Azo-linkage in compounds offer broad-spectrum photochromic and nonlinear optical (NLO) properties owing to their architectural flexibility. The present work reports the effects of amino acids, organic solvents and ionic surfactants on the azo-hydrazone tautomerism and hence NLO properties of Methyl Red (MR) dye via the Z-scan technique and spectral-luminescent measurements. From the spectral measurements, the azo-hydrazone transition in MR was observed with the addition of amino acids (l-Phenylalanine and l-Alanine) and ionic surfactants (AOT and CTAB) probably due to the charge interaction. While, this azo-hydrazone switching was not observed with the change of solvent polarity. Moreover, with the provision of the quantum perturbation theory, it was observed that the NLO values of MR also transmuted by changing the concentration of amino acids and surfactants as well as solvent polarity probably due to the fluctuation of the dipole moment of dye during tautomerism and thermal conductivity of solvent, respectively. The results can be integrated into the possible future applications of azo-based molecules in novel photonic and optoelectronic devices.

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