With the recent upsurge of interest in network structures, interpenetration has attracted considerable attention.1Although fascinating in its own right, interpenetration can present a problem in attempts to prepare porous materials as it inevitably leads to a reduction in pore size. There is, however, evidence that it can also impart a greater degree of stability to a metal–organic framework structure.2Although many of the interpenetrated structures that have been reported involve metal–organic frameworks, there are also examples involving hydrogen bonded networks.3–6The assembly of solid state structures through hydrogen bonds is an extremely topical area of chemistry.7In one of the best illustrations of crystal engineering, Ward and co-workers have shown that guanidinium cations and sulfonate anions assemble through hydrogen bonds into hexagonal sheets,8,9and by using disulfonates these sheets can be connected into three-dimensional arrays with predictable structures.10–12Guanidinium disulfonates have been used to achieve the shape-selective separation of molecular isomers13and second harmonic generation through the use of polar host frameworks.14We have been interested in introducing substituents onto the guanidinium cation to assess the effect the concomitant loss of hydrogen bond donors has on the supramolecular structure.15–18We found that typicallyN,N-dimethylguanidinium sulfonates form ribbons in the solid state in which cation–anion pairs, connected through a DD–AA interaction (graph set R22(8)) are linked into one-dimensional structures through further hydrogen bonds involving either R24(8) or R44(12) graph sets.In order to determine whether these conclusions extend to disulfonates, we have prepared and obtained crystal structures for the naphthalenedisulfonate compounds [C(NH2)2(NMe2)]2[1,5-C10H6(SO3)2]1Crystal data for1: C8H13N3O3S,M= 231.27, monoclinic, space groupP21/c,a= 11.8517(7),b= 10.8528(7),c= 9.1258(5) Å,β= 111.267(2)°,U= 1093.86(11) Å3,Z= 4,ρcalc= 1.404 g cm–3,µ= 0.288 mm–1,T= 150(2) K. Reflections collected 7222, independent reflections 3028 [Rint= 0.0399]. FinalRindices [I> 2σ(I)]:R1 = 0.0436,wR2 = 0.1078.and [C(NH2)2(NMe2)]2[2,6-C10H6(SO3)2]2Crystal data for2: C8H13N3O3S,M= 231.27, monoclinic, space groupP21/c,a= 7.2870(6),b= 19.4830(12),c= 14.679(2) Å,β= 94.837(5)°,U= 2076.6(4) Å3,Z= 8,ρcalc= 1.479 g cm–3,µ= 0.304 mm–1,T= 170(2) K. Reflections collected 36141, independent reflections 4724 [Rint= 0.1151]. FinalRindices [I> 2σ(I)]:R1 = 0.0517,wR2 = 0.1091.. The structures reveal that neither1nor2contains the anticipated hydrogen-bonded ribbons. Instead,1forms hydrogen-bonded sheets that are interlinked by the naphthalene groups into a three-dimensional array. In contrast, the structure of2contains interpenetrating two- and three-dimensional hydrogen-bonded networks.The asymmetric unit of1contains aN,N-dimethylguanidinium cation and one-half of a 1,5-naphthalenedisulfonate anion, the other half of which is generated by inversion symmetry. The cations and sulfonate groups form cation–anion pairs through the anticipated DD–AA interaction involving the unsubstituted cation face. These pairs are severely twisted, with an angle of 130° between the mean cation plane and the plane of the three sulfonate oxygen atoms. The cation–anion pairs are connected into sheets (Fig. 1a) by hydrogen bonds involving the two remaining NH groups. These sheets are interlinked by the naphthalene groups into a three-dimensional array (Fig. 1b).(a) Hydrogen bonded sheets in the structure of1. (b) Interlinking of the hydrogen-bonded sheets of1by the naphthalene groups into a three-dimensional network.The asymmetric unit of2contains two independent cations and two independent anion halves, the remainder of each being generated by inversion symmetry. There are two independent and structurally distinct, interpenetrating networks present in the crystal structure of2, one based on cations containing C(1) and anions containing S(1), and the other based on cations containing C(4) and anions containing S(2).The cations based on C(1) and sulfonate groups based on S(1) are connected into pairs by two hydrogen bonds involving the unsubstituted cation face, but in contrast to1these involve only one sulfonate oxygen atom, so generate the graph set R12(6). These cation–anion pairs are connected into sheets (Fig. 2a) by hydrogen bonds involving the two remaining NH groups, giving rings described by the graph set R66(20). These sheets are linked into a three-dimensional network through the naphthalene groups, which act as bridges between sulfonates (Fig. 2b). The sulfonate groups, when connected by either the naphthalene linker or O⋯H–N–H⋯O hydrogen bonds, define a 5-connected BN (bnn) network,19though there is distortion from trigonal bipyramidal towards square-pyramidal geometry about each node.(a) Hydrogen-bonded sheets in the structure of2. (b) Interlinking of the hydrogen-bonded sheets of2by the naphthalene groups into a three-dimensional network.The cation based on C(4) and sulfonate group based on S(2) form similar cation–anion pairs that contain the graph set R12(6) in contrast to R22(8), which was observed for1. These cation–anion pairs are interlinked through further N–H⋯O hydrogen bonds to form a one-dimensional network, in which rings described by the graph set R44(16) are present. The naphthalene groups connect these chains into sheets (Fig. 3) in which the sulfonate groups define a 4,4 net.One-dimensional hydrogen bonded chains in2interlinked by the naphthalene groups into a two-dimensional network.The three-dimensional network containing C(1) and S(1) interpenetrates with the two-dimensional network containing C(4) and S(2) as shown inFig. 4. This type of interpenetration is rare, with only a few reported examples involving metal–organic frameworks.20,21Compound2is, we believe, the first example involving strong hydrogen bonds, though interpenetration of a two-dimensional hexagonal network and a three-dimensional α-polonium network, both constructed from C–H⋯O interactions has recently been reported.22The gross structure of2consists of interpenetrated two- and