The absorption spectra and the stationary and time-resolved emissions of a series of the title compounds are investigated. Various combinations of ethinylene, p-phenylene, biphenyl-4,4′-diyl, fluorenyl-2,7-diyl, 3-or 4-pyridyl, phenanthroline-3,8-diyl, 2,2′-bipyridine-5,5′-diyl, and 2,2′-bipyridine-4,4′-diyl molecular units allow a systematic structure variation, e.g., size of π system, type of aza-substitution, linear or angular chains. Most compounds are highly fluorescent. Radiationless deactivation via internal conversion and to a lesser extend intersystem crossing become efficient if forbidden states exist close to the strongly allowed ππ* states (proximity effect) which can be traced back to a smaller size of the π system or reduced conjugation due to meta-linkages of heteroaromatic rings. Aza-substitution may change the deactivation behavior but it does insignificantly influence the absorption and fluorescence spectra. Replacing phenanthrene for 2,2′-bipyridine in the larger compounds does not alter the spectroscopic and the deactivation behaviors.

A series of ruthenium(II)-chelating poly(heteroaryleneethynylene)s were synthesized by the palladium-catalyzed cross-coupling polycondensation of diethynylbenzenes and dibromobipyridine-Ru-(II) chelates. The grafting of different alkoxy side chains including n-butoxy, (2-ethylhexyl)oxy, and n-octadecyloxy in the diethynylbenzene compounds enhances the solubility and processability of the new polymers. The same effect is attainable by tert-butyl substituents in the 2,2′-bipyridine ligands. The UV/ vis absorption showed a considerable red shift of the λ max from poly{bis(2,2′-bipyridine)-[2,2′-bipyridine-5,5′-diylethynylene-(2,5-dialkoxy)ethylene]ruthenium(II) bis(hexafluorophosphate)} ( 5) to the 4,4′diylethynylene isomers 6, suggesting an increase in the electronic delocalization between the backbone and ruthenium(II) chelate. The polymers are good photoconducting materials (IPh ) 3.7 × 10 -12 A at 18 000 cm -1 ), exhibiting an oxidation potential of 1.24 V vs SCE. The polymers are thermostable and exhibit a good solubility in acetone, DMF, DMSO, acetonitrile, and cyclohexanone. Last, an improved method of molecular weight determination by GPC was devised.

In this work, a novel bioresorbable bone adhesive based on radically polymerizable polylactide with methacrylate endgroups known from polymethylmethacrylate (PMMA) cements and varying amounts of bioresorbable/biodegradable lactide moieties was developed. The swelling and degradation properties as well as the hardening time, viscosity, and adhesion properties (tension and shear resistance) were subsequently measured in vitro and optimized. For a broad use in surgery the handling properties, the shelf life and the storage temperature are important issues. The finally developed material consists of three substances that have to be mixed to start the reaction: a highly viscous mixture of oligomers and two beta-tricalcium phosphate (beta-TCP, Cerasorb) powders with the radical starter and the promoter. The material has a processing time of 2 min and is completely cured after another minute. The tension and shear resistance of the material is 3.1-13.9 MPa that will decrease by storing the substance in a humid atmosphere. Degradation experiments showed a mass loss of 20-35% during the first 5 weeks. Tests with MC3T3-E1 cells showed an increase of the alkaline phosphatase activity over a period of 14 days. The mechanical and handling properties and the in vitro data are showing a promising biomaterial for bone regeneration.

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