ИСТИНА

The correlation between chemical composition, crystal structure and physical properties in class of low-dimensional or layered compounds is one of the major problems of modern inorganic chemistry and material sciences. Ions with lone electron pairs, such as Se4+, Te4+, Sb3+, Bi3+, Pb2+ etc, enhance formation of low-dimensional or layered structures. On the other hand, the distorted coordination environments of these ions may increase probability of non-centrosymmetric structures forming. Non-centrosymmetric character of crystal structure is one of the necessary requirements to the occurrence of non-linear optical, pyro-, or ferroelectric properties. The trend to form low-dimensional structures may be enhanced by introducing halide ions or d-metals in the crystal structure. The d-metal cations in such structures may give rise to magnetic spin correlations in the substances. Based on these statements, we performed systematic search for such struc-tures among complex selenite halides. In the present work, we have arrived to conclusions concerning synthetic conditions, structural data and functional prop-erties for REE (Bi) and d-metals selenite halides: MSeO3Cl (M = REE, Bi); structurally related compounds of REEs and alkaline or alkaline earth elements MNd10(SeO3)12Cl8 (M=Ca, Sr), Cs7Pr11(SeO3)12Cl16, K7Sm11(SeO3)12Cl16, Cu3M(SeO3)2O2X (M = РЗЭ, Х = Cl, Br); alkaline earth elements – d-metals se-lenite halides: M3(SeO3)2Cl2 (M = Ca, Sr), Sr2M’(SeO3)2Cl2 (M’ = Co, Ni, Cu) and SrCu2(SeO3)2Cl2. Some correlations between chemical composition, crystal structure character, magnetic properties or ability to SHG will be discussed. The work was supported by Russian Foundation for Basic Research, RFBR project 09-03-00799-a