Confinement-Driven Photophysics in Cages, Covalent-Organic Frameworks, Metal-Organic Frameworks, and DNA

J Am Chem Soc. 2020 Mar 11;142(10):4769-4783. doi: 10.1021/jacs.9b13505. Epub 2020 Mar 2.

Abstract

Photophysics tunability through alteration of framework aperture (metal-organic framework (MOF) = variable; guest = constant) was probed for the first time in comparison with previously explored concepts (MOF = constant; guest = variable). In particular, analysis of the confinement effect on a photophysical response of integrated 5-(3-chlorobenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one (Cl-BI) chromophore allowed us to establish a photophysics-aperture relationship. To shed light on the observed correlation, the framework confined environment was replicated using a molecular cage, Pd6(TPT)4 (TPT = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine), thus allowing for utilization of crystallography, spectroscopy, and theoretical simulations to reveal the effect a confined space has on the chromophore's molecular conformation (including disruption of strong hydrogen bonding and novel conformer formation) and any associated changes on a photophysical response. Furthermore, the chosen Cl-oHBI@Pd6(TPT)4 (Cl-oHBI = 5-(5-chloro-2-hydroxybenzylidene)-2,3-dimethyl-3,5-dihydro-4H-imidazol-4-one, chromophore) system was applied as a tool for targeted cargo delivery of a chromophore to the confined space of DNA, which resulted in promotion of chromophore-DNA interactions through a well-established intercalation mechanism. Moreover, the developed principles were applied toward utilizing a HBI-based chromophore as a fluorescent probe on the example of macrophage cells. For the first time, suppression of non-radiative decay pathways of a chromophore was tested by anchoring the chromophore to a framework metal node, portending a potential avenue to develop an alternative to natural biomarkers. Overall, these studies are among the first attempts to demonstrate the unrevealed potential of a confined scaffold environment for tailoring a material's photophysical response.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • DNA / chemistry*
  • Fluorescent Dyes / chemistry*
  • Fluorescent Dyes / radiation effects
  • HeLa Cells
  • Humans
  • Imidazoles / chemistry*
  • Imidazoles / radiation effects
  • Intercalating Agents / chemistry
  • Intercalating Agents / radiation effects
  • Light
  • Metal-Organic Frameworks / chemistry*
  • Molecular Conformation
  • Triazines / chemistry*

Substances

  • Fluorescent Dyes
  • Imidazoles
  • Intercalating Agents
  • Metal-Organic Frameworks
  • Triazines
  • DNA
  • 2,4,6-tripyridyl-s-triazine