Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

The synthesized compounds ZWK-1, DWK-1, JWK-1 and ZWK-2, DWK-2, JWK-2 form a
glassy structure in the solid state from volatile organic solvents. The glass transition temperature
of almost all compounds is higher than 110ºC. Absorption maxima lie between 450 nm to 550
nm, depending on electron acceptor and electron donor groups in the compound structure. The
maximum of luminescence spectra is observed between 580 nm and 690 nm. In the case of twodonor
groups (ZWK-2, DWK-2, JWK-2) the luminescence spectra consist of two bands in solid
state compared to the solution. The second band is attributed to the excimer states. The
photoluminescence quantum yield in solution is up to 0.54. It drops one order of magnitude in
the solid state due to the closer intermolecular distance between molecules and probable
formation of a high density of dimers, which results in a strong excitonic interaction in the thin
solid films. Incorporation of bulky trityloxyethyl groups results in less aggregate formation of
the dye molecules in the polymer films compared to the same type of molecules without the
trityloxyethyl groups.
FLUORESCENCE AND AMPLIFIED SPONTANEOUS EMISSION OF GLASS
FORMING COMPOUNDS CONTAINING STYRYL-4H-PYRAN-4-YLIDENE
FRAGMENT
Aivars Vembris 1 , Inta Muzikante 1 , Renata Karpicz 2 , Gytis Sliauzys 2 , Arunas
Miasojedovas 3 , Saulius Jursenas 3 and Vidmantas Gulbinas 2
Potential of glassy films of newly synthesised low molecular weight organic molecules for light
amplification and lasing applications has been investigated by analysing fluorescence, transient
differential absorption and amplified spontaneous emission properties. These non-symmetric and
symmetric molecules contain styryl-4H-pyran-4-ylidene fragment with three different electron
acceptor groups: dicyanomethylene, barbituric acid, indene-1,3-dione. Fluorescence quantum
yields of the investigated compounds in solutions are between 0.32 and 0.54, while they drop
down by an order of magnitude in thin solid films. Incorporation of bulky side groups reduced
excitonic interactions enabling manifestation of amplified spontaneous emission in the neat films
of the investigated derivatives.
Figure 1. Styryl-4H-pyran-4-ylidene fragment
containing derivatives ZWK-1, ZWK-2,
JWK-1, JWK-2, DWK-1, DWK-2.
Figure 3. Absorption (thin solid line),
fluorescence (dashed line) and differential
absorption (thick solid line) spectra of all
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