Nanoscale metallogel via self-assembly of self-assembled trinuclear coordination rings: multi-stimuli-responsive soft materials. Issue 34 (31st March 2015)

• Record Type: Journal Article
• Authors: Ganta, Sudhakar; Chand, Dillip Kumar
• Is Part Of: Dalton transactions. Volume 44:Issue 34(2015)
• Page Start: 15181
• Page End: 15188
• Publication Date: 2015-03-31
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c4dt03715d
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A multi-stimuli-responsive metallogel is obtained by the self-assembly of an already self-assembled trinuclear palladium(ii ) based coordination ring of the rare M3 L6 composition. Abstract : A rare variety of coordination rings having the M3 L6 composition are prepared by the combination of Pd(NO3 )2 with an imidazolyl or benzimidazolyl appended bidentate non-chelating ligand ( i.e. L1 orL2 ). The variable concentration 1 H NMR spectra of the trinuclear complexes [Pd3 (L1 )6 ](NO3 )6, 1a and [Pd3 (L2 )6 ](NO3 )6, 2a in DMSO-d6 provided valuable information on the self-assembly phenomenon of the already self-assembled complexes. Interestingly, the signals of2a are broadened upon increasing the concentration. The solution of2a in DMSO formed a supramolecular metallogel above a certain concentration ( i.e. 2% w/v), however, complex1a could not form any gel. This phenomenon is attributed to the presence of an auxiliary π-surface in the benzimidazole moiety inL2, in contrast to the imidazole moiety ofL1 . The influence of anions in gel formation was studied by preparing several samples using a variety of palladium(ii ) salts andL2 in DMSO. It was found that oxoanions like nitrate, perchlorate, triflate and tosylate are amicable for gel formation, probably due to their capabilities of forming H-bonds. The counter anions like tetrafluoroborate, hexafluorophosphate, or hexafluoroantimonate could not assist in the formation of gel. The stimuli-responsive nature of the gel and the reversible gel–sol conversion were demonstrated by dis-assembly and re-assembly processes of2a as controlled by a pair of stimuli such as halide-nitrate, DMAP-HNO3, and ethylenediamine-Pd(NO3 )2 . No gel could be prepared by the combination of Ni(NO3 )2 or Pt(NO3 )2 with ligandL2 . Thus, a subtle change in the ligand design, metal ion and counter anion is demonstrated as the responsible parameter for the construction of the three component multi-stimuli-responsive supramolecular gel.