Synthesis and phosphate ester cleavage properties of copper(II) complexes of guanidinium-bridged bis(1,4,7-triazacyclononane) ligands

Linda Tjioe, Tanmaya Joshi, Bim Graham, Leone Spiccia

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The synthesis and characterization of three new bis(1,4,7-triazacyclononane) ligands, L1, L2and L3, featuring a bridging guanidinium group between two macrocyclic units, is reported. The corresponding binuclear copper(II) complexes have been studied as agents to accelerate the cleavage of P–O bonds within two model phosphodiesters, namely bis(p-nitrophenyl)phosphate (BNPP) and 2-hydroxypropyl-p-nitrophenylphosphate (HPNPP). The results of a comparative study of cleavage rates, using the mononuclear copper(II)–tacn complexes bearing single alkylguanidinium groups as a reference, revealed that the binuclear copper(II) complexes are generally less effective cleavage agents, which may be related to a tendency to form hydrolytically inactive hydroxo-bridged species at near-neutral pH and above. However, at pH 7, these complexes produced 4–18-fold increases in the rate of BNPP hydrolysis compared to the parent complex, [Cu(tacn)(OH2)2]2+. Likewise, at pH 6, the complexes cleaved HPNP 5–130-fold faster than [Cu(tacn)(OH2)2]2+, suggesting some degree of cooperative interplay between the two proximal copper(II) centers and the protonated guanidinium bridging group in promoting phosphodiester hydrolysis under these conditions.

Original languageEnglish
Pages (from-to)11-17
Number of pages7
JournalPolyhedron
Volume120
DOIs
Publication statusPublished - 2016

Keywords

  • 1,4,7-Triazacyclononane derivatives
  • Copper(II) complexes
  • Kinetic studies
  • Phosphate ester cleavage
  • Synthetic nucleases

Cite this

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title = "Synthesis and phosphate ester cleavage properties of copper(II) complexes of guanidinium-bridged bis(1,4,7-triazacyclononane) ligands",
abstract = "The synthesis and characterization of three new bis(1,4,7-triazacyclononane) ligands, L1, L2and L3, featuring a bridging guanidinium group between two macrocyclic units, is reported. The corresponding binuclear copper(II) complexes have been studied as agents to accelerate the cleavage of P–O bonds within two model phosphodiesters, namely bis(p-nitrophenyl)phosphate (BNPP) and 2-hydroxypropyl-p-nitrophenylphosphate (HPNPP). The results of a comparative study of cleavage rates, using the mononuclear copper(II)–tacn complexes bearing single alkylguanidinium groups as a reference, revealed that the binuclear copper(II) complexes are generally less effective cleavage agents, which may be related to a tendency to form hydrolytically inactive hydroxo-bridged species at near-neutral pH and above. However, at pH 7, these complexes produced 4–18-fold increases in the rate of BNPP hydrolysis compared to the parent complex, [Cu(tacn)(OH2)2]2+. Likewise, at pH 6, the complexes cleaved HPNP 5–130-fold faster than [Cu(tacn)(OH2)2]2+, suggesting some degree of cooperative interplay between the two proximal copper(II) centers and the protonated guanidinium bridging group in promoting phosphodiester hydrolysis under these conditions.",
keywords = "1,4,7-Triazacyclononane derivatives, Copper(II) complexes, Kinetic studies, Phosphate ester cleavage, Synthetic nucleases",
author = "Linda Tjioe and Tanmaya Joshi and Bim Graham and Leone Spiccia",
year = "2016",
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language = "English",
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pages = "11--17",
journal = "Polyhedron",
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Synthesis and phosphate ester cleavage properties of copper(II) complexes of guanidinium-bridged bis(1,4,7-triazacyclononane) ligands. / Tjioe, Linda; Joshi, Tanmaya; Graham, Bim; Spiccia, Leone.

In: Polyhedron, Vol. 120, 2016, p. 11-17.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Synthesis and phosphate ester cleavage properties of copper(II) complexes of guanidinium-bridged bis(1,4,7-triazacyclononane) ligands

AU - Tjioe, Linda

AU - Joshi, Tanmaya

AU - Graham, Bim

AU - Spiccia, Leone

PY - 2016

Y1 - 2016

N2 - The synthesis and characterization of three new bis(1,4,7-triazacyclononane) ligands, L1, L2and L3, featuring a bridging guanidinium group between two macrocyclic units, is reported. The corresponding binuclear copper(II) complexes have been studied as agents to accelerate the cleavage of P–O bonds within two model phosphodiesters, namely bis(p-nitrophenyl)phosphate (BNPP) and 2-hydroxypropyl-p-nitrophenylphosphate (HPNPP). The results of a comparative study of cleavage rates, using the mononuclear copper(II)–tacn complexes bearing single alkylguanidinium groups as a reference, revealed that the binuclear copper(II) complexes are generally less effective cleavage agents, which may be related to a tendency to form hydrolytically inactive hydroxo-bridged species at near-neutral pH and above. However, at pH 7, these complexes produced 4–18-fold increases in the rate of BNPP hydrolysis compared to the parent complex, [Cu(tacn)(OH2)2]2+. Likewise, at pH 6, the complexes cleaved HPNP 5–130-fold faster than [Cu(tacn)(OH2)2]2+, suggesting some degree of cooperative interplay between the two proximal copper(II) centers and the protonated guanidinium bridging group in promoting phosphodiester hydrolysis under these conditions.

AB - The synthesis and characterization of three new bis(1,4,7-triazacyclononane) ligands, L1, L2and L3, featuring a bridging guanidinium group between two macrocyclic units, is reported. The corresponding binuclear copper(II) complexes have been studied as agents to accelerate the cleavage of P–O bonds within two model phosphodiesters, namely bis(p-nitrophenyl)phosphate (BNPP) and 2-hydroxypropyl-p-nitrophenylphosphate (HPNPP). The results of a comparative study of cleavage rates, using the mononuclear copper(II)–tacn complexes bearing single alkylguanidinium groups as a reference, revealed that the binuclear copper(II) complexes are generally less effective cleavage agents, which may be related to a tendency to form hydrolytically inactive hydroxo-bridged species at near-neutral pH and above. However, at pH 7, these complexes produced 4–18-fold increases in the rate of BNPP hydrolysis compared to the parent complex, [Cu(tacn)(OH2)2]2+. Likewise, at pH 6, the complexes cleaved HPNP 5–130-fold faster than [Cu(tacn)(OH2)2]2+, suggesting some degree of cooperative interplay between the two proximal copper(II) centers and the protonated guanidinium bridging group in promoting phosphodiester hydrolysis under these conditions.

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KW - Copper(II) complexes

KW - Kinetic studies

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KW - Synthetic nucleases

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