X-Ray Diffraction Investigation

The crystal structure of the 1-methyl-2,7-dioxo-2,3-dihydro-l//,7//-pyrido[3,2,l-y]cinnoline-8-carboxylate 22 was determined by means of an X-ray diffraction investigation <1995T11125>. In this case, the 1-methyl group is almost coplanar with the 4-oxoquinoline moiety. X-Ray investigations on l-methyl-7-oxo-2,3-dihydro-l//,7//-pyrido[3,2,l-y]cinnoline-8-carboxylate 23 revealed that 1-methyl group is perpendicular to the plane of the 4-quinolone moiety <1996BCJ1371>. 

Figure 13.1 Known modes of isocyanide coordination to one, two and three metals in compounds whose stmctures have been established by X-ray diffraction investigations.

The crystal structure of ethyl 4-(4-rert-butoxycarbonyl-l-piperazinyl)-5-fluoro-2,3-dihydro-l-methyl-2,7-dioxo-l//,7//-pyrido[3,2,l-iy]cinnoline-8-carboxylate (186, R = Et, R = tert-Qu, R = 4-tm-butoxycarbonyl-l-piperazinyl) was determined by means of X-ray diffraction investigation [95T11125]. 

The reaction between dry phosphine and hydrogen iodide, first described in 1817 by J. J.Houtonde la Billardiere produces phosphonium iodide. The simplest laboratory preparation of this compound is by the hydrolysis of an intimate mixture of diphosphorus tetraiodide and white phosphorus According to X-ray diffraction investigations, phosphonium iodide crystallises in a caesium chloride type lattice 3m,32s). 326) hydrogen atoms... 

A rmique tin-containing complex was recently solved by X-ray crystallography. X-ray diffraction investigation of... 

Limited knowledge exists with respect to detailed molecular structures of simple pyrans and heteropyrans. The semiempirical CNDO/2 calculations, using a full geometry optimization procedure, predict 4 and 5 to exhibit small deviations of the heterocyclic rings from the planar conformations.34 Unfortunately, similar calculated data for thiopyrans 6, 7, and 9 were not presented.45 Accounts of several X-ray diffraction investigations on compounds possessing pyran or thiopyran fragments are available.46 51... 

The solid-state structure of (lS)-5,8,9-trihydroxy-2,3-dihydro-l/7-pyrimido-[l,2-a]quinoline-l-carboxylic acid pentahydrate was determined by X-ray investigations [91ZN(C)933. The structure of an iron(III)-containing pseudobactin, a siderophore containing a (lS)-5-amino-8,9-dihydroxy-2,3-dihydro-l//-pyrimido[l,2-a]quinazoline-l-carboxylic acid moiety (8), was determined by X-ray diffraction investigations (81 Mil). 

One of the major difficulties associated with the X-ray diffraction investigations of the polyhalogenobenzenes is that although the heavy atom positions may be determined with some precision, the same cannot be said for the lighter atoms. This is brought out clearly, for example, by Gafner and Herbstein s analysis of 1,2,4,5-tetrabromobenzene, where the standard deviations in positional parameters of the bromine atoms are 0-003 A compared with 0-026 A for the carbon atoms. This does not make detailed description of the molecular geometry any easier. 

X-ray diffraction investigation (Co-Ka radiation) was made on the powder samples for the phase identification both the parent compound and its hydride and to determine the unit cell parameters. The magnetisation measurements were carried out with a SQUID (Quantum Design MPMS 5-S) magnetometer from 5 to 340 K in magnetic fields up to 50 kOe. 

We have performed X-ray diffraction investigation of the ledges obtained in various regimes of the arc. The X-ray peaks of hexagonal graphite have been only observed in all diffractions. It follows that the spherical particles observed in Fig. 1 mainly consist of graphite. 

This description seemed to be confirmed just months later when Lambert and co-workers succeeded in crystallizing Et3Si+TPFPB in toluene. [8] The X-ray diffraction investigation showed that counterion TPFPB is well separated from Si+ (closest contact distance 4.18 A) thus excluding any coordination between silylium cation and the anion. However, the structure determination also revealed that the unit cell contains eight toluene molecules, one of which has a contact distance of 2.18 A to the silylium cation. [8] Lambert and co-workers... 

As recent thermoanalytical and X-ray diffraction investigations show, SeCLi can be prepared in two polymorphic modifications, a metastable /3-form and a thermodynamically stable a-modification. CrystalUzation from solvents such as POCI3, sublimation of gaseous SeCLi into a zone with T < 150 °C, or crystallization from the melt (360 °C) yields /3-SeCL,. 

X-ray diffraction investigations explain the structure of this complex. The central ion is a halogen surrounded with eight Cu(I) atoms with sulfur donors. The coordination sphere of the Cu(II) is completed with amino groups of the penicillamine. ... 

Foss M, Feidenhansl R, Nielsen M, Findeisen E, Buslaps T, Johnson RL, Besenbacher F, Stensgaard I (1993) X-ray-diffraction investigation of the sulfur induced 4x1 reconstruction of Ni(llO). Surf Sci 296 283... 

D. Buttard, D. Bellet, andT. Baumbach, X-ray diffraction investigation ofporous silicon superlattices, Thin Solid Films 276, 69, 1996. 

There are really two phases in the pursuit of protein crystals for an X-ray diffraction investigation, and these are (1) the identification of chemical, biochemical, and physical conditions that yield some crystalline material, though it may be entirely inadequate, and (2) the systematic alteration of those initial conditions by incremental amounts to obtain optimal samples for diffraction analysis. The first of these is fraught with the greater risk, as some proteins simply refuse to form crystals, and any clues as to why are elusive or absent. The latter, however, often proves to be the more demanding, time-consuming, and frustrating. 

In X-ray diffraction investigations we are seldom interested in the magnetic component of the waves because it is the electric component that interacts with electrons around atoms and produces diffraction effects. It does, however, soothe the mind to remember that the magnetic component is where the extra energy is found when E is not at its maximum (in fact all of it when E = zero). If we consider the wave as a function of distance rather than time, we may express an X ray as a simple sine wave of electric energy E oscillating between its maximum, zero, and its minimum, as a wave represented mathematically as... 

The only study of the complex formation between selenate and trivalent lanthanides found is an X-ray diffraction investigation of some lanthanide selenate solutions by Johansson, Niinisto, and Wakita [85JOH/NI1], The radial distribution function was interpreted to show that inner-sphere complexes were formed. For Er an average of 0.4 SeO per Er was estimated for a solution containing 0.78 M Er and 1.55 M SeOj. The conditional equilibrium constant for the inner-sphere complex formation ... 

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