TY - JOUR
T1 - Mixed-ligand copper(II) complexes of dipicolylamine and 1,10-phenanthrolines
T2 - The role of diimines in the interaction of the complexes with DNA
AU - Ramakrishnan, S.
AU - Palaniandavar, M.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2005/3
Y1 - 2005/3
N2 - Mixed-ligand copper(II) complexes of the type [Cu(dipica)(diimine)] (ClO4)2) where dipica is di(2-picolyl)amine and diimine is 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), 2,9-dimethyl-1,10-phenanthroline (2,9-dmp) or dipyridoquinoxaline (dpq), have been isolated and characterized by analytical and spectral methods. The copper(II) complexes exhibit a broad band in the visible region around 675 nm and axial EPR spectra in acetonitrile glass (77 K) with g∥ and A∥ values of -2-22 and 185 × 10-4 cm-1 respectively, suggesting the presence of a square-based coordination geometry for the CuN 5 chromophore involving strong axial interaction. The interaction of the complexes with CT DNA has been studied using absorption, emission and circular dichroic spectral methods and viscosity measurements. Absorption spectral titrations reveal that the intrinsic DNA binding affinities are dependent upon the nature of the diimine ligand: dpq > 5,6-dmp > phen > 2,9-dmp. This suggests the involvement of the diimine rather than the dipica 'face' of the complexes in DNA binding. An intercalative mode of DNA interaction, which involves the insertion of dpq and to a lesser extent the phen ring of the complexes in between the DNA base pairs, is proposed. However, interestingly, the 5,6-dmp complex is involved in hydrophobic interaction of the 5,6-dmp ring in the grooves of DNA. The large enhancement in the relative viscosity of DNA on binding to the dpq and 5,6-dmp complexes supports the proposed DNA binding modes. Further, remarkably, the 5,6-dmp complex is selective in exhibiting a positive-induced CD band on binding to DNA suggesting the transition of the B form of CT DNA to A-like conformation. The variation in relative emission intensities of DNA-bound ethidium bromide observed upon treatment with the complexes parallels the trend in DNA binding affinities.
AB - Mixed-ligand copper(II) complexes of the type [Cu(dipica)(diimine)] (ClO4)2) where dipica is di(2-picolyl)amine and diimine is 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), 2,9-dimethyl-1,10-phenanthroline (2,9-dmp) or dipyridoquinoxaline (dpq), have been isolated and characterized by analytical and spectral methods. The copper(II) complexes exhibit a broad band in the visible region around 675 nm and axial EPR spectra in acetonitrile glass (77 K) with g∥ and A∥ values of -2-22 and 185 × 10-4 cm-1 respectively, suggesting the presence of a square-based coordination geometry for the CuN 5 chromophore involving strong axial interaction. The interaction of the complexes with CT DNA has been studied using absorption, emission and circular dichroic spectral methods and viscosity measurements. Absorption spectral titrations reveal that the intrinsic DNA binding affinities are dependent upon the nature of the diimine ligand: dpq > 5,6-dmp > phen > 2,9-dmp. This suggests the involvement of the diimine rather than the dipica 'face' of the complexes in DNA binding. An intercalative mode of DNA interaction, which involves the insertion of dpq and to a lesser extent the phen ring of the complexes in between the DNA base pairs, is proposed. However, interestingly, the 5,6-dmp complex is involved in hydrophobic interaction of the 5,6-dmp ring in the grooves of DNA. The large enhancement in the relative viscosity of DNA on binding to the dpq and 5,6-dmp complexes supports the proposed DNA binding modes. Further, remarkably, the 5,6-dmp complex is selective in exhibiting a positive-induced CD band on binding to DNA suggesting the transition of the B form of CT DNA to A-like conformation. The variation in relative emission intensities of DNA-bound ethidium bromide observed upon treatment with the complexes parallels the trend in DNA binding affinities.
KW - CD spectroscopy
KW - DNA binding studies
KW - Dipica and 1,10-phenanthrolines
KW - Mixed-ligand Cu(II) complexes
UR - http://www.scopus.com/inward/record.url?scp=17044377530&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=17044377530&partnerID=8YFLogxK
U2 - 10.1007/BF03356114
DO - 10.1007/BF03356114
M3 - Article
AN - SCOPUS:17044377530
SN - 0253-4134
VL - 117
SP - 179
EP - 186
JO - Journal of Chemical Sciences
JF - Journal of Chemical Sciences
IS - 2
ER -