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Mixed-Metal (Platinum, Palladium), Mixed-Pyrimidine (Uracil, Cytosine) Self-Assembling Metallacalix[n]arenes: Dynamic Combinatorial Chemistry with Nucleobases and Metal Species


Gil Bardají, Elisa; Freisinger, Eva; Costisella, Burkhard; Schalley, Christoph A; Brüning, Wolfgang; Sabat, Michal; Lippert, Bernhard (2007). Mixed-Metal (Platinum, Palladium), Mixed-Pyrimidine (Uracil, Cytosine) Self-Assembling Metallacalix[n]arenes: Dynamic Combinatorial Chemistry with Nucleobases and Metal Species. Chemistry - A European Journal, 13(21):6019-6039.

Abstract

Reactions between the mononuclear mixed-nucleobase complex [Pt(en)(UH-N1)(CH2-N3)]+ (1; en: ethylenediamine; UH-N1: uracil monoanion bonded through the N1 atom; CH2-N3: neutral cytosine bonded through the N3 atom) and [PdII(en)] or [PdII(2,2′-bpy)] (2,2′-bpy: 2,2′-bipyridine) lead to libraries of compounds of different stoichiometries and different connectivities. In these compounds, the palladium entity binds to or cross-links either the N3 sites of uracil and/or the N1 sites of cytosine, following deprotonation of these positions to give uracil dianions (U) and cytosine monoanions (CH). Cyclic species, which can be considered as metallacalix[n]arenes, have been detected in several cases, with n being 4 and 8. The complexity of the compounds formed not only results from the possibility of the two different nucleobases in building block 1 engaging in different connectivities with the Pd entities, but also from the potential for the formation of oligomers of different sizes and different conformations; in the case of cyclic tetranuclear Pt2Pd2 species, this can, in principle, lead to the various arrangements (cone, partial cone, 1,2-alternate, 1,3-alternate) known from calix[4]arene chemistry. A further complication arises from the fact that, depending on the mutual orientation of the exocyclic groups of the two nucleobases (O2 and O4 of uracil, O2 and N4 of cytosine), these sites can be engaged in additional chelation of [PdII(en)] and [PdII(2,2′-bpy)]. Thus, penta-, hexa-, and octanuclear complexes, Pt2Pd3, Pt2Pd4, and Pt2Pd6, derived from cyclic Pt2Pd2 tetramers have been isolated and characterized.

Abstract

Reactions between the mononuclear mixed-nucleobase complex [Pt(en)(UH-N1)(CH2-N3)]+ (1; en: ethylenediamine; UH-N1: uracil monoanion bonded through the N1 atom; CH2-N3: neutral cytosine bonded through the N3 atom) and [PdII(en)] or [PdII(2,2′-bpy)] (2,2′-bpy: 2,2′-bipyridine) lead to libraries of compounds of different stoichiometries and different connectivities. In these compounds, the palladium entity binds to or cross-links either the N3 sites of uracil and/or the N1 sites of cytosine, following deprotonation of these positions to give uracil dianions (U) and cytosine monoanions (CH). Cyclic species, which can be considered as metallacalix[n]arenes, have been detected in several cases, with n being 4 and 8. The complexity of the compounds formed not only results from the possibility of the two different nucleobases in building block 1 engaging in different connectivities with the Pd entities, but also from the potential for the formation of oligomers of different sizes and different conformations; in the case of cyclic tetranuclear Pt2Pd2 species, this can, in principle, lead to the various arrangements (cone, partial cone, 1,2-alternate, 1,3-alternate) known from calix[4]arene chemistry. A further complication arises from the fact that, depending on the mutual orientation of the exocyclic groups of the two nucleobases (O2 and O4 of uracil, O2 and N4 of cytosine), these sites can be engaged in additional chelation of [PdII(en)] and [PdII(2,2′-bpy)]. Thus, penta-, hexa-, and octanuclear complexes, Pt2Pd3, Pt2Pd4, and Pt2Pd6, derived from cyclic Pt2Pd2 tetramers have been isolated and characterized.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2007
Deposited On:27 Jun 2012 14:15
Last Modified:18 Feb 2018 13:02
Publisher:Wiley-Blackwell
ISSN:0947-6539
OA Status:Closed
Publisher DOI:https://doi.org/10.1002/chem.200601529

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