Redetermination of sperminium tetrachloride

In the title compound, 1,5,10,14-tetraazoniatetra­decane tetrachloride, C₁₀H₃₀N₄⁴⁺·4Cl⁻, the sperminium tetracation lies on a centre of symmetry. The two central C—N—C—C torsion angles are gauche and of opposite signs, and all the other torsion angles are trans. All NH groups participate in the three-dimensional hydrogen-bond network, which is additionally strengthened by C—H...Cl interactions.

S1. Comment

Spermine, along with putrescine and spermidine, are biologically important aliphatic biogenic polyamines that take part in the determination and stabilization of secondary and tertiary structures of nucleic acids. In biological systems, they exist as polycations that interact with nucleic-acid polyanions. The structures of the salts of these amines are therefore important in the modelling of nucleic acids. The crystal structure of sperminium tetrachloride was determined by Giglio et al. (1966), with 1500 visually estimated reflections collected by means of the Weissenberg method. The positions of the H atoms were calculated geometricaly, and the quality of the structure determination is - by today's standards - rather poor (R factor of 0.105, reported su. values of bond lengths of about 0.01 Å). Since spermine is important due to both its biological activity and its chelating properties, we performed a redetermination of the crystal structure of sperminium chloride, (I).

Giglio et al. (1966) described the structure in the standard space group P2₁/c, with a large β angle of 121.5 (2)°. We transformed this cell into the more convenient P2₁/n [transformation matrix (1 0 0 / 0 − 1 0 / −1 0 − 1)], with a β angle of 93.21 (1)°. Very good agreement between our unit-cell parameters and the results obtained almost 40 years ago by means of the precession photographs should be stressed; all differences are within 3σ.

The geometry of the centrosymmetric cation does not differ significantly from that described by Giglio et al. (1966). The conformation of the sperminium cation can be described as tttgtttgttt (where t denotes trans and g gauche) and is different from the all-trans conformation (ttttttttttt) found in the phosphate hexahydrate (Iitaka & Huse, 1966; Cohen et al., 1997) and in hydrogen sulfate dihydrate (Ilioudis et al. 2002). Still another type of conformation of this cation, gtttttttttg, was observed in tetranitrate, where the terminal N—C—C—C torsion angles are gauche [65.0 (4)°; Jaskólski, 1987]. In (I), the C4—N5—C6—C7 angle is 66.7 (2) °, and there are three approximately planar fragments in the cation, viz. N1/C2/C3/C4/N5/C6 and N5/C6/C7/C7'/C6'/N5'; the dihedral angle between the neighbouring planes is 63.22 (15)°.

Bond lengths and angles are typical. Because of the steric stress caused by the gauche conformation, the C4—N5—C6 and N5—C6—C7 bond angles are significantly wider than the perfect-tetrahedral values. Such widening was not observed in other sperminium salts.

The crystal packing is determined by N—H···Cl⁻ hydrogen bonds. All but one of the N/H groups act as hydrogen-bond donors for strong and directional bonds; the only exception is the N1/H12 group, which takes part in a bifurcated hydrogen bond in which the H···Cl distances are longer and the N—H···Cl angles are smaller than those in the other cases (Table 1). A number of secondary C—H···Cl hydrogen bonds also stabilize the crystal structure.

The crystal packing is complicated, as there are many different hydrogen bonds in the structure, but some general rules can be described. There are chains of molecules along [1–20], connected by bifurcated hydrogen bonds. These chains are connected via other cations into a two-dimensional grid by means of N5—H51···Cl1 and N1—H11···Cl1 hydrogen bonds (Fig. 1a). The second characteristic motif involves molecules connected by the [110] vector. These molecules are connected to one another by a system of eight hydrogen bonds involving four chloride anions (Fig. 1 b).

It might be also noted that the coordination around the two chloride anions is different. Atom Cl1 acts as an acceptor in four N—H···Cl hydrogen bonds (two strong and two weak), with approximately tetrahedral coordination. On the other hand, atom Cl2 accepts only two strong N—H···Cl hydrogen bonds, but the coordination of this anion is completed? by two relatively strong C4—H···Cl hydrogen bonds. The structure of (I) might therefore be regarded as another case in which C/H groups act as a substitute donor that mimics a stronger one (N/H in this case).

S2. Experimental

The title compound was obtained by slow diffusion of dioxane into the methanol solution of the spermine complex with lanthanum chloride.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2002); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. The two main packing motifs (Siemens, 1989) in (I). (a) The two-dimensional grid, as seen approximately along the [001] direction (b) A chain of molecules along the [110] direction, together with the labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are depicted as spheres of arbitrary radii. A prime denotes the symmetry operation 2 − x, 1 − y, 1 − z. [Additional symmetry code: (a) 1 − x,-y,1 − z.]

1,5,10,14-tetraazoniatetradecane tetrachloride

Crystal data

C10H30N4^4+·4Cl^−	F(000) = 372
Mr = 348.18	Dx = 1.314 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2927 reflections
a = 8.569 (1) Å	θ = 4–20°
b = 7.913 (1) Å	µ = 0.66 mm^−1
c = 13.002 (1) Å	T = 293 K
β = 93.21 (1)°	Block, colourless
V = 880.24 (17) Å^3	0.25 × 0.1 × 0.1 mm
Z = 2

Data collection

KUMA KM-4 CCD four-circle diffractometer	1902 independent reflections
Radiation source: fine-focus sealed tube	1382 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
ω scan	θmax = 27.0°, θmin = 2.9°
Absorption correction: multi-scan (SORTAV; Blessing, 1989)	h = −10→10
Tmin = 0.936, Tmax = 0.943	k = −10→10
8391 measured reflections	l = −10→16

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: difference Fourier map
wR(F^2) = 0.053	All H-atom parameters refined
S = 1.00	w = 1/[σ^2(Fo^2) + (0.02P)^2] where P = (Fo^2 + 2Fc^2)/3
1902 reflections	(Δ/σ)max = 0.016
142 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

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 F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.86523 (5)	−0.03768 (5)	0.38096 (3)	0.03227 (13)
Cl2	0.59188 (6)	0.25832 (6)	0.67679 (3)	0.05061 (16)
N1	0.2349 (2)	0.0764 (2)	0.37997 (14)	0.0339 (4)
H11	0.279 (2)	−0.018 (2)	0.3649 (13)	0.042 (6)*
H12	0.167 (2)	0.053 (2)	0.4211 (15)	0.055 (7)*
H13	0.188 (2)	0.109 (2)	0.3230 (14)	0.036 (5)*
C2	0.3506 (2)	0.2027 (3)	0.41895 (15)	0.0391 (5)
H21	0.386 (2)	0.174 (2)	0.4842 (14)	0.051 (6)*
H22	0.295 (2)	0.308 (3)	0.4200 (14)	0.064 (7)*
C3	0.4889 (2)	0.2134 (2)	0.35276 (14)	0.0322 (4)
H31	0.456 (2)	0.2426 (19)	0.2823 (15)	0.050 (5)*
H32	0.5349 (19)	0.111 (2)	0.3504 (12)	0.035 (5)*
C4	0.6060 (2)	0.3402 (2)	0.39674 (14)	0.0324 (4)
H41	0.6331 (18)	0.3166 (19)	0.4635 (13)	0.034 (5)*
H42	0.5674 (19)	0.451 (2)	0.3940 (12)	0.038 (5)*
N5	0.75101 (17)	0.3410 (2)	0.34029 (11)	0.0276 (3)
H51	0.793 (2)	0.243 (2)	0.3436 (12)	0.037 (5)*
H52	0.7269 (19)	0.362 (2)	0.2776 (13)	0.034 (5)*
C6	0.8691 (2)	0.4694 (3)	0.37704 (13)	0.0314 (4)
H61	0.9456 (19)	0.4662 (19)	0.3319 (12)	0.028 (5)*
H62	0.8122 (19)	0.574 (2)	0.3728 (12)	0.035 (5)*
C7	0.9378 (2)	0.4350 (2)	0.48443 (13)	0.0295 (4)
H71	0.9823 (18)	0.326 (2)	0.4879 (11)	0.031 (4)*
H72	0.8595 (18)	0.4308 (18)	0.5309 (12)	0.028 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0340 (2)	0.0361 (2)	0.0264 (2)	−0.0014 (2)	−0.00083 (17)	0.00073 (19)
Cl2	0.0655 (4)	0.0459 (3)	0.0395 (3)	0.0095 (2)	−0.0062 (2)	−0.0078 (2)
N1	0.0288 (10)	0.0394 (11)	0.0338 (9)	−0.0025 (8)	0.0041 (8)	0.0010 (8)
C2	0.0335 (11)	0.0488 (13)	0.0351 (11)	−0.0061 (10)	0.0042 (9)	−0.0077 (10)
C3	0.0287 (10)	0.0370 (11)	0.0307 (10)	−0.0023 (8)	0.0013 (8)	−0.0018 (8)
C4	0.0308 (10)	0.0353 (11)	0.0311 (10)	−0.0022 (8)	0.0012 (8)	−0.0036 (8)
N5	0.0319 (9)	0.0285 (8)	0.0217 (8)	−0.0028 (7)	−0.0034 (6)	0.0017 (6)
C6	0.0329 (10)	0.0337 (10)	0.0273 (9)	−0.0091 (9)	−0.0006 (8)	0.0014 (8)
C7	0.0297 (10)	0.0285 (10)	0.0299 (9)	−0.0028 (8)	−0.0007 (8)	0.0007 (8)

Geometric parameters (Å, º)

N1—C2	1.477 (2)	C4—H41	0.905 (16)
N1—H11	0.864 (19)	C4—H42	0.940 (17)
N1—H12	0.83 (2)	N5—C6	1.493 (2)
N1—H13	0.864 (18)	N5—H51	0.855 (17)
C2—C3	1.505 (3)	N5—H52	0.845 (17)
C2—H21	0.913 (18)	C6—C7	1.509 (2)
C2—H22	0.96 (2)	C6—H61	0.905 (16)
C3—C4	1.509 (2)	C6—H62	0.959 (17)
C3—H31	0.972 (19)	C7—C7^i	1.521 (3)
C3—H32	0.905 (16)	C7—H71	0.940 (17)
C4—N5	1.478 (2)	C7—H72	0.928 (16)
C2—N1—H11	111.9 (12)	N5—C4—H42	106.3 (10)
C2—N1—H12	114.3 (13)	C3—C4—H42	112.5 (10)
H11—N1—H12	106.3 (18)	H41—C4—H42	107.4 (14)
C2—N1—H13	111.3 (11)	C4—N5—C6	114.67 (14)
H11—N1—H13	104.7 (16)	C4—N5—H51	109.7 (12)
H12—N1—H13	107.7 (17)	C6—N5—H51	108.8 (12)
N1—C2—C3	112.13 (15)	C4—N5—H52	108.2 (11)
N1—C2—H21	109.4 (11)	C6—N5—H52	107.5 (11)
C3—C2—H21	108.3 (12)	H51—N5—H52	107.8 (16)
N1—C2—H22	105.7 (12)	N5—C6—C7	113.28 (15)
C3—C2—H22	111.3 (12)	N5—C6—H61	106.0 (10)
H21—C2—H22	109.9 (16)	C7—C6—H61	109.6 (9)
C2—C3—C4	110.42 (15)	N5—C6—H62	103.6 (10)
C2—C3—H31	110.7 (11)	C7—C6—H62	112.3 (10)
C4—C3—H31	110.7 (10)	H61—C6—H62	111.8 (14)
C2—C3—H32	109.1 (10)	C6—C7—C7^i	110.82 (18)
C4—C3—H32	109.2 (10)	C6—C7—H71	110.2 (9)
H31—C3—H32	106.7 (14)	C7^i—C7—H71	109.2 (10)
N5—C4—C3	111.98 (14)	C6—C7—H72	110.5 (9)
N5—C4—H41	107.4 (10)	C7^i—C7—H72	111.8 (9)
C3—C4—H41	110.8 (10)	H71—C7—H72	104.1 (13)
N1—C2—C3—C4	−178.51 (17)	C4—N5—C6—C7	66.7 (2)
C2—C3—C4—N5	173.82 (16)	N5—C6—C7—C7^i	177.4 (2)
C3—C4—N5—C6	177.39 (15)

Symmetry code: (i) −x+2, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···Cl2^ii	0.864 (19)	2.28 (2)	3.144 (2)	176.3 (16)
N1—H12···Cl1^ii	0.83 (2)	2.61 (2)	3.2848 (19)	139.3 (16)
N1—H12···Cl1^iii	0.83 (2)	2.70 (2)	3.2945 (18)	129.1 (16)
N1—H13···Cl2^iv	0.864 (18)	2.283 (18)	3.1351 (18)	168.9 (15)
C4—H41···Cl2	0.905 (16)	2.853 (17)	3.707 (2)	157.9 (13)
C4—H42···Cl2^v	0.940 (17)	2.801 (17)	3.701 (2)	160.7 (12)
N5—H51···Cl1	0.855 (17)	2.350 (18)	3.1873 (17)	166.6 (16)
N5—H52···Cl1^vi	0.845 (17)	2.308 (18)	3.1414 (15)	168.8 (15)

Symmetry codes: (ii) −x+1, −y, −z+1; (iii) x−1, y, z; (iv) x−1/2, −y+1/2, z−1/2; (v) −x+1, −y+1, −z+1; (vi) −x+3/2, y+1/2, −z+1/2.