Structural influence in the interaction of cysteine with five coordinated copper complexes: Theoretical and experimental studies

• Published in: Journal of molecular structure Vol. 1157; pp. 660 - 671
• Main Authors: Huerta-Aguilar, Carlos Alberto, Thangarasu, Pandiyan, Mora, Jesús Gracia
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.04.2018
• Subjects: Copper complex; cysteine interactions; DFT; TD DFT; DFT; Copper complex; cysteine interactions; TD DFT
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2017.12.090

Copper complexes of N,N,N′,N′-tetrakis(pyridyl-2-ylmethyl)-1,2-diaminoethane (L1) and N,N,N′,N′-tetrakis(pyridyl-2-ylmethyl)-1,3-diaminopropane (L2) prepared were characterized completely by different analytical methods. The X-structure of the complexes shows that Cu(II) presents in trigonal bi-pyramidal (TBP) geometry, consisting with the electronic spectra where two visible bands corresponding to five coordinated structure were observed. Thus TD-DFT was used to analyze the orbital contribution to the electronic transitions for the visible bands. Furthermore, the interaction of cysteine with the complexes was spectrally studied, and the results were explained through DFT analysis, observing that the geometrical parameters and oxidation state of metal ions play a vital role in the binding of cysteine with copper ion. It appears that the TBP structure is being changed into octahedral geometry during the addition of cysteine to the complexes as two bands (from complex) is turned to a broad band in visible region, signifying the occupation of cysteine molecule at sixth position of octahedral geometry. In the molecular orbital analysis, the existence of a strong overlapping of HOMOs (from cysteine) with LUMOs of Cu ion was observed. The total energy of the systems calculated by DFT shows that cysteine binds favorably with copper (I) than that with Cu(II). [Display omitted] •Structural influence for interaction of cysteine with copper complex.•DFT proof for the binding of cysteine with copper complex.•Electronic spectral and TD DFT analysis for complex adduct with cysteine.