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Cited by 275

The DOI matches its Crossref record; 32 of the 32 references it cites were found in a registry or an index.

Ternary Copper Complexes for Photocleavage of DNA by Red Light: Direct Evidence for Sulfur-to-Copper Charge Transfer and d−d Band Involvement

Dhar, Shanta, Senapati, Dulal, Das, Puspendu K., Chattopadhyay, Pabitra, Nethaji, Munirathinam, Chakravarty, Akhil R.·2003·Journal of the American Chemical Society
DOI 10.1021/ja036681q
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Abstract

A new class of ternary copper(II) complexes of formulation [Cu(L(n)B](ClO(4)) (1-4), where HL(n) is a NSO-donor Schiff base (HL(1), HL(2)) and B is a NN-donor heterocyclic base viz. 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmp), are prepared, structurally characterized, and their DNA binding and photocleavage activities studied in the presence of red light. Ternary complex [Cu(L(3))(phen)](ClO(4)) (5) containing an ONO-donor Schiff base and a binary complex [Cu(L(2))(2)] (6) are also prepared and structurally characterized for mechanistic investigations of the DNA cleavage reactions. While 1-4 have a square pyramidal (4 + 1) CuN(3)OS coordination geometry with the Schiff base bonded at the equatorial sites, 5 has a square pyramidal (4 + 1) geometry with CuN(3)O(2) coordination with the alcoholic oxygen at the axial site, and 6 has a square planar trans-CuN(2)O(2) geometry. Binding of the complexes 1-4 to calf thymus DNA shows the relative order: phen >> dmp. Mechanistic investigations using distamycin reveal minor groove binding for the complexes. The phen complexes containing the Schiff base with a thiomethyl or thiophenyl moiety show red light induced photocleavage. The dmp complexes are essentially photonuclease inactive. Complexes 5 and 6 are cleavage inactive under similar photolytic conditions. A 10 microM solution of 1 displays a 72% cleavage of SC DNA (0.5 microg) on an exposure of 30 min using a 603 nm Nd:YAG pulsed laser (60 mJ/P) in Tris-HCl buffer (pH 7.2). Significant cleavage of 1 is also observed at 694 nm using a Ruby laser. Complex 1 is cleavage inactive under argon or nitrogen atmosphere. It shows a more enhanced cleavage in pure oxygen than in air. Enhancement of cleavage in D(2)O and inhibition with sodium azide addition indicate the possibility of the formation of singlet oxygen as a reactive intermediate leading to DNA cleavage. The d-d band excitation with red light shows significant enhancement of cleavage yield. The results indicate that the phen ligand is necessary for DNA binding of the complex. Both the sulfur-to-copper charge transfer band and copper d-d band excitations helped the DNA cleavage. While the absorption of a red photon induces a metal d-d transition, excitation at shorter visible wavelengths leads to the sulfur-to-copper charge transfer band excitation at the initial step of photocleavage. The excitation energy is subsequently transferred to ground state oxygen molecules to produce singlet oxygen that cleaves the DNA.

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Metadata

Authors
Dhar, S., Senapati, D., Das, P. K., Chattopadhyay, P., Nethaji, M., & Chakravarty, A. R.
Venue
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Published
2003-09-12
Volume
125
Issue
40
Pages
12118-12124
ISSN
  • 0002-7863 (ISSN-L)
  • 1520-5126
DOI
10.1021/ja036681q
OpenAlex
W2032127613
Cited by
275
References
32
FWCI
5.81
Type
journal article
Language
en
Open access
closed

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