Alan J. Shusterman

Structures of Orthoborate Anions and Physical Properties of Their Lithium Salt Nonaqueous Solutions

We compare the physical properties and solution conductivities of three new lithium orthoborate salts with those of the well-known salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The three new lithium salts are lithium bis(perfluoropinacolato)borate (LiBPFPB), lithium bis(oxalato)borate, and lithium bis(malonato)borate (LiBMB). Computational models of the three orthoborate anions show that the borate oxygens in BPFPB - anion are the least exposed. The oxygens are electronically identical in BPFPB but not in the other anions. The three new lithium salts show conductivities that closely approach those of LiTFSI but show surprising and solvent-dependent orderings. The conductivity is nearly independent of the salt content in the salt concentration range of 0.5-1 M, which is advantageous for their applications. Self-diffusivity measurements for 7 Li. 19 F, and 1 H are presented and are consistent with the very high ionic dissociation levels proposed for these salts based on other evidence. The lithium-ion transport number at room temperature for LiBPFPB in nonaqueous solutions exceeds 0.5 and for LiBMB is about 0.4.

The structure-activity relationship of skin carcinogenicity of aromatic hydrocarbons and heterocycles

From a study of 239 aromatic and heteroaromatic compounds causing skin cancer in mice, a quantitative structure-activity relationship has been derived. Carcinogenicity depends heavily on the relative hydrophobicity of the chemicals as defined by octanol/water partition coefficients (log P). It is also correlated with the energy of the highest occupied molecular orbital and the presence of substituents on the L and K regions of the carcinogen. The results are discussed in terms of the bay region concept for carcinogenic activity.

The importance of the hydrophobic interaction in the mutagenicity of organic compounds

The derivation of new QSAR and the review of published QSAR for the mutagenicity of a variety of chemicals acting on a variety of bacterial systems uncovers two classes of equations. 12 examples include a term for hydrophobicity and of these 12, 11 require activation either by S9 or cytosolic enzymes for the reduction of nitro compounds. There are 4 examples of direct-acting mutagens which do not require activation. Of these 4, 3 do not contain a term for hydrophobicity. The odd example is that of the sulfonate esters which do not require activation, but contain a term in log P. The hydrophobicity factor is not correlated with the type of bacteria used for the test.

LiMOB, an Unsymmetrical Nonaromatic Orthoborate Salt for Nonaqueous Solution Electrochemical Applications

Synthesis, characterization, ionic conductivity, electrochemical stability, and lithium-ion transport number of an asymmetric version of the successful orthoborate lithium salt lithium bis(oxalato)borate (LiBOB), are described. The salt, lithium (malonato oxalato) borate (LiMOB), is thermally stable up to 273°C. It is poorly soluble in common organic solvents such as 1,2-dimethoxyethane, tetrahydrofuran, acetonitrile, dimethyl carbonate, and propylene carbonate, but has moderate solubility in γ-butyrolactone (GBL) and N,N-dimethylformamide (DMF), and high solubility in dimethyl sulfoxide (DMSO). The 0.5 M solutions of LiMOB in GBL, DMSO, and DMF show high conductivities (5.0 X 10 -3 S cm -1 , 5.1 × 10 -3 S cm -1 , and 11.8 X 10 -3 S cm -1 at 25°C, respectively) relative to most 0.5 M nonaqueous solutions. Even the room temperature conductivity of the 0.08 M LiMOB-PC solution is close to 10 -3 S cm -1 . The conductivities of LiMOB solutions are close to those of LiBOB solutions, which has been demonstrated in recent studies to be a successful substitute for LiPF 6 in lithium-ion batteries. The cyclic voltammograms show that LiMOB solutions in PC and GBL have electrochemical stability as high as 4.3 V vs. Li + /Li. The lithium-ion transport number at room temperature for 0.5 M LiMOB in DMSO-d 6 was 0.36, obtained from self-diffusivity measurement by the pulsed field gradient spin echo nuclear magnetic resonance technique. The highest occupied molecular orbital energy, which is usually correlated with electrochemical stability has been calculated, and electrostatic potential maps for the new anion and its fluorinated derivatives are presented. They suggest that the fluorinated analogue of LiMOB should be more stable and more soluble, and may have unique properties.

Tungsten—carbene—alkene complexes

Abstract Reaction of (CO)5W[C(OCH3)C6H4-p-CH3] with 3-buten-1-ol gives a butenyloxy carbene complex (CO)5W[C(OCH2CH2CHCH2)C6H4-p-CH3], 2. On heating to 38 °C in benzene, 2 decomposes to 1-(4-methylphenyl)-2-oxabicyclo[3.1.0] hexane, 4. An intermediate tetracarbonyltungsten—carbene—alkene complex 5 was detected by NMR during the course of the decomposition of 2 to cyclopropane 4. In the decomposition of 2 an initial induction period followed by an autocatalytic decomposition was observed. Reaction of (CO)5W[C(OCH3)C6H4-p-CH3] with allylamine produced a 1:1.2 mixture of isomers of (CO)5W[C(NHCH2CHCH2)C6H4-p-CH3], 9Z and 9E. Thermolysis of the mixture of 9Z and 9E produced a stable tetracarbonyltungsten—carbene—alkene complex, 11.

Toxicology of benzyl alcohols: a QSAR analysis

There is an evidence that benzyl alcohols may exhibit toxicity via a radical mechanism. To test this possibility, we studied the toxicity of para substituted benzyl alcohols on rapidly dividing cancer cells (L1210 leukemia). This system has previously found utility in studying the apparent radical toxicity of a variety of phenols. However, no evidence could be found for an electronic effect and the cellular toxicity was associated primarily with hydrophobicity. Comparison of this quantitative structure-activity relationships (QSAR) with others for the reactions of benzyl alcohols in diverse systems provides insight into mechanisms of action. A QSAR for the interaction of benzyl alcohols with protozoa yields an equation that is dependent on both hydrophobicity and acidity of the OH group versus a mixture of bacteria and fungi, the critical dependence on hydrophobicity prevails with a small dependence on a resonance-stabilized, radical mediated electronic effect. The chloramphenicols provide an instructive example, where the radical mediated electronic effect overshadows the hydrophobic contribution to bacterial toxicity. These various QSAR for benzyl alcohols indicate that mechanisms of growth inhibition in vitro vary depending on cell/organism type, the strength of the bond and lability of the hydrogen, and the strength of the initiating radical reagent.

The mechanism of organometallic migration reactions. A configuration mixing (CM) approach

Abstract The configuration mixing (CM) model is applied to the migratory insertion of carbon monoxide into a transition metalcarbon bond. A qualitative reaction profile for the reaction is constructed using an energy plot of the three electronic configurations, which describe the reactant, the product, and the five-coordinate intermediate. The model provides a simple picture of reactivity trends in these systems, as well as indicating the way in which a mechanistic spectrum, encompassing both step-wise and concerted pathways, is generated. The model analyzes the effect of modifications of the migrating group, the acceptor group, and the entering ligand. Migratory insertion assisted by either prior oxidation or reduction of the starting metal complex is also considered. The conclusions are supported by experimental and computational data.

QSAR for the cytotoxicity of 2-alkyl or 2,6-dialkyl, 4-X-phenols: the nature of the radical reaction

In a continuation of studies on the radical mediated toxicity of phenols to leukemia cells, a set of di- and tri- substituted phenols with mostly alkyl substituents in the ortho position were examined. These analogs are similar in structure to the commercial antioxidants BHA and BHT. A QSAR analysis of their growth inhibitory constants led to the formulation of this simple but unusual equation based on 18 congeners:ES-2 is the Taft steric parameter for the larger of the two ortho substituents while ER is Otsus radical parameter, which was originally defined to correlate radical reactions.

The role of hydrophobicity and electronic factors in regulating alcohol inhibition of cytochrome P-450-mediated aniline hydroxylation

The role of hydrophobicity and electronic factors in regulating alcohol inhibition of cytochrome P-450-mediated aniline p-hydroxylation has been investigated by the formulation of quantitative structure-activity relationships. The activity of linear primary alcohols and unhindered linear secondary alcohols shows a linear dependence on log P, where P is the octanol-water partition coefficient. Hindered primary and secondary alcohols are less active than this relationship predicts. An equation describing the activity of both hindered and unhindered primary and secondary alcohols shows that alcohol inhibition of aniline hydroxylation is regulated by hydrophobicity and steric effects. No role for electronic factors can be discerned. Similarities are found between alcohol inhibition and the binding of alkyl amines to cytochrome P-450, suggesting that alcohols may bind to the amine binding site.

Mechanistic Studies Related to the Olefin Metathesis Reaction

The olefin metathesis reaction1 has been proposed to proceed via interconversion of metal-carbene-alkene complexes and metalla-cyclobutanes.2 This proposal is supported both by studies of the reactions of metal carbene complexes with alkenes3 and by labelling experiments which show that the olefin metathesis reaction proceeds in a non-pairwise manner.4 Our interest in the metathesis reaction has led us to study the preparation of metal complexes containing both carbene and alkene ligands and to study rearrangement reactions of metallacyclobutanes.