A series of novel monomers and polymers containing
aromatic-donor and o-quinoid-acceptor
units was prepared, and the relationship between their spectral and
electrochemical
properties and their structures was investigated. X-ray structure
analyses of the monomers
possessing thiophene units revealed coplanar conformations, whereas
calculations of the
monomers containing N-methylpyrrole showed torsional
conformations. Cyclic voltammetry
showed amphoteric properties for all the monomers and p- and n-doping
processes for most
of the polymers. The reduction potentials were primarily dependent
on the electron-accepting
character of the o-quinoid-acceptor units. The
electrochemical behavior of the polymers was
characterized by cyclic voltammetry and suggested narrow-bandgap
systems. The bandgaps
determined from optical absorption spectra range from 0.5 to 1.4 eV.
The polymer composed
of thiophenes and
benzo[1,2-c;3,4-c‘]bis[1,2,5]thiadiazole
exhibited the narrowest bandgap.
A large amount of (all-E)-lycopene was successfully purified from tomato paste using an improved method that included a procedure to wash crystalline powder with acetone. The total yield of the pure (all-E) form was at least 30%. The melting point of (all-E)-lycopene was determined to be 176.35 °C by differential scanning calorimetry (DSC) measurements. Bathochromic shifts were observed in the absorption maxima of all solvents tested (at most a 36 nm shift for λ2 in carbon disulfide, as was observed in hexane) and were accompanied by absorbance decreases, namely, a hypochromic effect, showing a higher correlation between the position and the intensity of the main absorption bands. This bathochromic shift was dependent upon the polarizability of the solvent rather than its polarity. The structure of (all-E)-lycopene in CDCl3 and C6D6 was identified on the basis of one- and two-dimensional nuclear magnetic resonance (NMR) spectra, including (1)H and (13)C NMR, homonuclear correlation spectroscopy ((1)H-(1)H COSY), heteronuclear multiple-quantum coherence (HMQC), and heteronuclear multiple-bond connectivity (HMBC). The rate constants of the decrease in (all-E)-lycopene with hexane and benzene were calculated to be 3.19 × 10(-5) and 3.55 × 10(-5) s(-1), respectively. The equilibrium constants between (all-E) and (13Z) isomers were estimated to be 0.29 in hexane and 0.31 in benzene, respectively, from the point at which the amount of (13Z)-lycopene reached its maximum.
Lycopene has a large number of geometric isomers caused by E/Z isomerization at arbitrary sites within the 11 conjugated double bonds, offering varying characteristics related to features such as antioxidant capacity and bioavailability. However, the geometric structures of only a few lycopene Z-isomers have been thoroughly identified from natural sources. In this study, seven multi-Z-isomers of lycopene, (9Z,13'Z)-, (5Z,13Z,9'Z)-, (9Z,9'Z)-, (5Z,13'Z)-, (5Z,9'Z)-, (5Z,9Z,5'Z)-, and (5Z,9Z)-lycopene, were obtained from tomato samples by thermal isomerization, and then isolated by elaborate chromatography, and fully assigned using proton nuclear magnetic resonance. Moreover, the theoretically preferred pathway from (all-E)-lycopene to di-Z-isomers was examined with a computational approach using a Gaussian program. Fine-tuning of the HPLC separation conditions led to the discovery of novel multi-Z-isomers, and whose formation was supported by advanced theoretical calculations.
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