Dual emission from (E)-3-(4-methylamino-phenyl)-acrylic acid ethyl ester (MAPAEE) and its application as fluorescence probe for studying micellar and protein microenvironment

Steady state absorption, fluorescence and time resolved fluorescence spectroscopy have been used for studying the photoinduced intramolecular charge transfer reaction in (E)-3-(4-methylamino-phenyl)-acrylic acid ethyl ester (MAPAEE). The title molecule shows dual emission due to high energy local and a low energy charge transfer emission. Depending on the nature of solvent the red shifted emission band shows good correlation with the solvent polarity parameter, ET(30) parameter and hydrogen bonding parameter. Quantum chemicals calculations by density functional theory predict that a stabilized twisted intramolecular charge transfer excited state generated either by twisting of the donor group (NHMe) or the acceptor (- = COOEt) group is responsible for the red shifted charge transfer emission. The solvent polarity dependent red shifted emission from the excited charge transfer state of MAPAEE has been used as fluorosensor to study bovine serum albumin proteinous and sodium dodecyl sulphate micellar microenvironment.