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New multicationic organoru- thenium dendrimers (RuPF<inf>6</ inf>-Dabn, n =2, 4, 8, 16) have been synthesized by coupling of [Ru(n<sup>6</sup>-p-cymene)(κ<inf><sup>3</ inf></sup>-dpk- OCH<inf>2</inf>CH<inf>2</ inf>OH)]X (1PF<inf>6</inf>, dpk = 2,2′-di- pyridyl ketone, X = PF<inf>6</inf>) with 1,4-di- aminobutane (DAB) and polypropy- lenimine dendrimer DAB-dendr- (NH<inf>2</inf>) <inf>n</inf> n = 4, 8, 16 mediated by 1,1'- carbonyldiimidazole (CDI). The intermediate in the synthesis, [Ru(n<sup>6</sup>-p-cy- mene)(κ<sup>3</sup>-dpk-OCH<inf>2</ inf>CH<inf>2</inf>OC(o)lm]X (2PF<inf>6</inf>,Im = imidazole, X = PF<inf>6</inf>) has been isolated and characterized by single-crystal XRD. The intra- and supramolecular structures in a solution of RuPF<inf>6</inf>-Dabn dendrimer have been investigated by multidimensional and multinuclear NMR techniques. Diffusion NMR experiments on dilute solutions indicated that the linear distance between two metal centers (14.9-22.1 A˚ depending on the dendrimer generation) is much greater than the diameter of 1PF<inf>6</inf> (9.9 A). <sup>19</ sup>F,<sup>1</sup>H- HOESY NMR experiments (HOESY = heteronuclear Overhauser effect spectroscopy) showed that the counterion is positioned on the surface of the dendrimers and assumes the same relative anion-cation orientation as in 2PF<inf>6</inf>. Diffusion NMR experiments on RuPF<inf>6</inf>-Dabn dendrimers in CD<inf>2</ inf>Cl<inf>2</inf> at different concentrations revealed a process of supramolecular assembly of dendrimers to megamers that is strongly favored for the highest generations. Megamer formation is coupled with an increased fraction of free ions (a) and a consequent reduction in ion-paired ruthenium centers. Graphs of a versus C<inf>Ru</inf> (the concentration of ruthenium centers) showed a minimum for RuPF<inf>6</inf>-Dab4, RuPF<inf>6</inf>- Dab8, and RuPF<inf>6</inf>-Dab16 at a position coinciding with the significant presence of supramolecular dendritic dimers. The tendency to ion pairing decreases as the dendrimer generation increases..

Diffusion and NOE NMR studies on multicationic DAB-organoruthenium dendrimers: Size-dependent noncovalent self-assembly to megamers and ion pairing

CIANCALEONI, GIANLUCA;
2009-01-01

Abstract

New multicationic organoru- thenium dendrimers (RuPF6-Dabn, n =2, 4, 8, 16) have been synthesized by coupling of [Ru(n6-p-cymene)(κ3-dpk- OCH2CH2OH)]X (1PF6, dpk = 2,2′-di- pyridyl ketone, X = PF6) with 1,4-di- aminobutane (DAB) and polypropy- lenimine dendrimer DAB-dendr- (NH2) n n = 4, 8, 16 mediated by 1,1'- carbonyldiimidazole (CDI). The intermediate in the synthesis, [Ru(n6-p-cy- mene)(κ3-dpk-OCH2CH2OC(o)lm]X (2PF6,Im = imidazole, X = PF6) has been isolated and characterized by single-crystal XRD. The intra- and supramolecular structures in a solution of RuPF6-Dabn dendrimer have been investigated by multidimensional and multinuclear NMR techniques. Diffusion NMR experiments on dilute solutions indicated that the linear distance between two metal centers (14.9-22.1 A˚ depending on the dendrimer generation) is much greater than the diameter of 1PF6 (9.9 A). 19F,1H- HOESY NMR experiments (HOESY = heteronuclear Overhauser effect spectroscopy) showed that the counterion is positioned on the surface of the dendrimers and assumes the same relative anion-cation orientation as in 2PF6. Diffusion NMR experiments on RuPF6-Dabn dendrimers in CD2Cl2 at different concentrations revealed a process of supramolecular assembly of dendrimers to megamers that is strongly favored for the highest generations. Megamer formation is coupled with an increased fraction of free ions (a) and a consequent reduction in ion-paired ruthenium centers. Graphs of a versus CRu (the concentration of ruthenium centers) showed a minimum for RuPF6-Dab4, RuPF6- Dab8, and RuPF6-Dab16 at a position coinciding with the significant presence of supramolecular dendritic dimers. The tendency to ion pairing decreases as the dendrimer generation increases..
2009
Pettirossi, Stefania; Bellachioma, Gianfranco; Ciancaleoni, Gianluca; Zuccaccia, Cristiano; Zuccaccia, Daniele; Macchioni, Alceo
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/828405
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