Photocatalytic cleavage of hydroxytriazenes: a solid- state synthesis of azo-dyes under sunlight irradiation Prabhat Kumar Baroliya • Anita Mehta • Rekha Dashora • R. S. Chauhan • A. K. Goswami Received: 3 December 2011 / Accepted: 8 March 2012 / Published online: 25 March 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Sunlight-induced decomposition of hydroxytriazenes, and green pho- tochemical synthesis of azo-dyes is described. Three substituted hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (p-CFHT) were co-crystallized with b-naphthol in equimolar ratio and exposed to sunlight for 9–10 h. The reaction resulted in formation of azo-dyes which were identified by comparison with the products obtained by the conventional method (standard azo- dye), by use of HPLC. A probable mechanism has been suggested. This is first eco- friendly synthesis of azo-dyes using hydroxytriazenes. Keywords Hydroxytriazene Á Solid-state photolysis Á Azo-dye Introduction During the last few years, application of solar energy to chemical synthesis has acquired great importance [1–4]. Solid state photoreaction [3, 4] has also been reported. It has also been reported that organic compounds participate in photoad- dition [5, 6] and photodegradation [7, 8] reactions. In this work, therefore, we investigated the use of three hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1- (3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3- chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1- (3-chloro-4-fluorophenyl)triazene (p-CFHT) as photo-labile reagents for solid-state synthesis of azo-dyes. P. K. Baroliya Á A. Mehta Á R. Dashora Á R. S. Chauhan Á A. K. Goswami (&) Co-ordination Chemistry Lab., Department of Chemistry, Mohanlal Sukhadia University, Udaipur 313001, Rajasthan, India e-mail: akumargoswami@rediffmail.com 123 Res Chem Intermed (2012) 38:2149–2153 DOI 10.1007/s11164-012-0533-x