First experimental charge density study using a Bruker CMOS-type PHOTON 100 detector: the case of ammonium tetraoxalate dihydrate

The aim of this study was to test the applicability of a Bruker AXS CMOS-type PHOTON 100 detector for the purpose of a fine charge density quality data collection. A complex crystal containing oxalic acid, ammonium oxalate and two water molecules was chosen as a test case. The data was collected up to a resolution of 1.31 Å⁻¹ with high completeness (89.1%; R_mrg = 0.0274). The multipolar refinement and subsequent quantum theory of atoms in molecules (QTAIM) analysis resulted in a comprehensive description of the charge density distribution in the crystal studied. The residual density maps are flat and almost featureless. It was possible to derive reliable information on intermolecular interactions to model the anharmonic motion of a water molecule, and also to observe the fine details of the charge density distribution, such as polarization on O and H atoms involved in the strongest hydrogen bonds. When compared with our previous statistical study on oxalic acid data collected with the aid of CCD cameras, the complementary metal-oxide semiconductor (CMOS) detector can certainly be classified as a promising alternative in advanced X-ray diffraction studies.

Computing details

Figures

(CCDC994769)

Crystal data

C2H2O4·C2HO4·2(H2O)·H4N	Z = 2
Mr = 233.14	F(000) = 244
Triclinic, P1	Dx = 1.693 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.2372 (4) Å	Cell parameters from 50285 reflections
b = 7.1935 (5) Å	θ = 2.9–62.7°
c = 10.4745 (7) Å	µ = 0.17 mm^−1
α = 94.5207 (18)°	T = 100 K
β = 99.8882 (18)°	Block, colourless
γ = 96.7177 (19)°	0.24 × 0.21 × 0.09 mm
V = 457.45 (5) Å^3

Data collection

Bruker AXS CMOS-type PHOTON 100 detector diffractometer	14225 independent reflections
Radiation source: Mo sealed tube	9995 reflections with I > 3σ(I)
Bruker AXS TRIUMPH monochromator	Rint = 0.027
ω–scans	θmax = 62.7°, θmin = 2.9°
Absorption correction: multi-scan Blessing, R. H. (1995). Acta Cryst. A51, 33.	h = −15→15
Tmin = 0.966, Tmax = 0.985	k = −17→17
50285 measured reflections	l = −26→26

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.018	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.019	Weighting scheme based on measured s.u.'s
S = 0.89	(Δ/σ)max = −0.001
9995 reflections	Δρmax = 0.21 e Å^−3
349 parameters	Δρmin = −0.22 e Å^−3
11 restraints

Special details

Refinement. Charge density refinement with MOPRO.

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

	x	y	z	Uiso*/Ueq
C1	0.91907 (3)	0.99061 (2)	0.434750 (16)	0.008183 (18)
O1	0.99847 (3)	1.07806 (2)	0.347080 (18)	0.01122 (2)
O2	0.73730 (3)	0.89896 (2)	0.422253 (18)	0.011035 (19)
H1	0.8864 (7)	1.0737 (8)	0.2635 (3)	0.02215
C2	0.00527 (3)	0.54831 (2)	0.436891 (15)	0.007976 (18)
O3	−0.16034 (3)	0.49158 (2)	0.345256 (18)	0.011645 (19)
O4	0.16083 (3)	0.66736 (2)	0.432415 (18)	0.010331 (18)
H2	−0.1597 (10)	0.5606 (6)	0.2641 (3)	0.02258
C3	0.25600 (3)	0.32260 (2)	0.079880 (15)	0.008246 (19)
C4	0.22704 (3)	0.43423 (2)	−0.041301 (15)	0.008285 (19)
O5	0.31702 (3)	0.42913 (3)	0.188972 (19)	0.01331 (3)
O6	0.22397 (3)	0.15078 (3)	0.068753 (19)	0.01157 (2)
O7	0.26332 (3)	0.60867 (3)	−0.021946 (19)	0.01260 (3)
O8	0.17055 (3)	0.33476 (3)	−0.149168 (18)	0.01172 (3)
H3	0.3583 (11)	0.3526 (6)	0.2651 (3)	0.02424
N1	0.34265 (3)	0.84352 (2)	0.224738 (15)	0.009907 (18)
H4	0.2387 (7)	0.7924 (8)	0.2849 (4)	0.02287
H5	0.5015 (4)	0.8681 (8)	0.2773 (5)	0.02287
H6	0.3005 (9)	0.9689 (4)	0.1921 (5)	0.02287
H7	0.3302 (10)	0.7418 (5)	0.1472 (3)	0.02287
O9	0.73177 (3)	0.07349 (2)	0.144464 (17)	0.01065 (2)
H8	0.7342 (10)	0.1931 (4)	0.1100 (5)	0.02348
H9	0.7637 (9)	−0.0136 (6)	0.0785 (4)	0.02348
O10	0.44580 (7)	0.25116 (5)	0.37589 (9)	0.01327 (2)
H10	0.3578 (7)	0.2033 (7)	0.4355 (4)	0.02610
H11	0.5895 (4)	0.2977 (8)	0.4241 (5)	0.02610

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.00815 (5)	0.00918 (4)	0.00676 (4)	0.00034 (3)	0.00027 (3)	0.00162 (3)
O1	0.01042 (5)	0.01478 (5)	0.00787 (5)	−0.00084 (4)	0.00041 (4)	0.00404 (4)
O2	0.00902 (5)	0.01385 (5)	0.00884 (5)	−0.00195 (4)	−0.00071 (4)	0.00287 (3)
H1	0.01934	0.02964	0.01560	−0.00094	−0.00120	0.00667
C2	0.00944 (5)	0.00760 (4)	0.00638 (4)	−0.00049 (3)	0.00057 (3)	0.00190 (3)
O3	0.01319 (5)	0.01180 (5)	0.00779 (4)	−0.00314 (4)	−0.00204 (4)	0.00365 (4)
O4	0.01067 (5)	0.01120 (4)	0.00833 (4)	−0.00227 (4)	0.00092 (4)	0.00347 (3)
H2	0.02548	0.02398	0.01583	−0.00369	−0.00114	0.00827
C3	0.01159 (5)	0.00685 (4)	0.00616 (4)	0.00119 (3)	0.00081 (3)	0.00165 (3)
C4	0.01160 (5)	0.00688 (4)	0.00615 (4)	0.00113 (3)	0.00062 (3)	0.00167 (3)
O5	0.02403 (9)	0.00861 (5)	0.00626 (5)	0.00190 (4)	−0.00007 (4)	0.00100 (4)
O6	0.01907 (7)	0.00680 (5)	0.00811 (5)	0.00065 (3)	0.00062 (4)	0.00204 (3)
O7	0.02245 (8)	0.00664 (5)	0.00827 (5)	0.00165 (3)	0.00123 (4)	0.00195 (4)
O8	0.01921 (7)	0.00864 (5)	0.00592 (4)	−0.00011 (3)	−0.00050 (3)	0.00144 (3)
H3	0.03961	0.01794	0.01406	0.00453	0.00012	0.00419
N1	0.01177 (5)	0.00884 (4)	0.00870 (4)	0.00004 (3)	0.00129 (3)	0.00165 (3)
H4	0.02244	0.02699	0.01991	−0.00078	0.00674	0.00651
H5	0.01809	0.02781	0.02064	−0.00029	−0.00066	0.00392
H6	0.03067	0.01671	0.02161	0.00543	0.00274	0.00536
H7	0.03116	0.01891	0.01738	0.00313	0.00295	−0.00174
O9	0.01333 (6)	0.01079 (5)	0.00774 (4)	0.00203 (3)	0.00071 (4)	0.00241 (3)
H8	0.03065	0.01846	0.02228	0.00433	0.00427	0.00751
H9	0.03023	0.02227	0.01854	0.00582	0.00569	−0.00057
O10	0.01135 (5)	0.01727 (6)	0.01020 (5)	−0.00168 (4)	−0.00048 (4)	0.00603 (4)
H10	0.02397	0.03306	0.02173	−0.00208	0.00600	0.01020
H11	0.01860	0.03312	0.02319	−0.00328	−0.00255	0.00602

Geometric parameters (Å, º)

C1—O1	1.2879 (3)	C4—O8	1.2608 (3)
C1—O2	1.2238 (3)	O5—H3	1.0180 (9)
O1—H1	1.0180 (9)	N1—H7	1.0358 (9)
C2—O3	1.2860 (3)	N1—H5	1.0358 (9)
C2—O4	1.2266 (3)	N1—H6	1.0359 (9)
O3—H2	1.0180 (9)	N1—H4	1.0359 (9)
C3—O5	1.2970 (3)	O9—H9	0.9580 (9)
C3—O6	1.2217 (3)	O9—H8	0.9581 (9)
C3—C4	1.5506 (2)	O10—H10	0.9580 (9)
C4—O7	1.2428 (3)	O10—H11	0.9580 (9)
C1—O1—H1	112.3 (3)	O7—C4—O8	127.63 (3)
O1—C1—O2	126.76 (3)	H4—N1—H7	107.4 (4)
C2—O3—H2	113.9 (3)	H4—N1—H5	108.7 (4)
O3—C2—O4	126.67 (2)	H4—N1—H6	110.9 (5)
C3—O5—H3	111.7 (3)	H5—N1—H7	110.7 (5)
C3—C4—O7	117.271 (16)	H5—N1—H6	108.5 (4)
C3—C4—O8	115.096 (19)	H6—N1—H7	110.7 (4)
C4—C3—O5	113.458 (16)	H8—O9—H9	106.6 (5)
C4—C3—O6	121.13 (2)	H10—O10—H11	108.1 (5)
O5—C3—O6	125.41 (2)
O2—C1—O1—H1		O5—C3—C4—O8
O4—C2—O3—H2		O6—C3—O5—H3
C4—C3—O5—H3		O6—C3—C4—O7
O5—C3—C4—O7		O6—C3—C4—O8