may be used for an erasable secret documentation medium. The CaG gel showed
“OFF–ON” fluorescent switch controlled by Fe
3+ /H 2 PO 4
− [24] and Cd
2+ /I
− [25],
respectively, as well. Acylhydrazone gels were further explored to be adjusted by
more metal ions and anion-responsive [26]. Stable gel of 34 forms in DMF, which
shows brilliant blue AIE (Scheme 4.11). Addition of metal ions such as Cr
3+ , Fe
3+ ,
Cu
2+ , Hg
2+ to 34 gel results in non-fluorescent gels (CrG1, FeG1, CuG1, HgG1),
while addition of Zn
2+ leads to a yellow fluorescent gel (ZnG1). Interestingly,
different metallogels sense different anions with high fluorescent selectivity and
sensitivity (CN
− with CuG1 and FeG1, SCN
− with HgG1 and S
2− with CrG1)
(Fig. 4.10). The gel films act as convenient reversible anions detection test kits and
erasable security display materials.
A multi-functionalized acylhydrazone gelator 35 by introducing a coordination
site, –OH, has been reported (Scheme 4.11) [27]. The gel of 35 shows ability to
sense fourteen kinds of important ions with high selectivity and sensitivity in
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
Self-assembly
33
OG
M1
n+
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
M1G
M1
n+
M2
n+
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
M2G
M2
n+
X
nM1
n+
[M2X m ]
nN
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
Self-assembly
34
OG1
M
n+
N
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
MG1
N
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
34
X
n[MX m ]
nM
n+
+
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
Self-assembly
35
OG2
M
n+
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
MG2
N
NH
O
C 16 H 33 O
OC 16 H 33
OC 16 H 33
X
n[MX m ]
nM
n+
+
HO
O
HO
Scheme 4.11 Stimuli responsive mechanism for bimetal-acylhydrazone gels
4.1 Discrete Gelators
133