Radical Anions and Dianions of Naphthalenediimides Generated within Layer-by-Layer Zirconium Phosphonate Thin Films

Author(s)

Marcon, Rodrigo Oliveira ; Bonvent, Jean-Jacques ; Brochsztain, Sergio

• Document type: Journal article
• Source: Langmuir; v. 38, n. 6, p. 9-pg., 2022-02-15.

Abstract

Chemical reduction of N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) with the reducing agent sodium dithionite gave stable colored reduced species, both in homogeneous solutions and in self-assembled thin films. When colorless PNDI aqueous solutions were titrated with the reducing agent, stepwise reduction was observed, giving first the radical anion (PNDI-center dot) and then the dianion (PNDI2-) species, which were detected by UV-visible-NIR spectroscopy, allowing the unambiguous determination of absorption maxima and molar absorptivities for each species. The radical anion PNDI-center dot was found to form pi-dimers in water, but monomeric PNDI-center dot was formed in the presence of the cationic surfactant cetyltrimethylammonium bromide, indicating association with the micelles. Thin films of PNDI with 25 layers were grown by the zirconium phosphonate method on quartz substrates. Reduction of the films with sodium dithionite also produced radical anions and dianions of PNDI. However, reduction in the films was much slower than in solution, evidencing the compactness of the films. Moreover, reduction in the films did not proceed to completion, even with excess of the reducing agent, which can be attributed to the repulsion of negative charges within the film. (AU)

• FAPESP's process: 16/05496-2 - Synthesis and characterization of periodic mesoporous organosilicas containing aromatic imides for applications in the energy sector
• Grantee: Sergio Brochsztain
• Support Opportunities: Regular Research Grants
• FAPESP's process: 20/15230-5 - Research Centre for Greenhouse Gas Innovation - RCG2I
• Grantee: Julio Romano Meneghini
• Support Opportunities: Research Grants - Research Centers in Engineering Program