12 research outputs found
Crystalline to Crystalline Phase Transformations in Six Two-Dimensional Dynamic Metal–Organic Frameworks: Syntheses, Characterizations, and Sorption Studies
Six dynamic metal–organic
frameworks, namely, {[CdÂ(1,4-bib)Â(glut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>1</b>), {[ZnÂ(1,4-bib)Â(glut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>2</b>), {[CoÂ(1,4-bib)Â(3,5-pydc)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>3</b>), {[MnÂ(1,4-bib)Â(3,5-pydc)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>4</b>), {[ZnÂ(1,4-bib)Â(3-mglut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>5</b>), and {[ZnÂ(1,4-bib)Â(2,2′-dmglut)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>6</b>) from 1-(4-(1<i>H</i>-imidazole-1-yl)Âbutyl)-1<i>H</i>-imidazole (1,4-bib)
using four different dicarboxylic acids salt [disodium glutarate (Na<sub>2</sub>glut), pyridine-3,5-dicarboxylate (3,5-pydc), 3-methyl glutarate
(3-mglut), 2,2′-dimethyl glutarate (Na<sub>2</sub>2,2′-dmglut)],
and four different divalent transition metal ions have been synthesized.
Out of these, the structure of compound <b>3</b> has been previously
reported although synthesized in different method, whereas the rest
of the compounds are new. All of these synthesized compounds are characterized
by single crystal and powder X-ray diffraction and other physicochemical
methods. All the compounds exhibit 2D structure as evident by single
crystal X-ray studies. Interestingly, all of these compounds show
crystalline to crystalline phase transformation. Variable temperature
PXRD study indicates compounds <b>1</b> and <b>6</b> show
single-step phase transformation and the rest show two-step phase
transformation upon desolvation. All of these transformations have
also been established by IR spectroscopy. Among the structural transformations
listed, <b>1</b>–<b>5</b> show reversible crystalline
to crystalline phase transformation on desolvation and resolvation,
whereas <b>6</b> shows an irreversible transformation. All of
these transformations are thoroughly investigated by PXRD and IR spectroscopy.
Sorption studies with CO<sub>2</sub> and N<sub>2</sub> were also performed
for all the metal–organic frameworks and characteristic surface
adsorptions are found in all the cases
Azo Functionalized 5‑Nitro-1,3-benzenedicarboxylate Based Coordination Polymers with Different Dimensionality and Functionality
Five azo-functionalized coordination
polymers (CPs), namely, [ZnÂ(azbpy)Â(NO<sub>2</sub>-bdc)·H<sub>2</sub>O]<sub><i>n</i></sub> (<b>1</b>), [ZnÂ(azbpy)Â(NO<sub>2</sub>-bdc)]<sub><i>n</i></sub>·3H<sub>2</sub>O (<b>2</b>), {[CdÂ(azbpy)Â(NO<sub>2</sub>-bdc)·H<sub>2</sub>O]·2H<sub>2</sub>O}<sub><i>n</i></sub> (<b>3</b>), {[MnÂ(azbpy)<sub>2</sub>Â(NO<sub>2</sub>-bdc)]<sub>2</sub>}<sub><i>n</i></sub> (<b>4</b>), and {[CoÂ(azbpy)Â(NO<sub>2</sub>-bdc)Â(H<sub>2</sub>O)<sub>2</sub>]Â[CoÂ(azbpy)<sub>0.5</sub>Â(NO<sub>2</sub>-bdc)Â(H<sub>2</sub>O)<sub>3</sub>]}<sub><i>n</i></sub> (<b>5</b>) have been synthesized
using different transition
metal salts with 5-nitro-1,3-benzenedicarboxylate (NO<sub>2</sub>-bdc<sup>2–</sup>) and 4,4′-azobispyridine (azbpy) ligand using
a slow diffusion technique at room temperature. The complexes <b>1</b>–<b>5</b> were characterized by single crystal
X-ray diffraction analysis, elemental analysis, infrared spectroscopy
(IR), powder X-ray diffraction (PXRD), and thermogravimetric analysis
(TGA). In the solid state, compound <b>1</b> shows a wavy one-dimensional
(1D) ladder; constructed through the N,N′-donor azbpy and NO<sub>2</sub>-bdc<sup>2–</sup> ligands with the metal centers, whereas
compound <b>2</b> exhibits a bilayer two-dimensional (2D) sheet
containing a wavy 1D ladder of metal-carboxylate, and compound <b>3</b> shows a stairlike wavy 2D sheet. Compound <b>4</b> exhibits a novel 2-fold interdigitated 2D sheet of two similar layers
containing pendent azbpy ligands, whereas compound <b>5</b> displays
a polythreaded 2D structure with an intercalated 1D chain into the
pore. The solid state luminescence properties of <b>1</b>–<b>3</b> along with free N,N′-donor azbpy ligand have been
performed at room temperature, where all the complexes <b>1</b>–<b>3</b> show azbpy ligand based luminescence property.
The gas and solvent vapor adsorption study have been performed for
compounds <b>2</b>–<b>4</b>, and the dehydrated
frameworks of compounds <b>2</b>–<b>4</b> exhibit
selective CO<sub>2</sub> adsorption at 195 K over N<sub>2</sub> (at
both 77 and 195 K) due to the strong interactions between polar pore
walls of dehydrated frameworks with the CO<sub>2</sub> molecule having
quadruple moment
Four 3D Cd(II)-Based Metal Organic Hybrids with Different N,N′-Donor Spacers: Syntheses, Characterizations, and Selective Gas Adsorption Properties
Four new metal organic frameworks with bivalent cadmium,
disodium
succinate (Na<sub>2</sub>suc), and four different N,N′-donor
ligands, i.e., {[CdÂ(L1)Â(suc)]·(H<sub>2</sub>O)<sub>3</sub>}<sub><i>n</i></sub> (<b>1</b>), {[CdÂ(L2)Â(suc)]·(H<sub>2</sub>O)<sub>2</sub>}<sub><i>n</i></sub> (<b>2</b>), {[CdÂ(L3)Â(suc)]·(H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>3</b>), {[Cd<sub>3</sub>(L4)<sub>3</sub>(suc)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]·(NO<sub>3</sub>)<sub>2</sub> (H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>4</b>) [L1 = 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene,
L2 = <i>trans</i> 4,4′-azobispyridine, L3 = 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene,
L4 = 1, 2-bisÂ(4-pyridyl) ethane and suc = succinate dianion] have
been synthesized at room temperature and characterized by single-crystal
X-ray diffraction and other physicochemical methods. Structure determination
reveals that compounds <b>1</b> and <b>2</b> show honeycomb-like
three-dimensional (3D) architecture with water-filled channels. The
dehydrated frameworks of <b>1</b> and <b>2</b> exhibit
hydrogen and carbon dioxide adsorption properties. In compound <b>3</b>, change of linker (linear to bent) led to the blockage of
such regular channels which also affected the porosity and adsorption
properties of its dehydrated framework. In <b>4</b>, the used
spacer is linear but the resulting 3D framework contains blocked channels
filled with nitrate (NO<sub>3</sub><sup>–</sup>) anions and
lattice water
Four 3D Cd(II)-Based Metal Organic Hybrids with Different N,N′-Donor Spacers: Syntheses, Characterizations, and Selective Gas Adsorption Properties
Four new metal organic frameworks with bivalent cadmium,
disodium
succinate (Na<sub>2</sub>suc), and four different N,N′-donor
ligands, i.e., {[CdÂ(L1)Â(suc)]·(H<sub>2</sub>O)<sub>3</sub>}<sub><i>n</i></sub> (<b>1</b>), {[CdÂ(L2)Â(suc)]·(H<sub>2</sub>O)<sub>2</sub>}<sub><i>n</i></sub> (<b>2</b>), {[CdÂ(L3)Â(suc)]·(H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>3</b>), {[Cd<sub>3</sub>(L4)<sub>3</sub>(suc)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]·(NO<sub>3</sub>)<sub>2</sub> (H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>4</b>) [L1 = 2,5-bis-(4-pyridyl)-3,4-diaza-2,4-hexadiene,
L2 = <i>trans</i> 4,4′-azobispyridine, L3 = 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene,
L4 = 1, 2-bisÂ(4-pyridyl) ethane and suc = succinate dianion] have
been synthesized at room temperature and characterized by single-crystal
X-ray diffraction and other physicochemical methods. Structure determination
reveals that compounds <b>1</b> and <b>2</b> show honeycomb-like
three-dimensional (3D) architecture with water-filled channels. The
dehydrated frameworks of <b>1</b> and <b>2</b> exhibit
hydrogen and carbon dioxide adsorption properties. In compound <b>3</b>, change of linker (linear to bent) led to the blockage of
such regular channels which also affected the porosity and adsorption
properties of its dehydrated framework. In <b>4</b>, the used
spacer is linear but the resulting 3D framework contains blocked channels
filled with nitrate (NO<sub>3</sub><sup>–</sup>) anions and
lattice water
Selective CO<sub>2</sub> Adsorption by Nitro Functionalized Metal Organic Frameworks
Two
nitro functionalized CuÂ(II)-MOFs exhibit high CO<sub>2</sub> uptake
with nice selectivity over other gases like H<sub>2</sub>, N<sub>2</sub>, and CH<sub>4</sub>, which is potentially important
for the removal of carbon dioxide from industrial flue gas and natural
gas. Here the selective CO<sub>2</sub> adsorption by these MOFs is
primarily due to the presence of suitable voids with −NO<sub>2</sub> group functionalized pore walls in the dehydrated framework,
which is unprecedented
Two Series of Isostructural Coordination Polymers with Isomeric Benzenedicarboxylates and Different Azine Based N,N′-Donor Ligands: Syntheses, Characterization and Magnetic Properties
Seven
coordination polymers (CPs) with two types of framework structures,
namely, {[MÂ(4-bpdb)Â(1,3-bdc)]·(4-bpdb)<sub>0.5</sub>}<sub><i>n</i></sub> [M = Mn (<b>1</b>), Fe (<b>2</b>), and Co (<b>3</b>)], and {[MÂ(4-bpdh)Â(1,4-bdc)]}<sub><i>n</i></sub> (M = Mn (<b>4</b>), Fe (<b>5</b>), Co (<b>6</b>), and Cd (<b>7</b>)] have been synthesized
through the slow diffusion technique using 1,3-bdc and 1,4-bdc ligands
with two different azine based N,N′-donor linkers [1,3-bdc
= benzene-1,3-dicarboxylate, 1,4-bdc = benzene-1,4-dicarboxylate,
4-bpdb = <i>N,N</i>′-bis-pyridin-4-ylmethylene-hydrazine
and 4-bpdh = <i>N,N</i>′-bis-(1-pyridin-4-yl-ethylidene)-hydrazine].
Their structures have been determined by single-crystal X-ray diffraction
analysis and further characterized by elemental analysis, IR spectra,
and powder X-ray diffraction (PXRD) analysis. Compounds <b>1</b>–<b>3</b> are isostructural and feature a two-dimensional
(2D) framework structure formed by pillaring the one-dimensional [MÂ(1,3-bdc)]<sub><i>n</i></sub> double chains through 4-bpdb linkers. In
all cases of compounds <b>1</b>–<b>3</b>, free
4-bpdb linkers are present in the lattice and lattice 4-bpdb ligands
are involved in π–π and C–H···π
interactions with bridging 1,3-bdc and 4-bpdb ligands, to afford three-dimensional
(3D) supramolecular structures. Compounds <b>4</b>–<b>7</b> are also isostructural and here the bridging of 1,4-bdc
with the divalent metal centers forms a 2D layer of [MÂ(1,4-bdc)]<sub><i>n</i></sub> which is further pillared by 4-bpdh to form
a 3D pillared-layer framework. Variable temperature magnetic measurements
of two sets of isostructural complexes (<b>1</b>–<b>3</b> and <b>4</b>–<b>7</b>) have been carried
out. Compounds <b>1</b>–<b>6</b> clearly indicate
the existence of a weak antiferromagnetic interaction between the
metal ions through the bridging 1,3-bdc and 1,4-bdc ligands. The magnetic
properties depend strongly on the nature of the metal center. The
luminescence spectra of the complexes have been measured, which indicates
a ligand based emission for all seven compounds
Hydrogen Uptake by an Inclined Polycatenated Dynamic Metal–Organic Framework Based Material
A 2D + 2D → 3D inclined polycatenated
dynamic metal–organic
framework of {[CuÂ(4-bpe)Â(2-ntp)Â(H<sub>2</sub>O)<sub>2</sub>]·2H<sub>2</sub>O}<sub><i>n</i></sub> [<b>1</b>, where 2-ntp<sup>2–</sup> = 2-nitroterephthalate and 4-bpe = 1,2-bis-(4-pyridyl)Âethane]
has been synthesized and characterized. The variable-temperature powder
X-ray diffraction study indicates the dynamic nature of the inclined
polycatenated framework, and the dehydrated framework with exposed
metal centers exhibits excellent type I H<sub>2</sub> adsorption of
1.94 wt % at 77 K and 1 bar of pressure
Reversible Phase Transformation in Three Dynamic Mixed-Ligand Metal–Organic Frameworks: Synthesis, Structure, and Sorption Study
Three new dynamic metal–organic
frameworks (MOFs) namely
{[Cd<sub>2</sub>(3,4-pyrdc)<sub>2</sub>(4,4′-bipy)Â(H<sub>2</sub>O)<sub>2</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>), {[Mn<sub>2</sub>(3,4-pyrdc)<sub>2</sub>(bpee)Â(H<sub>2</sub>O)<sub>2</sub>]·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>), and {[Cu<sub>2</sub>(3,4- pyrdc)<sub>2</sub>(bpp)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]·5H<sub>2</sub>O}<sub><i>n</i></sub> (<b>3</b>), based on 3,4-pyridinedicarboxylate
(3,4-pyrdc) and three different N,N′-donor ligands [4,4′-bipyridine
(4,4′-bipy), 1,2-bisÂ(4-pyridyl)Âethylene (bpee), and 1,3-bisÂ(4-pyridyl)-propane
(bpp)] with various divalent transition metal ions have been synthesized
and characterized by single-crystal and powder X-ray diffraction and
other physicochemical methods. In compounds <b>1</b> and <b>2</b>, the 3,4-pyrdc ligand forms two-dimensional (2D) metal–carboxylate
sheets that are connected by N,N′-donor ligands to form three-dimensional
(3D) structures with water-filled channels. In compound <b>3</b>, the 3,4-pyrdc ligand affords one-dimensional metal–carboxylate
chains. These chains are connected by the more flexible bpp ligand
to form 2D structures, which are extended to a 3D supramolecular architecture
by H-bonding. Compounds <b>1</b> and <b>2</b> show a reversible
crystalline-to-crystalline phase transformation upon dehydration and
rehydration, whereas compound <b>3</b> exhibits an interesting
reversible crystalline-to-amorphous transformation. These transformations
have been established and monitored by exhaustive X-ray powder diffraction,
elemental analysis, IR spectroscopy, thermogravimetric analysis, and
morphology studies. The dehydrated forms of <b>1</b>–<b>3</b> selectively adsorb CO<sub>2</sub> over N<sub>2</sub> and
also exhibit stepwise water uptake
Sulfonic Group Functionalized Mixed Ligand Coordination Polymers: Synthesis, Characterization, Water Sorption, and Proton Conduction Studies
Five sulfonic acid
group functionalized mixed ligand coordination polymers (CPs), namely,
{[ZnÂ(bpeH)Â(5-sip)Â(H<sub>2</sub>O)]·(H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>1</b>), {[CuÂ(pyz)Â(5-Hsip)Â(H<sub>2</sub>O)<sub>2</sub>]·(H<sub>2</sub>O)<sub>2</sub>}<sub><i>n</i></sub> (<b>2</b>), {[CuÂ(bpee)<sub>0.5</sub>Â(5-sip)Â(H<sub>2</sub>O)<sub>2</sub>]·(H<sub>2</sub>O)<sub>4</sub>Â(bpeeH<sub>2</sub>)<sub>0.5</sub>}<sub><i>n</i></sub> (<b>3</b>), {[CuÂ(bpy)Â(5-Hsip)Â(H<sub>2</sub>O)]·(H<sub>2</sub>O)<sub>2</sub>}<sub><i>n</i></sub> (<b>4</b>), and
{[CuÂ(bpy)<sub>2</sub>Â(5-H<sub>2</sub>sip)<sub>2</sub>]·(H<sub>2</sub>O)<sub>6</sub>}<sub><i>n</i></sub> (<b>5</b>) [where sip<sup>3–</sup> = 5-sulfoisoÂphthalate; bpe
= 4,4′-bispyridylÂethane; pyz = pyrazine; bpee = 4,4′-bispyridylÂethylene;
bpy = 4,4′-bipyridine], have been synthesized with varying
different N,N′-donor linkers using slow diffusion techniques
at room temperature. The CPs possess guest water filled 1D channels
and noncoordinating sulfonic acid or coordinated sulfonate groups,
which are interconnected by means of extended intermolecular H-bonding
interaction, which supports the humidity dependent proton conductivity
of the samples. Under 95% relative humidity (% RH), the CPs exhibit
the temperature dependent proton conductivity which is maximum up
to in the range of ∼10<sup>–5</sup>–10<sup>–6</sup> S cm<sup>–1</sup> at 65 °C. In most of the cases, the
framework shows activation energies with the value ranging from 0.35
to 0.54 eV, suggesting mostly the contribution of the Grotthuss mechanism
of the proton conductivity
Two Series of Isostructural Coordination Polymers with Isomeric Benzenedicarboxylates and Different Azine Based N,N′-Donor Ligands: Syntheses, Characterization and Magnetic Properties
Seven
coordination polymers (CPs) with two types of framework structures,
namely, {[MÂ(4-bpdb)Â(1,3-bdc)]·(4-bpdb)<sub>0.5</sub>}<sub><i>n</i></sub> [M = Mn (<b>1</b>), Fe (<b>2</b>), and Co (<b>3</b>)], and {[MÂ(4-bpdh)Â(1,4-bdc)]}<sub><i>n</i></sub> (M = Mn (<b>4</b>), Fe (<b>5</b>), Co (<b>6</b>), and Cd (<b>7</b>)] have been synthesized
through the slow diffusion technique using 1,3-bdc and 1,4-bdc ligands
with two different azine based N,N′-donor linkers [1,3-bdc
= benzene-1,3-dicarboxylate, 1,4-bdc = benzene-1,4-dicarboxylate,
4-bpdb = <i>N,N</i>′-bis-pyridin-4-ylmethylene-hydrazine
and 4-bpdh = <i>N,N</i>′-bis-(1-pyridin-4-yl-ethylidene)-hydrazine].
Their structures have been determined by single-crystal X-ray diffraction
analysis and further characterized by elemental analysis, IR spectra,
and powder X-ray diffraction (PXRD) analysis. Compounds <b>1</b>–<b>3</b> are isostructural and feature a two-dimensional
(2D) framework structure formed by pillaring the one-dimensional [MÂ(1,3-bdc)]<sub><i>n</i></sub> double chains through 4-bpdb linkers. In
all cases of compounds <b>1</b>–<b>3</b>, free
4-bpdb linkers are present in the lattice and lattice 4-bpdb ligands
are involved in π–π and C–H···π
interactions with bridging 1,3-bdc and 4-bpdb ligands, to afford three-dimensional
(3D) supramolecular structures. Compounds <b>4</b>–<b>7</b> are also isostructural and here the bridging of 1,4-bdc
with the divalent metal centers forms a 2D layer of [MÂ(1,4-bdc)]<sub><i>n</i></sub> which is further pillared by 4-bpdh to form
a 3D pillared-layer framework. Variable temperature magnetic measurements
of two sets of isostructural complexes (<b>1</b>–<b>3</b> and <b>4</b>–<b>7</b>) have been carried
out. Compounds <b>1</b>–<b>6</b> clearly indicate
the existence of a weak antiferromagnetic interaction between the
metal ions through the bridging 1,3-bdc and 1,4-bdc ligands. The magnetic
properties depend strongly on the nature of the metal center. The
luminescence spectra of the complexes have been measured, which indicates
a ligand based emission for all seven compounds