Crystal structure of dilithium biphenyl-4,4′-disulfonate dihydrate

The asymmetric unit of the title compound consists of an Li ion, half of the diphenyl-4,4-disulfonate ligand, and a water molecule. The Li ion exhibits a four-coordinate tetrahedral geometry with three oxygen atoms of the Bph(SO3 −)2 ligands and a water molecule. The tetrahedral LiO4 units, which are interconnected by biphenyl moieties, form a layer structure parallel to (100). These layers are further connected by hydrogen-bonding interactions to yield a three-dimensional network.


Chemical context
Coordination networks (CNs) are crystalline materials composed of infinite arrays of s-block metal ions, connected by organic linkers, forming chain, layer or 3-D networks.These materials offer several advantages such as being non-toxic, abundant on the planet, and cheap and provide good results when gravimetric methods are used (Banerjee & Parise 2011).Li-dicarboxylates may be good candidates as electrode materials for eco-friendly alternatives to other inorganic materials, and have been reported for use in battery applications (Armand et al., 2009;Ogihara et al., 2014Ogihara et al., , 2023;;Yasuda & Ogihara, 2014;Mikita et al., 2020).To improve our chemistry and electrode applications, we investigated CNs using disulfonate ligands.While the structures of dicarboxylate salts of alkali metals have been reported (Banerjee & Parise, 2011), the CNs of the disulfonates of alkali metals are still scarcely reported.Our present investigation focuses on the use of diphenyl-4,4 0 -disulfonic acid [Bph(SO 3 H) 2 ] as a structural building block in the synthesis of CNs.Here, we report a rare example of a crystal structure of a Li-disulfonate CN material.

Structural commentary
The title compound [Li 2 (Bph(SO 3 ) 2 )(H 2 O) 2 ] (Fig. 1) consists of two Li cations, two water molecules, and a diphenyl-4,4 0disulfonate [Bph(SO 3 À ) 2 ] ligand.Its asymmetric unit consists of an Li ion, half of the Bph(SO 3 À ) 2 ligand, and a water molecule.The key feature of the structure is a di-periodic layer structure in which the layers are built up by LiO 4 units bridged by Bph(SO 3 À ) 2 ligands (Fig. 2).The biphenyl groups of the ligands exhibit a planar and herringbone-type arrangement in the layer (Fig. 3).Two parallel biphenyl groups are stacked not in a face-to-face but rather in a paralleldisplaced fashion.The slippage of the layers is 4.43 A ˚and the nearest intermolecular centroid-to-centroid distance between adjacent parallel phenyl groups is 5.47 A ˚.The angle formed by the two centroids of the phenyl rings and the ring plane is 34.5 � .Intermolecular distances between the carbon atoms of the planar biphenyl moieties of 3.66 A ˚are indicative of some degree of �-� stacking interaction along the crystallographic b-axis direction.Similar herringbone-type stacking of aromatic organic moieties are found in Li-dicarboxylate CN materials in which herringbone-type stacking structures play an important role in electron mobilities and electrode performance (Ogihara et al., 2017;Ozawa et al., 2018).The Li cation exhibits a four-coordinate tetrahedral geometry formed by an oxygen atom of a coordinated water molecule and three oxygen atoms coming from three different Bph(SO 3 À ) 2 ligands.The tetrahedrons are connected to one another by O-S-O bridges of the disulfonate group, and the shortest Li� � �Li distance is 4.80 A ˚.All the oxygen atoms of a sulfonate group coordinate to different Li cations.Thus, each sulfonate group coordinates to three Li cations to obtain a di-periodic layer.The bond distances between the Li cation and the oxygen atoms lie in the range 1.901 (5)-1.944(5) A ˚at angles of 103.7 (2)-114.8(2) � , which are shorter than those of reported Na 2 -disulfonate [2.313 (3)-2.560(3) A ˚] and K 2 -disulfonate [2.657 (3)-3.079(4) A ˚] complexes (Albat & Stock 2016;Smith et al., 2007).Similar trends of bond distances are observed in alkali metal-carboxylate network materials (Banerjee & Parise, 2011).

Supramolecular features
The hydrogen atoms of the coordinated water molecules are oriented in such a direction exiting the di-periodic layers to form hydrogen-bonding interactions (Table 1).A hydrogen atom of the water molecule (H4) and an oxygen atom of the Bph(SO 3 À ) 2 ligand acts as a hydrogen-bond donor and a hydrogen-bond acceptor, respectively, resulting in a threedimensional hydrogen-bonding network (Fig. 2).Because of the hydrogen-bonding interaction, another hydrogen atom of the coordinated water molecule (H1) is directed towards the oxygen atom of the Bph(SO 3 À ) 2 ligand, where the distance between the oxygen atoms of 3.204 (3) A ˚is indicative of some degree of interaction.Li 2 -dicarboxylates where the dicarboxylate is terephthalate, biphenyl dicarboxylate or naphthalene dicarboxylate, also consist of LiO 4 layers (Banerjee & Parise 2011;Kaduk et al., 2000;Armand et al., 2009

sup-2
Acta Cryst.(2024).E80, 22-24 Refinement.Refinement was performed using all reflections.The weighted R-factor (wR) and goodness of fit (S) are based on F 2 .R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 sigma(F 2 ) is used only for calculating Rfactor (gt). Fractional

Table 2
Experimental details.
atomic coordinates and isotropic or equivalent isotropic displacement parameters(Å 2 )