Carbon-13 nuclear magnetic resonance spectra of anti-inflammatory drugs: Phenylbutazone,oxyphenbutazone and indomethacin

The ¹³C nmr chemical shifts of phenylbutazone, oxyphenbutazone, indomethacin and indole-3-acetic acid are reported. The assignments of various carbon resonances are made on the basis of the substitution effects on benzene shifts, multiplicities generated in SFORD spectra, nuclear overhauser enhancement for protonated carbons, and the comparison with analogous compounds.     

Further aspects of the roaming mechanism in formaldehyde dissociation

Recently we reported a novel “roaming” dissociation pathway of formaldehyde in which one of the H atoms strays far from the minimum energy reaction path, explores a broad region of the potential energy surface, then abstracts the remaining H atom to form molecular products, without going near the configuration of the conventional transition state saddle point. The detailed dynamics of the abstraction mechanism and its energy dependence have already been reported. Here, with a combination of experimental and theoretical results, we examine the roaming behavior at the energetic extremes. We show evidence of roaming below the threshold of the radical dissociation channel and consider the implications of this and the possible existence of a transition state for the roaming mechanism. We also show the occurrence of roaming up to 3200 cm⁻¹ above the threshold of the triplet dissociation channel. In addition, we present results affording deeper insight into the dynamics of the roaming mechanism: we show evidence of roaming leading to CO in v = 1, and examine the issue of nuclear spin conservation during dissociation via the roaming mechanism.     

13C nmr of aryl substituted cations: the sigma-bridged coates cation and the 2-adamantyl cation

A series of aryl substituted Coates and 2-adamantyl cations were generated and their ¹³C NMR spectra determined to be consistent with sigma-bridged structures for the former, and unbridged structures for the latter.     

Crystal structure of 2,4-di-para-methoxyphenylcyclobutadiene-1,3-quinone

The crystal structure of 2,4-di-p-methoxyphenylcyclobutadiene-1,3-quinone has been been determined using three-dimensional X-ray data collected by means of a Picker FACS-1 four-circle diffractometer. The crystal used was one of four modifications of this compound, two low density (1.38 g cm^?3) and two high density (1.54 g cm^?3) forms, obtained by us, depending on crystallization conditions. The space group isP¯1, with unit cell dimensionsa = 3.89,b = 10.80,c = 9.03 Å, α = 77.88, β = 74.12, γ = 85.15 °D _m = 1.38 g cm^?3 andZ = 1. A least-squares refinement of the positional and anisotropic thermal parameters gave a finalR-value of 6.0% for 364 reflections and 121 variables. The zwitter-ionic nature of the molecule can be seen in both the partial delocalization of the bonds in the 4-membered ring (which is square-planar) and the bonds joining thep-phenylene and 4-membered rings. The nearly planarp-phenylene rings themselves are quinone-like in structure and are parallel, but not coplanar. The columnar packing of the molecules resembles that of graphite, and observed interplanar spacing is 3.64 Å.     

3-Methylpyrazolo [1,2-a] pyridazin-1-one. Selenium derivatives of 5,8-dihydropyrazolo[1,2-a]pyridazine

The dehydrogenation of the known 3-methyl-5,8-dihydropyrazolo[1,2-a]pyridazin-1-one (2) to the ten π electron heteroaromatic 3-methylpyrazolo[1,2-a]pyridazin-1-one ( 3 ) is reported. Conversions of the pyrazolone 2 to the pyrazoloselenone 6 via the chloropyrazolium chloride 7 , and of pyrazolones 2 and 3 and pyrazoloselenone 6 into the corresponding O or Se ethyl pyrazolium fluoroborates 5, 4 , and 8 by triethyloxonium fluoroborate are also described.     

Radial clustergrams: visualizing the aggregate properties of hierarchical clusters

A new radial space-filling method for visualizing cluster hierarchies is presented. The method, referred to as a radial clustergram, arranges the clusters into a series of layers, each representing a different level of the tree. It uses adjacency of nodes instead of links to represent parent-child relationships and allocates sufficient screen real estate to each node to allow effective visualization of cluster properties through color-coding. Radial clustergrams combine the most appealing features of other cluster visualization techniques but avoid their pitfalls. Compared to classical dendrograms and hyperbolic trees, they make much more efficient use of space; compared to treemaps, they are more effective in conveying hierarchical structure and displaying properties of nodes higher in the tree. A fisheye lens is used to focus on areas of interest, without losing sight of the global context. The utility of the method is demonstrated using examples from the fields of molecular diversity and conformational analysis.     

Modeling the influence of a laser pulse on the potential energy surface in optimal molecular control theory

Understanding and modeling the interaction between light and matter is essential to the theory of optical molecular control. While the effect of the electric field on a molecule's electronic structure is often not included in control theory, it can be modeled in an optimal control algorithm by a set or toolkit of potential energy surfaces indexed by discrete values of the electric field strength where the surfaces are generated by Born-Oppenheimer electronic structure calculations that directly include the electric field. Using a new optimal control algorithm with a trigonometric mapping to limit the maximum field strength explicitly, we apply the surface-toolkit method to control the hydrogen fluoride molecule. Potential energy surfaces in the presence and absence of the electric field are created with two-electron reduced-density-matrix techniques. The population dynamics show that adjusting for changes in the electronic structure of the molecule beyond the static dipole approximation can be significant for designing a field that drives a realistic quantum system to its target observable.     

Multi-frequency mode-locked lasers

A new theoretical model is constructed which describes the operation of multi-frequency, pulsed mode-locked laser cavities. The model, which is a combination of multi channel interactions in the canonical master mode-locking model subject to three different gain models which account for both self- and cross-saturation effects, results in mode-locking dynamics which qualitatively describe the observed experimental dual-frequency laser operation. Specifically, the combination of self- and cross-saturation in the gain allows for mode-locking at two frequencies simultaneously, which can be of significantly different energies and pulsewidths. The model gives a framework for understanding the operation and stability of the increasingly important and timely technology of dual- and multi-frequency mode-locked laser cavities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

MR imaging of multiple hepatic cysts in a patient with polycystic liver disease

We report a case of a 55-year-old woman with polycystic liver disease that we examined with magnetic resonance (MR) imaging, CT and ultrasound. The MR images demonstrated varying intensities in the cyst contents which we believe is due to different degrees and age of hemorrhage. Such variability among the cysts was not seen on the CT or ultrasound images.