Journal of Applied Spectroscopy, Vol. 87, No. 1, March, 2020 (Russian Original Vol. 87, No. 1, January–February, 2020) ELECTROOPTICAL EFFECT IN POLYMERIC COMPOSITES CONTAINING A HETEROMETALLIC Cu/V/Mo COMPLEX N. A. Davidenko, * V. N. Kokozay, S. L. Studzinsky, UDC 541.49 E. V. Mokrinskaya, H. I. Buvailo, and V. G. Makhankova The influence of an electric field on the transmission of linearly polarized light by polyvinylbutyral composite films doped with particles of the heterometallic complex (NH 4 ) 2 {[Cu(dien)(H 2 O)] 2 [α-V 2 Mo 6 O 26 ]}·5H 2 O (dien = diethylenetriamine) was studied. The absorption became anisotropic if an electrostatic field was applied during irradiation of the composites by linearly polarized light. The observed electrooptical effect was explained by photo-induced optical anisotropy that was caused by the linearly polarized light and changed in space due to reorientation of the dipole moment of photogenerated electron–hole pairs in the composite under the action of the external electric field. Keywords: heterometallic complex, composite films, d–d-transition, electrooptical effect, electrooptical media. Introduction. Polymeric composite films (PCFs) with complexes of transition metals in various spin states are capable of exhibiting photo- and electrophysical properties [1–3]. Therefore, they could be recommended for applications in photosensitive media or optoelectronics and molecular photonics [4–8]. Heterometallic compounds based on polyoxometallates are some of the most interesting classes of complexes and have valuable functional properties (e.g., catalytic [9, 10], sorption [11], magnetic [12], biological [13]). Also, the photophysical properties of this class of compounds are practically unstudied. Information on the ability to fabricate electrooptical light modulators from them is entirely lacking. Previously, the presence in a complex compound of electrically charged building blocks capable of changing their mutual orientation was shown by us to enhance the appearance of an electrooptical effect in a polymeric composite. The structures of heterometallic complexes (NH 4 ) 2 {[Cu(dien)(H 2 O)] 2 [α-V 2 Mo 6 O 26 ]}·5H 2 O (dien = diethylenetriamine) (HC) [14] and [Cu(en) 2 ][Mn 2 (C 2 O 4 ) 3 ]·6H 2 O (en = ethylenediamine) [15] were compared and shown to have similar cationic complexes [Cu(dien)(H 2 O)] 2+ and [Cu(en) 2 ] 2+ that acted as building blocks and made it probable that the compounds selected for the study would have an electrooptical effect. The goal of the present work was to study the effect of a constant external electric field on the transmission of monochromatic polarized light in polyvinylbutyral (PVB) PCFs doped with HC particles to observe possible electrooptical effects. Experimental. PCFs were prepared using PVB polymer with the required film-forming and optical properties. Experimental samples were constructed with a free surface, i.e., glass substrate–PCF and glass substrate–electrically conducting SnO 2 :In 2 O 3 layer–PCF. Samples were prepared by milling HC crystals and sieving. The HC concentration (particles < 10 3 nm) in the PCF with PVB was 50 mass%. PCFs were prepared by pouring PVB solution in CH 2 Cl 2 with added HC particles onto the corresponding substrates. The resulting PCFs were dried under vacuum in a drying cabinet at +80 o C for 1 d. The thickness of the obtained PCFs according to interference microscopy (MII-4) was L ≈ 2 μm. Absorption spectra and the quantity δI E = (I E – I 0 ), where I 0 and I E are intensities of monochromatic light passing through the sample before and after application of the external electric field, were measured for samples in the range λ = 350–900 nm. Both unpolarized and polarized light were used to irradiate the samples. In the latter instance, the sample was placed between two polarizers with a 90 o angle between the planes of polarization. The electric field strength Taras Shevchenko National University of Kyiv, Kyiv, 01601, Ukraine; email: ndav@univ.kiev.ua. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 87, No. 1, pp. 21–24, January–February, 2020. Original article submitted March 12, 2019. _____________________ * To whom correspondence should be addressed. 0021-9037/20/8701-0015 ©2020 Springer Science+Business Media, LLC 15 DOI 10.1007/s10812-020-00955-x