Crystal structure of N,N'-bis-(pyridin-4-ylmeth-yl)cyclo-hexane-1,4-di-ammonium dichloride dihydrate.

Treatment of N,N-bis-(pyridin-4-ylmeth-yl)cyclo-hexane-1,4-di-amine with hydro-chloric acid in ethanol led to the formation of the title salt, C18H26N42+·2Cl-·2H2O, which lies about a crystallographic inversion center at the center of the cyclo-hexyl ring. The asymmetric unit therefore comprises one half of the N,N-bis-(pyridin-4-ylmeth-yl)cyclo-hexane-1,4-di-ammonium dication, a chloride anion, and a solvent water mol-ecule. In the dication, the two trans-(4-pyridine)-CH2-NH2- moieties occupy equatorial sites at the 1- and 4-positions of the central cyclo-hexyl ring, which is in a chair conformation. The terminal pyridine ring is tilted by 27.98 (5)° with respect to the mean plane of the central cyclo-hexyl moiety (r.m.s. deviation = 0.2379 Å). In the crystal, dications, anions, and solvent water mol-ecules are connected via N/C/O-H⋯Cl and N-H⋯O hydrogen bonds together with C-H⋯π inter-actions, forming a three-dimensional network.

Chemical context

An enormous number of metal–organic frameworks (MOFs) have been developed over the last two decades because of their attractive topologies and their desirable applications in a wide range of fields (Silva et al., 2015 ▸; Furukawa et al., 2014 ▸). For the development of these MOFs, many chemists have designed and prepared various dipyridyl-type ligands (Robin & Fromm, 2006 ▸; Robson, 2008 ▸; Leong & Vittal, 2011 ▸). Our group has also focused on the search for extended dipyridyl-type ligands with a bulky central section for the development of MOFs with intriguing topologies or useful properties. As a part of our ongoing efforts, we prepared just such a dipyridyl-type ligand with a central cyclo­hexyl moiety, namely N,N-bis­(pyridin-4-ylmeth­yl)cyclo­hexane-1,4-di­amine, synthesized by a condensation reaction between 1,4-cyclo­hexa­nedi­amine and 4-pyridine­carboxaldehyde according to a literature procedure (Huh & Lee, 2007 ▸). Herein we report on the crystal structure of the title salt obtained by the protonation of both amine groups in this mol­ecule.

Structural commentary

The asymmetric unit of the centrosymmetric title salt, C18H26N4 2+.2Cl−.2H2O, comprises one half of N,N-bis­(pyridin-4-ylmeth­yl)cyclo­hexane-1,4-di­ammonium dication, a chloride anion and a solvent water mol­ecule (Fig. 1 ▸) due to the crystallographic inversion center located at the center of the cyclo­hexyl ring. The central cyclo­hexyl moiety of the dication adopts a chair conformation. The two trans-(4-pyridine)–CH2–NH2– moieties at the 1- and 4-positions of the central cyclo­hexyl ring occupy equatorial positions. The terminal pyridine ring is tilted by 27.98 (5)° with respect to the mean plane through the central cyclo­hexyl moiety (r.m.s. deviation = 0.2379 Å). The distance between the two terminal pyridine nitro­gen atoms in the dication is 15.864 (2) Å. This is slightly shorter than the N⋯N separation [15.970 (3) Å] in the dication ligand of a one-dimensional zigzag-like CoII coordination polymer built up from alternate CoII ions and the dication of the title salt (Lee & Lee, 2010 ▸).

Figure 1

A view of the mol­ecular structure of the title salt with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and yellow dashed lines represent the inter­molecular N—H⋯O and N—H⋯Cl hydrogen bonds. [Symmetry code: (i) −x + 1, −y + 1, −z + 2.]

Supra­molecular features

In the crystal, adjacent dications are linked by weak C—H⋯π inter­actions, Table 1 ▸ (light-blue dashed lines in Figs. 2 ▸ and 3 ▸), resulting in the formation of a two-dimensional undulating layer-like structure extending parallel to the bc plane. The undulating layer is further stabilized by N—H⋯O/Cl and C—H⋯Cl hydrogen bonds (yellow dashed lines in Fig. 2 ▸) between the dications and the solvent water mol­ecules/chloride anions, respectively. Furthermore, neighboring undulating layers are connected through O—H⋯N hydrogen bonds (black dashed lines in Fig. 3 ▸) between the solvent water mol­ecules and the pyridine nitro­gen atoms, forming a three-dimensional supra­molecular network. In addition, O—H⋯Cl hydrogen bonds (Fig. 1 ▸ and Table 1 ▸) between the solvent water mol­ecules and the chloride anions are also found in the crystal.

Table 1

Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the N2/C5–C9 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1NA⋯O1W	0.878 (18)	1.881 (18)	2.7456 (15)	168.1 (16)
N1—H1NB⋯Cl1	0.952 (17)	2.167 (18)	3.1166 (11)	174.8 (13)
C4—H4A⋯Cl1i	0.99	2.64	3.6133 (13)	168
C4—H4B⋯Cl1ii	0.99	2.64	3.5788 (13)	158
O1W—H1WA⋯Cl1iii	0.78 (2)	2.37 (2)	3.1444 (11)	170.8 (18)
O1W—H1WB⋯N2iv	0.86 (2)	1.99 (2)	2.8242 (15)	161 (2)
C8—H8⋯Cg1v	0.95	2.74	3.3882 (15)	126

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

Figure 2

The two-dimensional undulating layer formed through inter­molecular C—H⋯π inter­actions (light-blue dashed lines) and N—H⋯O/Cl and C—H⋯Cl hydrogen bonds (yellow dashed lines). H atoms not involved in inter­molecular inter­actions have been omitted for clarity.

Figure 3

The three-dimensional supra­molecular network formed through inter­molecular N—H⋯O hydrogen bonds (black dashed lines). Inter­molecular C—H⋯π inter­actions, and N—H⋯O/Cl and C—H⋯Cl hydrogen bonds within the two-dimensional undulating layer are shown as light-blue and yellow dashed lines, respectively. H atoms not involved in inter­molecular inter­actions have been omitted for clarity.

Synthesis and crystallization

2 M hydro­chloric acid in ethanol was added to an ethanol solution of N,N-bis­(pyridin-4-yl­methyl­ene)cyclo­hexane-1,4-di­amine, synthesized according to a literature method (Huh & Lee, 2007 ▸), until pH = 4-5. The resulting mixture was left to evaporate slowly over several days, resulting in the formation of X-ray quality single crystals of the title salt.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. All C-bound H atoms were positioned geometrically with d(C–H) = 0.95 Å for Csp 2—H, 0.99 Å for methyl­ene, 1.00 Å for methine H atoms, and were refined as riding with U iso(H) = 1.2U eq(C). The N- and O-bound H atoms involved in hydrogen bonding were located in difference Fourier maps and refined freely [N—H = 0.878 (18) and 0.952 (17) Å; O—H = 0.78 (2) and 0.86 (2) Å].

Table 2

Experimental details

Crystal data
Chemical formula	C18H26N4 2+·2Cl−·2H2O
M r	405.36
Crystal system, space group	Monoclinic, P21/c
Temperature (K)	173
a, b, c (Å)	8.2739 (2), 17.4955 (5), 7.2365 (2)
β (°)	108.756 (1)
V (Å3)	991.90 (5)
Z	2
Radiation type	Mo Kα
μ (mm−1)	0.35
Crystal size (mm)	0.45 × 0.38 × 0.28
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker 2013 ▸)
T min, T max	0.663, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	9616, 2475, 2199
R int	0.026
(sin θ/λ)max (Å−1)	0.669
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.034, 0.088, 1.04
No. of reflections	2475
No. of parameters	134
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.33, −0.28

Computer programs: APEX2 and SAINT (Bruker, 2013 ▸), SHELXS97 and SHELXTL (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and DIAMOND (Brandenburg, 2010 ▸).

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S2056989016014626/sj5507sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989016014626/sj5507Isup2.hkl

CCDC reference: 1504428

Additional supporting information: crystallographic information; 3D view; checkCIF report

C18H26N42+·2(Cl−)·2H2O	F(000) = 432
Mr = 405.36	Dx = 1.357 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.2739 (2) Å	Cell parameters from 4837 reflections
b = 17.4955 (5) Å	θ = 2.6–28.3°
c = 7.2365 (2) Å	µ = 0.35 mm−1
β = 108.756 (1)°	T = 173 K
V = 991.90 (5) Å3	Block, colourless
Z = 2	0.45 × 0.38 × 0.28 mm

Bruker APEXII CCD diffractometer	2199 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.026
Absorption correction: multi-scan (SADABS; Bruker 2013)	θmax = 28.4°, θmin = 2.6°
Tmin = 0.663, Tmax = 0.746	h = −10→11
9616 measured reflections	k = −23→18
2475 independent reflections	l = −7→9

Refinement on F2	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.034	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.088	w = 1/[σ2(Fo2) + (0.0443P)2 + 0.3432P] where P = (Fo2 + 2Fc2)/3
S = 1.04	(Δ/σ)max < 0.001
2475 reflections	Δρmax = 0.33 e Å−3
134 parameters	Δρmin = −0.28 e Å−3

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq
Cl1	0.16235 (4)	0.40135 (2)	1.27614 (5)	0.02515 (11)
N1	0.21335 (12)	0.39798 (6)	0.86785 (16)	0.0163 (2)
H1NA	0.243 (2)	0.3529 (10)	0.836 (2)	0.029 (4)*
H1NB	0.198 (2)	0.3956 (9)	0.993 (3)	0.027 (4)*
N2	−0.38725 (13)	0.28164 (7)	0.67407 (17)	0.0249 (3)
C1	0.48104 (14)	0.58254 (7)	0.96734 (19)	0.0195 (3)
H1A	0.5016	0.5882	0.8406	0.023*
H1B	0.4582	0.6339	1.0105	0.023*
C2	0.32520 (14)	0.53131 (7)	0.94108 (19)	0.0193 (3)
H2A	0.2981	0.5292	1.0647	0.023*
H2B	0.2254	0.5530	0.8390	0.023*
C3	0.36023 (14)	0.45089 (7)	0.88272 (17)	0.0162 (2)
H3	0.3791	0.4532	0.7531	0.019*
C4	0.05169 (14)	0.42138 (7)	0.71776 (18)	0.0195 (3)
H4A	0.0688	0.4217	0.5885	0.023*
H4B	0.0233	0.4741	0.7460	0.023*
C5	−0.09626 (14)	0.36983 (7)	0.70865 (17)	0.0172 (2)
C6	−0.25944 (15)	0.39624 (7)	0.60508 (18)	0.0202 (3)
H6	−0.2743	0.4451	0.5446	0.024*
C7	−0.39921 (15)	0.35070 (8)	0.59139 (19)	0.0228 (3)
H7	−0.5094	0.3694	0.5196	0.027*
C8	−0.23028 (16)	0.25662 (8)	0.7712 (2)	0.0259 (3)
H8	−0.2191	0.2073	0.8291	0.031*
C9	−0.08246 (15)	0.29821 (8)	0.79263 (19)	0.0221 (3)
H9	0.0261	0.2778	0.8638	0.027*
O1W	0.28682 (13)	0.26372 (6)	0.71524 (16)	0.0265 (2)
H1WA	0.263 (2)	0.2234 (13)	0.743 (3)	0.043 (6)*
H1WB	0.388 (3)	0.2576 (12)	0.707 (3)	0.056 (6)*

	U11	U22	U33	U12	U13	U23
Cl1	0.02915 (18)	0.02300 (19)	0.02559 (18)	0.00706 (12)	0.01200 (13)	0.00199 (12)
N1	0.0129 (4)	0.0159 (5)	0.0193 (5)	−0.0018 (4)	0.0040 (4)	−0.0008 (4)
N2	0.0176 (5)	0.0311 (6)	0.0261 (6)	−0.0060 (4)	0.0073 (4)	−0.0029 (5)
C1	0.0153 (5)	0.0144 (6)	0.0260 (6)	−0.0004 (4)	0.0027 (5)	−0.0002 (5)
C2	0.0131 (5)	0.0156 (6)	0.0275 (6)	0.0000 (4)	0.0042 (4)	−0.0017 (5)
C3	0.0129 (5)	0.0158 (6)	0.0197 (6)	−0.0025 (4)	0.0049 (4)	−0.0009 (4)
C4	0.0137 (5)	0.0208 (6)	0.0214 (6)	−0.0016 (4)	0.0021 (4)	0.0027 (5)
C5	0.0154 (5)	0.0204 (6)	0.0161 (5)	−0.0022 (4)	0.0052 (4)	−0.0044 (5)
C6	0.0186 (6)	0.0201 (6)	0.0202 (6)	0.0007 (5)	0.0040 (4)	−0.0024 (5)
C7	0.0147 (5)	0.0288 (7)	0.0237 (6)	0.0005 (5)	0.0044 (4)	−0.0051 (5)
C8	0.0226 (6)	0.0269 (7)	0.0272 (7)	−0.0053 (5)	0.0068 (5)	0.0041 (5)
C9	0.0158 (5)	0.0251 (7)	0.0234 (6)	−0.0015 (5)	0.0034 (5)	0.0030 (5)
O1W	0.0232 (5)	0.0182 (5)	0.0418 (6)	−0.0017 (4)	0.0155 (4)	0.0001 (4)

N1—C4	1.4839 (15)	C3—H3	1.0000
N1—C3	1.5037 (14)	C4—C5	1.5047 (16)
N1—H1NA	0.878 (18)	C4—H4A	0.9900
N1—H1NB	0.952 (17)	C4—H4B	0.9900
N2—C8	1.3361 (17)	C5—C9	1.3812 (18)
N2—C7	1.3378 (18)	C5—C6	1.3955 (16)
C1—C3i	1.5257 (16)	C6—C7	1.3814 (17)
C1—C2	1.5311 (16)	C6—H6	0.9500
C1—H1A	0.9900	C7—H7	0.9500
C1—H1B	0.9900	C8—C9	1.3883 (17)
C2—C3	1.5234 (17)	C8—H8	0.9500
C2—H2A	0.9900	C9—H9	0.9500
C2—H2B	0.9900	O1W—H1WA	0.78 (2)
C3—C1i	1.5257 (16)	O1W—H1WB	0.86 (2)
C4—N1—C3	113.58 (9)	C1i—C3—H3	108.9
C4—N1—H1NA	108.5 (11)	N1—C4—C5	113.32 (10)
C3—N1—H1NA	106.7 (11)	N1—C4—H4A	108.9
C4—N1—H1NB	110.1 (10)	C5—C4—H4A	108.9
C3—N1—H1NB	108.0 (10)	N1—C4—H4B	108.9
H1NA—N1—H1NB	109.9 (14)	C5—C4—H4B	108.9
C8—N2—C7	116.79 (11)	H4A—C4—H4B	107.7
C3i—C1—C2	111.21 (10)	C9—C5—C6	117.74 (11)
C3i—C1—H1A	109.4	C9—C5—C4	124.99 (11)
C2—C1—H1A	109.4	C6—C5—C4	117.26 (11)
C3i—C1—H1B	109.4	C7—C6—C5	119.38 (12)
C2—C1—H1B	109.4	C7—C6—H6	120.3
H1A—C1—H1B	108.0	C5—C6—H6	120.3
C3—C2—C1	110.33 (9)	N2—C7—C6	123.30 (12)
C3—C2—H2A	109.6	N2—C7—H7	118.3
C1—C2—H2A	109.6	C6—C7—H7	118.3
C3—C2—H2B	109.6	N2—C8—C9	124.02 (13)
C1—C2—H2B	109.6	N2—C8—H8	118.0
H2A—C2—H2B	108.1	C9—C8—H8	118.0
N1—C3—C2	111.53 (9)	C5—C9—C8	118.76 (12)
N1—C3—C1i	107.82 (9)	C5—C9—H9	120.6
C2—C3—C1i	110.72 (10)	C8—C9—H9	120.6
N1—C3—H3	108.9	H1WA—O1W—H1WB	104 (2)
C2—C3—H3	108.9
C3i—C1—C2—C3	−56.73 (15)	C9—C5—C6—C7	0.35 (18)
C4—N1—C3—C2	61.58 (13)	C4—C5—C6—C7	179.52 (12)
C4—N1—C3—C1i	−176.66 (10)	C8—N2—C7—C6	−1.06 (19)
C1—C2—C3—N1	176.51 (10)	C5—C6—C7—N2	0.4 (2)
C1—C2—C3—C1i	56.44 (15)	C7—N2—C8—C9	1.0 (2)
C3—N1—C4—C5	−177.89 (10)	C6—C5—C9—C8	−0.41 (19)
N1—C4—C5—C9	−14.96 (18)	C4—C5—C9—C8	−179.51 (12)
N1—C4—C5—C6	165.94 (11)	N2—C8—C9—C5	−0.3 (2)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1NA···O1W	0.878 (18)	1.881 (18)	2.7456 (15)	168.1 (16)
N1—H1NB···Cl1	0.952 (17)	2.167 (18)	3.1166 (11)	174.8 (13)
C4—H4A···Cl1ii	0.99	2.64	3.6133 (13)	168
C4—H4B···Cl1iii	0.99	2.64	3.5788 (13)	158
O1W—H1WA···Cl1iv	0.78 (2)	2.37 (2)	3.1444 (11)	170.8 (18)
O1W—H1WB···N2v	0.86 (2)	1.99 (2)	2.8242 (15)	161 (2)
C8—H8···Cg1vi	0.95	2.74	3.3882 (15)	126