Synthesis, characterization, DNA-binding and spectral properties of complexes [Ru(L)4(dppz)]2+ (L=Im and MeIm).
Two new Ru(II) complexes [Ru(L)(4)(dppz)](2+) (L=imidazole (Im), 1-methylimidazole (MeIm); dppz=dipyrido[3,2-a:2',3'-c]phenazine), have been synthesized and characterized in detail by elemental analysis, (1)H NMR, Electrospray ionization mass spectrometry (ESI-MS) and UV-visible (UV-Vis) spectroscopic techniques. The interaction of these complexes with calf thymus DNA (CT-DNA) has been explored by using electronic absorption titration, competitive binding experiment, circular dichroism (CD), thermal denaturation and viscosity measurements. The experimental results show that: both the two complexes can bind to DNA in an intercalation mode; the DNA-binding affinity of complex [Ru(Im)(4)(dppz)](2+)1 (K(b)=2.5 x 10(6)M(-1)) is greater than that of complex [Ru(MeIm)(4)(dppz)](2+)2 (K(b)=1.1 x 10(6)M(-1)). Moreover, it is very interesting to find that the circular dichroic spectrum of DNA-complex 1 adduct, in which both bands centered at 277 nm and 236 nm are all negative, is very different from those of DNA-complex 2 adduct and other Ru(II) complexes binding to DNA in general intercalation mode. It may be due to the hydrogen-bonding effect or the contribution of induced CD signals of complex 1. Another interesting finding is that the hypochromism of the complexes is not linear relation to their DNA-binding affinities. In order to deeply study these experimental phenomena and trends, the density functional theory (DFT) and time-dependent DFT (TDDFT) computations were carried out, and on the basis of the DFT/TDDFT results and the frontier molecular orbital theory, the trend in DNA-binding affinities, the spectral properties as well as the interesting phenomena of larger extent of hypochromism but relatively smaller K(b) values for the title complexes have been reasonably explained.
Chen
Lan-Mei
LM
Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China.
Liu
Jie
J
Chen
Jin-Can
JC
Tan
Cai-Ping
CP
Shi
Shuo
S
Zheng
Kang-Cheng
KC
Ji
Liang-Nian
LN
D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism*; D007093:Imidazoles / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D012428:Ruthenium / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
D007093:Imidazoles; D009942:Organometallic Compounds; D012428:Ruthenium; D004247:DNA; C427203:calf thymus DNA