5 research outputs found
Neutral-Type One-Dimensional Mixed-Valence Halogen-Bridged Platinum Chain Complexes with Large Charge-Transfer Band Gaps
One-dimensional (1D) electronic systems
have attracted significant attention for a long time because of their
various physical properties. Among 1D electronic systems, 1D halogen-bridged
mixed-valence transition-metal complexes (the so-called MX chains)
have been thoroughly studied owing to designable structures and electronic
states. Here, we report the syntheses, structures, and electronic
properties of three kinds of novel neutral MX-chain complexes. The
crystal structures consist of 1D chains of Pt–X repeating units
with (1<i>R</i>,2<i>R</i>)-(−)-diaminocychlohexane
and CN<sup>–</sup> in-plane ligands. Because of the absence
of a counteranion, the neutral MX chains have short interchain distances,
so that strong interchain electronic interaction is expected. Resonance
Raman spectra and diffuse-reflectance UV–vis spectra indicate
that their electronic states are mixed-valence states (charge-density-wave
state: Pt<sup>2+</sup>···X–Pt<sup>4+</sup>–X···Pt<sup>2+</sup>···X–Pt<sup>4+</sup>–X···).
In addition, the relationship between the intervalence charge-transfer
(IVCT) band gap and the degree of distortion of the 1D chain shows
that the neutral MX chains have a larger IVCT band gap than that of
cationic MX-chain complexes. These results provide new insight into
the physical and electronic properties of 1D chain compounds
Single-Atom-Based Vanadium Oxide Catalysts Supported on Metal–Organic Frameworks: Selective Alcohol Oxidation and Structure–Activity Relationship
We report the syntheses, structures,
and oxidation catalytic activities
of a single-atom-based vanadium oxide incorporated in two highly crystalline
MOFs, Hf-MOF-808 and Zr-NU-1000. These vanadium catalysts were introduced
by a postsynthetic metalation, and the resulting materials (Hf-MOF-808-V
and Zr-NU-1000-V) were thoroughly characterized through a combination
of analytic and spectroscopic techniques including single-crystal
X-ray crystallography. Their catalytic properties were investigated
using the oxidation of 4-methoxybenzyl alcohol under an oxygen atmosphere
as a model reaction. Crystallographic and variable-temperature spectroscopic
studies revealed that the incorporated vanadium in Hf-MOF-808-V changes
position with heat, which led to improved catalytic activity
Metal–Organic Framework with Structural Flexibility Responding Specifically to Acetylene and Its Adsorption Behavior
Flexible
metal–organic frameworks (MOFs) are one
kind of
stimuli-responsive materials that exhibit reversible structural transformations
in response to external stimuli. Exploring and understanding the stimuli
response behavior of flexible MOFs is challenging, as it involves
weak host–guest interaction. We report here the unique flexibility
of MOF Zn(int)(Ad) (TIF-A1, Hint = isonicotinic acid, Had = adenine)
induced by acetylene adsorption. TIF-A1 is rigid toward most gas molecules,
while only C2H2 can induce the flexibility of
TIF-A1. C2H2-loaded TIF-A1 is characterized
by single-crystal X-ray diffraction and molecular modeling. It is
revealed that the flexibility of TIF-A1 originates from the strong
interaction between acetylene and the framework, which pushes the
rotation of the int ligand and the expansion of the framework simultaneously.
This work is helpful in deeply understanding the flexibility of MOFs
and guides exploring new flexible MOFs in the future
Metal–Organic Framework with Structural Flexibility Responding Specifically to Acetylene and Its Adsorption Behavior
Flexible
metal–organic frameworks (MOFs) are one
kind of
stimuli-responsive materials that exhibit reversible structural transformations
in response to external stimuli. Exploring and understanding the stimuli
response behavior of flexible MOFs is challenging, as it involves
weak host–guest interaction. We report here the unique flexibility
of MOF Zn(int)(Ad) (TIF-A1, Hint = isonicotinic acid, Had = adenine)
induced by acetylene adsorption. TIF-A1 is rigid toward most gas molecules,
while only C2H2 can induce the flexibility of
TIF-A1. C2H2-loaded TIF-A1 is characterized
by single-crystal X-ray diffraction and molecular modeling. It is
revealed that the flexibility of TIF-A1 originates from the strong
interaction between acetylene and the framework, which pushes the
rotation of the int ligand and the expansion of the framework simultaneously.
This work is helpful in deeply understanding the flexibility of MOFs
and guides exploring new flexible MOFs in the future
MOF–Thermogel Composites for Differentiated and Sustained Dual Drug Delivery
In recent years, multidrug therapy has gained increasing
popularity
due to the possibility of achieving synergistic drug action and sequential
delivery of different medical payloads for enhanced treatment efficacy.
While a number of composite material release platforms have been developed,
few combine the bottom-up design versatility of metal–organic
frameworks (MOFs) to tailor drug release behavior, with the convenience
of temperature-responsive hydrogels (or thermogels) in their unique
ease of administration and formulation. Yet, despite their potential,
MOF–thermogel composites have been largely overlooked for simultaneous
multidrug delivery. Herein, we report the first systematic study of
common MOFs (UiO-66, MIL-53(Al), MIL-100(Fe), and MOF-808) with different
pore sizes, geometries, and hydrophobicities for their ability to
achieve simultaneous dual drug release when embedded within PEG-containing
thermogel matrices. After establishing that MOFs exert small influences
on the rheological properties of the thermogels despite the penetration
of polymers into the MOF pores in solution, the release profiles of
ibuprofen and caffeine as model hydrophobic and hydrophilic drugs,
respectively, from MOF–thermogel composites were investigated.
Through these studies, we elucidated the important role of hydrophobic
matching between MOF pores and loaded drugs in order for the MOF component
to distinctly influence drug release kinetics. These findings enabled
us to identify a viable MOF–thermogel composite containing
UiO-66 that showed vastly different release kinetics between ibuprofen
and caffeine, enabling temporally differentiated yet sustained simultaneous
drug release to be achieved. Finally, the MOF–thermogel composites
were shown to be noncytotoxic in vitro, paving the way for these underexploited
composite materials to find possible clinical applications for multidrug
therapy