Five
D-π-A-π-D
compounds consisting of
the same donor unit (dithieno[3,2-
b
:2′,3′-
d
]pyrrole,
DTP
), the same π-linker (2,5-thienylene),
and different acceptors of increasing electron-withdrawing ability
(1,3,4-thiadiazole (
TD
), benzo[
c
][1,2,5]thiadiazole
(
BTD
), 2,5-dihydropyrrolo[3,4-
c
]pyrrole-1,4-dione
(
DPP
), 1,2,4,5-tetrazine (
TZ
), and benzo[
lmn
][3,8]phenanthroline-1,3,6,8(2
H
,7
H
)-tetraone (
NDI
)) were synthesized.
DTP-TD
,
DTP-BTD
, and
DTP-DPP
turned
out to be interesting luminophores emitting either yellow (
DTP-TD)
or near-infrared (
DTP-BTD
and
DTP-DPP
)
radiation in dichloromethane solutions. The emission bands were increasingly
bathochromically shifted with increasing solvent polarity. Electrochemically
determined electron affinities (|EA|s) were found to be strongly dependent
on the nature of the acceptor changing from 2.86 to 3.84 eV for
DTP-TD
and
DTP-NDI
, respectively, while the ionization
potential (IP) values varied only weakly. Experimental findings were
strongly supported by theoretical calculations, which correctly predicted
the observed solvent dependence of the emission spectra. Similarly,
the calculated IP and EA values were in excellent agreement with the
experiment.
DTP-TD
,
DTP-BTD
,
DTP-TZ
, and
DTP-NDI
could be electropolymerized to yield polymers
of very narrow electrochemical band gap and characterized by redox
states differing in color coordinates and lightness.
Poly(DTP-NDI)
and
poly(DTP-TD)
showed promising electrochromic behavior,
not only providing a rich color palette in the visible but also exhibiting
near-infrared (NIR) electrochromism.