HIGH-MOLECULAR-WEIGHT RUTHENIUM(II) COORDINATION POLYMERS - SYNTHESISAND SOLUTION PROPERTIES

A synthetic strategy is presented that allows the preparation of high- molecular-weight ruthenium(II) coordination polymers 1a, b of homogene ous molecular constitution. The key to this success was the developmen t of an efficient procedure leading to highly pure ''metal monomers'' [Ru(R(2)bpy)Cl-3](x) (3a, b) with (b: R = C6H5) and without (a: R = H) lateral phenyl substituents. Their conversion with equimolar quantiti es of ''ligand monomer'' tetrapyrido[3, 2-a:2', 3'-c:3'', 2''-h:2''',3 '''2j]phenazine (2) gave excellently soluble ruthenium(II) coordinatio n polymers 1a and 1b, respectively, the molecular constitution of whic h was proven with high-resolution H-1 and C-13 NMR spectroscopy. The d egrees of polymerization were estimated to be P-n greater than or equa l to 30 because of the complete lack of end group absorptions in the N MR spectra. This estimate could be verified by small-angle X-ray scatt ering (SAXS) for the phenyl-substituted polymer 1b: according to these investigations, the molecular weight reaches M-W approximate to 47 00 0, and the radius of gyration was found to be R-G = 8.4 nm. The intrin sic viscosities of high-molecular-weight polymers 1a and 1b were found to be [eta] x 12 mL.g(-1) for both polymers (0.01 M NaCl/DMA). At low ionic strengths, on the other hand, the unsubstituted polymer 1a disp lays a much more pronounced polyelectrolyte effect in solvents like et hanol/water than the phenyl-substituted polymer 1b of similar P-n. Con sidering all these results, the surprisingly high solubility of the co nformationally rigid, ribbonlike polyelectrolytes 1a and 1b can be con sidered to be the result of (i) the coiled shape of the polymers, (ii) the intermolecular Coulomb repulsion and, in the case of the phenyl-s ubstituted polymer 1b, (iii) the laterally-attached phenyl substituent s.