Beilstein J. Org. Chem. 2016, 12, 1229–1235.
measured their electronic absorption and emission spectra in
this solvent has been reported [28], we found that this is not the
case of the compounds under study. To avoid excimer forma-
tion, spectra were recorded at low sample concentrations
(
1 μM). We have found that all compounds under study were
0.7 (Table 1). The typical absorption and emission spectrum
≈
are shown in Figure 1. The spectra are closely similar and show
vibronic structure characteristic for monomeric fluorophores.
The spectra of 5 are slightly shifted bathochromically (9 nm and
4
nm for the absorption and emission spectrum, respectively) in
noticed that spectra reported in [9] were measured at signifi-
cantly higher concentrations (0.5 mM) and are broad and struc-
tureless. Therefore, they should rather be assigned to fluoro-
phore aggregates (excimers).
Figure 1: Normalized electronic absorption and emission spectra of
3Aj and pyrene in chloroform (c = 1 μM).
Table 1: Absorption and emission maxima and fluorescence quantum
yields (ΦF) for the synthesized compounds in chloroform solution
(c = 1 μM).
Compd. Absorption
Emissiona
ΦFb
λmax (nm)
λmax (nm)
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
5
Aa
Ba
Ca
Ab
Bb
Cb
Ac
Bc
Cc
Ad
Bd
Cd
Ae
Be
Af
304, 317, 330, 347 378, 388, 399
304, 316, 331, 347 378, 388, 398
304, 316, 331, 348 378, 389, 399
0.06
0.06
0.06
304, 317, 331, 348 382, 397, 424, 444 <0.01
304, 318, 330, 348 382, 397, 443
305, 318, 332, 349 382, 397, 455
304, 317, 331, 348 380, 395, 485
304, 316, 330, 448 380, 395, 484
304, 317, 330, 448 380, 396, 485
304, 317, 331, 348 380, 398,
304, 317, 330, 348 380, 398
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.10
Figure 2: Emission spectra of compound 3Aj in various solvents. The
spectra are normalized at ≈378 nm (pyrene band I).
The highest emission quantum yield (0.68) was found for
aminophosphonic acid 4a in aqueous buffer (pH 7.4). A similar
phenomenon of higher emission efficiency of 1-(pyrene-1-
sponding aminophosphonate was earlier reported [29].
304, 317, 331, 348 381, 398
303, 316, 330, 347 378, 390, 398
303, 316, 330, 346 377, 389, 397
303, 317, 330, 347 378, 390, 398
0.10
0.09
Ag
Ai
316, 330, 347
378, 390, 398
0.05
303, 316, 330, 347 380, 395
<0.01
0.11
Aj
318, 331, 347
378, 389, 397
The aforementioned data suggest possible application of com-
pound 3Aj (and other exhibiting similar emission quantum
yield) as molecular probes monitoring micropolarity of the
fluorophore environment. On the other hand, water-soluble 4a
might be used for biological imaging.
ac
303, 316, 329, 345 378, 397, 419
0.68
A
317, 330, 347
377, 388, 396
0.13
aExcitation was set at the maximum of the lowest energy absorption
band. bMeasured for aerated solutions. Quenching by dissolved
dioxygen was not observed. cMeasured for an aqueous 0.01 PBS
(
phosphate-buffered saline) solution (pH 7.4)
Investigation of cytotoxic effects of studied
Figure 2) and display the well-known Ham effect (dependence The cytotoxic effects of dimethyl aminophosphonates 3Aa,
polarity) [26]. yl)methyl]phosphonate (5A) were investigated with two human
(
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