catena-Poly[bis(4-aminopyridinium) [[diaquamanganese(II)]-di-μ-chlorido] dichloride]

Single crystals of the title organic–inorganic hybrid, {(C5H7N2)2[MnCl2(H2O)2]Cl2}n, were synthesized from an ethanol solution containing manganese(II) chloride tetrahydrate and 4-aminopyridine under acidic conditions. The asymmetric unit contains a disordered organic cation (occupancies in the ratio 0.72:0.28), a chloride anion and an MnCl(H2O) moiety with the MnII atom located on an inversion center. The structure is built up of infinite chains of edge-sharing [MnCl4(H2O)2] octahedra developing parallel to the a axis which are separated by the 4-aminopyridinium ions and discrete chloride ions. The organic cations occupy the empty space around each inorganic chain. Structural cohesion is organized through N—H⋯Cl and O—H⋯Cl hydrogen bonds, which build up a three-dimensional network.


Experimental
Crystal data (C 5

S1. Comment
Studies of organic-inorganic hybrid compounds continue to be a focus area in chemistry and material science because they combine properties of organic and inorganic compounds within one single molecular scale, such as second order nonlinear optical (NLO) response, magnetism, luminescence, and even multifunctional properties (Mitzi et al. (2001); Lacroix et al. (1994)).
This kind of materials, generally expressed as (R-NH 3 ) 2 -MX 4 or (NH 3 -R-NH 3 ) MX 4 (where R: organic group, M: divalent metal and X: halogen) can be regarded as semiconductor/insulator multiple quantum well system consisting of metal halide semiconductor layers sandwiched between organic ammonium insulator layers (Calabrese et al. (1991); Hong et al. (1992). In this paper, we report the synthesis and single-crystal X-ray diffraction studies of the organic-  Table 1). It is worthy to note that the second kind of hydrogene bonds are stronger than the first one.
The [C 5 H 8 N 2 ] + cations is disordered over two positions which are rotated with respect to each other by about 141°. Thus, the amine group of one component lies close to the carbon atom C1 of the other component so that both components are more or less coplanar one to another (Fig. 3).
The distances and angles througout the structure are in good agreement with those encountered in several compounds of literature (Zeng et al. (2008); Hachuła et al. (2009)).

S2. Experimental
An aqueous HCl (1M) solution, 4-aminopyridine (C 5 H 6 N 2 ) and manganese dichloride tetrahydrate (MnCl 2 .4H 2 O) in a 2:1:1 molar ratio were mixed and dissolved in sufficient ethanol. Crystal for X-Ray diffraction structural analysis were grown by slow evaporation at room temperature and then set aside for few days to obtain colourless crystals.

S3. Refinement
All H atoms attached to C atoms and N atom were fixed geometrically and treated as riding with C-H = 0.93 Å and N-H = 0.86 Å with U iso (H) = 1.2U eq (C or N). H atoms of water molecule were located in difference Fourier maps and included in the subsequent refinement using restraints (O-H= 0.82 (1)Å and H···.H= 1.39 (2) Å) with U iso (H) = 1.5U eq (O). In the last stage of refinement, they were treated as as riding on the O atom.
The organic cation is disordered over two positions twisted to each other by about 141° around an axis perpendicular to their mean planes. The two components were refined using the tools available in SHELXL97 (Sheldrick, 2008): PART, SAME and EADP. In the first step of refinement the occupancy factor for each domain has been determined to be in the ration 0.72/0.28 by using the FREE variable option.

Special details
Experimental. 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^ > 2sigma(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. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.