Cinnamate ester containing liquid crystalline side chain polymers

The synthesis of methacrylate esters of 4-cyanophenyl-(4-(ω-hydroxyalkyloxy)) cinnamates, with spacer lengths of 2 and 6 methylene units and the synthesis of the corresponding acrylate ester with a spacer of 2 methylene units are described. The methacrylate monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with the analogous benzoate monomer of spacer length 6. The acrylate ester could not be polymerized successfully under the same reaction conditions. Polymers were characterized by NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermo-optic observations. Of the monomers prepared, only the cinnamate with a hexamethylene spacer shows a mesophase, seen on supercooling of the melt. All of the polymers prepared were liquid crystalline, with smectic behavior predominating in the polymethacrylates with the longer spacer group. A narrow nematic region is seen just below the clearing temperature with a range of 3–9°C, nematic character is increased in the copolymer series with the degree of incorporation of the cinnamate monomer with the spacer group of length 2.     

Super/subcritical fluid chromatography chiral separations with macrocyclic glycopeptide stationary phases

The chiral recognition capabilities of three macrocyclic glycopeptide chiral selectors, namely teicoplanin (Chirobiotic T), its aglycone (Chirobiotic TAG) and ristocetin (Chirobiotic R), were evaluated with supercritical and subcritical fluid mobile phases. A set of 111 chiral compounds including heterocycles, analgesics (nonsteroidal antiinflamatory compounds), beta-blockers, sulfoxides, N-protected amino acids and native amino acids was separated on the three chiral stationary phases (CSPs). All separations were done with an outlet pressure regulated at 100 bar, 31 degrees C and at 4 ml/min. Various amounts of methanol ranging from 7 to 67% (v/v) were added to the carbon dioxide along with small amounts (0.1 to 0.5%, v/v) of triethylamine and/or trifluoroacetic acid. The Chirobiotic TAG CSP was the most effective closely followed by the Chirobiotic T column. Both columns were able to separate, partially or fully, 92% of the enantiomers of the compound set. The ristocetin chiral selector could partially or baseline resolve only 60% of the enantiomers tested. All separations were done in less than 15 min and 70% were done in less than 4 min. The speed of the separations is the main advantage of the use of SFC compared to normal-phase HPLC. In addition, SFC is advantageous for preparative separations with easy solute recovery and solvent disposal.     

Fullerenols revisited as stable radical anions

The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene.     

Novel annulene dications from methylated [2.2]metacyclophane monoenes and [e]-ring benzannelated dimethyldihydropyrene

Tetramethyl- and hexamethyl-substituted [2.2]metacyclophane monoenes (10 and 11) are transformed into their corresponding trans-dimethyldihydroethanophenanthrenium dications (14(2+) and 15(2+)) in FSO(3)H x SbF(5) (4:1) and FSO(3)H x SbF(5) (1:1) with SO(2)ClF or SO(2) as the solvent; these 10 pi-dications are equivalent to the C-4/C-5 diprotonated dications of the 2,7-dimethyl derivative of trans-DMDHP, 3a. The trans-12c,12d-dimethyl-12c,12d-dihydrobenzo[e]pyrene (6) reacts with FSO(3)H/SO(2)ClF under surprisingly mild conditions to give initially a persistent diprotonated dication (6H(2)(2+)) and, subsequently, the oxidation dication (6(2+)); the 6(2+):6H(2)(2+) ratio reaches 4:1 after 1 week at low temperature. Protonation of the anti-metacyclophane (13) was also examined. Charge delocalization mode and tropicity in the resulting dications are gauged via detailed NMR studies at 500 MHz.     

Determination of boron in glass by the nuclear track technique

Summary Determination of Boron in Glass by the Nuclear Track Technique The nuclear track technique using the¹⁰B(n)⁷Li reaction, has been applied to determine boron in concentration ranges (1.59 to 7.75%) ordinarily considered high for nuclear determinations. Factors limiting the overall precision of the method and restricting the linear dependence of track density on boron concentration are examined. Boron alpha track densities are used to construct planar profiles of boron distribution within the surface region of bulk glass and CVD films. Calibration curves for quantitative lateral profiling of surfaces are constructed and show the selective corrosion of borosilicate glass surface resulting in boron depletion.     

Oxidative addition of dialkylphosphites to complexes of iridium(I) and rhodium(I)

The PH bond of dialkylphosphites (dimethylphosphite, 5,5-dimethyl-1,3-dioxa-2-phosphorinane and 4,4,5,5-tetramethyl-1,3-dioxa-2-phospholane) oxidatively adds to irClL₂(L = PPh₃, AsPh₃) and IrCl(PMe₂Ph)₃ generated in situ to give six-coordinate hydrido(dialkylphosphonato)iridium(III) complexes, e.g. IrHClL₂[{(MeO)₂-PO}₂H] and IrHCl(PMe₂Ph)₃[PO(OMe)₂]. Addition of triphenylphosphine to a solution containing [IrCl(C₈H₁₄)₂]₂ and dimethylphosphite in a 1:2 mol ratio gives a five-coordinate hydrido (dimethylphosphonato)iridium(III) complex IrHCl(PPh₃)₂{PO(OMe)₂}, from which six-coordinate pyridine and acetylacetonato complexes IrHCl(PPh₃)₂(C₅H₅N){PO(OMe)₂} and IrH(PPh₃)₂(acac){PO(OMe)₂} can be obtained. The ligand arrangements in the various complexes are inferred from IR, ¹H and ³¹P NMR data.