Stereo-Structural Fine Tuning of Chromaticity.

Lanthanoid carboxylates were synthesized, in situ self-assembled in primitive crystals to illustrate temperature-driven evolution in chromaticity. Evolution in structure (crystallinity), composition, luminosity and chromaticity investigated revealing the coupled role of divergence in order/structure (spatial organization), and composition in tuning observed color. Loss of crystallinity or increase in residual carbon leads to decrease in luminosity even with increase in hue. Comparing Ho and Er congeners shows that the density of accessible transitions relates to shifts in low and high wavelength components of color. This work demonstrates that, just as interface dipoles can lead to change in semiconductor bandgap, structure and composition can analogously alter observed color.

In vivo antimalarial activity of Ajuga remota water extracts against Plasmodium berghei in mice.

We investigated the in vivo activity of crude water extracts of Ajuga remota Benth (Labiatae) against Plasmodium berghei in mice using plants harvested from two areas in Kenya where the plant is commonly used to treat malaria. The extract was tested using a 4-day test at a dose of 30 mg/kg/day (equivalent to 0.2 ml solution per mouse). Wet leaf extract was the most effective with 90.4% suppression of parasitemia. Extract from air-dried and powdered flowers were the least effective with 17.2% suppression of parasitemia.

The potential of photochemical transition metal reactions in prebiotic organic synthesis. I. Observed conversion of methanol into ethylene glycol as possible prototype for sugar alcohol formation.

Photochemical processes involving redox reactions between metal ions and organic substrates possess the versatile potential for having harnessed solar energy for prebiotic organic synthesis. The present study in our Laboratory has shown that ultraviolet irradiation of transition metal ions such as of Ni, Co, Fe, Cu and Ti dissolved in primary or secondary alcohols causes photoreduction of the metal ions with the concomitant oxidation of the alcohol to aldehyde or ketone. An observed accompaniment of this novel 'light' reaction has been the known 'dark' pinacol reaction, whereby the carbonyl derivative underwent bimolecular coupling to the diol by the photogenerated reduced transition metal reagent. These tandem 'light-dark' processes possess the potential for the stepwise synthesis of dimeric 1,2-diols from simpler alcohols under conditions that might have prevailed on the prebiotic earth. Experiments reported here have demonstrated that such a tandem 'light-dark' conversion of methanol into ethylene glycol, via formaldehyde, does in fact occur, when nickel(II) acetylacetonate solutions in methanol undergo prolonged irradiation at 185-254 nm. Since ethylene glycol can be considered as the simplest sugar alcohol, these findings may provide novel insight into the prebiotic oligomerization of formaldehyde into higher sugar alcohols or even sugars.