4 research outputs found
Guest Exchange in a Robust Hydrogen-Bonded Organic Framework: Single-Crystal to Single-Crystal Exchange and Kinetic Studies
The salt 3,4-lutidinium
pamoate crystallizes as its hemihydrate,
forming a hydrogen-bonded organic framework with tetrahydrofuran (THF)
as a guest in channels in the structure (<b>1路THF</b>).
Extensive investigation has shown this framework to be highly robust:
the THF in the channels can be exchanged for 20 different compounds,
with 13 of these exchanges occurring in a single-crystal to single-crystal
manner. The THF can also be exchanged for the volatile solids pyrazine
or iodine, both via single-crystal to single-crystal transformations.
Stepwise exchange of solvents is also possible, with a sequence of
five exchanges occurring before the crystals begin to deteriorate.
Investigation of the kinetics of exchange in <b>1路THF</b> revealed that exchange occurs according to a deceleratory kinetic
model for contracting volume
Selectivity Behavior of a Robust Porous Organic Salt Based on the Pamoate Ion
The
selectivity of a porous hydrogen-bonded framework, <b>1</b>,
toward various solvent mixtures has been investigated. Framework <b>1</b>, which is the hydrate of 3,4-lutidinium pamoate, crystallizes
as its THF solvate, <b>1路THF</b>. Solvent exchange can
take place either by exposing crystals of <b>1路THF</b> to
solvent vapors or by immersing the crystals in a solvent. Framework <b>1</b> shows preferential inclusion of particular solvents when
exposed to mixed solvent vapors, or to mixed solvents in the liquid
form. Analysis showed that solvents are included in the same ratios
when exposed to mixed solvents in the liquid or vapor phase, despite
the significant differences in mole ratios between the liquid and
vapor phases due to the different vapor pressures of the solvents
investigated. In some cases, when immersed in solvent mixtures containing
acetonitrile or acetone, <b>1路THF</b> recrystallizes as
an acetonitrile or acetone solvate of 3,4-lutidinium pamoate. The
crystal structures of these two new solvates are also reported
A Series of Polymorphs of Hexakis(4-fluorophenoxy)cyclotriphosphazene
A series of conformational polymorphs of hexakis颅(4-fluorophenoxy)颅cyclotriphosphazene
have been identified and characterized. Three of the four polymorphs
are previously unreported. Thermal analysis coupled with variable
temperature powder X-ray diffraction has shown that conversion between
polymorphs occurs at well-defined temperatures. The high temperature
form is metastable at room temperature and is never obtained from
solution. Two forms are observed in solution crystallization experiments,
a monoclinic form and a triclinic form. Slurry experiments revealed
that the triclinic form is the most stable at room temperature. The
fourth polymorph is observed only at low temperatures. Interconversion
between three of the polymorphs occurs in a single-crystal to single-crystal
manner
A Series of Polymorphs of Hexakis(4-fluorophenoxy)cyclotriphosphazene
A series of conformational polymorphs of hexakis颅(4-fluorophenoxy)颅cyclotriphosphazene
have been identified and characterized. Three of the four polymorphs
are previously unreported. Thermal analysis coupled with variable
temperature powder X-ray diffraction has shown that conversion between
polymorphs occurs at well-defined temperatures. The high temperature
form is metastable at room temperature and is never obtained from
solution. Two forms are observed in solution crystallization experiments,
a monoclinic form and a triclinic form. Slurry experiments revealed
that the triclinic form is the most stable at room temperature. The
fourth polymorph is observed only at low temperatures. Interconversion
between three of the polymorphs occurs in a single-crystal to single-crystal
manner