A chiral (1R,2R)-N,N′-bis-(salicylidene)-1,2-diphenyl-1,2-ethanediamine Schiff base dye: synthesis, crystal structure, Hirshfeld surface analysis, computational study, photophysical properties and in silico antifungal activity

We report synthesis, structural and computational studies, and photophysical properties of a chiral (1R,2R)-N,N′-bis-(salicylidene)-1,2-diphenyl-1,2-ethanediamine Schiff base dye (1). The structure of 1 was found to be in the enol-imine tautomer, stabilized by two intramolecular O–H···N hydrogen bonds. Molecules are packed into a 1D supramolecular chain through intermolecular C–H···O interactions. 1D chains are interlinked through intermolecular C–H···π intercations. As a result of intermolecular interactions, molecules of 1 are packed into a 3D supramolecular framework, yielding a pcu alpha-Po primitive cubic; 6/4/c1; sqc1 topology defined by the point symbol of (412·63). Favoured intermolecular H···H, H···C and H···O contacts are responsible for the overall crystal packing of the dye. Energy frameworks have been calculated to additionally analyse the overall crystal packing of 1. The absorption spectra of 1 in THF, CH2Cl2 and CH3CN each exhibit three intense bands in the UV region. The absorption spectra of 1 in EtOH, nPrOH, iPrOH and nBuOH, besides the same three intense bands in the UV region, contain an additional band in the visible region centred at about 410 nm, corresponding to the cis-keto-enamine tautomer. The absorption spectrum of 1 in MeOH contains an additional intense shoulder at about 350 nm. The emission spectrum of 1 in MeOH contains a broad band at 438 nm, arising from the emission of the enol-imine* form. Theoretical calculations based on density functional theory (DFT) were performed to verify the structure of 1 as well as its electronic and optical properties. The global chemical reactivity descriptors were estimated from the energy of the HOMO and LUMO orbitals. Molecular docking studies were performed to evaluate the antifungal activity of 1 against cytochrome P450 14 alpha-sterol demethylase (CYP51).