5 research outputs found
Temperature-Dependent Semiconducting Behavior of an Organic Cocrystal Driven by the Stacking Mode of Interaction of a 4,4′-Bipyridine Molecule
Organic cocrystals based on H-bonding as well as π-stacking
interactions between 4,4′-bipyridine–pyromellitic acid
(1) and 4,4′-bipyridine–phthalic acid (2) are reported. Cocrystals 1 and 2 were fully characterized by single-crystal X-ray diffraction and
NMR and IR spectroscopy. The single-crystal X-ray diffraction shows
the H stacking pattern of the adjacent 4,4′-bipyridine molecules
in the construction of a 3D chain structure for cocrystal 1. Cocrystal 2, however, formed a zigzag 3D chain where
the adjacent 4,4′-bipyridyl molecules are involved in a J-stacking
mode. Experimental conductivity measurements of the cocrystals 1 and 2 with a Keithley 4200 SCS parameter analyzer
showed the temperature-dependent semiconducting behavior in the case
of cocrystal 1, whereas cocrystal 2 remained
as an insulator. The favorable H-stacking interaction of 4,4′-bipyridine
molecules which is the prime origin of semiconductivity in cocrystal 1 may become out of phase due to the free rotation along the
C–C bond of 4,4′-bipyridine with an increase in temperature.
Although the semiconducting behavior of a material increases with
increasing temperature and decreases in resistivity, in the case of
cocrystal 1 due to the probable phase transition of the
4,4′-bipyridyl molecules the material became an insulator with
an increase in temperature from 20 °C to higher temperature,
whereas the semiconducting behavior was restored after cooling the
crystals to 20 °C again. The theoretical study conducted with
the optimized structures of 1 and 2 showed
the higher electron hopping rate in the case of cocrystal 1 as compared to 2 which can account for the charge conduction
in the case of 1
Terbium(III), Europium(III), and Mixed Terbium(III)–Europium(III) Mucicate Frameworks: Hydrophilicity and Stoichiometry-Dependent Color Tunability
Two 3D porous terbiumÂ(III) mucicate frameworks, {[Tb<sub>2</sub>(Mu<sup>2–</sup>)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>) and {[TbÂ(Mu<sup>2–</sup>)Â(Ox<sup>2–</sup>)<sub>0.5</sub>(H<sub>2</sub>O)]·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>), have been synthesized under hydrothermal conditions
by changing
the pH of the reaction medium. Isostructural europiumÂ(III) and seven
mixed terbiumÂ(III)–europiumÂ(III) mucicates were synthesized
by doping different percentages of Eu<sup>III</sup> under similar
reaction conditions and unveiling different emission colors ranging
from green to red under the same wavelength. Both dehydrated Tb<sup>III</sup> metal–organic frameworks exhibit selective H<sub>2</sub>O vapor sorption over other solvent molecules (MeOH, MeCN,
and EtOH) of less polarity and bigger size and have been correlated
to the highly hydrophilic pore surfaces decorated with −OH
groups and O atoms from the carboxyl groups of mucicate
Terbium(III), Europium(III), and Mixed Terbium(III)–Europium(III) Mucicate Frameworks: Hydrophilicity and Stoichiometry-Dependent Color Tunability
Two 3D porous terbiumÂ(III) mucicate frameworks, {[Tb<sub>2</sub>(Mu<sup>2–</sup>)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>) and {[TbÂ(Mu<sup>2–</sup>)Â(Ox<sup>2–</sup>)<sub>0.5</sub>(H<sub>2</sub>O)]·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>), have been synthesized under hydrothermal conditions
by changing
the pH of the reaction medium. Isostructural europiumÂ(III) and seven
mixed terbiumÂ(III)–europiumÂ(III) mucicates were synthesized
by doping different percentages of Eu<sup>III</sup> under similar
reaction conditions and unveiling different emission colors ranging
from green to red under the same wavelength. Both dehydrated Tb<sup>III</sup> metal–organic frameworks exhibit selective H<sub>2</sub>O vapor sorption over other solvent molecules (MeOH, MeCN,
and EtOH) of less polarity and bigger size and have been correlated
to the highly hydrophilic pore surfaces decorated with −OH
groups and O atoms from the carboxyl groups of mucicate
Bimodal Magneto-Luminescent Dysprosium (Dy<sup>III</sup>)‑Potassium (K<sup>I</sup>)‑Oxalate Framework: Magnetic Switchability with High Anisotropic Barrier and Solvent Sensing
We
report synthesis, characterization, and properties of a multifunctional
oxalate framework, {KDyÂ(C<sub>2</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>1</b>) (C<sub>2</sub>O<sub>4</sub><sup>2–</sup> = oxalate dianion)
composed of two absolutely different metal ions in terms of their
size, charge, and electronic configuration. Dehydrated framework (<b>1′</b>) exhibits permanent porosity and interesting solvent
(H<sub>2</sub>O, MeOH, CH<sub>3</sub>CN, and EtOH) vapor sorption
characteristics based on specific interactions with unsaturated alkali
metal sites on the pore surface. Compound <b>1</b> shows solvent
responsive bimodal magnetic and luminescence properties related to
the Dy<sup>III</sup> center. Compound <b>1</b> exhibits reversible
ferromagnetic to antiferromagnetric phase transition upon dehydration
and rehydration, hitherto unknown for any lanthanide based coordination
polymer or metal–organic frameworks. Both the compounds <b>1</b> and <b>1′</b> exhibit slow magnetic relaxation
with very high anisotropic barrier (417 ± 9 K for <b>1</b> and 418 ± 7 K for <b>1′</b>) which has been ascribed
to the single ion magnetic anisotropy of the Dy<sup>III</sup> centers.
Nevertheless, compound <b>1</b> shows a metal based luminescence
property in the visible region and H<sub>2</sub>O molecules exhibit
the strongest quenching effect compared to other solvents MeOH, MeCN,
and EtOH, evoking <b>1′</b> as a potential H<sub>2</sub>O sensor
Bimodal Magneto-Luminescent Dysprosium (Dy<sup>III</sup>)‑Potassium (K<sup>I</sup>)‑Oxalate Framework: Magnetic Switchability with High Anisotropic Barrier and Solvent Sensing
We
report synthesis, characterization, and properties of a multifunctional
oxalate framework, {KDyÂ(C<sub>2</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>1</b>) (C<sub>2</sub>O<sub>4</sub><sup>2–</sup> = oxalate dianion)
composed of two absolutely different metal ions in terms of their
size, charge, and electronic configuration. Dehydrated framework (<b>1′</b>) exhibits permanent porosity and interesting solvent
(H<sub>2</sub>O, MeOH, CH<sub>3</sub>CN, and EtOH) vapor sorption
characteristics based on specific interactions with unsaturated alkali
metal sites on the pore surface. Compound <b>1</b> shows solvent
responsive bimodal magnetic and luminescence properties related to
the Dy<sup>III</sup> center. Compound <b>1</b> exhibits reversible
ferromagnetic to antiferromagnetric phase transition upon dehydration
and rehydration, hitherto unknown for any lanthanide based coordination
polymer or metal–organic frameworks. Both the compounds <b>1</b> and <b>1′</b> exhibit slow magnetic relaxation
with very high anisotropic barrier (417 ± 9 K for <b>1</b> and 418 ± 7 K for <b>1′</b>) which has been ascribed
to the single ion magnetic anisotropy of the Dy<sup>III</sup> centers.
Nevertheless, compound <b>1</b> shows a metal based luminescence
property in the visible region and H<sub>2</sub>O molecules exhibit
the strongest quenching effect compared to other solvents MeOH, MeCN,
and EtOH, evoking <b>1′</b> as a potential H<sub>2</sub>O sensor