Structure characterization

In recent years, advances in experimental capabilities have fueled a great deal of activity in the study of the electrified solid-liquid interface. This has been the subject of a recent workshop and review article [145] discussing structural characterization, interfacial dynamics and electrode materials. The field of surface chemistry has also received significant attention due to many surface-sensitive means to interrogate the molecular processes occurring at the electrode surface. Reviews by Hubbard [146, 147] and others [148] detail the progress. In this and the following section, we present only a brief summary of selected aspects of this field. 

Time-of-flight mass spectrometers have been used as detectors in a wider variety of experiments tlian any other mass spectrometer. This is especially true of spectroscopic applications, many of which are discussed in this encyclopedia. Unlike the other instruments described in this chapter, the TOP mass spectrometer is usually used for one purpose, to acquire the mass spectrum of a compound. They caimot generally be used for the kinds of ion-molecule chemistry discussed in this chapter, or structural characterization experiments such as collision-induced dissociation. Plowever, they are easily used as detectors for spectroscopic applications such as multi-photoionization (for the spectroscopy of molecular excited states) [38], zero kinetic energy electron spectroscopy [39] (ZEKE, for the precise measurement of ionization energies) and comcidence measurements (such as photoelectron-photoion coincidence spectroscopy [40] for the measurement of ion fragmentation breakdown diagrams). 

Porter M D, Bright T B, Allara D L and Chidsey C E D 1987 Spontaneously organized molecular assemblies. 4. Structural characterization of normal-alkyl thiol monolayers on gold by optical ellipsometry, infrared-spectroscopy, and electrochemistry J. Am. Chem. Soc. 109 3559-68... 

Nuzzo R G, Dubois L FI and Allara D L 1990 Fundamental-studies of microscopic wetting on organic-surfaces. 1. formation and structural characterization of a self-consistent series of polyfunctional organic monolayers J. Am. Chem. Soc. 112 558-69... 

Bawendi M G ef a/1989 X-ray structural characterization of larger CdSe semiconductor clusters J. Chem. Phys. 91 7282... 

Fast and accurate predictions of H NMR chemical shifts of organic compounds arc of great intcrc.st for automatic stnicturc elucidation, for the analysi.s of combinatorial libraries, and, of course, for assisting experimental chemists in the structural characterization of small data sets of compounds. 

BW Beck, Q Xie, T Ichiye. Computational study of S—H S hydrogen bonds m [4Ee-4S]-type ferredoxm x-ray and NMR structures Characterization and implications for redox potentials. Protein Sci, submitted. 

Element-selective phase identification and quandfica-tion, structural characterization of disordered states... 

A,/2 for topography characterization much smaller for periodic structure characterization (A, is the laser wavelength used to illuminate the sample)... 

Raman spectroscopy is primarily a structural characterization tool. The spectrum is more sensitive to the lengths, streng ths, and arrangement of bonds in a material than it is to the chemical composition. The Raman spectmm of crystals likewise responds more to details of defects and disorder than to trace impurities and related chemical imperfections. 

Rodrigucz-Rcinoso, F., Activated carbon structure, characterization,... 

Radical cations can be derived from aromatic hydrocarbons or alkenes by one-electron oxidation. Antimony trichloride and pentachloride are among the chemical oxidants that have been used. Photodissociation or y-radiation can generate radical cations from aromatic hydrocarbons. Most radical cations derived from hydrocarbons have limited stability, but EPR spectral parameters have permitted structural characterization. The radical cations can be generated electrochemically, and some oxidation potentials are included in Table 12.1. The potentials correlate with the HOMO levels of the hydrocarbons. The higher the HOMO, the more easily oxidized is the hydrocarbon. 

High-resolution transmission electron microscopy (HREM) is the technique best suited for the structural characterization of nanometer-sized graphitic particles. In-situ processing of fullerene-related structures may be performed, and it has been shown that carbonaceous materials transform themselves into quasi-spherical onion-like graphitic particles under the effect of intense electron irradiation[l 1],... 

Pleated p sheet (Section 27.19) Type of protein secondary structure characterized by hydrogen bonds between NH and C=0 groups of adjacent parallel peptide chains. The individual chains are in an extended zigzag conformation. 

The thiotrithiazyl cation in [S4N3]C1 was one of the first S-N heterocycles to be prepared and structurally characterized. It is obtained as a reasonably air-stable, yellow solid by the reaction of S4N4 or [SsNaClJCl with S2CI2 in CCI4 (Eq. 5.12)." ... 

A variety of complexes of the thionyl imide anion [NSO] with both early and late transition-metal complexes have been prepared and structurally characterized. Since both ionic and covalent derivatives of this anion are readily prepared, e.g., K[NSO], McsMNSO (M = Si, Sn) or Hg(NSO)2, metathetical reactions of these reagents with transition-metal halide complexes represent the most general synthetic method for the preparation of these complexes (Eq. 7.10 and 7.11). ... 

MeNSO and 120° in HNSO, cf. 119° in SO2. The trityl derivative PhsCNSO is the only alkyl derivative to have been structurally characterized in the solid state. 

A number of transition-metal complexes of RNSO ligands have been structurally characterized. Three bonding modes, r(A,5), o-(5)-trigonal and o (5 )-pyramidal, have been observed (Scheme 9.1). Side-on (N,S) coordination is favoured by electron-rich (et or j °) metal centers, while the ff(S)-trigonal mode is preferred for less electron-rich metal centres (or those with competitive strong r-acid co-ligands). As expected ti (N,S)... 

There is no evidence for the tellurium analogues ArN=Te, but the cyclic trimers (EN Bu)3 (E = Se, Te) are stable crystalline solids that have been structurally characterized (Section 6.3). 

The only selenium diimide to be structurally characterized in the solid state, Se(NAd)2 (Ad = adamantyl), ° adopts the cis, trans conformation consistent with conclusions based on H and C NMR studies for Se(N Bu)2. ... 

The structure of the isomeric benzo-l,2,3-thiadiazole 11.30 is unknown, but the 1 1 adduct with AsFs (11.31) has been structurally characterized. The AsFs molecule is coordinated to the carbon-bonded nitrogen atom. Cycloocteno-l,2,3-selenadiazole is an effective source of selenium for the production of semi-conductors such as cadmium selenide." ... 

---