Structure and reactivity of [Ru-II(terpy)(NN)Cl]Cl complexes: consequences for biological applications

Chrzanowska M, Katafias A, Impert O, Kozakiewicz A, Surdykowski A, Brzozowsk P, Franke A, Zahl A, Puchta R, van Eldik R (2017)


Publication Status: Published

Publication Type: Journal article

Publication year: 2017

Journal

Publisher: ROYAL SOC CHEMISTRY

Book Volume: 46

Pages Range: 10264-10280

Journal Issue: 31

DOI: 10.1039/c7dt01669g

Abstract

The crystal structures of [Ru-II(terpy)(bipy)Cl]Cl center dot 2H(2)O and [Ru-II(terpy)(en) Cl]Cl center dot 3H(2)O, where terpy = 2,2':6',2 ''-terpyridine, bipy = 2,2'-bipyridine and en = ethylenediamine, were determined and compared to the structure of the complexes in solution obtained by multi-nuclear NMR spectroscopy in DMSOd-6 as a solvent. In aqueous solution, both chlorido complexes aquate fully to the corresponding aqua complexes, viz. [Ru-II(terpy)(bipy)(H2O)](2+) and [Ru-II(terpy)(en)(H2O)](2+), within ca. 2 h and ca. 2 min at 37 degrees C, respectively. The spontaneous aquation reactions can only be suppressed by chloride concentrations as high as 2 to 4 M, i.e. concentrations much higher than that found in human blood. The corresponding aqua complexes are characterized by pK(a) values of ca. 10 and 11, respectively, which suggest a more labile coordinated water molecule in the case of the [Ru-II(terpy)(en)(H2O)](2+) complex. Substitution reactions of the aqua complexes with chloride, cyanide and thiourea show that the [Ru-II(terpy)(en)(H2O)](2+) complex is 30-60 times more labile than the [Ru-II(terpy)(bipy)(H2O)](2+) complex at 25 degrees C. Water exchange reactions for both complexes were studied by O-17-NMR and DFT calculations (B3LYP(CPCM)/def2tzvp//B3LYP/def2svp and omega B97XD(CPCM)/def2tzvp//B3LYP/def2svp). Thermal and pressure activation parameters for the water exchange and ligand substitution reactions support the operation of an associative interchange (I-a) process. The difference in reactivity between these complexes can be accounted for in terms of pi-back bonding effects of the terpy and bipy ligands and steric hindrance on the bipy complex. Consequences for eventual biological application of the chlorido complexes are discussed.

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APA:

Chrzanowska, M., Katafias, A., Impert, O., Kozakiewicz, A., Surdykowski, A., Brzozowsk, P.,... van Eldik, R. (2017). Structure and reactivity of [Ru-II(terpy)(NN)Cl]Cl complexes: consequences for biological applications. Dalton Transactions, 46(31), 10264-10280. https://dx.doi.org/10.1039/c7dt01669g

MLA:

Chrzanowska, Marta, et al. "Structure and reactivity of [Ru-II(terpy)(NN)Cl]Cl complexes: consequences for biological applications." Dalton Transactions 46.31 (2017): 10264-10280.

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