| abstract |
A compound is disclosed that has a metal coordination complex structure having at least two ligands coordinated to the metal; wherein the compound has a first substituent R 1 at one of the ligands' periphery; wherein a first distance is defined as the distance between the metal and one of the atoms in R 1 where that atom is the farthest away from the metal among the atoms in R 1 ; wherein the first distance is also longer than any other atom-to-metal distance between the metal and any other atoms in the compound; and wherein when a sphere having a radius r is defined whose center is at the metal and the radius r is the smallest radius that will allow the sphere to enclose all atoms in the compound that are not part of R 1 , the first distance is longer than the radius r by at least 2.9 Å. |