1,12-Bis(2-carboxyphenyl)-5,8-dioxa-2,11-diazadodecane-2,11-diium dichloride methanol solvate

In the title salt hydrate, C22H30N2O6 2+·2Cl−·CH4O, the dication adopts a U-shaped conformation whereby the benzene rings are splayed out from the chain linking them. All components of the asymmetric unit are linked into a cohesive entity by a combination of O—H⋯Cl−, N+—H⋯Cl− and N+—H⋯O charge-assisted hydrogen-bonding interactions. The assemblies thus formed are linked into supramolecular helical chains along [010] via C—H⋯O contacts. The resulting chains are, in turn, consolidated into the three-dimensional crystal structure by C—H⋯π contacts.

In the title salt hydrate, C 22 H 30 N 2 O 6 2+ Á2Cl À ÁCH 4 O, the dication adopts a U-shaped conformation whereby the benzene rings are splayed out from the chain linking them. All components of the asymmetric unit are linked into a cohesive entity by a combination of O-HÁ Á ÁCl À , N + -HÁ Á ÁCl À and N + -HÁ Á ÁO charge-assisted hydrogen-bonding interactions. The assemblies thus formed are linked into supramolecular helical chains along [010] via C-HÁ Á ÁO contacts. The resulting chains are, in turn, consolidated into the three-dimensional crystal structure by C-HÁ Á Á contacts. 3 restraints H-atom parameters constrained Á max = 0.51 e Å À3 Á min = À0.34 e Å À3 Table 1 Hydrogen-bond geometry (Å , ).  Ghiladi et al., 1997;Kitagawa et al. 2004). Such ligands have also attracted attention in supramolecular and materials chemistry owing to their variety of structural topologies and potential applications in the rational design of metal-organic frameworks (Bradshaw et al., 2005). Motivated by the above, the title compound, (I), was prepared as part of a on-going study aimed at developing this chemistry.

Related literature
The crystallographic asymmetric unit of (I) comprises a 1,12-bis(2-carboxyphenyl)-5,8-dioxa-2,11-diazadodecane-2,11diium dianion, two chloride anions, and a methanol molecule of solvation, Fig. 1 The most prominent interactions linking the asymmetric units are of the type C-H···O, Table 1. These involve the solvent methanol molecule which in turn is connected to both the Cl1 anion and the carboxylic acid-O2 atom of a second cation. In this fashion a supramolecular helical chain is formed along [0 1 0], Fig. 3. Fig. 3 clearly illustrates the differences between the chlorides in that the Cl1anion forms three significant hydrogen bonding contacts and the Cl2atom only forms two. The supramolecular chains are consolidated into the crystal structure via C-H···π interactions, Fig.   4 and Table 1. These occur between methylene-C8-H8b and the ring centroid, Cg, of the C16-C21 ring so that H8b···Cg i = 2.88 Å, C8···Cg i = 3.6364 (16) Å with an angle of 134 ° subtended at the H8b atom, for symmetry operation i:

S2. Experimental
In a 200 ml round bottom flask, 2-carboxybenzaldehyde (4.0424 g, 0.027 mol) was dissolved in methanol (30 ml Single crystals were obtained by slow evaporation of an acidic (1M HCl) aqueous solution of (I).

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq