Bis(Acylhydrazone)-Based Bolaamphiphiles: Effect of Spacer Length on Metalloorganogel Formation, Fluorescence, and Conductance Properties

Abstract

Gelation of chain-length-selective bolaamphiphiles (1 % w/v) from succinic (n=2, H2SL) and adipic acid (n=4, H2AL) derived ligands from six different bis(acylhydrazone)-based saturated homologous dicarboxlylates has been demonstrated. Deprotonation of H2SL (SL2−) with LiOH led to the formation of a fluorescent metalloorganogel upon addition of Cd(OAc)2. The coordination complexes responsible for metalloorganogel or solution formation have been studied with UV/Vis, Job's plot, ESI-MS and fluorescence studies. Transmission electron microscopy (TEM) of the diluted metalloorganogel revealed unusual nanospherical aggregates (∼50 nm diameter) aligned together to create fibrous morphology, which was further supported by scanning electron microscopy (SEM) imaging. Nyquist impedance plot indicated that the metalloorganogel has a much lower resistance (R1=3.6 kΩ) than its non-gelling counterpart (R2=5.6 kΩ) suggesting the formation of well-organized fibres. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.