6710-91-4Relevant academic research and scientific papers
Site-selective recognition of amino acids by Co(III) complexes containing a (N)(O)3-type tripodal tetradentate ligand
Kumita,Morioka,Ozawa,Jitsukawa,Einaga,Masuda
, p. 1035 - 1042 (2007/10/03)
The bis-N,N-carboxymethy-(S)-phenylalaninato carbonato cobalt(III) complex, [Co(bcmpa)(CO3)]2-, has been prepared as a simple model that enables the recognition of an amino acid (Haa) whose coordination behaviours in solution have been characterized by electronic absorption (AB), circular dichroism (CD) and 1H NMR spectroscopies. The reaction of the K2[Co(bcmpa)(CO3)] complex with amino acids (Haa) has predominantly afforded the [Co(bcmpa)(aa)] complex in the trans(N)-configuration mode, rather than in the cis(N)-form. By using amino acid derivatives with bulky substituents at their amino or carboxylate sites under a neutral condition, the reactions have been demonstrated to be initiated by coordination of the amino nitrogen site. Interestingly, the cis(N)-complex, which is isolated as a minor product, isomerizes to the trans(N)-form in the presence of active charcoal under pH 7 in an aqueous solution. The site-selective coordination of Haa to the [Co(bcmpa)(CO3)]2- complex and the stereoselective isomerization of the [Co(bcmpa)(aa)]- complex have been explained to be regulated by weak non-covalent interactions within the ligands, whose origin has been discussed based on a detailed examination of the crystal structures of the trans(N)- and cis(N)-K[Co(bcmpa)(aa)] complexes.
