Platinum(ii) complexes with hybrid amine-imidazolin-2-imine ligands and their reactivity toward bio-molecules. (5th April 2016)

• Record Type: Journal Article
• Authors: Bogojeski, Jovana; Volbeda, Jeroen; Bugarčić, Živadin D.; Freytag, Matthias; Tamm, Matthias
• Is Part Of: New journal of chemistry. Volume 40:Number 5(2016:May)
• Page Start: 4818
• Page End: 4825
• Publication Date: 2016-04-05
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c5nj03360h
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Two new Pt(ii ) complexes with imidazolin-2-imines as ancillary ligands were synthesized and characterized and their reactivity toward bio-molecules was tested. Abstract : Two new Pt(ii ) complexes with imidazolin-2-imines as ancillary ligands, [Pt(DMEAIm iPr )Cl2 ] and [Pt(DPENIm iPr )Cl2 ], were synthesized and characterized. Substitution reactions of these complexes with nucleophiles – thiourea (TU), l -methionine (l -Met), l -histidine (l -His) and guanosine-5′-monophosphate (5′-GMP) – were carried out in 25 mM Hepes buffer in the presence of 30 mM NaCl. The reactions were monitored using variable-temperature UV-Vis spectrophotometry and were followed under pseudo-first-order conditions with a large excess of nucleophiles. A slightly higher reactivity was found for [Pt(DMEAIm iPr )Cl2 ], while the reactivity of the nucleophiles decreased in the order TU >l -Met >l -His > 5′-GMP. The negative values reported for the entropy of activation confirmed an associative substitution mode. Spectrophotometric acid–base titrations were performed to determine the p K a values of the coordinated water molecules in the diaqua complexes [Pt(DMEAIm iPr )(H2 O)2 ] 2+ and [Pt(DPENIm iPr )(H2 O)2 ] 2+ . Solubility measurements revealed good solubility of the studied imidazolin-2-imine complexes in water. The crystal structure of [Pt(DMEAIm iPr )Cl2 ] was determined by X-ray diffraction analysis. The coordination geometries around the platinum atoms are distorted square-planar; the [Pt(DMEAIm iPr )Cl2 ] complex displays Pt–N distances of 2.0162(19) and 2.0663(19) Å. Attempts to coordinate Au(iii ) ions to different imidazolin-2-imine ligands did not result in the formation of coordination complexes, but rather in the reduction of the Au(iii ) precursor. This was evidenced by the X-ray crystal structure of [(DACH(Im iPr H)2 )(AuCl2 )2 ], which formed during the reaction of KAuCl4 with the ligand DACH(Im iPr )2 .