1-ethyl gallate-2-substituted phenoxymethyl benzimidazoles: Synthesis,molecular structure,antimicrobial activities and complex with Cr(III)

Summary: the design of gallate and benzimidazole containing derivatives is expected to produce new bioactive molecules with multiple applications. here the synthesis of eight novel benzimidazole compounds containing ethyl gallate and substituted phenoxymethyl units are reported. firstly,the ring closure reaction between o-phenylendiamine and substituted phenoxyacetic acids resulted in 2-substituted phenoxymethyl benzimidazoles that were then modified by the n-hydroxyethylation with 2-chloroethyl alcohol under a phase transfer catalysis condition. the obtained 1-hydroxyethyl-2-substituted phenoxymethyl benzimidazoles were finally translated into the target title compounds 8a-h by an indirect esterification method in which three o-h groups of gallic acid were first protected by acetyls and deprotected after the esterification reaction by adding hydrazine hydrate. the structures of the title products 8a-h were fully characterized and confirmed by elemental analysis,ms,ir,1h-nmr,13c-nmr and single crystal x-ray diffraction techniques. antimicrobial tests by inhibition zones indicated that these compounds exhibited diverse inhibitory effects against the test bacteria and fungi,and the type and position of the substituent groups in the phenoxymethyl moieties had obvious influence on their antimicrobial activities. furthermore,the cr(iii) complex of 8h was synthesized,and various spectral,elemental and thermal analysis results confirmed that the central cr(iii) atom coordinated with adjacent hydroxyl groups of two 8h ligands,nitrate and h2o,respectively.