does not change the H‐bonding motif of each isomer, that is, H₂O binding either to the CN or the NH site of 4ABN, denoted as 4ABN–W(CN) and 4ABN–W(NH), respectively. The IR spectra of 4ABN⁺–W in the doublet cation ground electronic state (D₀) are measured by generating them either in an electron ionization source (EI‐IR) or through resonant multiphoton ionization (REMPI‐IR). The EI‐IR spectrum shows only transitions of the most stable isomer of the cation, which is assigned to 4ABN⁺–W(NH). The REMPI‐IR spectrum obtained through isomer‐selective resonant photoionization of 4ABN–W(NH) is essentially the same as the EI‐IR spectrum. The REMPI‐IR spectrum obtained by ionizing 4ABN–W(CN) is also similar to that of the 4ABN⁺–W(NH) isomer, but differs from that calculated for 4ABN⁺–W(CN), indicating that the H₂O ligand migrates from the CN to the NH site upon ionization with a yield of 100 %. The mechanism of this CN→NH site‐switching reaction is discussed in the light of the calculated potential energy surface and the role of intracluster vibrational energy redistribution.     

Nanoscale chemical structure variations in nano-patterned and nano-porous low-k dielectrics: A comparative photothermal induced resonance and infrared spectroscopy investigation

The recent development of the photothermal induced resonance (PTIR) technique has enabled atomic force microscope based infrared (AFM-IR) spectroscopy and imaging to be achieved at the nanometer scale. However, a direct correspondance between PTIR/AFM-IR and more traditional Fourier transform IR (FTIR) spectroscopy has been prohibited for nanometer scale features due to Rayleigh diffraction constraints that limit the latter to few micron spatial resolution. In this regard, we have overcome this challenge by fabricating 1 cm² arrays of 90 nm wide fins in a nano-porous low dielectric constant (i.e. low-k) amorphous hybrid inorganic-organic silicate material using standard nano-electronic fabrication techniques. With these structures, we demonstrate both a general correspondance between AFM-IR, FTIR, and Germanium attenuated total reflection (GATR) IR spectroscopy, as well as differences in the sensitivities that these techniques exhibit to the nanoscale variations in chemical structure induced in the low-k dielectric by the nanopatterning method. To further illustrate the sensitivity of AFM-IR to changes in chemical structure with nanometer resolution, the nanopatterned low-k dielectric was exposed to additional oxidizing plasma ash cleans post patterning. Focusing on the Si-CH₃ deformation band at ∼1275 cm⁻¹, both the AFM-IR, FTIR and GATR measurements show a clear reduction in the concentration of terminal methyl groups in the low-k dielectric as the oxidation potential of the plasma ash clean increased. These results further establish the power of AFM-IR to perform nanoscale IR spectroscopy and demonstrates a stronger correspondance between AFM-IR and well-known micron scale IR techniques such as FTIR and GATR.