X-ray structure, spectral characteristics, thermal and redox behavior of quinoline encapsulated in sulfonatocalix[4]arene

• Published in: Journal of molecular liquids 2017-11, Vol.246, p.187-196
• Main Authors: Thorave, Rupali G., Lande, Dipali N., Athare, Sulakshana V., Gejji, Shridhar P., Gonnade, Rajesh G., Malkhede, Dipalee D.
• Format: Article
• Language: English
• Subjects: 1H NMR; DFT; Fluorescence; Sulfanatocalixarene; TGA-DTA; X-ray crystal structure
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2017.09.061

Structure and spectral characteristics of the inclusion complex between quinoline guest and the host para-sulfonatocalix[4]arene (SCX4) have been studied employing single crystal X-ray diffraction, 1H NMR, fluorescence, cyclic voltammetry and TG-DTA experiments. The crystal structure analysis of the inclusion complex Q⊂SCX4 revealed partial encapsulation of one of the quinoline (guest) with its pyridine moiety confined within the SCX4 cavity via CH∙∙∙π and CH∙∙∙O interactions which reflect in the deshielding of guest protons in its 1H NMR spectra. Host-guest binding emerges with signature in frequency up-shift of the characteristic Ar-OH and SO3− stretchings in measured infrared spectra. Inclusion phenomena brings forth remarkable enhancement in fluorescence of quinoline dye. TG-DTA experiments showed that the complex is thermally stable. The cyclic voltammetry experiments suggest the complexation is diffusion controlled. On the theoretical front the ωB97x-D based density functional theory points to the hydrogen bonding cooperativity in the lower and upper rims of the SCX4 and further provides molecular insights for supramolecular binding in the host-guest complex. The inferences on the structure and vibrational spectra drawn from experiments are corroborated by theoretical calculations. [Display omitted] •XRD crystal structure of the inclusion complex between quinoline and SCX4 was derived.•The partial encapsulation of the guest with 1:1 stoichiometry was observed.•Enhanced fluorescence intensity of quinoline guest was observed on complexation.•Conducing of the complex is characterized from 1H NMR and vibrational spectroscopy experiments.