ISSN 0018-1439, High Energy Chemistry, 2018, Vol. 52, No. 3, pp. 240–248. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © I.R. Mardaleishvili, G.V. Lyubimova, L.S. Kol’tsova, A.I. Shienok, P.P. Levin, A.S. Tatikolov, N.L. Zaichenko, 2018, published in Khimiya Vysokikh
Energii, 2018, Vol. 52, No. 3, pp. 219–225.
Effect of Substituents on Luminescence of New
I. R. Mardaleishvili
*, G. V. Lyubimova
, L. S. Kol’tsova
, A. I. Shienok
, P. P. L e v i n
A. S. Tatikolov
, and N. L. Zaichenko
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334 Russia
Received October 26, 2017
Abstract⎯The effect of OMe and NO
substituents in the phenol ring of hydroxytetraphenylimidazole
(HTPI) derivatives on their luminescence in solutions and in the solid phase has been studied. The presence
of the nitro group leads to multiple luminescence. In addition to the band of the photoproduct of intramo-
lecular proton transfer, which is single for unsubstituted HTPI, nitrosubstituted imidazoles additionally have
emission bands at shorter and longer wavelengths. The ratio between the bands depends on the solvent, con-
centration, and excitation wavelength. In solutions and polymer media, it is possible to switch luminescence
by changing the excitation wavelength, and under certain conditions, white light emission is observed.
Keywords: hydroxytetraphenylimidazole, multiple luminescence, intramolecular proton transfer
The aim of this work was to synthesize and to study
molecules that exhibit multiple luminescence, to cre-
ate in future polymeric materials with different lumi-
nescence regulated by changing the wavelength of
exciting light, or luminescing with white light.
Compounds capable of excited state intramolecu-
lar proton transfer (ESIPT) were the first examples of
substances demonstrating multiple (double) lumines-
cence [1, 2]. On the basis of such compounds (benzox-
azoles, thiazoles, azomethines), structures with sev-
eral luminescence bands in a wide spectral range were
created by varying substituents [3–10] or combining
several fluorescent centers [1, 2, 11–14]. The standard
method for obtaining white light luminescence is to
create systems based on three primary colors: red,
green, and blue, which provides covering the entire
range of visible light from 400 to 700 nm, or to com-
bine two complementary colors. Upon creation of sys-
tems with controlled switchable luminescence, it is
important to achieve high separation of the emission
bands. Hence, one of the problems in the synthesis of
new luminescent compounds with multiple lumines-
cence is the need to ensure the maximum red shift of
the longer-wavelength emission band observed.
In this work, we studied luminescence of new
hydroxyimidazole derivatives with possible ESIPT.
We supposed to achieve the bathochromic shift of the
luminescence emission bands by introducing substitu-
ents in the aryl rings of arylimidazoles. In , com-
pounds I–IV were synthesized on the basis of
hydroxytetraphenylimidazole, with the electron-
donating and withdrawing substituents OMe and
, respectively, on the phenol ring and the OMe
donor group on the 4,5-aryl rings. The presence of a
linker in these compounds is necessary for further
combination into more complex molecules, whose
structure is, for example, a combination of com-
pounds I and III.
We studied the spectral and luminescent properties
of compounds I–IV in the crystalline state, solvents of
different polarity, and polymer films of poly(methyl
methacrylate) (PMMA), polyvinyl butyral (PVB),
ethyl cellulose, and polymer matrices obtained by
photopolymerization of oligomers based on acrylate.
The synthesis of I–IV is reported in .
To prepare solutions of the compounds studied,
organic solvents of spectroscopic grade (Acros) were
used. The absorption spectra of the solutions were
measured on a MultiSpec-1501 spectrophotometer.
Luminescence measurements were performed on a
PerkinElmer LS 55 spectrofluorimeter. PMMA and
PVB polymeric films 10–100 μm thick doped with the
studied compounds with concentrations of 5 × 10
5 × 10
were prepared by coating of co-solu-
tions of the polymers and the luminophores in methy-
lene chloride and methanol, respectively. Samples of
copolymers based on acrylate with concentrations of