Halide Ion Mediated Aldehyde‐Amine Condensation Leading to Schiff–base and Cyclized Non‐Schiff–base Ligand Complexes of CdII: A Combined Experimental and Theoretical Investigation. Issue 15 (20th September 2016)

• Record Type: Journal Article
• Authors: Purkait, Suranjana; Chakraborty, Prateeti; Bauzá, Antonio; Frontera, Antonio; Massera, Chiara; Das, Debasis
• Is Part Of: ChemistrySelect. Volume 1:Issue 15(2016)
• Page Start: 4539
• Page End: 4549
• Publication Date: 2016-09-20
• Subjects: Schiff-base -- Cadmium -- Crystal Structure -- Iminium Salt -- Density functional calculations; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201600967
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: The reactions of pyridine‐2‐carbaldehyde with aminoalcohols N‐(2‐hydroxyethyl)ethylenediamine and 2‐(3‐aminopropylamino)ethanol in presence of Cd II X2 (X=Cl, Br, I) have been investigated. Structure analyses reveal that four complexes, namely [Cd2 (L 1 )2 (Br)4 ] (2 ), [Cd(L 1 )(I)2 ](3), [Cd(L 1 )(Br)2 ](5) and [Cd(L 2 )(I)2 ](6) are formed with the expected Schiff‐base ligands ( E )‐2‐(2‐(pyridin‐2‐ylmethyleneamino)ethylamino)ethanol (L 1 ) and ( E )‐2‐(3‐(pyridin‐2‐ylmethyleneamino)propylamino)ethanol (L 2 ). Interestingly, when X=Cl two dinuclear complexes of general formula [Cd2 (L 1C /L 2C )2 (Cl)4 ] (complex1 and4, respectively) have been structurally characterized, where the ligands are no longer Schiff‐bases but contain an imidazolidine/hexahydro‐pyrimidine cyclic part instead [L 1C = 2‐(2‐Pyridin‐2‐yl‐imidazolidin‐1‐yl)‐ethanol and L 2C = 2‐(2‐Pyridin‐2‐yl‐tetrahydro‐pyrimidin‐1‐yl)‐ethanol]. In order to understand whether the solid state structure is retained in solution various NMR analysis like 1 H, 13 C NMR and DEPT‐135 have been performed. When X=I, the equilibrium is shifted towards the formation of the Schiff‐base ligands, thus complexes3 and6 are obtained as sole products. However, with X=Br or Cl, a mixture of products is present, comprising complexes containing both Schiff‐bases as well as cyclized ligands. DFT calculations have been performed to rationalize the influence of the halide ligands on the reactivity of the Schiff‐base and the formation of the cyclized ligand. Abstract : The extent of shifting of equilibrium between Schiff‐base and cyclized non‐Schiff‐base ligands is controlled by the nature of halide ion leading to new coordination chemistry of Cd II as are explored by combined experimental and theoretical investigations.