Phosphorescence of hydrogen-capped polyenes in solid neon at 20 K
T. Wakabayashi,1 K. Ozaki,1 R. Sata,1 H. Suzuki,1 Y. Morisawa,1 and U. Szczepaniak2
Department of Chemistry, School of Science and Engineering, Kindai University, Japan
2Institute of Physical Chemistry, Polish Academy of Sciences, Poland

1

Linear carbon chain molecules are highly reactive and thought to be reaction intermediates
converted to carbon nanostructures such as fullerenes, nanotubes, and graphene.
Terminated by hydrogen or chemically inert moieties such as a cyano-group, the carbon
chain molecules acquire intrinsic stability to be isolated in solutions at ambient temperature.
We have developed a method to produce, isolate, and concentrate in solutions a series ofhydrogen-end-capped molecules, namely polyynes H(C≡C)nH (n = 4-8), to characterizethem by UV absorption, IR absorption [1], and resonance Raman spectroscopy [2].
Formation mechanism of cyanopolyynes, H(C≡C)nC≡N (n = 3-6), was also investigated by
NMR spectroscopy using 13C isotope-enriched samples [3]. Recently, phosphorescence
spectra were reported for cyanopolyynes through HC5N to HC9N in solid rare-gas matrices[4-6]. In the present work, size-separated polyynes were co-condensed with the solvent
molecules of hexane at 20 K in vacuum and subjected to phosphorescence spectroscopy.

Figure 1: Phosphorescence spectrum of C8H2 in solid hexane at 20 K. Peaks in vibrational progression of
the symmetric stretching 2 mode of the sp-carbon chain (~2190 cm-1) are conspicuous at 532, 603, 694,
815, and 988 nm for 0- bands ( = 0-4). Inset shows phosphorescence lifetime of ~31.0 ms for the a3u+→ X1g+ transition of C8H2 at 20 K.

References
1.
2.
3.
4.
5.

[1] Y. Wada et al. Chem. Phys. Lett. 541, 54-59, (2012).
[2] T. Wakabayashi et al. Chem. Phys. Lett. 433, 296-300, (2007).
[3] T. Wakabayashi et al. Carbon 50, 47-56, (2012).
[4] M. Turowski et al. J. Chem. Phys. 133, 074310 (2010).
[5] I. Couturier-Tamburelli et al. J. Chem. Phys. 140 (2014) 044329.
6. [6] U. Szczepaniak et al. J. Phys. Chem. A 121, 7374 (2017).

Phosphorescence of Size-Selective Polyynes at 20 K
T. Wakabayashi1, K. Ozaki1, R. Sata1, H. Suzuki1, Y. Morisawa1, U. Szczepaniak2
1
2

Department of Chemistry, Kindai University, Japan

Institute of Physical Chemistry, Polish Academy of Sciences, Poland
wakaba@chem.kindai.ac.jp

Linear carbon chain molecules are highly reactive thus thought as reaction intermediates whoseaggregates are converted to carbon nanostructures such as fullerenes, nanotubes, and graphene.
Terminated by hydrogen or chemically inert moieties such as a cyano-group, the carbon chain
molecules acquire intrinsic stability to be isolated in solutions at ambient temperature. We havedeveloped a method to produce, isolate, and concentrate in solutions a series of hydrogen-endcapped molecules, namely polyynes H(C≡C)nH (n = 4-8), to characterize them by UV
absorption, IR absorption [1], and resonance Raman spectroscopy [2]. Formation mechanismof cyanopolyynes, H(C≡C)nC≡N (n = 3-6), was investigated by NMR spectroscopy using 13C
isotope-enriched samples [3]. Recently, phosphorescence spectra were reported forcyanopolyynes through HC5N to HC9N in solid rare-gas matrices [4-6]. In the present work,size-separated polyynes and cyanopolyynes were co-condensed with the solvent molecules at
20 K in vacuum and subjected to phosphorescence spectroscopy.
0-00-1

Intensity=3C8H2

1.0msec

Excitation @231 nm
Detection @603 nm

0.00
0-2

0.02

0.04
Time / sec

0.06

0.08

Excitation @231.8 nm
0-3600700
800
Wavelength / nm

0-49001000

Figure 1: Phosphorescence spectrum of C8H2 in solid hexane at 20 K. Vibrational progression
at 532, 603, 694, 815, and 988 nm is conspicuous for the 0-n bands (n = 0-4) of the symmetricstretching n2 mode of the sp-carbon chain (~2190 cm-1). Inset shows phosphorescence lifetimeof ~30 ms for the a3Su+ → X1Sg+ transition of C8H2 at 20 K.
[1] Y. Wada, Y. Morisawa, T. Wakabayashi, Chem. Phys. Lett. 541, 54-59, (2012).
[2] T. Wakabayashi, H. Tabata, T. Doi, H. Nagayama, K. Okuda, R. Umeda, I. Hisaki, M. Sonoda, Y.
Tobe, T. Minematsu, K. Hashimoto, S. Hayashi, Chem. Phys. Lett. 433, 296-300, (2007).
[3] T. Wakabayashi, M. Saikawa, Y. Wada, T. Minematsu, Carbon 50, 47-56, (2012).
[4] M. Turowski, C. Crépin, M. Gronowski, J.-C. Guillemin, A. Coupeaud, I. Couturier-Tamburelli, N.
Pietri, R. Kołos, J. Chem. Phys. 133, 074310 (2010).
[5] I. Couturier-Tamburelli, N. Piétri, C. Crépin, M. Turowski, J.-C. Guillemin, R. Kołos, J. Chem. Phys.
140 (2014) 044329.
[6] U. Szczepaniak, R. Kołos, M. Gronowski, M. Chevalier, J.-C. Guillemin, M. Turowski, T. Custer, C.
Crépin, J. Phys. Chem. A 121, 7374 (2017).