We report on a known Schiff base dye salen. The crystal structure of salen is in the enol-enol tautomer. Molecules are packed into a 3D supramolecular framework through C-H center dot center dot center dot pi interactions. The absorption spectrum of salen in CH2Cl2 exhibits three bands in the UV region, while the spectrum in MeOH contains an additional band at 403 nm and a shoulder at 280 nm, corresponding to the cis-keto tautomer. The emission spectrum of salen in MeOH exhibits a band at 435 and 457 nm upon irradiation at 280 and 400 nm, respectively, arising from the enol-cis-keto* and/or cis-keto-cis-keto* tautomers. The solution of salen in CH2Cl2 showed dual emission with the bands at 349 and 462 nm upon irradiation at 290 nm with the low-energy emission band arising from the enol-cis-keto* and/or cis-keto-cis-keto* tautomers, while the high-energy band corresponds to the enol-enol* tautomer. The emission spectrum of salen in CH2Cl2 exhibits a single band at 464 nm upon irradiation at 380 nm, arising from the different conformers of the enol-cis-keto* and/or cis-keto-cis-keto* tautomers. The DFT calculations revealed that the enol-enol tautomer is the most favorable, followed by the enol-cis-keto tautomer. The global chemical reactivity descriptors were estimated from the HOMO and LUMO. The DFT calculations were also applied to probe salen as a potential corrosion inhibitor for some important metals used in implants. The enol-cis-keto and enol-trans-keto tautomers exhibit the best electron charge transfer from the molecule to the surface of all the studied metals, of which the most efficient electron charge transfer was established for Ni, Au, and Co. Molecular docking was applied to study interaction of tautomers of salen with a series of the SARS-CoV-2 proteins, of which the best binding affinity was found toward nsp14 (N7-MTase).