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Unexpected Structure of a Helical N 4 ‐Schiff‐Base Zn(II) Complex and Its Demetallation: Experimental and Theoretical Studies
Author(s) -
Lamine Walid,
Boughdiri Salima,
Jeanneau Erwan,
Sanglar Corinne,
Morell Christophe,
Christ Lorraine,
Chermette Henry
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800514
Subject(s) - schiff base , monoclinic crystal system , chemistry , crystal structure , ligand (biochemistry) , crystallography , zinc , reaction mechanism , stereochemistry , organic chemistry , catalysis , biochemistry , receptor
A new Zn‐N 4 ‐Schiff base L=((±)‐ trans ‐N,N’‐Bis(2‐aminobenzylidene)‐1,2‐diaminocyclohexane) complex was synthesized and fully characterized, showing an unexpected self‐assembled double‐stranded helicate structure. The X‐ray crystal analysis of the Zn 2 L 2 complex ((C 40 H 44 N 8 Zn 2 ,CH 2 Cl 2 , a=14.2375(3) Å, b=16.7976(4) Å, c=16.1613(4) Å, monoclinic, P 2 1 / n , Z=4) shows a centrosymmetrical structure in which zinc atoms are in distorted tetrahedral environments, revealing an M‐ ( R , R ) left‐handed helicity in its asymmetric unit. However, it was observed that this dinuclear complex is thermodynamically unstable in the presence of small water amounts and undergoes demetallation into free N4‐Schiff base ligand and ZnO nanoparticles. This hydrolysis process was thoroughly identified and monitored through detailed 1 H NMR, DOSY NMR analysis. The reaction mechanism of this demetallation event was elucidated by using the DFT method, involving an activation energy smaller than 13 kcal/mol. Besides, a theoretical mechanism of the demetallation process is given for the first time.