posted on 2014-09-16, 00:00authored byNagappanpillai Adarsh, Megha
S. Krishnan, Danaboyina Ramaiah
With an objective to develop optical
probes for biologically important
anions and neutral molecules, we synthesized three novel NIR absorbing
aza-BODIPY derivatives, 3a–3c, and
have systematically tuned their photophysical properties by changing
the peripheral substitution. A profound red-shift was observed in
the absorption and fluorescence spectra of the aza-BODIPY dyes with
the change in substitution from azido (3a) to amino (3b) to dimethylamino (3c) groups. Theoretical
calculations of 3a–3c showed a consistent
decrease in bandgap, which supports the observed spectral changes.
The study of their interactions with various analytes revealed that
the azido-aza-BODIPY 3a selectively interacts with hydrogen
sulfide (H2S) when compared to other molecules. Uniquely,
the detection of H2S can be visualized through a change
in color from bright blue to purple with a detection limit of 0.5
ppm. The sensitivity of the probe was observed to be ∼20-fold
higher than the allowed exposure limits of H2S as defined
by EPA (10 ppm). The aza-BODIPY derivative 3b, on the
other hand, exhibited selective interactions with nitrite ions (NO2–) and nitric oxide (NO) in aqueous medium
through a visible color change from blue to green with a sensitivity
of 20 and 0.15 ppb, respectively. In contrast, the dimethylamino-aza-BODIPY
derivative, 3c, showed negligible affinity for the anions
and neutral molecules tested. By tuning the photophysical properties
through the judicious functionalization, the aza-BODIPY dyes thus
synthesized can be utilized for the sensitive on-site detection and
analysis of H2S, NO2–, and
NO in the aqueous medium.