Photochemical properties of 4-coumarinylmethyl derivatives (CM− X, X= Br, Cl, OH, OPh, SH, and SPh) in solution were studied by laser flash photolysis and DFT calculations. It was found that CM− Br and CM− SPh undergo photoinduced bond dissociation in the lowest excited singlet state, yielding the 4-coumarinylmethyl radical (CMR) and the corresponding radical with quantum yields of∼ 0.25. Laser flash photolysis of CM− Cl, OH, OPh, and SH ...