An efficient one pot syntheses of aryl-3,3′-bis(indolyl)methanes and studies on their spectral characteristics, DPPH radical scavenging-, antimicrobial-, cytotoxicity-, and antituberculosis activity

An efficient one-pot syntheses of aryl-3,3′-bis(indolyl)methanes (BIMs) from indole/2-methylindole and formylphenoxyaliphatic acid(s) is described. Esterification of carboxylic acid and aromatic electrophilic substitution reactions are achieved simultaneous in the presence of potash alum as a catalyst. This catalyst could be recovered and reused without substantial loss in its catalytic activity and the methodology could be applied on a range of closely related substrates. The solvation characteristics in ground and excited states of the compounds by monitoring the absorbance and fluorescence band maxima have been studied. The fluorescence studies in protic and aprotic solvents were rationalized on the basis of solute–solvent interaction and substituents effect on these photophysical processes analyzed. The compounds prepared showed efficient antimicrobial effect against human pathogens, cytotoxicity against A431 cell line, and DPPH radical scavenging effect. Single crystal XRD studies have been carried out for a few compounds synthesized in this work.

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► An efficient one-pot synthesis of BIMs esters using potash alum as a catalyst.
► Single crystal XRD of acid and ester BIMs have different H-bonding pattern.
► Absorption spectra show solvent independent, but diminished emission intensities in polar solvents.
► BIMs display better radical scavenging-, moderate antimicrobial-, and less cytotoxicity.