The development of organometallic and purely organic compounds showing room temperature phosphorescence (RTP) has several promising applications. We report a relationship between the phosphorescence characteristics and deuteration position in a purely organic aromatic compound. Hydrogen-deuterium exchange at the carbons where the lowest unoccupied molecular orbital is located is the most effective method to enhance the RTP lifetime and quantum yield. The increase in RTP lifetime comes from a decrease in the Franck-Condon factor while the enhancement of RTP yield is caused by an increase in intersystem crossing from the lowest singlet excited state to the lowest triplet excited state. (C) 2013 Elsevier B.V. All rights reserved.