Interaction of 1,8-acridinedione dye with urea dimer in methanol Chellappan Selvaraju a , Viruthachalam Thiagarajan a , Perumal Ramamurthy a,b, * a Department of Inorganic Chemistry, University of Madras, Guindy campus, Chennai 600 025, India b National Centre for Ultrafast Processes, University of Madras, Taramani Campus, Chennai 600 113, India Received 9 May 2003; in final form 25 August 2003 Published online: 17 September 2003 Abstract The hydrogen-bonding interaction between acridinedione dye (ADD) and urea dimer in methanol is reported by using steady state and time resolved fluorescence techniques. Ó 2003 Elsevier B.V. All rights reserved. 1. Introduction The behaviour of urea in solution is a very im- portant topic in biological science because of its involvement as a waste product. Due to the com- plicated hydrogen bonding and the acid–base properties associated with both the carbonyl group and amines in the urea molecule, it has distinct chemical and physical properties in solutions such as demicellization [1], denaturation of proteins [2], dissolution and interaction of hydrophobic species in aqueous solution [3], etc. Various models such as hydrogen bond breaking [4], replacement of sol- vent molecule from the solvation layer [5], inter- action with the hydrophobic moieties of the molecules and association of urea molecules [6] have been proposed to explain the anomalous behaviour of urea in solution. 1,8-Acridinedione (ADD) dye has biological importance due to its structural similiarity with coenzyme NADH [7–9]. These dyes form inclusion complexes with cyclodextrin [10,11]. In this Letter, we report the interaction of urea molecules with the following ADD dye in methanol by using the steady state and time resolved fluorescence techniques. 2. Experimental The ADD dye was prepared by following the procedure reported in the literature [8]. Urea (molecular biology grade) was obtained from SRL and used as received. Methanol used in this Chemical Physics Letters 379 (2003) 437–442 www.elsevier.com/locate/cplett * Corresponding author. Fax: +91444926709. E-mail address: prm60@hotmail.com (P. Ramamurthy). 0009-2614/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2003.08.062