*Article* **Crystal Chemical Relations in the Shchurovskyite Family: Synthesis and Crystal Structures of K2Cu[Cu3O]2(PO4)4 and K2.35Cu0.825[Cu3O]2(PO4)4**

**Ilya V. Kornyakov 1,2 and Sergey V. Krivovichev 1,3,\***


**Abstract:** Single crystals of two novel shchurovskyite-related compounds, K2Cu[Cu3O]2(PO4)4 (**1**) and K2.35Cu0.825[Cu3O]2(PO4)4 (**2**), were synthesized by crystallization from gaseous phase and structurally characterized using single-crystal X-ray diffraction analysis. The crystal structures of both compounds are based upon similar Cu-based layers, formed by rods of the [O2Cu6] dimers of oxocentered (OCu4) tetrahedra. The topologies of the layers show both similarities and differences from the shchurovskyite-type layers. The layers are connected in different fashions via additional Cu atoms located in the interlayer, in contrast to shchurovskyite, where the layers are linked by Ca2+ cations. The structures of the shchurovskyite family are characterized using information-based structural complexity measures, which demonstrate that the crystal structure of **1** is the simplest one, whereas that of **2** is the most complex in the family.

**Keywords:** shchurovskyite; synthesis; X-ray diffraction; crystal structure; oxocentered tetrahedra
