Solvatochromic fluorescence behavior of 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile: A sensitive fluorescent probe for detection of pH and water composition in binary aqueous solutions

A new class of fluorescence sensor for detection of water in organic solvents based on photo-induced electron transfer (PET) of substituted pyrimidine appended with dimethoxyphenyl system has been designed and characterized. The probe 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile AHDPC (I) was synthesized by one step three-component condensation reaction. The solvatochromic fluorescence behavior of AHDPC featuring electron withdrawing CN group, electron donating ―OCH3, NH2, OH groups and various π-conjugated backbones in varying polar and non-polar solvents has been investigated. The fluorescence of the compound exhibits red shift from its absorption spectra and correlated with solvent polarity. AHDPC exhibited significant spectral shifts in λem as a function of water composition in binary aqueous solvent systems. The changes are due to the specific interactions of AHDPC by intramolecular hydrogen bonding with water, photoinduced electron transfer as well as general solvent effect. The observed solvatochromic fluorescence characteristic of AHDPC could used as a new probe for micro-environmental polarity changes as well as a sensitive sensor for the determination of water composition in binary aqueous solutions. This study shows that due to the solvent sensitive emission, pyrimidine derivatives are good candidates to be used as fluorescent probes.