Thioxanthonation of fluorenone resulted in a new visible light initiator namely, indeno [1,2-b]thioxanthene-7,13-dione (TX-FN). The detailed photophysical properties of the singlet and the triplet excited states of TX-FN are reported using steady-state absorption, fluorescence, and phosphorescence, as well as laser flash photolysis techniques. Photoinitiated polymerization of MMA with TX-FN and CQ has been investigated in the presence and absence of a co-initiator (MDEA). Additionally, Photo-DSC studies were performed both in mono-and multiacrylate systems with TX-FN and parent compounds TX and FN. The obtained results were compared for formulations consisting of CQ. At low initiator concentrations, the conversions were lower than those obtained with TX-FN. (C) 2015 Wiley Periodicals, Inc.