Calculated triplet excited state potential energy surfaces are presented for a set of three bis-tridentate Ru-II-polypyridyl dies covering a wide range of room temperature excited state lifetimes: [Ru-II(tpy)(2)](2+), 250 ps; [Ru-II(bmp)(2)](2+), 15 ns; and [Ru-II(dqp)(2)](2+), 3 mu s (tpy is 2,2':6',2 ''-terpyridine, bmp is 6-(2-picoly1)-2,2'-bipyridine, and dqp is 2,6-di(quinolin-8-yl)Fridine). The computational results provide a multidimensional view of the (MLCT)-M-3-(MC)-M-3 transition for the investigated complexes. Recently reported results of significantly prolonged (MLCT)-M-3 excited state lifetimes of bis-tridentate Ru-II-complexes, for example [Ru-II(dqp)(2)](2+), are found to correlate with substantial differences in their triplet excited state multidimensional potential energy surfaces. In addition to identification of low-energy transition paths for (MLCT)-M-3-3MC conversion associated with simultaneous elongation of two or more Ru-N bonds for all investigated complexes, the calculations also suggest significant differences in (MLCT)-M-3 state volume in the multidimensional reaction coordinate space formed from various combinations of Ru-N bond distance varix:ions. This is proposed to be an important aspect for understanding the large differences in experimentally observed (MLCT)-M-3 excited state lifetimes. The results demonstrate the advantage of considering multidimensional potential energy surfaces beyond the Franck-Condon region in order to predict photophysical and photochemical properties of bis-tridentate Ru-II-polypyridyl dyes and related metal complexes.