Two-dimensional infrared spectra of peptides are introduced that the direct analogues two- and three-pulse multiple quantum NMR. Phase matching heterodyning used to isolate phase amplitudes electric fields vibrational photon echoes as a function pulse delays. Structural information is made available on time scale few picoseconds. Line narrowed acyl-proline-NH 2 cross peaks implying coupling between its amide-I modes obtained, phases various contributions signals. Solvent-sensitive structural...

Chemical reactions that break alkane carbon-hydrogen (C–H) bonds are normally carried out under conditions of high temperature and pressure because these extremely strong (∼100 kilocalories per mole), but certain metal complexes can activate C–H in solution the mild room pressure. Time-resolved infrared experiments probing initial femtosecond dynamics through nano- microsecond kinetics to final stable products have been used generate a detailed picture activation reaction. Structures all...

The stimulated infrared photon echo of N-methylacetamide-D [NMAD; CH3(CO)ND(CH3)] was measured and used to determine the vibrational frequency correlation function. function modeled as a single exponential plus constant, it found that most NMAD distribution is motionally narrowed with pure dephasing time 1.12 ps. two-dimensional (2D IR) spectrum also obtained by heterodyning field weak local oscillator pulse. real imaginary portions 2D IR exhibit multiple peaks due υ=0–1 1–2 coherences are...

The ultrafast dynamics of the dissociation M(CO)6 (M = Cr, W, Mo) in alkane solutions were studied by femtosecond IR spectroscopy. After UV photolysis at 295 nm, both bleach parent molecules and absorption pentacarbonyl intermediate probed with 240 fs time resolution. Oscillatory perturbed free induction decay signals before t 0 observed well characterized realistic parameters system. recovery found to be wavelength dependent, indicating that hot are formed is determined vibrational cooling...

Although polydimethylsiloxane (PDMS) transfer during microcontact printing (microCP) has been observed in previous reports, which generally focused on only one or a few different substrates, this work we investigate the extent of PDMS onto series surfaces with wide range hydrophobicities using an uninked, unpatterned stamp. These include clean silicon, titanium, gold, "dirty" polystyrene, Teflon, modified PEG, amino, dodecyl, and hexadecyl monolayers, also two loose molecular materials. The...

A quick and convenient method was developed to synthesize organically functionalized silicon nanocrystals via a one-step reaction, which is green chemistry route.

The Si−H bond activation reactions by group VIIB, d6 organometallic compounds η5-CpM(CO)3 (M = Mn, Re; Cp C5 H5) were studied in neat triethylsilane under ambient conditions. Utilizing femtosecond and nanosecond pump−probe spectroscopic methods, the spectral evolution of CO stretching bands was monitored from 300 fs to tens microseconds following UV photolysis. reactive intermediates observed on ultrafast time scale also using ab initio quantum chemical modeling. It found that photolysis...

Here we describe a new and simple method for preparing alkyl monolayers on silicon, which consists of mechanically scribing oxide-coated silicon while it is wet with 1-alkenes or 1-alkynes (neat in inert solvents) under ambient conditions. X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, wetting data, stability tests suggest covalent bonding unsaturated species to exposed surfaces. Enclosures (hydrophobic corrals) made by that hydrophobic hold droplets water...

We examined complexes between cucurbit[6]uril and each of ortho-, meta-, para-phenylenediamine using computational methods, Fourier transform ion cyclotron resonance mass spectrometry, mobility spectrometry. These fundamental gas phase studies show that the lowest energy binding sites for ortho- meta-phenylenediamine are on exterior cucurbit[6]uril, whereas preferentially binds in interior, a pseudorotaxane fashion. This conclusion is based reactivity with tert-butylamine, where exchange...

The photochemical C-H activation reactions of eta(3)-TpRh(CO)(2) (Tp = HB-Pz(3), Pz 3,5-dimethylpyrazolyl) and CpRh(CO)(2) (Cp C(5)H(5)) have been studied in a series linear, cyclic, aromatic hydrocarbon solvents on femtosecond to microsecond time scale. These results revealed that the structure substrate affects final bond step, which is accordance with known preference toward primary sites. In case activation, reaction divided into parallel channels involving sigma- pi-solvated...

Protein arrays continue to increase in importance as tools for analysis of biological samples. This paper describes a new method preparing bioarrays that is compatible with high throughput manufacturing. First, native oxide terminated silicon substrate coated monolayer polyethylene-glycol-containing silane. The then placed beneath microlens array (MA) and the irradiated brief (4 ns) pulse 532 nm laser light. MA focuses light onto substrate, causing removal. microlenses employed this work are...

A synthesis of the hasubanan alkaloids hasubanonine, runanine, and aknadinine via a unified route was attempted. Construction key phenanthrene intermediates by Suzuki coupling−Wittig olefination−ring-closing metathesis sequence allowed convergent flexible approach. Conversion phenanthrenes into target structures projected to involve six steps including phenolic oxidation, ketone allylation, anionic oxy-Cope rearrangement, acid-promoted cyclization. The final step thwarted pinacol-like...

The interpretation of vibrationally resonant sum-frequency generation (VR-SFG) spectra is often complicated by two factors: spectral congestion and the presence a nonresonant signal. With broadband VR-SFG systems, are further distorted because incomplete sampling, or apodization, free induction decay (FID) in time domain. An experimental method presented that takes advantage these time-domain effects to obtain more accurate parameters than can be achieved fitting single spectrum. acquired at...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUltrafast Infrared Studies of Bond Activation in Organometallic ComplexesHaw Yang, Kenneth T. Kotz, Matthew C. Asplund, J. Wilkens, and Charles B. HarrisView Author Information Department Chemistry, University California, Berkeley, California 94720, Chemical Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, 94720 Cite this: Acc. Chem. Res. 1999, 32, 7, 551–560Publication Date (Web):February 26, 1999Publication History...

The selective adsorption of reagents is often essential for bioarray and lab-on-a-chip type devices. As the starting point a bioarray, alkyl monolayer terminated silicon shards were photopatterned in few nanoseconds with thousands wells (spots) using an optical element, microlens array. Polyallylamine (PAAm), primary amine containing polymer, adsorbed little selectivity to spots, i.e., oxide, over hydrophobic background. However, at appropriate concentrations, addition cationic surfactant...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTFemtosecond Infrared Studies of Silane Silicon−Hydrogen Bond ActivationH. Yang, K. T. Kotz, M. C. Asplund, and B. HarrisView Author Information Department Chemistry, University California Berkeley, 94720 Cite this: J. Am. Chem. Soc. 1997, 119, 40, 9564–9565Publication Date (Web):October 8, 1997Publication History Received20 May 1997Published online8 October inissue 1...

Vibrational photon echo experiments on the CO stretching mode of carbon monoxide bound to hemoglobin revealed pronounced oscillations with a beat frequency which corresponds anharmonicity vibrator. Intensity-dependent measurements show that oscillatory signal is due interference between third- and fifth-order polarization. Such cannot occur in third-order unless inhomogeneous width exceeds anharmonicity. An expression derived simultaneously describes intensity dependence, phase, damping...

Methyl-terminated and acyl chloride terminated monolayers are produced when silicon is scribed under mono- diacid chlorides, respectively. To the best of our knowledge, this first report reaction between a bare surface acid chlorides. This takes place by wetting in air with scribing. Scribing activates removing its passivation layer. We propose that abstracts chlorine from an to form Si-Cl bond resulting radical diffuses back condense alkyl monolayer. X-ray photoelectron spectroscopy (XPS)...

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed on monolayers prepared by scribing silicon under a homologous series of 1-alkenes, 1-alkynes, and 1-haloalkanes: CH2CH(CH2)nCH3 (n = 2, 5, 9), HC⋮C(CH2)nCH3 Cl(CH2)nCH3 4, 7, Br(CH2)nCH3 11), I(CH2)nCH3 0, 1, I13CH3. Numerous SiCxHy+ CxHy+ fragments adduct ions were observed. The results support proposed binding model that 1-haloalkanes bind to the surface through one C−Si bond 1-alkenes 1-alkynes generally two bonds....

The reaction of epoxides with a bare silicon surface is reported (see scheme). Diepoxides yield amine-reactive monolayers on scribed silicon. Controlled levels epoxide functionality are obtained in mixed 1,2-epoxyoctane and 1,2,7,8-diepoxyoctane. Supporting information for this article available the WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z50846_s.pdf or from author. Please note: publisher not responsible content any supporting supplied by authors. Any queries (other than...