A family of (1,10-phenanthroline) rhenium(I)(CO)(3)Cl complex cored first generation dendrimers with one, two or three dendrons have been prepared. The first generation dendrons attached to the core complex are comprised of biphenyl units with 2-ethylhexyloxy surface groups at their distal ends. The number and position of attachment of the dendron to the core was found to have an effect on the properties of the dendrimers. When dendrons were attached to both the 2- and 9-positions of the 1,10-phenanthroline ligand, thus straddling the rhenium( I), the dendrimers became more electrochemically stable and less susceptible to solvatochromism. The dendrimers were generally found to have their emission blue-shifted and a higher photoluminescence quantum yield in the solid state than in the solution. The origin of this rigidochromism effect is discussed. A single layer device with a neat dendrimer film was found to have an external quantum efficiency of 0.4% (0.8 cd A(-1)) and power efficiency of 0.2 lm W-1 at 100 cd m(-2) and 12.8 V.