摘要:
The monomeric complexes, Ru(bpy)(2)1,4-DHAQ(+) and Ru(bpy)(2)1,5-DHAQ(+) (bpy=2,2'-bipyridine and DHAQ=dihydroxyanthraquinone), were synthesized by the reaction of Ru(bpy)(2)Cl-2 . 2H(2)O with an excess of either 1,4-DHAQ or I,5-DHAQ. The complexes were purified chromatographically and characterized spectroscopically and electrochemically. Comparisons between the data for these monomers and data from the corresponding free ligands and ruthenium bipyridyl dimers were made. The lowest energy spectral transition in the visible region was assigned as an MLCT transition to the DHAQ based on the red shifting from monomer to the corresponding dimer and the solvatochromism of the transition. In aqueous solution the pK(a) for both the 1,4- and 1,5-DHAQ monomer was determined to be 10.1+/-0.2 and for the 1,8-DHAQ monomer, 10.5+/-0.2. In all cases, pK(al) of the uncomplexed dihydroxyanthraquinones was more acidic measured under the same conditions. From the properties of the coordinated DHAQs attempts were made to evaluate whether they were sigma donating or pi accepting.