To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1016/j.jphotochem.2016.01.017 Byline: Nurcan Karaca (a), Nuket Ocal (a), Nergis Arsu [firstname.lastname@example.org] (a,*), Steffen Jockusch [email@example.com] (b,*) Keywords Thioxanthone; Photoinitiator; Photopolymerization; Laser flash Photolysis Highlights * Thioxanthone-benzothiophenes absorb in the visible spectral region. * These new conjugates show high extinction coefficients and high triplet yields. * The triplet states react with tertiary amines to generate free radicals. * These compounds are efficient photoinitiators for free radical polymerization. Abstract Photoinitiators for free radical polymerization based on the thioxanthone chromophore that contains benzothiophene were synthesized and characterized. Compared to thioxanthone, these compounds show a bathochromic shifted absorption up to ~460 nm. High quantum yields for intersystem crossing generate sufficient amounts of triplet states. Initiator radicals are generated by reaction of the triplet states with tertiary amines, such as diethanolamine with high rate constants (2--6 x 10.sup.9M.sup.-1s.sup.-1) as determined by laser flash photolysis. Photoinitiated polymerization experiments of MMA showed efficient polymerization with initiator concentrations as low as 0.1 mM. Author Affiliation: (a) Department of Chemistry, Yildiz Technical University, Davutpasa Campus, Istanbul 34210, Turkey (b) Department of Chemistry, Columbia University, 3000 Broadway, New York, NY 10027, United States * Corresponding authors. Article History: Received 3 November 2015; Revised 12 January 2016; Accepted 14 January 2016 (footnote)[white star] Dedicated to Professor Yoshihisa Inoue for his retirement from Osaka University and his contribution to photochemistry.