3-(7-Dimethylamino)coumarin N-phenylsemicarbazones in solution and polymer matrices: Tuning their fluorescence via para-phenyl substitution

•Five new 3-(7-dimethylamino)coumarin N-phenylsemicarbazones were synthesized.•Tuning their fluorescent properties via para-phenyl substitution was investigated.•Solvent polarity (TICT state formation, hydrogen bonds) and polymer matrix effects are discussed.•Unusual formation of fluorescent H-aggregates in both protic and aprotic polar solvents was observed.•Several coumarin-semicarbazones qualify as laser dyes in the given medium.

The photo-physical properties of five new para-phenyl substituted derivatives of 3-(7-dimethylamino)coumarin N-phenylsemicarbazone with various electron-withdrawing substituents R (RF, Br, CF3, CN or NO2) in the para-position on the phenyl ring were investigated in solvents and in polymer matrices. Tuning their fluorescent properties via para-substitution is discussed in terms of Twisted Intra-molecular Charge-Transfer (TICT) state formation, specific solute–solvent interactions (hydrogen bonding), fluorescent H-aggregates formation, and the solvent polarity and polymer matrix effects.

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