should be attributed to the polymeric network supported by Ni
2+ that preventing the
disruption of the entire coordination network.
Metal–organic gels of tetrazole-appended ligand 66 (Scheme 3.14) and Co
2+
were prepared in polar solvents by Shinkai and co-workers [90]. The gels have
spherical morphology structure with 20–30 nm diameter. Powder XRD pattern
reveals a crystalline structure with 2D coordination polymer structure for the
freeze-dried gels. The gels show potential application as chemosensors or adsorbents for toxic gases. The 66-CoBr 2 gel selectively recognizes toxic gases containing chloride atoms, such as HCl, SOCl 2 , (COCl) 2 and COCl 2 .
Tripodal terpyridine has been used in coordination polymeric gels as well. Tb
3+
or Eu
3+ ion coordinates to terpyridine-appended chiral ligand 67 (Scheme 3.15)
results in green and pink emissive coordination polymer gels, respectively [91].
Control over stoichiometry of L:Tb
3+ :Eu
3+ leads to yellow and white light emitting
bimetallic gels (Fig. 3.25).
Terpyridine-appended chiral ligand 68 (Scheme 3.15) forms luminescent gels
without and with Tb
3+ or Eu
3+ in H 2 O-DMSO (3:7 v/v) [92]. By AFM observations, these gels show well-defined right-handed helical nanofibres formed by
coordination bonds (Fig. 3.26). The helical pitch lengths are strongly dependent on
the concentrations of lanthanide ions. A gel can be prepared when 1 wt% of 68 was
dissolved in a mixture of DMSO and various solvents such as CH 2 Cl 2 , CHCl 3 ,
toluene, ethyl acetate, MeOH, EtOH, MeCN, acetone, THF and water. The gels can
be used in a water-compatible inkjet printing system to generate luminescent
metallogels on A4-sized paper.
Terech and co-workers inserted a coordinating cyclam macrocycle
(1,4,8,11-tetraazacyclotetradecane) as a spacer between two terminal chelating
terpyridine units [93, 94]. A metal–organic gel with remarkable self-healing
property is fabricated based on 69 (Scheme 3.15) through the coordination of nickel
ion and nitrogen atom of terpyridine and cyclam. Ni
2+ ion is in the centre of 69
coordinating with four N-atoms, and the network is connected by coordination
N
N
N
NH N
N HN
N
N
N
O NH
NH
N
N
N
O
HN
HN
N
N
N
O
NH
NH
N
N
N
O
NH
NH
N
N
N
O
HN
HN
N
N
N
O
HN
HN
N
N
N
71
O NH
NH
N
N
N
H
N
H
N
O
N
N
N
H
N
H
N
O
N
N
N
70
N
N
N
O
NH
O
NH
O
O
N
N
N
*
*
68
69
67
Scheme 3.15 Terpyridyl derivatives 67–71
3.2 Coordination Polymer Gelators
93
2+ that preventing the
disruption of the entire coordination network.
Metal–organic gels of tetrazole-appended ligand 66 (Scheme 3.14) and Co
2+
were prepared in polar solvents by Shinkai and co-workers [90]. The gels have
spherical morphology structure with 20–30 nm diameter. Powder XRD pattern
reveals a crystalline structure with 2D coordination polymer structure for the
freeze-dried gels. The gels show potential application as chemosensors or adsorbents for toxic gases. The 66-CoBr 2 gel selectively recognizes toxic gases containing chloride atoms, such as HCl, SOCl 2 , (COCl) 2 and COCl 2 .
Tripodal terpyridine has been used in coordination polymeric gels as well. Tb
3+
or Eu
3+ ion coordinates to terpyridine-appended chiral ligand 67 (Scheme 3.15)
results in green and pink emissive coordination polymer gels, respectively [91].
Control over stoichiometry of L:Tb
3+ :Eu
3+ leads to yellow and white light emitting
bimetallic gels (Fig. 3.25).
Terpyridine-appended chiral ligand 68 (Scheme 3.15) forms luminescent gels
without and with Tb
3+ or Eu
3+ in H 2 O-DMSO (3:7 v/v) [92]. By AFM observations, these gels show well-defined right-handed helical nanofibres formed by
coordination bonds (Fig. 3.26). The helical pitch lengths are strongly dependent on
the concentrations of lanthanide ions. A gel can be prepared when 1 wt% of 68 was
dissolved in a mixture of DMSO and various solvents such as CH 2 Cl 2 , CHCl 3 ,
toluene, ethyl acetate, MeOH, EtOH, MeCN, acetone, THF and water. The gels can
be used in a water-compatible inkjet printing system to generate luminescent
metallogels on A4-sized paper.
Terech and co-workers inserted a coordinating cyclam macrocycle
(1,4,8,11-tetraazacyclotetradecane) as a spacer between two terminal chelating
terpyridine units [93, 94]. A metal–organic gel with remarkable self-healing
property is fabricated based on 69 (Scheme 3.15) through the coordination of nickel
ion and nitrogen atom of terpyridine and cyclam. Ni
2+ ion is in the centre of 69
coordinating with four N-atoms, and the network is connected by coordination
N
N
N
NH N
N HN
N
N
N
O NH
NH
N
N
N
O
HN
HN
N
N
N
O
NH
NH
N
N
N
O
NH
NH
N
N
N
O
HN
HN
N
N
N
O
HN
HN
N
N
N
71
O NH
NH
N
N
N
H
N
H
N
O
N
N
N
H
N
H
N
O
N
N
N
70
N
N
N
O
NH
O
NH
O
O
N
N
N
*
*
68
69
67
Scheme 3.15 Terpyridyl derivatives 67–71
3.2 Coordination Polymer Gelators
93