surface-functionalized ZL hybrids [109] for the construction of complex functional
ZL patterns are innovative approaches for obtaining fascinating arrangement.
6 Structure of the Guest-ZL Composites
The structure of the host ZL is well known [12, 23, 24, 148]. This provides a sound
basis for elucidating the structure and interactions of the guests within the host. The
current powerful techniques available to study host-guest compounds have been
reviewed by Tabacchi [1]. The presence of guests usually lowers the symmetry of
the objects, thus complicating structural characterization of the confined species with
standard crystallographic methods. These limitations have been overcome in modern
crystallographic techniques which can integrate single crystal, powder, and neutron
diffraction data with pair distribution function analyses. This has allowed, as an
example, to determine the structure of self-assembled composites of ZL with the
perylene diimide dye tb-DXP, revealing the fundamental host-guest interactions at
atomistic level [44]. Vibrational spectroscopy (IR, Raman, INS) are prime techniques for elucidating host-guest interaction pattern [40, 44, 55]. Confocal luminescence spectroscopy tells us the orientation of the electronic transition dipole moment
(ETDM) which is directly connected to the orientation of the molecules with respect
to the channels [14, 149, 150]. Electronic absorption and luminescence properties of
the guests are sensitive and sometimes very sensitive to interactions of the guests
with the environment and on the guest-guest distances and orientations as we shall
discuss in the next two chapters. Computational studies are of overwhelming
importance for advancing our understanding of host-guest systems. They enable to
capture structural and dynamical features and provide explanations otherwise difficult or impossible to gather directly from experiments [44, 49, 56, 79, 151–160]. Calculations, combined with experiments, have shown that dye-ZL composites can
withstand GPa pressures without alteration in the organization of the guests. This
is an important information regarding the extension of the application of ZL-based
optical devices [49, 160, 161].
Newsam presents in 1989 the complete structure results of powder neutron
diffraction studies of a dehydrated potassium ZL at 298 and 78 K and of the same
ZL at 78 K containing, on average, one molecule of perdeuteriobenzene/u.c
[148]. He observed that little change in structure accompanies dehydration, benzene
sorption, or temperature change in the range of 298 to 78 K. The non-framework K
+
configuration shows only subtle changes over the range of conditions studied.
Perdeuteriobenzene was observed at 78 K in “capping” positions above the channel
wall K
+
. Simple atom-atom potential modeling of the benzene site based on the
structural results yields only a small activation barrier to benzene molecule
reorientation.
It was a surprise to observe that nearly every u.c. could be filled with one
methylviologen cation MV
2+ using room temperature ion exchange, despite of the
fact that the length of this molecule exceeds by far the 0.75 nm length of a u.c. This
28
G. Calzaferri
ZL patterns are innovative approaches for obtaining fascinating arrangement.
6 Structure of the Guest-ZL Composites
The structure of the host ZL is well known [12, 23, 24, 148]. This provides a sound
basis for elucidating the structure and interactions of the guests within the host. The
current powerful techniques available to study host-guest compounds have been
reviewed by Tabacchi [1]. The presence of guests usually lowers the symmetry of
the objects, thus complicating structural characterization of the confined species with
standard crystallographic methods. These limitations have been overcome in modern
crystallographic techniques which can integrate single crystal, powder, and neutron
diffraction data with pair distribution function analyses. This has allowed, as an
example, to determine the structure of self-assembled composites of ZL with the
perylene diimide dye tb-DXP, revealing the fundamental host-guest interactions at
atomistic level [44]. Vibrational spectroscopy (IR, Raman, INS) are prime techniques for elucidating host-guest interaction pattern [40, 44, 55]. Confocal luminescence spectroscopy tells us the orientation of the electronic transition dipole moment
(ETDM) which is directly connected to the orientation of the molecules with respect
to the channels [14, 149, 150]. Electronic absorption and luminescence properties of
the guests are sensitive and sometimes very sensitive to interactions of the guests
with the environment and on the guest-guest distances and orientations as we shall
discuss in the next two chapters. Computational studies are of overwhelming
importance for advancing our understanding of host-guest systems. They enable to
capture structural and dynamical features and provide explanations otherwise difficult or impossible to gather directly from experiments [44, 49, 56, 79, 151–160]. Calculations, combined with experiments, have shown that dye-ZL composites can
withstand GPa pressures without alteration in the organization of the guests. This
is an important information regarding the extension of the application of ZL-based
optical devices [49, 160, 161].
Newsam presents in 1989 the complete structure results of powder neutron
diffraction studies of a dehydrated potassium ZL at 298 and 78 K and of the same
ZL at 78 K containing, on average, one molecule of perdeuteriobenzene/u.c
[148]. He observed that little change in structure accompanies dehydration, benzene
sorption, or temperature change in the range of 298 to 78 K. The non-framework K
+
configuration shows only subtle changes over the range of conditions studied.
Perdeuteriobenzene was observed at 78 K in “capping” positions above the channel
wall K
+
. Simple atom-atom potential modeling of the benzene site based on the
structural results yields only a small activation barrier to benzene molecule
reorientation.
It was a surprise to observe that nearly every u.c. could be filled with one
methylviologen cation MV
2+ using room temperature ion exchange, despite of the
fact that the length of this molecule exceeds by far the 0.75 nm length of a u.c. This
28
G. Calzaferri