Charge-density studies of energetic materials: CL-20 and FOX-7

Experimental electron densities and derived properties have been determined for the two energetic materials CL-20 (3,5,9,11-tetraacetyl-14-oxo-1,3,5,7,9,11-hexaazapentacyclo-[5.5.3.02,6.04,10.08,12]pentadecane), and FOX-7 (1,1-diamino-2,2-dinitroethylene) from single-crystal diffraction. Synchrotron data extending to high scattering angles were measured at low temperature. Low figures-of-merit and excellent residuals were obtained. The Hansen & Coppens multipole-model electron density was compared with results from theoretical calculations via structure factors simulating an experiment. Chemical bonding in the molecules is discussed and a topological analysis gives insight especially into the character of those bonds that are thought to play a key role in the decomposition of the molecules. A comparison of theoretical and experimental electrostatic potentials shows no obvious evidence supporting earlier findings on other nitroheterocyclic molecules that electron-density maxima near the C-NO₂ bonds mapped on the electron-density isosurface can be correlated with impact sensitivities. For FOX-7 periodic Hartree-Fock calculations were performed to investigate the influence of the crystal field on the electron density distribution.

Computing details

For both compounds, program(s) used to refine structure: Koritsanszky et al., (2003); molecular graphics: Koritsanszky et al., (2003); software used to prepare material for publication: Koritsanszky et al., (2003).

Figures

(FOX7)

Crystal data

C2H4N4O4	Z = 4
Mr = 148.09	Dx = 1.941 (1) Mg m^−3
Monoclinic, P21/n	Synchrotron radiation, λ = ? Å
a = 6.922 (1) Å	µ = 0.78 mm^−1
b = 6.501 (1) Å	T = 100 K
c = 11.262 (1) Å	Prismatic, yellow
β = 90.485 (1)°	0.27 × 0.25 × 0.22 mm
V = 506.77 Å^3

Data collection

Beamline E2; HASYLAB-DESY diffractometer	Rint = 2.7
rotation photographs scans	θmax = 33.6°
143788 measured reflections	h = ?→?
6093 independent reflections	k = ?→?
5329 reflections with I > 3σ(I)	l = ?→?

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.021	w1 = 1/[s^2(Fo)]
wR(F^2) = 0.027	(Δ/σ)max < 0.001
S = 2.05	Δρmax = 0.29 e Å^−3
5329 reflections	Δρmin = −0.36 e Å^−3
184 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(11)	0.19465 (3)	0.33585 (3)	0.337060 (10)	0.012
O(12)	−0.02049 (2)	0.44648 (3)	0.212860 (10)	0.012
O(21)	0.58078 (2)	0.30104 (3)	0.081000 (10)	0.013
O(22)	0.52188 (2)	0.44511 (3)	0.250780 (10)	0.011
N(11)	0.14219 (2)	0.37539 (2)	0.234300 (10)	0.008
N(12)	0.46434 (2)	0.35837 (3)	0.158330 (10)	0.008
N(21)	−0.00504 (3)	0.24524 (3)	0.010100 (10)	0.01
N(22)	0.29804 (3)	0.19871 (3)	−0.061820 (10)	0.012
C(1)	0.26649 (2)	0.33329 (3)	0.137210 (10)	0.008
C(2)	0.18528 (3)	0.25991 (3)	0.025590 (10)	0.008
H(11)	−0.05872	0.20059	−0.0691	0.019
H(12)	−0.09554	0.3016	0.07155	0.02
H(21)	0.23363	0.15195	−0.13755	0.021
H(22)	0.44262	0.20052	−0.05163	0.021

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(11)	0.00986 (6)	0.02106 (7)	0.00607 (4)	0.00095 (5)	−0.00045 (4)	0.00124 (4)
O(12)	0.00833 (5)	0.01748 (7)	0.00902 (5)	0.00364 (5)	0.00016 (4)	−0.00032 (4)
O(21)	0.00724 (5)	0.02178 (8)	0.01128 (5)	0.00018 (5)	0.00135 (4)	−0.00422 (5)
O(22)	0.00894 (5)	0.01527 (7)	0.00918 (5)	−0.00146 (5)	−0.00206 (4)	−0.00226 (4)
N(11)	0.00711 (5)	0.01076 (6)	0.00589 (4)	0.00047 (4)	−0.00013 (4)	−0.00015 (3)
N(12)	0.00650 (5)	0.01119 (6)	0.00728 (4)	−0.00021 (4)	−0.00041 (4)	−0.00082 (4)
N(21)	0.00753 (6)	0.01386 (7)	0.00862 (5)	−0.00034 (5)	−0.00146 (4)	−0.00171 (4)
N(22)	0.00952 (6)	0.01779 (8)	0.00761 (5)	−0.00047 (6)	0.00078 (4)	−0.00344 (5)
C(1)	0.00653 (6)	0.01114 (6)	0.00621 (5)	−0.00018 (5)	−0.00017 (4)	−0.00103 (4)
C(2)	0.00730 (6)	0.00988 (6)	0.00623 (5)	−0.00040 (5)	−0.00024 (4)	−0.00038 (4)
H(11)	0.0131	0.0296	0.0128	−0.0075	−0.0052	−0.0017
H(12)	0.0137	0.0326	0.0151	0.0046	0.0073	0.0013
H(21)	0.02	0.0352	0.0089	0.0023	−0.0004	−0.0097
H(22)	0.0086	0.0312	0.024	0.0023	0.0026	−0.0057

Geometric parameters (Å, º)

O(11)—N(11)	1.2370 (2)	N(21)—H(11)	1.0061 (2)
O(12)—N(11)	1.2391 (2)	N(21)—H(12)	1.0064 (2)
O(21)—N(12)	1.2486 (2)	N(22)—C(2)	1.3227 (2)
O(22)—N(12)	1.2464 (2)	N(22)—H(21)	1.0061 (2)
N(11)—C(1)	1.4237 (2)	N(22)—H(22)	1.0064 (2)
N(12)—C(1)	1.3976 (2)	C(1)—C(2)	1.4532 (2)
N(21)—C(2)	1.3308 (2)
O(11)—N(11)—O(12)	121.260 (18)	C(2)—N(22)—H(21)	117.496 (19)
O(11)—N(11)—C(1)	120.268 (17)	C(2)—N(22)—H(22)	120.274 (17)
O(12)—N(11)—C(1)	118.439 (15)	H(21)—N(22)—H(22)	122.230 (18)
O(21)—N(12)—O(22)	120.938 (19)	N(11)—C(1)—N(12)	116.397 (14)
O(21)—N(12)—C(1)	118.940 (15)	N(11)—C(1)—C(2)	119.709 (15)
O(22)—N(12)—C(1)	120.045 (17)	N(12)—C(1)—C(2)	123.840 (15)
C(2)—N(21)—H(11)	119.646 (18)	N(21)—C(2)—N(22)	118.074 (18)
C(2)—N(21)—H(12)	120.328 (16)	N(21)—C(2)—C(1)	120.811 (16)
H(11)—N(21)—H(12)	119.161 (18)	N(22)—C(2)—C(1)	121.070 (17)

(CL20)

Crystal data

C8H6N12O12	Z = 4
Mr = 438.23	Dx = 2.08 Mg m^−3
Monoclinic, P21/n	Synchrotron radiation, λ = ? Å
a = 8.789 (1) Å	µ = 0.20 mm^−1
b = 12.474 (1) Å	T = 100 K
c = 13.279 (1) Å	Rectangular, colourless
β = 106.578 (1)°	0.31 × 0.26 × 0.24 mm
V = 1395.31 (1) Å^3

Data collection

Beamline E2; HASYLAB-DESY diffractometer	Rint = 2.9
rotation photographs scans	θmax = 33.6°
486590 measured reflections	h = ?→?
16427 independent reflections	k = ?→?
14455 reflections with I > 3σ(I)	l = ?→?

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.028	w1 = 1/[s^2(Fo)]
wR(F^2) = 0.033	(Δ/σ)max < 0.001
S = 1.98	Δρmax = 0.82 e Å^−3
14455 reflections	Δρmin = −0.51 e Å^−3
360 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O(1)	−0.08987 (3)	0.61182 (2)	0.35504 (3)	0.02
O(2)	−0.26363 (3)	0.72388 (2)	0.38327 (2)	0.014
O(3)	−0.34843 (3)	0.73615 (2)	0.15074 (2)	0.014
O(4)	−0.28990 (3)	0.79812 (2)	0.01228 (2)	0.015
O(5)	0.07974 (3)	1.11271 (2)	0.11098 (2)	0.013
O(6)	0.09800 (3)	1.16082 (2)	0.27229 (2)	0.011
O(7)	0.30886 (3)	0.94544 (2)	0.51124 (2)	0.018
O(8)	0.12322 (3)	1.06521 (2)	0.49096 (2)	0.013
O(9)	0.46340 (3)	0.88244 (2)	0.27417 (2)	0.014
O(10)	0.35068 (3)	0.90223 (2)	0.10622 (2)	0.019
O(11)	0.09773 (3)	0.67837 (2)	0.03994 (2)	0.016
O(12)	0.09723 (3)	0.58507 (2)	0.17845 (2)	0.014
N(1)	−0.14830 (3)	0.70052 (2)	0.35472 (2)	0.011
N(2)	−0.06949 (3)	0.78652 (2)	0.32188 (2)	0.008
N(3)	−0.28694 (3)	0.80023 (2)	0.10500 (2)	0.009
N(4)	−0.20831 (3)	0.88574 (2)	0.16283 (2)	0.008
N(5)	0.04928 (3)	1.10367 (2)	0.19532 (2)	0.008
N(6)	−0.05252 (3)	1.02319 (2)	0.20331 (2)	0.008
N(7)	0.18681 (3)	0.98863 (2)	0.46207 (2)	0.01
N(8)	0.11037 (3)	0.94578 (2)	0.36423 (2)	0.009
N(9)	0.35017 (3)	0.89290 (2)	0.19742 (2)	0.011
N(10)	0.19820 (3)	0.90273 (2)	0.21599 (2)	0.008
N(11)	0.08105 (3)	0.66692 (2)	0.12686 (2)	0.01
N(12)	0.02713 (3)	0.75811 (2)	0.17128 (2)	0.008
C(1)	0.06797 (3)	0.76375 (2)	0.28698 (2)	0.008
C(3)	−0.16053 (3)	0.88079 (2)	0.27894 (2)	0.008
C(5)	−0.08676 (3)	0.93829 (2)	0.12516 (2)	0.007
C(7)	−0.04681 (3)	0.98132 (2)	0.30786 (2)	0.008
C(9)	0.18339 (3)	0.86343 (2)	0.31731 (2)	0.008
C(11)	0.06223 (3)	0.86242 (2)	0.13295 (2)	0.008
H(1)	−0.13559	0.96918	0.0455	0.017 (2)
H(2)	0.08777	0.85813	0.05725	0.023 (2)
H(3)	−0.26335	0.88575	0.30938	0.020 (2)
H(4)	−0.08608	1.04119	0.35502	0.019 (2)
H(5)	0.29816	0.84247	0.37177	0.020 (2)
H(6)	0.12363	0.68842	0.32005	0.025 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O(1)	0.01760 (10)	0.00910 (10)	0.03170 (10)	−0.00050 (10)	0.01080 (10)	0.00480 (10)
O(2)	0.01351 (8)	0.01450 (8)	0.01492 (8)	−0.00420 (7)	0.00814 (7)	−0.00039 (6)
O(3)	0.01352 (8)	0.01426 (8)	0.01308 (7)	−0.00684 (7)	0.00491 (6)	−0.00238 (6)
O(4)	0.01774 (9)	0.01681 (9)	0.00729 (6)	−0.00497 (8)	0.00149 (6)	−0.00252 (6)
O(5)	0.01409 (8)	0.01268 (8)	0.01037 (7)	−0.00161 (7)	0.00538 (6)	0.00197 (6)
O(6)	0.01162 (7)	0.00852 (7)	0.01292 (7)	−0.00201 (6)	0.00350 (6)	−0.00295 (5)
O(7)	0.01700 (10)	0.01940 (10)	0.01250 (10)	0.00250 (10)	−0.00600 (10)	−0.00130 (10)
O(8)	0.01482 (8)	0.01395 (8)	0.01068 (7)	−0.00360 (7)	0.00480 (6)	−0.00526 (6)
O(9)	0.00665 (7)	0.01383 (8)	0.02086 (9)	0.00032 (6)	0.00270 (6)	−0.00260 (7)
O(10)	0.01482 (9)	0.02605 (12)	0.01743 (9)	−0.00334 (9)	0.01066 (8)	−0.00164 (8)
O(11)	0.02250 (10)	0.01200 (10)	0.01500 (10)	0.00120 (10)	0.01070 (10)	−0.00280 (10)
O(12)	0.01546 (9)	0.00687 (7)	0.01665 (8)	0.00160 (6)	0.00279 (7)	0.00057 (6)
N(1)	0.01046 (8)	0.00963 (8)	0.01109 (7)	−0.00279 (6)	0.00357 (6)	0.00119 (6)
N(2)	0.00792 (7)	0.00817 (7)	0.00844 (6)	−0.00056 (6)	0.00287 (5)	0.00173 (5)
N(3)	0.00796 (7)	0.01045 (7)	0.00791 (6)	−0.00190 (6)	0.00082 (5)	−0.00144 (5)
N(4)	0.00662 (6)	0.00872 (7)	0.00693 (6)	−0.00108 (6)	0.00096 (5)	−0.00049 (5)
N(5)	0.00786 (7)	0.00651 (6)	0.00938 (6)	0.00003 (6)	0.00249 (5)	0.00042 (5)
N(6)	0.00836 (7)	0.00638 (7)	0.00737 (7)	−0.00041 (7)	0.00191 (6)	0.00012 (5)
N(7)	0.01094 (7)	0.01034 (7)	0.00641 (6)	−0.00282 (6)	0.00069 (5)	−0.00056 (5)
N(8)	0.00760 (7)	0.00992 (7)	0.00683 (6)	0.00026 (6)	0.00009 (5)	−0.00186 (5)
N(9)	0.00801 (7)	0.00915 (8)	0.01560 (8)	−0.00124 (6)	0.00566 (6)	−0.00197 (6)
N(10)	0.00607 (6)	0.00860 (7)	0.00861 (6)	−0.00055 (5)	0.00229 (5)	−0.00035 (5)
N(11)	0.00905 (7)	0.00694 (7)	0.01216 (7)	0.00028 (6)	0.00298 (6)	−0.00159 (5)
N(12)	0.00850 (7)	0.00611 (6)	0.00763 (6)	0.00027 (5)	0.00232 (5)	−0.00013 (5)
C(1)	0.00729 (7)	0.00715 (7)	0.00785 (6)	0.00001 (6)	0.00142 (6)	0.00102 (5)
C(3)	0.00675 (7)	0.00841 (7)	0.00728 (6)	−0.00045 (6)	0.00211 (5)	−0.00039 (5)
C(5)	0.00758 (7)	0.00726 (7)	0.00642 (6)	0.00008 (6)	0.00112 (5)	0.00051 (5)
C(7)	0.00725 (7)	0.00782 (7)	0.00719 (6)	−0.00020 (6)	0.00207 (5)	−0.00078 (5)
C(9)	0.00628 (7)	0.00804 (8)	0.00795 (7)	0.00006 (6)	0.00073 (5)	0.00021 (5)
C(11)	0.00787 (7)	0.00713 (7)	0.00721 (6)	−0.00024 (6)	0.00244 (6)	−0.00003 (5)

Geometric parameters (Å, º)

O(1)—N(1)	1.2193 (4)	N(4)—C(5)	1.4581 (3)
O(2)—N(1)	1.2147 (3)	N(5)—N(6)	1.3689 (3)
O(3)—N(3)	1.2195 (3)	N(6)—C(5)	1.4528 (3)
O(4)—N(3)	1.2243 (3)	N(7)—N(8)	1.3881 (3)
O(5)—N(5)	1.2288 (3)	N(8)—C(7)	1.4405 (3)
O(6)—N(5)	1.2192 (3)	N(8)—C(9)	1.4434 (3)
O(7)—N(7)	1.2115 (4)	N(10)—C(11)	1.4646 (3)
O(8)—N(7)	1.2226 (3)	N(12)—C(11)	1.4618 (3)
O(9)—N(9)	1.2113 (4)	C(1)—H(6)	1.0920 (2)
O(10)—N(9)	1.2180 (3)	C(3)—H(3)	1.0920 (2)
O(11)—N(11)	1.2126 (3)	C(5)—H(1)	1.0920 (2)
O(12)—N(11)	1.2151 (3)	C(7)—H(4)	1.0920 (2)
N(2)—C(1)	1.4403 (3)	C(9)—H(5)	1.0920 (2)
N(2)—C(3)	1.4450 (3)	C(11)—H(2)	1.0920 (2)
N(3)—N(4)	1.3792 (3)
O(1)—N(1)—O(2)	127.21 (3)	N(7)—N(8)—C(9)	121.46 (2)
C(1)—N(2)—C(3)	117.021 (19)	C(7)—N(8)—C(9)	118.25 (2)
O(3)—N(3)—O(4)	126.98 (3)	O(9)—N(9)—O(10)	127.71 (3)
O(3)—N(3)—N(4)	116.90 (2)	O(11)—N(11)—O(12)	127.53 (3)
O(4)—N(3)—N(4)	116.10 (2)	N(2)—C(1)—H(6)	111.159 (19)
N(3)—N(4)—C(5)	117.157 (19)	N(2)—C(3)—H(3)	108.879 (19)
O(5)—N(5)—O(6)	126.50 (2)	N(4)—C(5)—N(6)	96.047 (18)
O(5)—N(5)—N(6)	117.07 (2)	N(4)—C(5)—H(1)	111.53 (2)
O(6)—N(5)—N(6)	116.41 (2)	N(6)—C(5)—H(1)	112.26 (2)
N(5)—N(6)—C(5)	119.075 (19)	N(8)—C(7)—H(4)	109.002 (19)
O(7)—N(7)—O(8)	126.31 (3)	N(8)—C(9)—H(5)	108.971 (19)
O(7)—N(7)—N(8)	116.80 (2)	N(10)—C(11)—N(12)	104.558 (19)
O(8)—N(7)—N(8)	116.88 (2)	N(10)—C(11)—H(2)	111.835 (19)
N(7)—N(8)—C(7)	120.28 (2)	N(12)—C(11)—H(2)	113.340 (19)