OXADIAZOLE

Schiff base synthesis of 1,3,4 oxadiazole  derivatives containing
Indole moiety bearing thiazolidinone ring were synthesized by the
condensation  of  2-(3-(4-oxo-3-(p-tolyl)  1H-tetrazol-5-yl)-1Hindol-1-yl)-N-(1,1,1-trifluoropropan-2-    ylidene)  acetohydrazide
with acetic anhydride. To this reaction was subjected in schiff base
reaction. It forms 2-(1-((4-acetyl-5-methyl-5-(trifluoromthyl)-4, 5-dihyro-1,  3,  4-oxadiazol-2-yl)  methyl)-1H-indol-3yl)-3-(p-tolyl)
1H-tetrazol-5-yl).  The  structure  of  these  newly  synthesized
compounds was characterized by
1
H NMR,
13
CNMR, Mass, IR,
and elemental analysis.

An efficient synthesis of some new benzimidazole derivatives linked to various heterocyclic scaffolds was performed by multistep reaction sequences. The structures of synthesized compounds were elucidated by spectral studies (infrared, nuclear magnetic resonance [ 1 H NMR], 13 C NMR, and mass spectrometry). The compounds were evaluated for their antibacterial activity against few Gram-positive and Gram-negative bacteria. Among the screened compounds, compound 7 showed the most potent inhibitory activity.

A structure–property study across a series of donor–acceptor–donor structures composed of mono- and bi-(1,3,4-oxadiazole) units symmetrically substituted with alkyl functionalized bi-, ter- and quaterthiophene segments is presented. Synthetically tailoring the ratio of electron-withdrawing 1,3,4-oxadiazole to electron-releasing thiophene units and their alkyl grafting pattern permitted us to scrutinize the impact of these structural factors on the redox, absorptive and emissive properties of these push–pull molecules. Contrasting trends of redox potentials were observed, with the oxidation potential closely following the donor-to-acceptor ratio, whereas the reduction potential being tuned independently by either the number of acceptor units or the conjugation length of the donor–acceptor system. Increasing the thiophene unit contribution delivered a shift from blue to green luminescence, while the structural rigidity afforded by intramolecular non-covalent interactions between 1,3,4-oxadiazole and the thiophene moieties has been identified as the prime factor determining the emission efficiency of these molecules. All six structures investigated electro-polymerize easily, yielding electroactive and electrochromic polymers. The polymer doping process is largely influenced by the length of the oligothiophene repeating unit and the alkyl chain grafting density. Polymers with relatively short oligothiophene segments are able to support polarons and polaron-pairs, whereas those with segments longer than six thiophene units could also stabilize diamagnetic charge carries – bipolarons. Increasing the alkyl chain grafting density improved the reversibility and broadened the working potential window of the p-doping process. Stable radical anions have also been investigated, bringing detailed information about the conjugation pattern of these electron-surplus species. This study delivers interesting clues towards the conscious structural design of bespoke frontier energy level oligothiophene functional materials and their polymers by incorporating a structurally matching 1,3,4-oxadiazole unit.