ATR-FTIR spectroscopic investigation of the cis- and trans- bis-( α -amino acids) copper(II) complexes

The crystalline phases of the trans -( a ) and cis -( b )-isomers of bis-( α -amino acids) copper(II) complexes [Cu( b L) 2 ] 1–5 ( b L - bidentate ligand: gly ( 1 ), S -ala ( 2 ), R,S -val ( 3 ), (±)-thr ( 4 ), R,S -phe ( 5 )) were studied by ATR-FTIR spectroscopy in the mid region IR spectrum. It was established that asymmetric ν as (COO) and symmetric ν s (COO) stretching vibrations of carboxylic groups of 1 – 5 are sensitive to change of the geometric structure and have a different maxima for the trans ( a )- and cis ( b )-isomers. It found that ν as (COO) and ν s (COO) stretching vibrations of cis -isomers are broadened and shifted to longer wavelengths ( b ) as compared with trans -isomers ( a ). Shown that peculiarities of crystal packing molecules of geometric isomers may affect on carboxylate stretching vibration bis-α-amino acids complexes copper(II) 1–5 a,b .