Steric protection of a photosensitizer in a N,N-bis[2-(2-pyridyl)ethyl]-2- phenylethylamine-copper(II) bowl that enhances red light-induced DNA cleavage activity

Shanta Dhar, Munirathinam Nethaji, Akhil R. Chakravarty

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Ternary copper(II) complexes [Cu(py2phe)B](CIO4)2 (1-3), where py2phe is a tripodal ligand N,N-bis[2-(2-pyridyl)-ethyl] -2-phenylethylamine and B is a heterocyclic base (viz., 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2′,3′-f]-quinoxaline (dpq, 2), or dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 3)), are prepared and their DNA-binding and photoinduced DNA-cleavage activities are studied. Complex 1 has been structurally characterized by single crystal X-ray crystallography. The molecular structure shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the phen ligand binds at the basal plane. The tripodal ligand py2phe displays an axial-equatorial binding mode with the amine nitrogen bonded at the axial site. A chemically significant CH-π interaction involving the CH moiety of the phenyl group of the tripodal ligand and the aromatic ring of phen is observed. The complexes display good binding propensity to calf thymus DNA giving a relative order of 3 (dppz) > 2 (dpq) > 1 (phen). The DNA binding constants (Kb) for 1-3, determined from absorption spectral studies, are 6.2 × 103, 1.0 × 104, and 5.7 × 104 M-1, respectively. The complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent forming hydroxyl radicals as the cleavage active species. The photoinduced DNA-cleavage activity of the complexes has been studied using UV radiation of 365 nm and red light of 632.8 and 694 nm. The phen complex in absence of any photosensitizing moiety does not show any DNA cleavage upon photoirradiation. The dpq and dppz ligands with their photoactive quinoxaline and phenazine moieties display significant photoinduced DNA-cleavage activity. The dppz complex is more active than its dpq analogue because of the better steric protection of the DNA-bound photosensitizing dppz ligand from the solvent molecules. Control experiments reveal the formation of singlet oxygen in the light-induced DNA-cleavage reactions. The observed efficient photoinduced DNA-cleavage activity of 2 and 3 is akin to the "light switch" effect known for the tris-chelates of ruthenium(II).

Original languageEnglish (US)
Pages (from-to)8876-8883
Number of pages8
JournalInorganic Chemistry
Volume44
Issue number24
DOIs
StatePublished - Nov 28 2005
Externally publishedYes

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Photosensitizing Agents
Copper
cleavage
deoxyribonucleic acid
copper
DNA
Ligands
ligands
Quinoxalines
quinoxalines
3-Mercaptopropionic Acid
phenethylamine
methylidyne
nuclease
Singlet Oxygen
Ruthenium
X ray crystallography
Reducing Agents
calves
hydroxyl radicals

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Steric protection of a photosensitizer in a N,N-bis[2-(2-pyridyl)ethyl]-2- phenylethylamine-copper(II) bowl that enhances red light-induced DNA cleavage activity. / Dhar, Shanta; Nethaji, Munirathinam; Chakravarty, Akhil R.

In: Inorganic Chemistry, Vol. 44, No. 24, 28.11.2005, p. 8876-8883.

Research output: Contribution to journalArticle

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abstract = "Ternary copper(II) complexes [Cu(py2phe)B](CIO4)2 (1-3), where py2phe is a tripodal ligand N,N-bis[2-(2-pyridyl)-ethyl] -2-phenylethylamine and B is a heterocyclic base (viz., 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2′,3′-f]-quinoxaline (dpq, 2), or dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 3)), are prepared and their DNA-binding and photoinduced DNA-cleavage activities are studied. Complex 1 has been structurally characterized by single crystal X-ray crystallography. The molecular structure shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the phen ligand binds at the basal plane. The tripodal ligand py2phe displays an axial-equatorial binding mode with the amine nitrogen bonded at the axial site. A chemically significant CH-π interaction involving the CH moiety of the phenyl group of the tripodal ligand and the aromatic ring of phen is observed. The complexes display good binding propensity to calf thymus DNA giving a relative order of 3 (dppz) > 2 (dpq) > 1 (phen). The DNA binding constants (Kb) for 1-3, determined from absorption spectral studies, are 6.2 × 103, 1.0 × 104, and 5.7 × 104 M-1, respectively. The complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent forming hydroxyl radicals as the cleavage active species. The photoinduced DNA-cleavage activity of the complexes has been studied using UV radiation of 365 nm and red light of 632.8 and 694 nm. The phen complex in absence of any photosensitizing moiety does not show any DNA cleavage upon photoirradiation. The dpq and dppz ligands with their photoactive quinoxaline and phenazine moieties display significant photoinduced DNA-cleavage activity. The dppz complex is more active than its dpq analogue because of the better steric protection of the DNA-bound photosensitizing dppz ligand from the solvent molecules. Control experiments reveal the formation of singlet oxygen in the light-induced DNA-cleavage reactions. The observed efficient photoinduced DNA-cleavage activity of 2 and 3 is akin to the {"}light switch{"} effect known for the tris-chelates of ruthenium(II).",
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T1 - Steric protection of a photosensitizer in a N,N-bis[2-(2-pyridyl)ethyl]-2- phenylethylamine-copper(II) bowl that enhances red light-induced DNA cleavage activity

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N2 - Ternary copper(II) complexes [Cu(py2phe)B](CIO4)2 (1-3), where py2phe is a tripodal ligand N,N-bis[2-(2-pyridyl)-ethyl] -2-phenylethylamine and B is a heterocyclic base (viz., 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2′,3′-f]-quinoxaline (dpq, 2), or dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 3)), are prepared and their DNA-binding and photoinduced DNA-cleavage activities are studied. Complex 1 has been structurally characterized by single crystal X-ray crystallography. The molecular structure shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the phen ligand binds at the basal plane. The tripodal ligand py2phe displays an axial-equatorial binding mode with the amine nitrogen bonded at the axial site. A chemically significant CH-π interaction involving the CH moiety of the phenyl group of the tripodal ligand and the aromatic ring of phen is observed. The complexes display good binding propensity to calf thymus DNA giving a relative order of 3 (dppz) > 2 (dpq) > 1 (phen). The DNA binding constants (Kb) for 1-3, determined from absorption spectral studies, are 6.2 × 103, 1.0 × 104, and 5.7 × 104 M-1, respectively. The complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent forming hydroxyl radicals as the cleavage active species. The photoinduced DNA-cleavage activity of the complexes has been studied using UV radiation of 365 nm and red light of 632.8 and 694 nm. The phen complex in absence of any photosensitizing moiety does not show any DNA cleavage upon photoirradiation. The dpq and dppz ligands with their photoactive quinoxaline and phenazine moieties display significant photoinduced DNA-cleavage activity. The dppz complex is more active than its dpq analogue because of the better steric protection of the DNA-bound photosensitizing dppz ligand from the solvent molecules. Control experiments reveal the formation of singlet oxygen in the light-induced DNA-cleavage reactions. The observed efficient photoinduced DNA-cleavage activity of 2 and 3 is akin to the "light switch" effect known for the tris-chelates of ruthenium(II).

AB - Ternary copper(II) complexes [Cu(py2phe)B](CIO4)2 (1-3), where py2phe is a tripodal ligand N,N-bis[2-(2-pyridyl)-ethyl] -2-phenylethylamine and B is a heterocyclic base (viz., 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2′,3′-f]-quinoxaline (dpq, 2), or dipyrido[3,2-a:2′,3′-c]phenazine (dppz, 3)), are prepared and their DNA-binding and photoinduced DNA-cleavage activities are studied. Complex 1 has been structurally characterized by single crystal X-ray crystallography. The molecular structure shows an axially elongated square-pyramidal (4 + 1) coordination geometry in which the phen ligand binds at the basal plane. The tripodal ligand py2phe displays an axial-equatorial binding mode with the amine nitrogen bonded at the axial site. A chemically significant CH-π interaction involving the CH moiety of the phenyl group of the tripodal ligand and the aromatic ring of phen is observed. The complexes display good binding propensity to calf thymus DNA giving a relative order of 3 (dppz) > 2 (dpq) > 1 (phen). The DNA binding constants (Kb) for 1-3, determined from absorption spectral studies, are 6.2 × 103, 1.0 × 104, and 5.7 × 104 M-1, respectively. The complexes show chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent forming hydroxyl radicals as the cleavage active species. The photoinduced DNA-cleavage activity of the complexes has been studied using UV radiation of 365 nm and red light of 632.8 and 694 nm. The phen complex in absence of any photosensitizing moiety does not show any DNA cleavage upon photoirradiation. The dpq and dppz ligands with their photoactive quinoxaline and phenazine moieties display significant photoinduced DNA-cleavage activity. The dppz complex is more active than its dpq analogue because of the better steric protection of the DNA-bound photosensitizing dppz ligand from the solvent molecules. Control experiments reveal the formation of singlet oxygen in the light-induced DNA-cleavage reactions. The observed efficient photoinduced DNA-cleavage activity of 2 and 3 is akin to the "light switch" effect known for the tris-chelates of ruthenium(II).

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