Electronic structure
modulation of metal–organic frameworks
(MOFs) through the connection of linker “wires” as a
function of an external stimulus is reported for the first time. The
established correlation between MOF electronic properties and photoisomerization
kinetics as well as changes in an absorption profile is unprecedented
for extended well-defined structures containing coordinatively integrated
photoresponsive linkers. The presented studies were carried out on
both single crystal and bulk powder with preservation of framework
integrity. An LED-containing electric circuit, in which the switching
behavior was driven by the changes in MOF electronic profile,
was built for visualization of experimental findings. The demonstrated
concept could be used as a blueprint for development of stimuli-responsive
materials with dynamically controlled electronic behavior.
Cooperative metal–photoswitch
interfaces comprise an application-driven
field which is based on strategic coupling of metal cations and organic
photochromic molecules to advance the behavior of both components,
resulting in dynamic molecular and material properties controlled
through external stimuli. In this Perspective, we highlight the ways
in which metal–photoswitch interplay can be utilized as a tool
to modulate a system’s physicochemical properties and performance
in a variety of structural motifs, including discrete molecular complexes
or cages, as well as periodic structures such as metal–organic
frameworks. This Perspective starts with photochromic molecular complexes
as the smallest subunit in which metal–photoswitch interactions
can occur, and progresses toward functional materials. In particular,
we explore the role of the metal–photoswitch relationship for
gaining fundamental knowledge of switchable electronic and magnetic
properties, as well as in the design of stimuli-responsive sensors,
optically gated memory devices, catalysts, and photodynamic therapeutic
agents. The abundance of stimuli-responsive systems in the natural
world only foreshadows the creative directions that will uncover the
full potential of metal–photoswitch interactions in the coming
years.
The effect of donor (D)–acceptor (A) alignment on the materials electronic structure was probed for the first time using novel purely organic porous crystalline materials with covalently bound two‐ and three‐dimensional acceptors. The first studies towards estimation of charge transfer rates as a function of acceptor stacking are in line with the experimentally observed drastic, eight‐fold conductivity enhancement. The first evaluation of redox behavior of buckyball‐ or tetracyanoquinodimethane‐integrated crystalline was conducted. In parallel with tailoring the D‐A alignment responsible for “static” changes in materials properties, an external stimulus was applied for “dynamic” control of the electronic profiles. Overall, the presented D–A strategic design, with stimuli‐controlled electronic behavior, redox activity, and modularity could be used as a blueprint for the development of electroactive and conductive multidimensional and multifunctional crystalline porous materials.
We report the first examples of purely organic donor-acceptor materials with integrated π-bowls (πBs) that combine not only crystallinity and high surface areas but also exhibit tunable electronic properties, resulting in a four-orders-of-magnitude conductivity enhancement in comparison with the parent framework. In addition to the first report of alkyne-azide cycloaddition utilized for corannulene immobilization in the solid state, we also probed the charge transfer rate within the Marcus theory as a function of mutual πB orientation for the first time, as well as shed light on the density of states near the Fermi edge. These studies could foreshadow new avenues for πB utilization for the development of optoelectronic devices or a route for highly efficient porous electrodes.
Confinement‐imposed photophysics was probed for novel stimuli‐responsive hydrazone‐based compounds demonstrating a conceptual difference in their behavior within 2D versus 3D porous matrices for the first time. The challenges associated with photoswitch isomerization arising from host interactions with photochromic compounds in 2D scaffolds could be overcome in 3D materials. Solution‐like photoisomerization rate constants were realized for sterically demanding hydrazone derivatives in the solid state through their coordinative immobilization in 3D scaffolds. According to steady‐state and time‐resolved photophysical measurements and theoretical modeling, this approach provides access to hydrazone‐based materials with fast photoisomerization kinetics in the solid state. Fast isomerization of integrated hydrazone derivatives allows for probing and tailoring resonance energy transfer (ET) processes as a function of excitation wavelength, providing a novel pathway for ET modulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.