10.1002/chem.201703364
Chemistry - A European Journal
COMMUNICATION
and disc-like (with no hydrogen bonding) self-assembled
structures. Further, this type of lamellar (Sm) to hexagonal
transformation is also seen in some lyotropic systems.[17]
The photo-physical properties of compound 3b and 3c were
carried out both in solution (chloroform as a solvent) as well as in
solid state (Fig. S15, ESI). In solution state, compounds 3b and
3c show well resolved two peaks at 270 & 330 nm which are likely
due to π-π* and n-π* transitions, respectively.[18] The emission
spectra, however, exhibited one peak centered at 446 nm for 3b
and 487 nm for 3c along with a shoulder peak at 412 nm. On the
other hand, in the solid state, compounds 3b and 3c show their
respective absorption peaks at 274 & 334 nm while the emission
spectra showed a maxima centered at 475 nm for both the
compounds (Fig. S15, ESI).
In summary, we present here the first report of heptazine based
DLCs, possessing a stable Colh phase and a Sm phase at ambient
temperature. They are strong blue light emitters when fabricated
into solid thin films. Such materials with ease of synthesis, room
temperature mesophase, solid state emitters along with low band
gap are expected to be better candidates for future optoelectronic
applications with the advantages that LCs offer.
Acknowledgements
SKP, IB and KK acknowledge CSIR, 02(0311)/17/EMR-II, CSIR-
NET, DST-SERB (ECR/2016/001469), DST-Nano Mission
(SR/NM/NT-06/2016) for financial support, respectively. We are
grateful to NMR, HRMS and SAXS/WAXS facility at IISER Mohali.
Keywords: heptazine • room temperature • blue light • columnar
hexagonal • smectic
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Figure 4. Plausible molecular packing model: (a) compound 3b in Sm phase, (i
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