1567709-38-9Relevant articles and documents
Cooperative anion recognition in copper(II) and zinc(II) complexes with a ditopic tripodal ligand containing a urea group
Carreira-Barral, Israel,Rodriguez-Blas, Teresa,Platas-Iglesias, Carlos,De Blas, Andres,Esteban-Gomez, David
, p. 2554 - 2568 (2014/03/21)
The ability of CuII and ZnII complexes of the ditopic receptor H2L [1-(2-((bis(pyridin-2-ylmethyl)amino)methyl)phenyl)-3- (3-nitrophenyl)urea] for anion recognition is reported. In the presence of weakly coordinating anions such as ClO4-, the urea group binds to the metal ion (CuII or ZnII) through one of its nitrogen atoms. The study of the interaction of the metal complexes with a variety of anions in DMSO shows that SO42- and Cl - bind to the complexes through a cooperative binding involving simultaneous coordination to the metal ion and different hydrogen-bonding interactions with the urea moiety, depending on the shape and size of the anion. On the contrary, single crystal X-ray diffraction studies show that anions such as NO3- and PhCO2- form 1:2 complexes (metal/anion) where one of the anions coordinates to the metal center and the second one is involved in hydrogen-bonding interaction with the urea group, which is projected away from the metal ion. Spectrophotometric titrations performed for the CuII complex indicate that this system is able to bind a wide range of anions with an affinity sequence: MeCO2 - ～ Cl- (log K11 > 7) > NO 2- > H2PO4- ～ Br- > HSO4- > NO3- (log K11 2- or F-, competitive processes associated with the deprotonation of the coordinated N-H group of the urea moiety take place. Thus, N-coordination of the urea unit to the metal ion increases the acidity of one of its N-H groups. DFT calculations performed in DMSO solution are in agreement with both an anion-hydrogen bonding interaction and an anion-metal ion coordination collaborating in the stabilization of the metal salt complexes with tetrahedral anions.
