protected by a fluorenyl-9-methoxycarbonyl (Fmoc) group at the N-terminus.
Gelators 14 and 15 (Scheme 3.6) are capable of gelating various common organic
solvents, such as mixed solvent-systems of alcohol and water, especially alcohols,
via the intermolecular hydrogen bonds of the dipeptide segment and p–p stacking
of the fuorenyl moiety in the protecting group. SEM and TEM imagines of these
metallogels showed fibrous morphologies, and the density of the fibres changed
with the different solvent. Addition of b-CD to the gel systems led to the gel
collapse because the host–guest interactions between ferrocene and b-CD destroyed
the gel network. Moreover, changing of the redox state of ferrocene resulted in a
reversible gel–sol transition (Fig. 3.7).
Yang and co-workers reported a family of ethynyl-pyrene-modified platinumacetylide organometallic gelators (16–19, Scheme 3.6) which exhibit good gel
formation properties in the mixed solvents of alkane and benzene via p–p stacking
and hydrogen bonding interaction [31]. The monoethynyl pyrene-modified complex
could form stable hybrid gels with graphene through the large aromatic surface of
graphene and the charge transfer interactions between the aromatic ethynyl-pyrene
moiety, which was proved by the decrease of emission intensity of the hybrid
metallogels at around 500 nm. Comparing with the native gel, the graphene-containing hybrid metallogel was more rigid and still maintained the entangled
nanofibrillar structure.
O
N
H
H
N
O
N
H
H
N O
O
O
Fe
14
O
N
H
H
N
O
N
H
H
N O
O
O
Fe
15
Pt
Pt
HN
O
RO
RO
OR
Et 3 P
PEt 3
PEt 3
Et 3 P
NH
O
OR
OR
OR
Pt
Pt
HN
O
RO
RO
OR
Et3P
PEt3
PEt3
Et 3 P
NH
O
OR
OR
OR
16 R = C 12 H 25
17 R = C 18 H 37
18 R = C12H25
19 R = C 18 H 37
Scheme 3.6 Molecular structures of 14–19
Fig. 3.7 Photographs of the reversible gel–sol phase transition of gel 14 triggered by chemical
redox and gel–sol phase transition of gel 14 triggered by two molar equivalents of b-CD. Adapted
with permission from [25]. Copyright © 2014, Royal Society of Chemistry
3.1 Discrete Gelators
71
Gelators 14 and 15 (Scheme 3.6) are capable of gelating various common organic
solvents, such as mixed solvent-systems of alcohol and water, especially alcohols,
via the intermolecular hydrogen bonds of the dipeptide segment and p–p stacking
of the fuorenyl moiety in the protecting group. SEM and TEM imagines of these
metallogels showed fibrous morphologies, and the density of the fibres changed
with the different solvent. Addition of b-CD to the gel systems led to the gel
collapse because the host–guest interactions between ferrocene and b-CD destroyed
the gel network. Moreover, changing of the redox state of ferrocene resulted in a
reversible gel–sol transition (Fig. 3.7).
Yang and co-workers reported a family of ethynyl-pyrene-modified platinumacetylide organometallic gelators (16–19, Scheme 3.6) which exhibit good gel
formation properties in the mixed solvents of alkane and benzene via p–p stacking
and hydrogen bonding interaction [31]. The monoethynyl pyrene-modified complex
could form stable hybrid gels with graphene through the large aromatic surface of
graphene and the charge transfer interactions between the aromatic ethynyl-pyrene
moiety, which was proved by the decrease of emission intensity of the hybrid
metallogels at around 500 nm. Comparing with the native gel, the graphene-containing hybrid metallogel was more rigid and still maintained the entangled
nanofibrillar structure.
O
N
H
H
N
O
N
H
H
N O
O
O
Fe
14
O
N
H
H
N
O
N
H
H
N O
O
O
Fe
15
Pt
Pt
HN
O
RO
RO
OR
Et 3 P
PEt 3
PEt 3
Et 3 P
NH
O
OR
OR
OR
Pt
Pt
HN
O
RO
RO
OR
Et3P
PEt3
PEt3
Et 3 P
NH
O
OR
OR
OR
16 R = C 12 H 25
17 R = C 18 H 37
18 R = C12H25
19 R = C 18 H 37
Scheme 3.6 Molecular structures of 14–19
Fig. 3.7 Photographs of the reversible gel–sol phase transition of gel 14 triggered by chemical
redox and gel–sol phase transition of gel 14 triggered by two molar equivalents of b-CD. Adapted
with permission from [25]. Copyright © 2014, Royal Society of Chemistry
3.1 Discrete Gelators
71