Fluorescent Environment-Sensitive Dyes as Reporters of Biomolecular Interactions - Progress in Molecular Biology and Translational Science - page 39

2. SINGLE-BAND SOLVATOCHROMIC DYES: DESIGN
AND APPLICATIONS

Representative examples of single-band solvatochromic dyes are
shown in Fig. 2.3 . All these molecules bear an electron-donor and
electron-acceptor group attached to a conjugated (usually aromatic) system.
These dyes present a single emission band, which changes its position and
sometimes intensity in response to changes in the environment polarity.
Their spectroscopic and solvatochromic properties are shown in Table 2.1 .
As a general trend, it can be noticed that these dyes are characterized by an
absorption in the violet or ultraviolet (UV) region as well as by a relatively
low extinction coefficient, compared to the classical fluorescent dyes (rho-
damine, fluorescein, cyanines, etc.). Two dye families, phenoxazine and
nitrobenzoxadiazole (NBD) derivatives, present red-shifted absorption
but are characterized by relatively weak fluorescence solvatochromism.
Most solvatochromic dyes show relatively high fluorescence quantum yields
in apolar solvents, which drop drastically in polar solvents, especially in
water. From Table 2.1 , it is clear that, though there is a large variety
of

solvatochromic dyes, there is none that could feature excellent

R

H

R O

O

R
N

R

O R

N

R
N

HN

O O

O

O O

OO S

O O

HO
O

S

HN

N

N

N

N

N

N

N

1,8-ANS Dansyl Prodan Anthradan FR0 4DMP 6DMN 4DMN

R

H

N

N

R NC

O O

S

C O

O

O

R CN O

O

O

R

O

N + O

CN O

NO

N O

N N

O

O

O

N

N

N

N

N

N

HR

N

N

Fluoroprobe Dapoxyl NBD Oxazines DCDHF 3MC-2

Figure 2.3 Examples of fluorescent solvatochromic dyes. Schematic presentation of
fluorophore structure: electron-donor and -acceptor groups are shown in red and blue,
respectively. Group R indicates the common point of the dye conjugation.