A Racemic and Enantiopure Unsymmetric Diiron(III) Complex with a Chiral o‐Carborane‐Based Pyridylalcohol Ligand: Combined Chiroptical,Magnetic, and Nonlinear Optical Properties

The design of molecule‐based systems combining magnetic, chiroptical and second‐order optical nonlinear properties is still very rare. We report an unusually unsymmetric diiron(III) complex 1 , in which three bulky chiral carboranylpyridinealkoxide ligands ( o CB hmp^?) bridge both metal ions and the complex shows the above‐mentioned properties. The introduction of o‐carborane into the 2‐(hydroxymethyl)pyridine (hmpH) architecture significantly alters the coordination of the simple or aryl‐substituted 2‐hmpH. The unusual architecture observed in 1 seems to be triggered by the poor nucleophilicity of our alkoxide ligand ( o CB hmp^?). A very rare case of spontaneous resolution takes place on precipitation or exposure to solvent vapor for the bulk compound, as confirmed by a combination of single‐crystal and powder X‐ray diffraction, second‐harmonic generation, and circular dichroism. The corresponding enantiopure complexes (+) 1 and (?) 1 have also been synthesized and fully characterized. This research provides a new building block with unique geometry and electronics to construct coordination complexes with multifunctional properties.     

Synthetic efforts toward the C22-C36 subunit of halichondrin B utilizing local and imposed symmetry

The C22-C34 portion (2) of halichondrin B was synthesized from meso-symmetric bis-silyl protected cyclopentenediol (7) in 20 steps and 7% overall yield. This was accomplished through a two-directional synthesis/terminus differentiation strategy that proceeded via achiral, meso-symmetric intermediates for eight steps and employed a Pd(0)-mediated asymmetric double cycloetherification to establish both tetrahydropyran rings. [Structure: see text]     

Communication: partial polarization transfer for single-scan spectroscopy and imaging

A method is presented to partially transfer nuclear spin polarization from one isotope S to another isotope I by the way of heteronuclear spin couplings, while minimizing the loss of spin order to other degrees of freedom. The desired I spin polarization to be detected is a design parameter, while the sequence of pulses at the two Larmor frequencies is optimized to store the greatest unused S spin longitudinal polarization for subsequent use. The unitary evolution for the case of I(N)S spin systems illustrates the potentially ideal efficiency of this strategy, which is of particular interest when the spin-lattice relaxation time of S greatly exceeds that of I. Explicit timing and pulses are tabulated for the cases for which M ≤ 10 partial transfers each result in equal final polarization of 1/M or more compared to the final I polarization expected in a single transfer for N = 1, 2, or 3 I spins. Advantages for the ratiometric study of reacting molecules and hyperpolarized initial conditions are outlined.     

The social impact in a high-risk community: A cellular automata model

This research examines the spread of criminal behavior and hard drug consumption using a mathematical approach called cellular automata (CA). This CA model is based on two behavioral concepts. Firstly, peer association impacts criminal involvement. Secondly, addiction can heighten criminal activity. The model incorporates four types of actors who interact in a high-risk social community and one intervention method. The actors exert a social influence on each other by encouraging or discouraging drug use and criminal behavior. The intervention method called Incapacitation has a probabilistic impact on the individuals in the model. The results identify the threshold where positive influences on a population reduce the number of high-rate offenders in the community. These results are discussed to further the knowledge about the social influences in a high-risk community and how these influences can effect decisions on offender management.     

Search for fractional-charge particles in meteoritic material

We have used an automated Millikan oil drop method to search for free fractional-charge particles in a sample containing in total 3.9 mg of pulverized Allende meteorite suspended in 259 mg of mineral oil. The average diameter of the drops was 26.5 microm with the charge on about 42 500 000 drops being measured. This search was motivated by the speculation that isolatable, fractional-charge particles produced in the early Universe and present in our Solar System are more likely to be accumulated in asteroids than on Earth's surface. No evidence for fractional-charge particles was found. With 95% confidence, the concentration of particles with fractional-charge more than 0.25 e (e being the magnitude of the electron charge) from the nearest integer charge is less than 1.3 x 10(-21) particles per nucleon in the meteoritic material and less than 1.9 x 10(-23) particles per nucleon in the mineral oil.     

Ground state 14N quadrupole couplings in the microwave spectra of N,N'-dimethylaniline and 4,4'-dimethylaminobenzonitrile

Microwave spectra of N,N'-dimethylaniline and 4,4'-dimethylaminobenzonitrile have been recorded in a pulsed supersonic jet using chirped pulse techniques. Experimental substitution structures have been determined for both molecules by detection of the spectra of all (13)C and (15)N isotopomers in natural abundance using a broadband spectrometer. Additionally, a narrowband spectrometer has been used to reveal the (14)N quadrupole splittings at high resolution, from which the orbital occupancy numbers of the amino- and cyano-nitrogen atoms have been determined. An apparent direct relationship between these values and the barriers to inversion of the amino groups is discussed.