Unusual hydrogen bonding in L-cysteine hydrogen fluoride

L-Cysteine hydrogen fluoride, or bis­(L-cysteinium) difluoride-L-cysteine-hydro­gen fluoride (1/1/1), 2C₃H₈NO₂S⁺·2F^-·C₃H₇NO₂S·HF or L-Cys⁺(L-Cys...L-Cys⁺)F^-(F^-...H-F), provides the first example of a structure with cations of the `triglycine sulfate' type, i.e. A⁺(A...A⁺) (where A and A⁺ are the zwitterionic and cationic states of an amino acid, respectively), without a doubly charged counter-ion. The salt crystallizes in the monoclinic system with the space group P2₁. The dimeric (L-Cys...L-Cys⁺) cation and the dimeric (F^-...H-F) anion are formed via strong O-H...O or F-H...F hydrogen bonds, respectively, with very short O...O [2.4438 (19) Å] and F...F distances [2.2676 (17) Å]. The F...F distance is significantly shorter than in solid hydrogen fluoride. Additionally, there is another very short hydrogen bond, of O-H...F type, formed by a L-cysteinium cation and a fluoride ion. The corresponding O...F distance of 2.3412 (19) Å seems to be the shortest among O-H...F and F-H...O hydrogen bonds known to date. The single-crystal X-ray diffraction study was complemented by IR spectroscopy. Of special inter­est was the spectral region of vibrations related to the above-mentioned hydrogen bonds.

Computing details

Data collection: X-AREA (Stoe & Cie, 2007); cell refinement: X-AREA (Stoe & Cie, 2007); data reduction: X-RED (Stoe & Cie, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and X-STEP32 (Stoe & Cie, 2000); molecular graphics: Mercury (Macrae et al., 2006) and ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009).

Bis(L-cysteinium) difluoride–L-cysteine–hydrogen fluoride (1/1/1)

Crystal data

2C3H8NO2S^+·2F^−·C3H7NO2S·HF	F(000) = 444
Mr = 423.52	Dx = 1.541 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 11.8730 (6) Å	Cell parameters from 20131 reflections
b = 5.2291 (2) Å	θ = 1.8–29.6°
c = 15.3459 (9) Å	µ = 0.47 mm^−1
β = 106.602 (4)°	T = 150 K
V = 913.03 (8) Å^3	Needle, colorless
Z = 2	0.47 × 0.15 × 0.07 mm

Data collection

Stoe IPDS 2 diffractometer	4386 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	4013 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.033
Detector resolution: 6.67 pixels mm^-1	θmax = 28.3°, θmin = 1.8°
rotation method scans	h = −15→15
Absorption correction: numerical (X-RED; Stoe & Cie, 2007)	k = −6→6
Tmin = 0.874, Tmax = 0.969	l = −20→20
14224 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.029	Only H-atom coordinates refined
wR(F^2) = 0.064	w = 1/[σ^2(Fo^2) + (0.0372P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
4386 reflections	Δρmax = 0.46 e Å^−3
289 parameters	Δρmin = −0.43 e Å^−3
1 restraint	Absolute structure: Flack (1983), 1888 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.03 (5)

Special details

Experimental. Single crystal X-ray diffraction experiments was performed using a STOE IPDS-II diffractometer, equipped with a molybdenum X-ray tube (λ = 0.71073 Å) and an image plate detector. Data were collected at 150 K. Data collection, indexing and integration of reflections as well as data reduction were performed using the X-Area software (Stoe & Cie GmbH, 2007). Crystal structure was refined using SHELXL (Sheldrick, 1997; Sheldrick, 2008) integrated in the X-Step32 shell (Stoe & Cie GmbH, 2000).

Parameters characterizing data collection and refinement, as well as crystal data, are summarized in Table 1. Mercury (Macrae et al., 2006), ORTEP-3 (Farrugia, 2012) and PLATON (Spek, 2003) were used for visualization and analysis of the crystal structures

The structural data for (I) at 150 K are available as Supporting information, and have been deposited as a CIF to the Cambridge Crystallographic Data Base (CCDC No. 1016828). It can be downloaded freely from the following site: https://www.ccdc.cam.ac.uk.

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
S1B	0.04538 (4)	0.21024 (9)	0.19770 (3)	0.02548 (10)
H7B	0.1214 (19)	0.080 (5)	0.2302 (15)	0.031*
S1A	0.62700 (4)	1.61011 (10)	0.68321 (4)	0.03243 (12)
H7A	0.626 (2)	1.710 (5)	0.6145 (16)	0.039*
F1	0.57027 (10)	1.0857 (2)	0.83518 (8)	0.0320 (3)
H1F	0.548 (2)	0.905 (5)	0.8599 (18)	0.038*
O2B	0.06232 (12)	0.7961 (3)	0.45929 (9)	0.0261 (3)
O2A	0.31075 (12)	0.9714 (3)	0.66065 (10)	0.0289 (3)
N1A	0.39684 (14)	1.4267 (3)	0.72580 (11)	0.0208 (3)
H5A	0.430 (2)	1.322 (5)	0.7698 (16)	0.025*
H4A	0.321 (2)	1.452 (5)	0.7212 (15)	0.025*
H6A	0.433 (2)	1.561 (5)	0.7446 (15)	0.025*
F3	−0.17077 (11)	−0.0244 (3)	0.28363 (10)	0.0531 (5)
O1A	0.34290 (13)	1.0371 (3)	0.52546 (10)	0.0319 (3)
H8A	0.290 (2)	0.862 (5)	0.4988 (17)	0.038*
C1A	0.54278 (16)	1.3215 (4)	0.64300 (13)	0.0229 (4)
H1A	0.5735 (19)	1.185 (5)	0.6862 (15)	0.028*
H2A	0.555 (2)	1.288 (5)	0.5864 (16)	0.028*
C1B	0.09375 (15)	0.4669 (3)	0.27949 (12)	0.0187 (3)
H2B	0.1742 (19)	0.491 (4)	0.2887 (14)	0.022*
H1B	0.0516 (18)	0.609 (4)	0.2551 (14)	0.022*
O1B	0.23874 (10)	0.6526 (3)	0.45526 (9)	0.0266 (3)
C3B	0.12722 (14)	0.6443 (3)	0.43553 (10)	0.0189 (3)
C2B	0.07312 (14)	0.4223 (3)	0.37209 (11)	0.0173 (3)
H3B	0.1067 (18)	0.270 (4)	0.4007 (14)	0.021*
C2A	0.41244 (15)	1.3502 (3)	0.63704 (11)	0.0193 (3)
H3A	0.3759 (19)	1.493 (5)	0.5936 (15)	0.023*
N1B	−0.05445 (14)	0.4043 (4)	0.36405 (11)	0.0251 (3)
H5B	−0.088 (2)	0.554 (5)	0.3412 (17)	0.030*
H4B	−0.062 (2)	0.382 (5)	0.4187 (18)	0.030*
H6B	−0.084 (2)	0.281 (5)	0.3301 (18)	0.030*
C3A	0.34884 (14)	1.0962 (4)	0.60840 (11)	0.0211 (3)
S1C	0.13977 (4)	0.66918 (9)	0.06077 (4)	0.03172 (12)
H7C	0.217 (2)	0.644 (5)	0.1156 (16)	0.038*
N1C	0.37888 (13)	0.8327 (3)	−0.00018 (11)	0.0231 (3)
H6C	0.3788 (19)	0.717 (5)	0.0378 (16)	0.028*
H4C	0.417 (2)	0.794 (5)	−0.0406 (17)	0.028*
H5C	0.412 (2)	0.970 (5)	0.0290 (16)	0.028*
O1C	0.16396 (11)	1.1844 (3)	−0.16936 (9)	0.0302 (3)
H8C	0.170 (2)	1.309 (5)	−0.2111 (18)	0.036*
O2C	0.35190 (12)	1.2685 (3)	−0.09541 (10)	0.0315 (3)
C1C	0.18091 (17)	0.9535 (4)	0.00988 (14)	0.0256 (4)
H2C	0.112 (2)	1.034 (5)	−0.0198 (16)	0.031*
H1C	0.217 (2)	1.064 (5)	0.0558 (16)	0.031*
C3C	0.26318 (14)	1.1399 (4)	−0.10910 (11)	0.0210 (3)
C2C	0.25708 (14)	0.9019 (3)	−0.05326 (12)	0.0203 (3)
H3C	0.2270 (18)	0.760 (4)	−0.0936 (15)	0.024*
F2	0.50953 (10)	0.7137 (2)	0.88290 (7)	0.0295 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1B	0.0283 (2)	0.0276 (2)	0.0219 (2)	−0.00605 (18)	0.00945 (16)	−0.00723 (18)
S1A	0.0280 (2)	0.0356 (3)	0.0360 (3)	−0.0151 (2)	0.01298 (19)	−0.0139 (2)
F1	0.0364 (6)	0.0298 (6)	0.0288 (6)	−0.0032 (5)	0.0077 (5)	−0.0032 (5)
O2B	0.0291 (7)	0.0257 (7)	0.0238 (6)	0.0016 (5)	0.0080 (5)	−0.0040 (5)
O2A	0.0316 (7)	0.0277 (7)	0.0287 (7)	−0.0095 (6)	0.0105 (5)	−0.0011 (6)
N1A	0.0194 (7)	0.0232 (8)	0.0199 (7)	0.0014 (6)	0.0056 (6)	−0.0027 (6)
F3	0.0325 (7)	0.0843 (11)	0.0508 (8)	−0.0328 (7)	0.0252 (6)	−0.0442 (8)
O1A	0.0399 (8)	0.0330 (8)	0.0242 (7)	−0.0170 (6)	0.0116 (6)	−0.0102 (6)
C1A	0.0206 (8)	0.0230 (9)	0.0273 (9)	−0.0045 (7)	0.0101 (7)	−0.0048 (7)
C1B	0.0177 (8)	0.0180 (8)	0.0205 (8)	−0.0014 (6)	0.0056 (6)	−0.0013 (6)
O1B	0.0185 (5)	0.0266 (7)	0.0310 (6)	−0.0044 (5)	0.0012 (5)	−0.0087 (6)
C3B	0.0219 (7)	0.0180 (8)	0.0156 (7)	−0.0017 (6)	0.0034 (5)	0.0000 (6)
C2B	0.0158 (7)	0.0184 (8)	0.0171 (8)	−0.0021 (6)	0.0036 (6)	0.0010 (6)
C2A	0.0198 (8)	0.0208 (8)	0.0172 (8)	−0.0020 (6)	0.0053 (6)	−0.0015 (6)
N1B	0.0209 (7)	0.0364 (9)	0.0184 (8)	−0.0091 (7)	0.0061 (6)	−0.0028 (7)
C3A	0.0175 (7)	0.0253 (9)	0.0205 (8)	−0.0041 (7)	0.0052 (6)	−0.0024 (7)
S1C	0.0302 (2)	0.0300 (3)	0.0389 (3)	−0.00468 (19)	0.01631 (19)	0.0079 (2)
N1C	0.0185 (7)	0.0265 (8)	0.0246 (8)	0.0007 (6)	0.0067 (6)	0.0063 (7)
O1C	0.0200 (6)	0.0308 (7)	0.0343 (7)	−0.0013 (6)	−0.0009 (5)	0.0093 (6)
O2C	0.0235 (6)	0.0343 (8)	0.0320 (7)	−0.0086 (6)	0.0006 (5)	0.0129 (6)
C1C	0.0247 (9)	0.0204 (9)	0.0350 (10)	0.0005 (7)	0.0140 (8)	0.0039 (8)
C3C	0.0198 (7)	0.0224 (9)	0.0206 (8)	−0.0001 (6)	0.0056 (6)	0.0000 (7)
C2C	0.0159 (7)	0.0201 (8)	0.0241 (8)	−0.0004 (6)	0.0047 (6)	0.0003 (7)
F2	0.0333 (5)	0.0288 (6)	0.0264 (5)	−0.0009 (5)	0.0086 (4)	0.0003 (5)

Geometric parameters (Å, º)

S1B—C1B	1.8153 (18)	C2B—N1B	1.487 (2)
S1B—H7B	1.13 (2)	C2B—H3B	0.94 (2)
S1A—C1A	1.8183 (19)	C2A—C3A	1.529 (2)
S1A—H7A	1.17 (2)	C2A—H3A	1.01 (2)
F1—H1F	1.08 (3)	N1B—H5B	0.90 (3)
O2B—C3B	1.232 (2)	N1B—H4B	0.87 (3)
O2A—C3A	1.217 (2)	N1B—H6B	0.84 (3)
N1A—C2A	1.481 (2)	S1C—C1C	1.810 (2)
N1A—H5A	0.87 (2)	S1C—H7C	1.06 (2)
N1A—H4A	0.90 (2)	N1C—C2C	1.488 (2)
N1A—H6A	0.83 (3)	N1C—H6C	0.84 (3)
O1A—C3A	1.292 (2)	N1C—H4C	0.89 (3)
O1A—H8A	1.12 (3)	N1C—H5C	0.88 (3)
C1A—C2A	1.531 (2)	O1C—C3C	1.294 (2)
C1A—H1A	0.97 (2)	O1C—H8C	0.93 (3)
C1A—H2A	0.94 (2)	O2C—C3C	1.216 (2)
C1B—C2B	1.527 (2)	C1C—C2C	1.527 (3)
C1B—H2B	0.93 (2)	C1C—H2C	0.91 (2)
C1B—H1B	0.91 (2)	C1C—H1C	0.92 (2)
O1B—C3B	1.272 (2)	C3C—C2C	1.524 (3)
O1B—H8A	1.34 (3)	C2C—H3C	0.97 (2)
C3B—C2B	1.533 (2)	F2—H1F	1.20 (3)
C1B—S1B—H7B	94.9 (12)	C3A—C2A—H3A	111.7 (13)
C1A—S1A—H7A	101.6 (13)	C1A—C2A—H3A	110.3 (12)
C2A—N1A—H5A	113.2 (15)	C2B—N1B—H5B	108.0 (15)
C2A—N1A—H4A	110.8 (14)	C2B—N1B—H4B	107.8 (15)
H5A—N1A—H4A	112 (2)	H5B—N1B—H4B	109 (2)
C2A—N1A—H6A	111.1 (16)	C2B—N1B—H6B	109.5 (17)
H5A—N1A—H6A	101 (2)	H5B—N1B—H6B	111 (2)
H4A—N1A—H6A	108 (2)	H4B—N1B—H6B	111 (2)
C3A—O1A—H8A	115.0 (13)	O2A—C3A—O1A	126.52 (17)
C2A—C1A—S1A	112.78 (13)	O2A—C3A—C2A	121.49 (15)
C2A—C1A—H1A	106.8 (13)	O1A—C3A—C2A	111.98 (15)
S1A—C1A—H1A	108.4 (14)	C1C—S1C—H7C	99.4 (14)
C2A—C1A—H2A	112.6 (14)	C2C—N1C—H6C	111.1 (15)
S1A—C1A—H2A	104.8 (15)	C2C—N1C—H4C	106.4 (15)
H1A—C1A—H2A	112 (2)	H6C—N1C—H4C	115 (2)
C2B—C1B—S1B	115.29 (12)	C2C—N1C—H5C	108.0 (15)
C2B—C1B—H2B	108.0 (13)	H6C—N1C—H5C	109 (2)
S1B—C1B—H2B	108.1 (14)	H4C—N1C—H5C	107 (2)
C2B—C1B—H1B	106.9 (13)	C3C—O1C—H8C	112.6 (15)
S1B—C1B—H1B	106.8 (14)	C2C—C1C—S1C	114.23 (14)
H2B—C1B—H1B	111.8 (19)	C2C—C1C—H2C	111.7 (15)
C3B—O1B—H8A	116.1 (11)	S1C—C1C—H2C	106.4 (16)
O2B—C3B—O1B	127.20 (16)	C2C—C1C—H1C	111.7 (15)
O2B—C3B—C2B	119.46 (14)	S1C—C1C—H1C	108.1 (15)
O1B—C3B—C2B	113.30 (14)	H2C—C1C—H1C	104 (2)
N1B—C2B—C1B	111.28 (13)	O2C—C3C—O1C	126.18 (17)
N1B—C2B—C3B	109.43 (14)	O2C—C3C—C2C	122.16 (15)
C1B—C2B—C3B	109.01 (13)	O1C—C3C—C2C	111.65 (15)
N1B—C2B—H3B	105.7 (13)	N1C—C2C—C3C	108.15 (14)
C1B—C2B—H3B	113.8 (13)	N1C—C2C—C1C	110.79 (15)
C3B—C2B—H3B	107.5 (13)	C3C—C2C—C1C	110.15 (15)
N1A—C2A—C3A	108.53 (14)	N1C—C2C—H3C	106.7 (13)
N1A—C2A—C1A	111.18 (14)	C3C—C2C—H3C	109.5 (13)
C3A—C2A—C1A	109.86 (14)	C1C—C2C—H3C	111.4 (13)
N1A—C2A—H3A	105.2 (13)
S1B—C1B—C2B—N1B	−63.75 (18)	C1A—C2A—C3A—O2A	111.21 (19)
S1B—C1B—C2B—C3B	175.48 (11)	N1A—C2A—C3A—O1A	169.92 (15)
O2B—C3B—C2B—N1B	−10.8 (2)	C1A—C2A—C3A—O1A	−68.33 (19)
O1B—C3B—C2B—N1B	171.54 (15)	O2C—C3C—C2C—N1C	−12.9 (2)
O2B—C3B—C2B—C1B	111.15 (17)	O1C—C3C—C2C—N1C	168.12 (15)
O1B—C3B—C2B—C1B	−66.56 (18)	O2C—C3C—C2C—C1C	108.3 (2)
S1A—C1A—C2A—N1A	−56.45 (19)	O1C—C3C—C2C—C1C	−70.7 (2)
S1A—C1A—C2A—C3A	−176.60 (12)	S1C—C1C—C2C—N1C	−73.53 (18)
N1A—C2A—C3A—O2A	−10.5 (2)	S1C—C1C—C2C—C3C	166.86 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1A—H4A···F3^i	0.90 (2)	1.76 (2)	2.659 (2)	175 (2)
N1A—H5A···F1	0.87 (2)	2.08 (3)	2.874 (2)	150 (2)
N1A—H5A···O2C^ii	0.87 (2)	2.51 (2)	3.055 (2)	120.9 (19)
N1A—H6A···F2^iii	0.83 (3)	2.21 (2)	2.830 (2)	132 (2)
N1A—H6A···O2A^iii	0.83 (3)	2.70 (2)	3.094 (2)	110.6 (18)
O1A—H8A···O1B	1.12 (3)	1.34 (3)	2.4438 (19)	169 (2)
S1A—H7A···O1A^iv	1.17 (2)	2.45 (3)	3.3440 (15)	130.9 (18)
N1B—H4B···O2B^v	0.87 (3)	1.93 (3)	2.797 (2)	172 (2)
N1B—H5B···F3^iii	0.90 (3)	2.47 (3)	3.374 (3)	177 (2)
N1B—H6B···F3	0.84 (3)	1.93 (3)	2.735 (2)	162 (2)
S1B—H7B···S1A^vi	1.13 (2)	2.91 (2)	3.8318 (7)	139.3 (16)
N1C—H4C···F2^vii	0.89 (3)	1.87 (3)	2.757 (2)	175 (2)
N1C—H5C···F2^iv	0.88 (3)	1.90 (3)	2.757 (2)	166 (2)
N1C—H6C···F1^viii	0.84 (3)	1.99 (3)	2.751 (2)	150 (2)
O1C—H8C···F3^ix	0.93 (3)	1.42 (3)	2.3412 (19)	172 (3)
S1C—H7C···F1^viii	1.06 (2)	2.44 (2)	3.3840 (12)	147.9 (18)
F1—H1F···F2	1.08 (3)	1.20 (3)	2.2676 (17)	172 (3)
N1B—H5B···O1C^x	0.90 (3)	2.62 (3)	3.247 (2)	127.0 (19)

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