title: Reversal in solvatochromism in some novel styrylpyridinium dyes having a hydrophobic cleft.
abstract: The influence of solvent polarity on the electronic transition of four different N-hexadecyl styrylpyridinium dyes has been investigated in 15 solvents. The E(T)(30) scale has been used to propose a quantitative approach towards the relative stability of the electronic ground and excited state species. The extents of contribution of dipolar aprotic solvents towards the solvation of the excited species have been determined to be 42-48% for some of the dyes. Instead of a steady solvatochromism, all the dyes suffer a reversal in solvatochromism. The transitions of the solvatochromism, referred to as solvatochromic switches, are found to be at E(T)(30) values of approximately 50 for methyl and N,N-dimethylamino substituted dyes while at 37.6 for hydroxyl substituted dye and approximately 45 for 4-(1-methyl-2-phenylethenyl) pyridinium dye. A reversal in the trend of solvent effect in the later dye corresponding to 4-(4-methyl styryl)pyridinium dye has been attributed to an analogy of series and parallel electron flow.
authors.affiliation: Centre of Studies in Surface Science and Technology, Department of Chemistry, Sambalpur University, Jyoti Vihar, India.
authors.forename: Mallika
authors.initials: M
authors.lastname: Panigrahi
authors.forename: Sukalyan
authors.initials: S
authors.lastname: Dash
authors.forename: Sabita
authors.initials: S
authors.lastname: Patel
authors.forename: P K
authors.initials: PK
authors.lastname: Behera
authors.forename: B K
authors.initials: BK
authors.lastname: Mishra
mesh_terms: D000818:Animals; D002417:Cattle; D004396:Coloring Agents / Q000737:chemistry*; D004583:Electrons; D057927:Hydrophobic and Hydrophilic Interactions; D011726:Pyridinium Compounds / Q000737:chemistry*; D012997:Solvents; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: D004396:Coloring Agents; D011726:Pyridinium Compounds; D012997:Solvents