XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
112
T8: O–1
Intermolecular interactions studied using
vibrational circular dichroism
Joanna E. Rode
1
1
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw,
Poland, e-mail: jrode@icho.edu.pl
Chiroptical spectroscopy methods supported by the quantum mechanical calculations are
powerful tool in assignment of absolute configuration, monitoring structural changes in chiral
molecules with the change of environment, and studies of conformational analysis. The
chiroptical spectra appear as a difference in absorbance/scattering of the left and right circularly
polarized light. The choice of the best experimental method depends on the goal of the planned
studies, kind of studied molecules, environment etc. The Vibrational Circular Dichroism (VCD)
seems to be especially useful for studying intermolecular interactions in organic solvent
solutions and in solid states. Despite the fact that the VCD effect is a 1000 times weaker than the
parent IR spectroscopy, sometimes the VCD spectra are more selective and specific. Indeed, in
VCD spectra the influence on the band frequency can be accompanied by a significant intensity
change in which even the band sign can be inverted. Moreover, in VCD spectra it is possible to
study the chirality transfer (ChT) phenomenon. ChT appears a result of interaction of a chiral
molecule with an achiral one. In such a case, if the interaction is strong enough, the bands of the
achiral molecule become visible in the VCD spectra. It was demonstrated that ChT is a
promising tool for investigations of the intermolecular interactions in the hydrogen bonded (HB)
and electron-donor-acceptor (EDA) systems. It allows to distinguish between geometries of the
intermolecular complex and to indicate the interaction sites. The VCD ChT phenomenon was
studied in systems in which the dissolved chiral molecule interacted with an achiral solvent. In
such a case, the effect is induced by the solute. On the other hand, the ChT effect can also be
generated by a chiral solvent interacting with an achiral molecule. Such a situation was not
studied before. This approach brings new possibilities to monitor interactions and conformations
of achiral solutes using the VCD method. In the lecture, examples of various applications of
VCD to studies of intermolecular interactions in the solid state and in solutions will be shown.
They are supported by calculations of the ChT effect in those various situations.
Acknowledgment
This work was supported by the National Science Centre in Poland Grant No. UMO-2015/19/B/ST4/03759.
The Świerk Computing Centre and PL-Grid infrastructure are acknowledged for generous allotment of
computing time.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
113
T8: O–2
Optical-optical double resonance spectroscopy of CdAr van der Waals
dimers produced in pulsed supersonic molecular beam source
Tomasz Urbanczyk
1
, and Jaroslaw Koperski
1
1
Smoluchowski Institute of Physics, Jagiellonian University, ul. Łojasiewicza 11, 30-348 Krakow,
Poland, e-mail: tomek.urbanczyk@uj.edu.pl
In optical-optical double resonance (OODR) method, two laser beams are used to excite the
low-lying Rydberg state via the intermediate electronic state. We have used this method to
examine rotational energy structure of different vibrational components of the
E
3
Σ
+
(6
3
S
1
)←A
3
Π
0+
(5
3
P
1
) transition in CdAr van der Waals dimer produced in molecular beam
using a high temperature pulsed source [1].
We present how a change of wavelength and spectral bandwidth of the laser beam, which
excites the molecule to the intermediate level (A
3
Π
0+
←X
1
0
+
(5
1
S
0
)) can be used to excite only
selected isotopologues to the E
3
Σ
+
state. The presented method leads to simplification of the
observed laser induced fluorescence (LIF) excitation spectra (see Fig.1), which significantly
facilitates their analysis. Additionally, new ro-vibrational characteristics of the E
3
Σ
+
state of
CdAr will be presented.
19944
19946
19948
19950
19952
19954
L
IF
s
ig
n
a
l
[a
.u
.]
Laser wavenumber [cm
-1
]
a)
b)
Fig. 1. LIF excitation spectrum of the E
3
Σ
+
(υ′=1)←A
3
Π
0+
(υ″=5) transition in CdAr. (a) Experimental spectrum
encompassing signals originating from several isotopologues (including
116
Cd
40
Ar,
114
Cd
40
Ar and
112
Cd
40
Ar).
(b) Experimental spectrum encompassing signal for
116
Cd
40
Ar isotopologue only.
Keywords: CdAr vdW dimer, OODR method, molecular isotopic structure
Acknowledgment
This work was supported by the National Science Centre Poland under grant number UMO-
2015/17/B/ST4/04016.
References
[1] T. Urbanczyk, J. Koperski, Rev. Sci. Instrum. 83 (2012) 083114.
Dostları ilə paylaş: |