ИСТИНА

It is known that photo-initiated solid-state reactions affect the physical properties of coordination polymers, and are able to afford unusual architectures. However, the construction of new photosensitive coordination polymers requires an understanding of the factors that determine the relative position of the reactive fragments. The main method for understanding these factors is XRD analysis, which allows obtaining the positions of atoms before and after the reaction. We’ve used the X-ray diffraction analysis to study two zinc (II) malonate complexes with 1,2-di(pyridin-4-yl)ethylene and their response to UV-irradiation. The planes of N-containing ligands in discrete complexes [Zn(bpe)2(H2O)4]2+ in [Zn(H2O)4(bpe)2](HEt2Mal)2 are parallel, and the distance between equivalent atoms is sufficient for the photo-initiated reaction in a single crystal. After UV-irradiation the [2+2] cycloaddition reaction takes place with the formation of a chain coordination compound {[Zn(H2O)4(bpe)2]0.15[Zn(H2O)4(tpcb)]0.85(HEt2mal)4}n. Relative positions of bpe-ligands allow to obtain rctt-tetra(pyrid-4-yl)cyclobutane as a bridging ligand with a yield of 85% irrespective of the time of irradiation of the sample. Location of bpe ligands in [Zn(bpe)(Me2mal)]∙H2O is less effective for the [2+2] cycloaddition reaction (Fig. 1). As a result of irradiation on air, the complex lost water, which probably leads to a change in the mutual arrangement of molecules in the crystal and promotes the course of photo-initiated reaction. We achieved a maximum yield of 50%, so that the reaction product has the composition [Zn(bpe)(Me2Mal)]2[Zn2(tpcb)(Me2Mal)2]∙H2O and contains the rtct isomer of the bridged tetracoordinated tetra(pyrid-4-yl)cyclobutane. Thus, this reaction proceeds according to the type of 3D→3D with a change in the coordination polymer topology. This work was supported by the Russian Science Foundation (Grant No. 17-13-01442).