Synthesis and molecular structure of V-shaped liquid crystalline compounds: Spectroscopic, mesomorphic, DFT investigations, electrochemical and fluorescence studies

•Synthesis, structural and liquid crystalline studies of a new series of V-shaped liquid crystals were reported.•The mesomorphic, theoretical models derived from DFT, electrochemical and fluorescence properties of the V-shaped compounds were investigated.•The efficiency of title compounds toward the detection of hydrogen peroxide has been attributed to the presence of even n parity of alkyl chain CnH2n+1 along the elongated arms of which the molecular conformations were evaluated by computational modelling using the Chem3D Pro method and Gaussian 16 calculation.•The functionality as prominent probe for the Zn2+ ion has been verified using the target compound which possesses the shortest alkyl carbon chain lengths (n=6). A series of V-shaped compounds consisting of a central phenyl core connected by two identical mesogenic units which possess the imine (C=N) and ester (COO) bonds along with the terminal alkoxy chain (-OCnH2n+1) where n = 6-12. The ultimate compounds were synthesised and characterized by CHN elemental analysis, Fourier-Transform Infrared (FT-IR), nuclear magnetic resonance (1H-NMR), and UV-Visible (UV-Vis) spectroscopic techniques. The mesomorphic properties, thermal behaviour and conformation of compounds were studied by using polarised optical microscopy (POM), and differential scanning calorimetry (DSC). It can be generalized from present study that the V-shaped compounds with odd n carbon number in alkoxy chains were non-mesogenic. Whilst the compounds with shorter alkoxy chains of n = 6 and 8 were monotropic nematic, the compounds which possess longer alkoxy chains (n = 10 and 12) exhibited enantiotropic nematic phase. The computational method Chem3D Pro suggests the molecular structures of all the compounds with even n carbon number in the alkoxy chain. The Gaussian calculation with B3LYP/6-31G+(d,p) condition was employed to further demonstrate the chemical reactivity for all target compounds based on HOMO-LUMO analysis, the energy difference between HOMO-LUMO and surface charges. The target molecules of which the member containing the even n parity along the mesogenic arms have shown the same trend of electrocatalytic behaviour particularly toward the detection of hydrogen peroxide via the cyclic voltammetry study. Furthermore, the member with n=12 has been validated as a remarkable fluorogenic probe for the detection of Zn2+ ion.