When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical

Joint refinement of X-ray and polarized neutron diffraction data has been carried out in order to determine charge and spin density distributions simultaneously in the nitro­nyl nitroxide (NN) free radical Nit(SMe)Ph. For comparison purposes, density functional theory (DFT) and complete active-space self-consistent field (CASSCF) theoretical calculations were also performed. Experimentally derived charge and spin densities show significant differences between the two NO groups of the NN function that are not observed from DFT theoretical calculations. On the contrary, CASSCF calculations exhibit the same fine details as observed in spin-resolved joint refinement and a clear asymmetry between the two NO groups.

Computing details

(I)

Crystal data

C28H38N4O4S2	F(000) = 596
MONOCLINIC,	Dx = 1.305 Mg m^−3
a = 9.34 Å	Mo Kα radiation, λ = 0.71073 Å
b = 19.482 Å	µ = 0.23 mm^−1
c = 8.634 Å	T = 293 K
β = 115.13°	Spherical, colorless
V = 1422.4 Å^3	0.12 × 0.11 × 0.1 mm
Z = 2

Data collection

8800 independent reflections	θmax = 40.3°, θmin = 2.6°
7301 reflections with I > 2σ(I)

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

	x	y	z	Uiso*/Ueq
S	0.255160 (10)	0.533470 (10)	0.477150 (10)	0.02244 (4)
O2	0.30684 (4)	0.71903 (3)	−0.14381 (4)	0.02690 (10)
O1	0.29505 (4)	0.874580 (10)	0.25753 (3)	0.02480 (10)
N2	0.30117 (4)	0.77492 (2)	−0.06913 (4)	0.01820 (10)
N1	0.29036 (3)	0.84854 (2)	0.11910 (4)	0.01710 (10)
C1	0.30447 (4)	0.78121 (2)	0.08832 (4)	0.01580 (10)
C2	0.30795 (4)	0.72411 (2)	0.19885 (4)	0.01540 (10)
C7	0.37939 (4)	0.66139 (2)	0.19219 (4)	0.01740 (10)
C6	0.36578 (4)	0.60520 (2)	0.28365 (5)	0.01760 (10)
C5	0.27731 (4)	0.60962 (2)	0.38032 (4)	0.01670 (10)
C4	0.21125 (4)	0.67264 (2)	0.39262 (4)	0.0202 (2)
C3	0.22810 (4)	0.72950 (2)	0.30408 (5)	0.01870 (10)
C9	0.30051 (4)	0.84340 (2)	−0.14955 (4)	0.01780 (10)
C8	0.24759 (4)	0.89124 (2)	−0.03905 (4)	0.01630 (10)
C12	0.33259 (5)	0.95994 (2)	0.00754 (5)	0.02470 (10)
C10	0.06903 (5)	0.90237 (2)	−0.11262 (6)	0.02520 (10)
C11	0.47000 (5)	0.85696 (3)	−0.12594 (6)	0.0310 (2)
C13	0.18925 (6)	0.84061 (2)	−0.33844 (5)	0.0275 (2)
C14	0.14777 (5)	0.56097 (2)	0.59714 (5)	0.0284 (2)
H7	0.4473 (7)	0.65479 (3)	0.1206 (7)	0.0400 (4)
H6	0.4225 (7)	0.5575 (3)	0.2830 (7)	0.0417 (4)
H4	0.1428 (7)	0.6771 (3)	0.4654 (8)	0.0423 (4)
H3	0.1707 (8)	0.7766 (3)	0.3083 (8)	0.0377 (4)
H121	0.4549 (8)	0.9506 (2)	0.0823 (9)	0.0477 (5)
H122	0.3264 (8)	0.9850 (3)	−0.1059 (8)	0.0403 (5)
H123	0.2773 (8)	0.9922 (3)	0.0692 (9)	0.0513 (5)
H101	0.0349 (7)	0.9336 (4)	−0.2264 (9)	0.0470 (5)
H102	0.0393 (8)	0.92814 (4)	−0.0178 (8)	0.0510 (4)
H103	0.0066 (7)	0.8548 (3)	−0.1394 (8)	0.0420 (5)
H111	0.5506 (7)	0.8599 (4)	0.0065 (8)	0.0407 (4)
H112	0.4722 (8)	0.9031 (4)	−0.1912 (9)	0.0507 (5)
H113	0.4996 (9)	0.8152 (4)	−0.1889 (10)	0.0587 (5)
H131	0.1778 (8)	0.8908 (4)	−0.3982 (8)	0.0470 (5)
H132	0.2324 (9)	0.8045 (4)	−0.4017 (8)	0.0533 (5)
H133	0.0762 (9)	0.8215 (4)	−0.3555 (8)	0.0463 (4)
H141	0.0363 (8)	0.5831 (4)	0.5088 (9)	0.0550 (5)
H142	0.2147 (8)	0.5966 (4)	0.6947 (8)	0.0533 (5)
H143	0.1352 (9)	0.5152 (4)	0.6595 (9)	0.0520 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S	0.02991 (5)	0.01742 (5)	0.01998 (5)	−0.00415 (3)	0.00859 (4)	0.00219 (3)
O2	0.0379 (2)	0.02110 (10)	0.02170 (10)	0.00380 (10)	0.01630 (10)	−0.00150 (10)
O1	0.0365 (2)	0.01820 (10)	0.01980 (10)	−0.00160 (10)	0.01510 (10)	−0.00200 (10)
N2	0.02160 (10)	0.01740 (10)	0.01570 (10)	0.00180 (10)	0.00940 (10)	0.00060 (10)
N1	0.02080 (10)	0.01460 (10)	0.01600 (10)	−0.00020 (10)	0.00890 (10)	0.00050 (10)
C1	0.01710 (10)	0.01510 (10)	0.01530 (10)	0.00070 (10)	0.00790 (10)	0.00140 (10)
C2	0.01580 (10)	0.01480 (10)	0.01580 (10)	0.00080 (10)	0.00760 (10)	0.00130 (10)
C7	0.01740 (10)	0.0160 (2)	0.01890 (10)	0.00150 (10)	0.00940 (10)	0.00090 (10)
C6	0.01900 (10)	0.01470 (10)	0.0191 (2)	0.00150 (10)	0.00770 (10)	0.00100 (10)
C5	0.01900 (10)	0.01550 (10)	0.01570 (10)	−0.00160 (10)	0.00620 (10)	0.00100 (10)
C4	0.0228 (2)	0.0179 (2)	0.0199 (2)	0.00050 (10)	0.01270 (10)	0.0020 (2)
C3	0.0206 (2)	0.01630 (10)	0.0191 (2)	0.00220 (10)	0.0116 (2)	0.00190 (10)
C9	0.01840 (10)	0.0201 (2)	0.01500 (10)	0.00150 (10)	0.00690 (10)	0.00340 (10)
C8	0.01600 (10)	0.01530 (10)	0.01760 (10)	−0.00090 (10)	0.00670 (10)	0.00230 (10)
C12	0.0308 (2)	0.0199 (2)	0.0236 (2)	−0.00810 (10)	0.0106 (2)	0.00020 (10)
C10	0.0181 (2)	0.0249 (2)	0.0326 (2)	0.00460 (10)	0.0106 (4)	0.0083 (2)
C11	0.0241 (2)	0.0332 (2)	0.0358 (2)	0.0038 (2)	0.0194 (2)	0.0098 (2)
C13	0.0383 (2)	0.0289 (2)	0.0154 (2)	0.0031 (2)	0.0044 (2)	0.00190 (10)
C14	0.0324 (2)	0.0307 (2)	0.0221 (2)	−0.0099 (2)	0.0132 (2)	0.0013 (2)
H7	0.044 (4)	0.035 (4)	0.041 (4)	0.010 (3)	0.031 (3)	0.005 (3)
H6	0.054 (4)	0.020 (4)	0.051 (4)	0.011 (3)	0.029 (3)	0.006 (3)
H4	0.048 (4)	0.035 (4)	0.044 (4)	0.000 (3)	0.034 (3)	0.001 (3)
H3	0.047 (4)	0.025 (4)	0.041 (4)	0.007 (3)	0.030 (4)	0.003 (3)
H121	0.039 (5)	0.048 (5)	0.056 (5)	−0.005 (4)	0.010 (4)	0.015 (4)
H122	0.057 (5)	0.029 (4)	0.035 (4)	−0.006 (3)	0.019 (4)	0.010 (3)
H123	0.065 (5)	0.028 (4)	0.061 (5)	−0.005 (4)	0.035 (4)	−0.012 (4)
H101	0.043 (4)	0.049 (5)	0.049 (5)	0.005 (3)	0.023 (4)	0.019 (4)
H102	0.045 (4)	0.058 (5)	0.050 (5)	0.016 (4)	0.027 (4)	0.005 (4)
H103	0.029 (4)	0.041 (5)	0.056 (5)	0.001 (3)	0.012 (3)	0.013 (4)
H111	0.023 (4)	0.071 (5)	0.028 (4)	−0.001 (3)	0.006 (3)	0.009 (4)
H112	0.041 (4)	0.049 (5)	0.062 (5)	−0.001 (3)	0.028 (4)	0.029 (4)
H113	0.058 (5)	0.049 (5)	0.069 (5)	0.001 (4)	0.042 (4)	0.010 (4)
H131	0.067 (5)	0.038 (5)	0.036 (4)	0.001 (4)	0.016 (4)	0.012 (4)
H132	0.081 (6)	0.054 (5)	0.034 (4)	0.019 (4)	0.027 (4)	−0.002 (4)
H133	0.054 (5)	0.048 (5)	0.037 (4)	−0.006 (4)	0.012 (4)	−0.014 (3)
H141	0.045 (4)	0.067 (5)	0.053 (5)	−0.001 (4)	0.024 (4)	0.010 (4)
H142	0.059 (5)	0.052 (5)	0.049 (4)	−0.015 (4)	0.028 (4)	−0.012 (4)
H143	0.064 (5)	0.036 (5)	0.056 (5)	−0.005 (4)	0.027 (4)	0.012 (4)