Disaggregation induced solvatochromic switch: A study of dansylated polyglycerol dendrons in binary solvent mixture

• Interesting solvatochromism in polyether dendron aggregates in mixed aqueous media.
• Reversal in solvatochromic behaviour depending on percentage of nonaqueous solvent.
• Negative-solvatochromism due to progressive disaggregation of dendron aggregates.
• Positive-solvatochromism is shown by the dendron monomers.
• Higher dendron hydrophobicity requires more of second solvent for disaggregation.

A reversal in solvatochromic behaviour was observed in second and third generation glycerol based dansylated polyether dendrons in water on addition of a second solvent like methanol or acetonitrile. Below a certain percentage of the nonaqueous solvent there is a negative-solvatochromism observed and above that there is a switch to positive-solvatochromism. The negative-solvatochromism is attributed to the progressive disaggregation of the dendron aggregates by the nonaqueous solvent component. Once the disaggregation process is complete, positive-solvatochromism is exhibited by the dendron monomers. Higher the hydrophobicity of the dendron more is the amount of the second solvent required for disaggregation.

Reversal in solvatochromic behaviour of dendrons in aqueous medium on addition of a nonaqueous solvent. Negative-solvatochromism is attributed to the progressive disaggregation of dendron aggregates and the positive-solvatochromism is exhibited by the dendron monomers.Figure optionsDownload as PowerPoint slide