*3.2. Topological Analysis*

The anion topology of the U-S layer in **1** (Figure 2b) was determined using the approach described in [14]. It belonged to the 544132-I topological type according to the classification suggested in [15], and it has been observed in the structures of several synthetic uranyl sulfates [16,17], chromates [18], and phosphates [19]. Topology consisted of chains of pentagons, half of which were occupied by the *Ur* edge-sharing dimers, separated by the groups of one square and two triangles. Each triangle corresponded to the 3-connected face of the sulfate tetrahedra, while the squares were vacant. The orientation of non-shared vertex in the structure of **1** alternated by rows (Figure 2a): in the first row, all vertices were oriented *down*, in the second–*up*, then again *down*, etc. Thus, the geometric isomer represented in **1** was described by the (**u**)(**d**) matrix. It should be noted that the layered complex in the structure of **1** was very similar to those found in the structures of uranyl sulfate minerals as deliensite, Fe[(UO2)2(SO4)2(OH)2](H2O)7 [20], plášilite, Na(UO2)(SO4)(OH)·2H2O [21], and others [22]. But their topologies were significantly distinct due to various arrangements of the uranyl dimers within the layer. In the structure of **1**, dimers were stacked in a ladder fashion, while in the structures of aforementioned minerals, dimers were arranged parallel to each other, thus forming, typical for minerals, so-called phosphuranylite topology [23]. Differences between these topological isomers have been recently described in [17].

The crystal structure of **2** [8] was based on the layered complexes of the [(UO2)4(SO4)2O3(OH)]6<sup>−</sup> composition (Figure 2c,d). Its topology was described by the 524332 ring symbol and was related to one of the most common topological types among the natural uranyl sulfates [22], the so-called zippeite topology. Topology consisted of zig-zag infinite chains of edge-sharing pentagons separated by chains of squares and triangles.

The topology of the uranyl sulfate chain in the structure of **3** (Figure 2f) could be visualized using the theory of graphical representation [24]. Double links between the black and white vertices in a graph indicate the sharing of an edge between uranyl coordination polyhedra and sulfate oxyanion. The chain topology in **3** was unprecedented for the structural chemistry of inorganic oxysalts and belonged to the novel *cc*1-2:5-1 type.

The graph of the uranyl sulfate layered complex in the structure of **4** belonged to the *cc*2–1:2–21 topological type (Figure 2h) and consisted of dense 4-membered and large 12-membered rings. This topology is rather rare but has been observed in the structures of a few actinide-bearing compounds. It has been described at first in the structure of isotypic Cs neptunyl sulfate compound [25], and later in the structures of Ba uranyl selenite [26] and organically templated uranyl sulfate [27].
