9 research outputs found
Photochromic Hybrid Containing <i>In Situ</i>-Generated Benzyl Viologen and Novel Trinuclear [Bi<sub>3</sub>Cl<sub>14</sub>]<sup>5–</sup>: Improved Photoresponsive Behavior by the π···π Interactions and Size Effect of Inorganic Oligomer
Two new member of (V)<sub>(2<i>n</i>+2)/2</sub>[Bi<sub>2<i>n</i></sub>Cl<sub>8<i>n</i>+2</sub>] series hybrids, (BzV)<sub>2</sub>[Bi<sub>2</sub>Cl<sub>10</sub>] (<b>1</b>) and (BzV)<sub>5</sub>[Bi<sub>3</sub>Cl<sub>14</sub>]<sub>2</sub>·(C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>)<sub>2</sub>O (<b>2</b>) (where BzV<sup>2+</sup> = <i>N</i>,<i>N</i>′-dibenzyl-4,4′-bipyridinium
and (C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>)<sub>2</sub>O = dibenzyl
ether) have been obtained, and compound <b>2</b> contains an
unprecedented discrete trimer [Bi<sub>3</sub>Cl<sub>14</sub>]<sup>5–</sup> counterion. The novel <i>in situ</i>-synthesized
symmetric viologen cation with aromatic groups on both sides of 4,4′-bipy
would provide more opportunities to create π···π
interactions to optimize the photochromic property of the hybrid,
and different bismuthated-halide oligomers enable us to discuss the
size effect in this series of compounds. Both <b>1</b> and <b>2</b> are photochromic, and their photoresponsive rate is faster
than that of reported viologen–metal halide hybrids. Experimental
and theoretical data illustrated that the size of the inorganic oligomer
can significantly influence the photoresponsive rate of the viologen
dication, and the π···π interaction behaves
as not only a powerful factor to stabilize the viologen monocation
radical but also the second electron-transfer pathway, from a π-conjugated
substituent to a viologen cation, for the photochromic process
Improved Photochromic Properties on Viologen-Based Inorganic–Organic Hybrids by Using π‑Conjugated Substituents as Electron Donors and Stabilizers
A series of inorganic–organic hybrid compounds
L<sub>2</sub>(Bi<sub>2</sub>Cl<sub>10</sub>) (L = HMV<sup>2+</sup> = <i>N</i>-proton-<i>N</i>′-methyl-4,4′-bipyridinium
for <b>1</b>, L = HBzV<sup>2+</sup> = <i>N</i>-proton-<i>N</i>′-benzyl-4,4′-bipyridinium for <b>2</b>, and L = HPeV<sup>2+</sup> = <i>N</i>-proton-<i>N</i>′-phenethyl-4,4′-bipyridinium for <b>3</b>) have
been successfully synthesized by an in situ solvothermal reaction.
Compounds <b>1</b>–<b>3</b>, with the same metal
halide as anions but different asymmetric viologen molecules as cations,
are ideal model compounds for investigating the detailed effect of
different photochromically active molecules on the photochromic properties
of the hybrids. Compound <b>1</b> shows no photochromic behavior,
but compounds <b>2</b> and <b>3</b> possess photochromism
and show a faster photoresponse rate than other reported viologen
metal halide hybrids. Studies on the relationship between the structure
and photochromic behavior clearly reveal that π-conjugated substituents
could be used to improve the photoresponsibility and enrich the developed
color efficiently and that the π···π interaction
among organic components may not only be a powerful factor to stabilize
the viologen monocation radical but also act as the second path of
electron transfer from the π-conjugated substituent to the viologen
cation for the photochromic process, which significantly influences
the photochromic properties
Optimized Separation of Acetylene from Carbon Dioxide and Ethylene in a Microporous Material
Selective
separation of acetylene (C<sub>2</sub>H<sub>2</sub>)
from carbon dioxide (CO<sub>2</sub>) or ethylene (C<sub>2</sub>H<sub>4</sub>) needs specific porous materials whose pores can realize
sieving effects while pore surfaces can differentiate their recognitions
for these molecules of similar molecular sizes and physical properties.
We report a microporous material [ZnÂ(dps)<sub>2</sub>(SiF<sub>6</sub>)] (<b>UTSA-300</b>, dps = 4,4′-dipyridylsulfide) with
two-dimensional channels of about 3.3 Ã…, well-matched for the
molecular sizes of C<sub>2</sub>H<sub>2</sub>. After activation, the
network was transformed to its closed-pore phase, <b>UTSA-300a</b>, with dispersed 0D cavities, accompanied by conformation change
of the pyridyl ligand and rotation of SiF<sub>6</sub><sup>2–</sup> pillars. Strong C–H···F and π–π
stacking interactions are found in closed-pore <b>UTSA-300a</b>, resulting in shrinkage of the structure. Interestingly, <b>UTSA-300a</b> takes up quite a large amounts of acetylene (76.4 cm<sup>3</sup> g<sup>–1</sup>), while showing complete C<sub>2</sub>H<sub>4</sub> and CO<sub>2</sub> exclusion from C<sub>2</sub>H<sub>2</sub> under ambient conditions. Neutron powder diffraction and molecular
modeling studies clearly reveal that a C<sub>2</sub>H<sub>2</sub> molecule
primarily binds to two hexafluorosilicate F atoms in a head-on orientation,
breaking the original intranetwork hydrogen bond and subsequently
expanding to open-pore structure. Crystal structures, gas sorption
isotherms, molecular modeling, experimental breakthrough experiment,
and selectivity calculation comprehensively demonstrated this unique
metal–organic framework material for highly selective C<sub>2</sub>H<sub>2</sub>/CO<sub>2</sub> and C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub> separation
Optimized Separation of Acetylene from Carbon Dioxide and Ethylene in a Microporous Material
Selective
separation of acetylene (C<sub>2</sub>H<sub>2</sub>)
from carbon dioxide (CO<sub>2</sub>) or ethylene (C<sub>2</sub>H<sub>4</sub>) needs specific porous materials whose pores can realize
sieving effects while pore surfaces can differentiate their recognitions
for these molecules of similar molecular sizes and physical properties.
We report a microporous material [ZnÂ(dps)<sub>2</sub>(SiF<sub>6</sub>)] (<b>UTSA-300</b>, dps = 4,4′-dipyridylsulfide) with
two-dimensional channels of about 3.3 Ã…, well-matched for the
molecular sizes of C<sub>2</sub>H<sub>2</sub>. After activation, the
network was transformed to its closed-pore phase, <b>UTSA-300a</b>, with dispersed 0D cavities, accompanied by conformation change
of the pyridyl ligand and rotation of SiF<sub>6</sub><sup>2–</sup> pillars. Strong C–H···F and π–π
stacking interactions are found in closed-pore <b>UTSA-300a</b>, resulting in shrinkage of the structure. Interestingly, <b>UTSA-300a</b> takes up quite a large amounts of acetylene (76.4 cm<sup>3</sup> g<sup>–1</sup>), while showing complete C<sub>2</sub>H<sub>4</sub> and CO<sub>2</sub> exclusion from C<sub>2</sub>H<sub>2</sub> under ambient conditions. Neutron powder diffraction and molecular
modeling studies clearly reveal that a C<sub>2</sub>H<sub>2</sub> molecule
primarily binds to two hexafluorosilicate F atoms in a head-on orientation,
breaking the original intranetwork hydrogen bond and subsequently
expanding to open-pore structure. Crystal structures, gas sorption
isotherms, molecular modeling, experimental breakthrough experiment,
and selectivity calculation comprehensively demonstrated this unique
metal–organic framework material for highly selective C<sub>2</sub>H<sub>2</sub>/CO<sub>2</sub> and C<sub>2</sub>H<sub>2</sub>/C<sub>2</sub>H<sub>4</sub> separation
Boosting Antibacterial Photodynamic Therapy in a Nanosized Zr MOF by the Combination of Ag NP Encapsulation and Porphyrin Doping
Antibacterial
photodynamic therapy (aPDT) is regarded as one of
the most promising antibacterial therapies due to its nonresistance,
noninvasion, and rapid sterilization. However, the development of
antibacterial materials with high aPDT efficacy is still a long-standing
challenge. Herein, we develop an effective antibacterial photodynamic
composite UiO-66-(SH)2@TCPP@AgNPs by Ag encapsulation and
4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic
acid) (TCPP) dopant. Through a mix-and-match strategy in the self-assembly
process, 2,5-dimercaptoterephthalic acid containing –SH groups
and TCPP were uniformly decorated into the UiO-66-type framework to
form UiO-66-(SH)2@TCPP. After Ag(I) impregnation and in
situ UV light reduction, Ag NPs were formed and encapsulated into
UiO-66-(SH)2@TCPP to get UiO-66-(SH)2@TCPP@AgNPs.
In the resulting composite, both Ag NPs and TCPP can effectively enhance
the visible light absorption, largely boosting the generation efficiency
of reactive oxygen species. Notably, the nanoscale size enables it
to effectively contact and be endocytosed into bacteria. Consequently,
UiO-66-(SH)2@TCPP@AgNPs show a very high aPDT efficacy
against Gram-negative and Gram-positive bacteria as well as drug-resistant
bacteria (MRSA). Furthermore, the Ag NPs were firmly anchored at the
framework by the high density of –SH moieties, avoiding the
cytotoxicity caused by the leakage of Ag NPs. By in vitro experiments,
UiO-66-(SH)2@TCPP@AgNPs show a very high antibacterial
activity and good biocompatibility as well as the potentiality to
promote cell proliferation
Photochromic Metal Complexes of <i>N</i>-Methyl-4,4′-Bipyridinium: Mechanism and Influence of Halogen Atoms
Photochromism of <i>N</i>-methyl-4,4′-bipyridinium
(MQ<sup>+</sup>) salts and their metal complexes has never been reported.
A series of MQ<sup>+</sup> coordinated halozinc complexes [(MQ)ÂZnX<sub>3</sub>] (X = Cl (<b>1</b>), Br (<b>2</b>), I (<b>3</b>)) and [(MQ)ÂZnCl<sub>1.53</sub>I<sub>1.47</sub>]<sub>2</sub>(MQ)ÂZnCl<sub>1.68</sub>I<sub>1.32</sub> (<b>4</b>), with better
physicochemical stability than halide salts of the MQ<sup>+</sup> cation,
have been found to exhibit different photochromic behaviors. Compounds <b>1</b>–<b>3</b> are isostructural, but only <b>1</b> and <b>2</b> show photochromism. Introduction of partial
Cl atoms to nonphotochromic compound <b>3</b> yields compound <b>4</b>, which also displays photochromism. The photochromic response
of <b>1</b>, <b>2</b>, and <b>4</b> indicates the
presence of their long-lived charge separation states, which originate
from X → MQ<sup>+</sup> electron transfer according to ESR
and XPS measurements. Studies on the influence of different coordinated
halogen atoms demonstrate that the Cl atom may be a more suitable
electron donor than Br and I atoms to design redox photochromic metal
complexes
Photochromic Metal Complexes of <i>N</i>-Methyl-4,4′-Bipyridinium: Mechanism and Influence of Halogen Atoms
Photochromism of <i>N</i>-methyl-4,4′-bipyridinium
(MQ<sup>+</sup>) salts and their metal complexes has never been reported.
A series of MQ<sup>+</sup> coordinated halozinc complexes [(MQ)ÂZnX<sub>3</sub>] (X = Cl (<b>1</b>), Br (<b>2</b>), I (<b>3</b>)) and [(MQ)ÂZnCl<sub>1.53</sub>I<sub>1.47</sub>]<sub>2</sub>(MQ)ÂZnCl<sub>1.68</sub>I<sub>1.32</sub> (<b>4</b>), with better
physicochemical stability than halide salts of the MQ<sup>+</sup> cation,
have been found to exhibit different photochromic behaviors. Compounds <b>1</b>–<b>3</b> are isostructural, but only <b>1</b> and <b>2</b> show photochromism. Introduction of partial
Cl atoms to nonphotochromic compound <b>3</b> yields compound <b>4</b>, which also displays photochromism. The photochromic response
of <b>1</b>, <b>2</b>, and <b>4</b> indicates the
presence of their long-lived charge separation states, which originate
from X → MQ<sup>+</sup> electron transfer according to ESR
and XPS measurements. Studies on the influence of different coordinated
halogen atoms demonstrate that the Cl atom may be a more suitable
electron donor than Br and I atoms to design redox photochromic metal
complexes
Influence of Supramolecular Interactions on Electron-Transfer Photochromism of the Crystalline Adducts of 4,4′-Bipyridine and Carboxylic Acids
We
have studied the electron-transfer photochromism of the crystalline
adducts of 4,4′-bipyridine (Bpy) and carboxylic acids and revealed
the key structural parameters that decide whether the photochromism
can happen for the first time. Experimental and theoretical analyses
on nine known examples showed that the hydrogen bonds, instead of
π–π stacking interactions, are the defining factor
to the photochromism. Only the presence of N–H···O
hydrogen bonds can fulfill the electron transfer from the carboxylate
group to the Bpy part, although both the N···O separations
of O–H···N and N–H···O
hydrogen bonds are suitable for the so-called through-space electron
transfer. These results can not only help to screen out the photochromic
species from the known hundreds of Bpy–carboxylic acid adducts
deposited in the Cambridge Crystallographic Data Centre (CCDC) database
but also guide the design and syntheses of new adducts using diverse <i>N</i>-heterocyclic aromatic molecules and carboxylic acids
Design and Syntheses of Electron-Transfer Photochromic Metal–Organic Complexes Using Nonphotochromic Ligands: A Model Compound and the Roles of Its Ligands
The model compound [ZnÂ(HCOO)<sub>2</sub>(4,4′-bipy)] (<b>1</b>; 4,4′-bipy = 4,4′-bipyridine)
is selected in this work to demonstrate the effectiveness of our previously
proposed design strategy for electron-transfer photochromic metal–organic
complexes. The electron-transfer photochromic behavior of <b>1</b> has been discovered for the first time. Experimental and theoretical
data illustrate that the photochromism of <b>1</b> can be attributed
to the electron transfer from formato to 4,4′-bipy and the
formation of a radical photoproduct. The electron transfer prefers
to occur between formato and 4,4′-bipy, which are combined
directly by the ZnÂ(II) atoms. A high-contrast (up to 8.3 times) photoluminescence
switch occurs during the photochromic process. The similarity of photochromic
behaviors among <b>1</b> and its analogues as well as viologen
compounds has also been found. Photochromic studies of this model
compound indicate that new electron-transfer photochromic metal–organic
complexes can be largely designed and synthesized by the rational
assembly of nonphotochromic electron-donating and electron-accepting
ligands