Ternary Complexes of Zinc(II), Cyclen and Pyridinecarboxylic Acids

Amino acids binding to Zn2+‐cyclen molecular receptor in aqueous solution

“…-, nevertheless follows their decreasing trend from Gly, (S)-Ala, (Gao et al, 2003), (Kruppa et al, 2006), neither different basicity of nitrogen atom of amino acids that is different for glycine and picolinic acid, nevertheless, the log K's are virtually the same (Vargová et al, 2007). We can only observe huge difference from log K values found for [ZnL] 2þ systems with nicotinic acid (1.95) and nicotiamide (0.7); however, both the ligands are not able to form a chelate.…”

“…As was mentioned above (Kruppa et al, 2006), the imidazole substrate is recognized by [ZnL] 2þ receptor. Our previous results also point to the ability of [ZnL] 2þ complex to interact with nicotinic and picolinic acids and forms ternary complexes (Vargová et al, 2007). The [ZnL] 2þ complex seems to be very efficient system for amino acid recognition and thus, we report here the [ZnL] 2þ complex (Scheme) interactions toward to amino acids…”

“…19.1(6) 9.9(6) 7.6 4.1 Zn 2þ -cyclen-(S)-Ala 26.6 (7) 19 (1) 11 (1) 7.4 4.0 Zn 2þ -cyclen-(S)-Phe 25.9(5) 18.5(7) 9.8(9) 7.4 3.5 nicotinic, picolinic, or dipicolinic acids investigated previously (Vargová et al, 2007), in systems [ZnL] 2þ -glycine no protonation of cyclen in the ternary complexes was observed probably because of higher pK values of nitrogen atom of glycine in comparison with nicotinic and picolinic acids. The chemical signal of CH 2 glycine in the ternary system protons shifts from 3.55 (pH ¼ 4) to 3.4 ppm (pH ¼ 9).…”

“…In the acid region the dependences of the 1 H shifts on pH 2-4 of the ternary mixtures correspond with analogous dependences of free amino acid and free cyclen, and thus formation of any complexes is improbable. The chemical shift assignment for cyclen in [ZnL] 2þ complex was accomplished previously (Vargová et al, 2007) and is characteristic by typical multiplet. A formation of this species starts at pH about 3.5 and is finished at pH about 4.…”

Synthesis and structures of pyridinecarboxylate-containing zinc(II) complexes in dien and tren system

“…Little attention has been devoted to zinc-pyridinecarboxylate complexes in mixed ligand system. Only a few of zinc(II) complexes containing ancillary ligand such as tetrazolate [22], 1,4,7,10-tetraazacyclododecane (cyclen) [23], Schiff base macrocycle [14] and C 2 O 4 2À [24] have been reported. We are interested in the preparation of zinc(II) nicotinate/isonicotinate complexes containing dien and tren as main ligand for the following reasons.…”