series of challenging questions in the field of chemical reactor design, molecular
analytics and other industrial processes. Further applications can be expected, e.g.
the combination with rapid-mixing experiments as an alternative variant for an
externally triggered reaction. Possible other realizations will involve 2D IR
spectroscopy in conjunction with combinatorial chemistry. In a similar manner, the
combination of 2D IR spectroscopy with microscopy is just taking off and will
possibly add a completely new dimension to microscopic sample characterizations
in biological systems, polymer samples or functional materials. Currently, it is
extremely challenging for other methods to achieve the chemical sensitivity of IR
spectroscopy and allow for a similarly high degree in experimental flexibility in
characterizing ultrafast dynamics and intermolecular interactions with high spatial
resolution. In the same context, one important application of 2D IR spectroscopy
has still to be tackled, that is, scattering scanning near-field optical microscopy (sSNOM) 2D IR as the combination of sub-100 fs temporal resolution and sub-50 nm
spatial resolution in a single experiment. Although recent reports aiming in this
direction appear very promising [373, 374, 393–395], the realization of 2D IR
s-SNOM will still require most likely quite some time. However, this variant will
allow the ultimate way to characterize intermolecular interactions and dynamics in
space and time and its impact can hardly be overrated.
Despite the impressive achievements and the tremendous current efforts
regarding further development of different forms of 2D IR spectroscopy, the
method is generally still considered as a specialized technique by many researcher
outside the field. In other words, 2D IR has not yet been fully established as a
standard analytical tool for characterizing molecular structure, dynamics and
intermolecular interactions. An important reason for this is the often comparatively
short vibrational lifetimes (pico- to nanoseconds), which intrinsically limit the
temporal observation window. Additionally, 2D IR spectra from a large range of
vibrational modes contain often only weak or even absent cross peaks, which are
due to vibrational coupling or energy transfer. These missing cross peaks are
particularly of importance in case of through-space, intermolecular interactions. In
general, such interactions are very short-ranged, often only reaching to distances
less than a nanometer. Although this is typically also the distance on which 2D
NMR experiments reveal structural information about the sample, the strongly
nonlinear dependence of dipolar interactions on the (often weak) transition dipole
moments complicates the exploitation of intermolecular coupling in IR studies.
Finally, performing day-to-day experiments as well as detailed data interpretation
often still requires skilled spectroscopists and costly laboratory equipment. In this
regard, important developments currently focus on facilitated and automated data
acquisition for 2D IR. Progress in this direction will allow a more widespread
application of the method and possibly the day-to-day use for a variety of disciplines
in life sciences.
Acknowledgements I would like to thank Peter Hamm for many valuable discussions, the productive
research atmosphere as well as his continuous and generous support.
Top Curr Chem (Z) (2017) 375:86
123
188
Reprinted from the journal
analytics and other industrial processes. Further applications can be expected, e.g.
the combination with rapid-mixing experiments as an alternative variant for an
externally triggered reaction. Possible other realizations will involve 2D IR
spectroscopy in conjunction with combinatorial chemistry. In a similar manner, the
combination of 2D IR spectroscopy with microscopy is just taking off and will
possibly add a completely new dimension to microscopic sample characterizations
in biological systems, polymer samples or functional materials. Currently, it is
extremely challenging for other methods to achieve the chemical sensitivity of IR
spectroscopy and allow for a similarly high degree in experimental flexibility in
characterizing ultrafast dynamics and intermolecular interactions with high spatial
resolution. In the same context, one important application of 2D IR spectroscopy
has still to be tackled, that is, scattering scanning near-field optical microscopy (sSNOM) 2D IR as the combination of sub-100 fs temporal resolution and sub-50 nm
spatial resolution in a single experiment. Although recent reports aiming in this
direction appear very promising [373, 374, 393–395], the realization of 2D IR
s-SNOM will still require most likely quite some time. However, this variant will
allow the ultimate way to characterize intermolecular interactions and dynamics in
space and time and its impact can hardly be overrated.
Despite the impressive achievements and the tremendous current efforts
regarding further development of different forms of 2D IR spectroscopy, the
method is generally still considered as a specialized technique by many researcher
outside the field. In other words, 2D IR has not yet been fully established as a
standard analytical tool for characterizing molecular structure, dynamics and
intermolecular interactions. An important reason for this is the often comparatively
short vibrational lifetimes (pico- to nanoseconds), which intrinsically limit the
temporal observation window. Additionally, 2D IR spectra from a large range of
vibrational modes contain often only weak or even absent cross peaks, which are
due to vibrational coupling or energy transfer. These missing cross peaks are
particularly of importance in case of through-space, intermolecular interactions. In
general, such interactions are very short-ranged, often only reaching to distances
less than a nanometer. Although this is typically also the distance on which 2D
NMR experiments reveal structural information about the sample, the strongly
nonlinear dependence of dipolar interactions on the (often weak) transition dipole
moments complicates the exploitation of intermolecular coupling in IR studies.
Finally, performing day-to-day experiments as well as detailed data interpretation
often still requires skilled spectroscopists and costly laboratory equipment. In this
regard, important developments currently focus on facilitated and automated data
acquisition for 2D IR. Progress in this direction will allow a more widespread
application of the method and possibly the day-to-day use for a variety of disciplines
in life sciences.
Acknowledgements I would like to thank Peter Hamm for many valuable discussions, the productive
research atmosphere as well as his continuous and generous support.
Top Curr Chem (Z) (2017) 375:86
123
188
Reprinted from the journal