Reddy Pattubala A N, Santra Bidyut K, Nethaji Munirathinam, Chakravarty Akhil R
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Sir C. V. Raman Avenue, Bangalore 560012, India.
J Inorg Biochem. 2004 Feb;98(2):377-86. doi: 10.1016/j.jinorgbio.2003.11.008.
Ternary copper(II) complexes CuLL', where HL is NSO-donor Schiff base (2-(methylthio)phenyl)salicylaldimine and L' is NN-donor phenanthroline bases like 1,10-phenanthroline (phen), dipyridoquinoxaline (dpq) and 2,9-dimethyl-1,10-phenanthroline (dmp), are prepared and structurally characterized by X-ray crystallography. The complexes have a distorted square-pyramidal (4+1) CuN(3)OS coordination geometry. While CuL(phen) and CuL(dpq) show axial sulfur ligation, CuL(dmp) has the sulfur bonded at the equatorial site. The one-electron paramagnetic complexes exhibit axial electron paramagnetic resonance (EPR) spectra in dimethylformamide glass at 77 K. The complexes are redox active and a quasireversible electron transfer process near 0.0 V vs saturated calomel electrode (SCE) in DMF-Tris buffer (1:4 v/v at pH 7.2) involving Cu(II)/Cu(I) couple is observed for the phen and dpq complexes. The dmp complex exhibits an irreversible reduction process forming bis(dmp)copper(I) species. A profound effect of the substituents of the phenanthroline bases is observed on the binding of the complexes to the calf thymus (CT) and in the cleavage of supercoiled (SC) pUC19 DNA. The phen and dpq complexes show DNA cleavage activity in presence of mercaptopropionic acid (MPA). The dmp complex is cleavage inactive in presence of MPA. All the complexes show photocleavage activity when irradiated with a monochromatic UV light of 312 nm. The dpq complex also cleaves SC DNA on visible light irradiation at 436, 532 and 632.8 nm but with a longer exposure time and higher complex concentration. The cleavage reactions in presence of MPA are found to involve hydroxyl radical. The photocleavage reactions are found to occur under aerobic conditions showing an enhancement of cleavage in D(2)O and inhibition with azide addition suggesting formation of singlet oxygen as a reactive species. The roles of sulfur of the Schiff base as photosensitizer and the phenanthroline bases as minor groove binder, and their influence on the photocleavage activity are discussed. The quinoxaline ligand exhibits significant photosensitizing effect assisted by the copper(II) center.
制备了三元铜（II）配合物CuLL'，其中HL是NSO供体席夫碱（2-(甲硫基)苯基）水杨醛亚胺，L'是NN供体菲咯啉碱，如1,10-菲咯啉（phen）、二吡啶并喹喔啉（dpq）和2,9-二甲基-1,10-菲咯啉（dmp），并通过X射线晶体学对其进行了结构表征。这些配合物具有扭曲的四方锥（4+1）CuN₃OS配位几何结构。虽然CuL(phen)和CuL(dpq)表现出轴向硫配位，但CuL(dmp)中的硫键合在赤道位置。这些单电子顺磁性配合物在77K的二甲基甲酰胺玻璃中表现出轴向电子顺磁共振（EPR）光谱。这些配合物具有氧化还原活性，在DMF-Tris缓冲液（pH 7.2时体积比为1:4）中，相对于饱和甘汞电极（SCE）在0.0V附近观察到涉及Cu(II)/Cu(I)电对的准可逆电子转移过程，对于phen和dpq配合物。dmp配合物表现出不可逆的还原过程，形成双（dmp）铜（I）物种。观察到菲咯啉碱取代基对配合物与小牛胸腺（CT）的结合以及超螺旋（SC）pUC19 DNA的切割有深远影响。phen和dpq配合物在巯基丙酸（MPA）存在下表现出DNA切割活性。dmp配合物在MPA存在下无切割活性。当用312nm的单色紫外光照射时，所有配合物都表现出光切割活性。dpq配合物在436、532和632.8nm的可见光照射下也能切割SC DNA，但需要更长的照射时间和更高的配合物浓度。发现在MPA存在下的切割反应涉及羟基自由基。发现在有氧条件下发生光切割反应，在D₂O中切割增强，添加叠氮化物则受到抑制，表明形成单线态氧作为反应物种。讨论了席夫碱的硫作为光敏剂和菲咯啉碱作为小沟结合剂的作用，以及它们对光切割活性的影响。喹喔啉配体在铜（II）中心的辅助下表现出显著的光敏作用。
