In this study, we
report the first example of polymorphic Sn(IV)-tetrapyridyl
porphyrins axially armed with halogen (Cl, Br)-substituted carboxyphenyl
ligands (structural formula [Sn(tPyP)2+(A−)2], where A is the axial ligand = 3,5-dichloro/dibromo benzoic
acid). The two polymorphs of chloro-substituted Sn(IV)-tetrapyridyl
porphyrin (1α and 1β) display
distinct photophysical and morphological properties in the solid state.
X-ray diffraction study reveals that these polymorphs 1α and 1β greatly differ in supramolecular architecture
and noncovalent interactions, which is responsible for their distinct
solid-state properties. Molecules of the two polymorphs adopt different
conformations of the axial carboxyphenyl ligand. Crystal packing of
these polymorphs are dominated by intermolecular C–H···Npyridine, C–H···O, C–H···π,
and Cl···Npyridin interactions. Theoretical
study showed that the energy difference between the two polymorphs
is ∼8 kcal/mol. In addition to these polymorphs, a reference
compound 2 with an axial bromo-substituted carboxyphenyl
ligand is also synthesized and structurally characterized.
In
this study, we report a synthetically simple donor–acceptor (D–A)-type organic solid-state
emitter
1
that displays unique fluorescence switching
under mechanical stimuli. Orange and yellow emissive crystals of
1
(
1O
,
1Y
) exhibit an unusual “back
and forth” fluorescence response to mechanical force. Gentle
crushing (mild pressure) of the orange or yellow emissive crystal
results in hypsochromic shift to cyan emissive fragments (λ
em
= 498–501 nm) with a large wavelength shift Δλ
em
= −71 to −96 nm, while further grinding results
in bathochromic swing to green emissive powder λ
em
= 540–550 nm, Δλ
em
= +40 to 58 nm.
Single-crystal X-ray diffraction study reveals that molecules are
packed by weak interactions, such as C–H···π,
C–H···N, and C–H···F,
which facilitate intermolecular charge transfer in the crystal. With
the aid of structural, spectroscopic, and morphological studies, we
established the interplay between intermolecular and intramolecular
charge-transfer interaction that is responsible for this elusive mechanochromic
luminescence. Moreover, we have also demonstrated the application
of this organic material for chlorine gas sensing in solid state.
We report here a new green fluorescent organic crystal of amide functionalized acrylonitrile derivative (E-ArF2) that displays various types of macroscopic response when illuminated with UV light (390 nm). The...
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