DNA-like Photophysics in Self-Assembled Silver(I)–Nucleobase\nNanofibers

Abstract

Supramolecular assemblies\nform when silver nitrate is added to an aqueous solution of adenine\n(Ade) or 2-aminopurine (2AP) in a 2:1 mole ratio. Atomic force microscopy\nimages reveal nanofibers that are ∼30 nm in diameter and micrometers\nin length in the dried film formed from a room-temperature solution.\nFemtosecond broadband transient absorption spectroscopy was used to\ninvestigate the dynamics of excited states formed by UV excitation\nof the nanofibers in room-temperature aqueous solutions in an effort\nto learn how nonradiative decay pathways of the uncomplexed nucleobases\nare altered in the silver-ion-mediated assemblies. The changes in\nthe spectroscopy and dynamics of Ade and 2AP upon forming nanofibers\nwith silver ions closely parallel the ones seen when these bases are\norganized into DNA strands. The similarities strongly suggest that\nthese structures feature extensive π–π stacking\ninteractions between nucleobases. The results show that time-resolved\nspectroscopy combined with growing understanding of the photophysics\nof DNA strands can deliver new insights into the properties of metal–nucleobase\nnanoassemblies.