A [Ru(phen)(3)](2+) complex (phen = 1,10-phenanthroline) having an arylethynyl group at the 4-position of one of the three phen ligands (aryl: (dimesityl)borylduryl group = [RuBE](2+) or duryl group = [RuDE](2+)) showed dual emissions at low temperature in propylene carbonate (PC). The shorter emission lifetime components (tau(em)(s) approximate to 13 mu s) that originated from the lowest-energy excited triplet states (T-1) of the complexes were almost independent of temperature (T = 77-320 K), while the longer emission lifetime components (tau(em)(l)), as the T-2 emissions appeared below the fluid-to-glass transition temperature (T-g approximate to 220 K) in PC, were almost constant at 27 mu s in the range of T = 77-220 K. The tau(em)(s) components of the complexes were assigned to the emissions from the metal-to-ligand charge transfer (MLCT) excited states possessing relatively large ligand-centered (LC) excited-state characters (T-1(MLCT/LC)), while the tau(em)(l) components were shown to be originating from the T-2(MLCT) excited states. The T-2(MLCT) states of the complexes became nonemissive above Tg in PC due to fast nonradiative decay through solvent reorganization around the T-2(MLCT) excited states. The photophysical properties of the complexes were also shown to be characterized by the presence of the arylethynyl units at the 4-positions of the phen ligands.