Cobalt(II) coordination compounds of ethyl 4-methyl-5-imidazolecarboxylate: chemical and biochemical characterization on photosynthesis and seed germination.

In this work we present the synthesis, structural and spectroscopic characterization of Co(2+) coordination compounds with ethyl 4-methyl-5-imidazolecarboxylate (emizco). The effects of emizco, the metal salts CoCl(2).6H(2)O, CoBr(2), Co(NO(3))(2).6H(2)O and their metal coordination compounds [Co(emizco)(2)Cl(2)], [Co(emizco)(2) Br(2)].H(2)O, [Co(emizco)(2) (H(2)O)(2)(NO(2))(2).2H(2)O were evaluated on photosynthesis in spinach chloroplasts. Seed germination and seedling growth of the monocotyledonous species Lolium multiflorum and Triticum aestivum and the dicotyledonous species Trifolium alexandrinum and Physalis ixocarpa were also assayed under the effect of the compounds and salts. The results showed that cobalt(II) salts and their emizco coordination compounds inhibit photosynthetic electron flow and ATP-synthesis, behaving as Hill reaction inhibitors. Coordination compounds are more potent inhibitors than the salts. It was found that the salts target is at the b(6)f level while the complexes targets are at Q(B)(D1)-protein and b(6)f level. The Q(B) inhibition site was confirmed by variable chlorophyll a fluorescence yield. On the other hand, emizco inhibits seed germination, root and shoot development, in both weed and crop species. Cobalt(II) coordination compounds are the most effective photosynthesis inhibitors, but they are less potent than emizco in germination and seedling growth, while the metal salts are the least active of all.