Pyridoxinium trichloro­acetate

In the title compound, C₈H₁₂NO₃⁺·C₂Cl₃O₂⁻, the –CH₂OH groups are twisted out of the plane of the pyridine ring. There is an intra­molecular hydrogen bond between the phenol OH and the adjacent –CH₂OH group with an S(6) motif. Closed R₂⁴(16) rings are observed around the inversion centres of the unit cell as a result of N—H...O and O—H...O inter­actions. Two zigzag chain C₂²(11) motifs are also formed by the hydrogen-bonding inter­actions of the cations and the anions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.005 Å
• Disorder in main residue
• R factor = 0.045
• wR factor = 0.133
• Data-to-parameter ratio = 13.2

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for        C12

Alert level C
PLAT301_ALERT_3_C Main Residue  Disorder .........................       5.00 Perc.
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          5
PLAT779_ALERT_2_C Suspect or Irrelevant (Bond) Angle in CIF ......      29.20 Deg.
              O42  -C41  -O41     1.555   1.555   1.555
PLAT779_ALERT_2_C Suspect or Irrelevant (Bond) Angle in CIF ......      29.40 Deg.
              H41A -C41  -H42A    1.555   1.555   1.555
PLAT779_ALERT_2_C Suspect or Irrelevant (Bond) Angle in CIF ......      27.70 Deg.
              H41B -C41  -H42B    1.555   1.555   1.555

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Vitamin B6, a water-soluble vitamin, is also known as pyridoxine. It is essential for both mental and physical health. Other forms of vitamin B6 include pyridoxal and pyridoxamine. Pyridoxine is involved in the production of antibodies, which protect humans against bacterial diseases. Furthermore, the combination of pyridoxine with immunosuppressive drugs improves the efficiency of that therapy (Trakatellis et al., 1992). Pyridoxal phosphate can bind to steroid hormone receptors and may have a role in regulating steroid hormone action. Pyridoxal phosphate can be converted to pyridoxamine phosphate which can also serve as an enzyme cofactor (Leklem, 1990). Pyridoxine has been found to play an essential role in the nervous system and aids in the metabolism of fats, carbohydrates and proteins. The crystal structures of pyridoxine (Longo et al., 1982), pyridoxinium chloride (Bacon & Plant, 1980), pyridoxamine monohydrochloride (Longo & Richardson, 1980), copper complexes of neutral pyridoxamine (Franklin & Richardson, 1980), cis-(oxalato-O,O')-bis (pyridoxine-N)-palladium (II) (Dey et al., 2003), 6-dimethyl aminopyridoxine-α⁴-(t-butyldimethylsilyl ether) (Culbertson et al., 2003) and aqua-bis (2-methyl-4,5-bis(hydroxymethyl) pyridinium-3-oxalato-O,O')-dioxo-uranium dichloride, (Bonfada et al., 2005) are already known. The crystal structure of pyridoxinium picrate was already investigated from our laboratory (Anitha et al., 2006). In the present work, the crystal structure of pyridoxinie trichloroacetate is reported.

The asymmetric part of the unit cell of (I), contains a pyridoxinium cation and a trichloroacetate anion (Fig. 1). One of the –CH₂OH groups, is disordered over two positions. Generally, many of the vitamin B6 structures so far determined exist as zwitterions in which the phenolic group is deprotonated and pyridine N atom is protonated (Cambridge Structural Database; Version 5.28; Allen, 2002), a form found in metal–pyridoxine complexes such as bis(µ₂–pyridoxinato)diaquatetrachlorodiiron(III) (Sabirov et al., 1993). In the present structure, both the phenolic group and the pyridine N atom are protonated like pyridoxinium picrate (Anitha et al., 2006) as evidenced by the C3—O3 and C—N1 bond distances (Table 1). Twisting of the –CH₂OH groups is a characteristic feature of all pyridoxine complexes. Twisting in the present structure can be notified from the torsional angles involved in the –CH₂OH groups (Table 1). The deviations of atoms O41, O42 and O52 from the plane of the ring are -0.166 (11), 0.537 (15) and -0.029 (6) Å, respectively.

An ntramolecular hydrogen bond forms between the phenolic OH and the adjacent –CH₂OH group, generating an S(6) hydrogen-bonded graph-set motif (Etter et al., 1990). This S(6) intramolecular motif is observed in many pyridoxine complexes, and is an another characterestic feature. The pyridoxinium cation is linked to the anion and forms a closed ring structure through N—H—O and O—H···O hydrogen bonds around the inversion centres of the unit cell leading to the graph-set motif of R₂⁴(16) (Fig 2). The disordered –CH₂OH group and the phenolic –OH group are making interaction with the anion through O—H···O hydrogen bonds leading to zigzag chain C₂²(11) motif. Another C₂²(11) motif propogating along the b axis is seen through N—H···O and O—H···O hydrogen bonds (Table 2).

Related literature

For related literature on hydrogen-bond motifs see Etter et al. (1990) and for values of bond lengths and angles see Allen (2002). For related structures see Longo et al. (1982), Bacon & Plant (1980), Longo & Richardson, (1980), Franklin & Richardson (1980), Dey et al. (2003), Culbertson et al. (2003), Bonfada et al. (2005) and Anitha et al. (2006). For other related literature, see: Leklem (1990); Sabirov et al. (1993); Trakatellis et al. (1992).

S2. Experimental

The title compound (I), was crystallized from an aqueous mixture of pyridoxine and trichloroacetic acid in the stoichiometric ratio of 1:1 at room temperature by the technique of slow evaporation.

S3. Refinement

All the hydrogen atoms were placed in geometrically calculated positions and included in the refinement as riding-model approximation, with O—H = 0.82 Å, C—H = 0.93–0.97 Å and N—H = 0.86 Å and U_iso equal to 1.2–1.5 U_eq of the carrier atom. In the cation, O atom in one of the –CH₂OH groups is disordered over two postions with the site occupancies of 0.57 and 0.43.

Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXTL/PC (Bruker, 2000); program(s) used to refine structure: SHELXTL/PC; molecular graphics: ORTEP-3 (Farrugia, 1997), Mercury (Macrae et al., 2006) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL/PC.

Figures

	Fig. 1. The molecular structure of title compound with atom numbering scheme and 50% probability displacement ellipsoids. H-bonds are shown as dashed lines.
	Fig. 2. A packing diagram of (I), viewed down the a axis. Only the major components of the disordered atoms are shown for claritly. H atoms not involved in the H-bonds (dashed lines) are removed for clarity.

Pyridoxinium trichloroacetate

Crystal data

C8H12NO3^+·C2Cl3O2^−	F(000) = 680
Mr = 332.56	Dx = 1.576 Mg m^−3 Dm = 1.56 (1) Mg m^−3 Dm measured by flotation using a liquid-mixture of xylene and carbon tetrachloride
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 5.8552 (5) Å	θ = 9.6–13.6°
b = 17.1467 (15) Å	µ = 0.67 mm^−1
c = 14.0988 (10) Å	T = 293 K
β = 97.948 (17)°	Block, colourless
V = 1401.9 (2) Å^3	0.21 × 0.19 × 0.17 mm
Z = 4

Data collection

Nonius MACH3 diffractometer	1531 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.016
Graphite monochromator	θmax = 25.0°, θmin = 2.4°
ω–2θ scans	h = 0→6
Absorption correction: ψ scan (North et al., 1968)	k = −1→20
Tmin = 0.881, Tmax = 0.899	l = −16→16
2906 measured reflections	3 standard reflections every 60 min
2459 independent reflections	intensity decay: none

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.133	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0554P)^2 + 1.5035P] where P = (Fo^2 + 2Fc^2)/3
2459 reflections	(Δ/σ)max < 0.001
186 parameters	Δρmax = 0.45 e Å^−3
0 restraints	Δρmin = −0.36 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	Occ. (<1)
N1	0.0773 (5)	0.09533 (16)	0.09102 (19)	0.0420 (7)
H1	0.1052	0.1338	0.0553	0.050*
C2	−0.0916 (6)	0.1034 (2)	0.1446 (2)	0.0400 (8)
C21	−0.2235 (7)	0.1776 (2)	0.1420 (3)	0.0578 (10)
H21A	−0.1525	0.2157	0.1057	0.087*
H21B	−0.2242	0.1963	0.2062	0.087*
H21C	−0.3792	0.1686	0.1126	0.087*
C3	−0.1321 (6)	0.0409 (2)	0.2035 (2)	0.0401 (8)
O3	−0.3063 (5)	0.05226 (16)	0.2563 (2)	0.0581 (7)
H3	−0.3096	0.0160	0.2940	0.087*
C4	0.0004 (6)	−0.02650 (19)	0.2062 (2)	0.0396 (8)
C41	−0.0325 (7)	−0.0941 (2)	0.2707 (3)	0.0554 (10)
H41A	−0.0410	−0.1419	0.2336	0.067*	0.53
H41B	0.1005	−0.0979	0.3199	0.067*	0.53
H42A	−0.1220	−0.1348	0.2351	0.067*	0.47
H42B	0.1163	−0.1156	0.2967	0.067*	0.47
O41	−0.2380 (18)	−0.0869 (7)	0.3159 (9)	0.074 (3)	0.57
H41	−0.2351	−0.1194	0.3588	0.112*	0.57
O42	−0.146 (3)	−0.0673 (8)	0.3456 (11)	0.072 (4)	0.43
H42	−0.1816	−0.1046	0.3769	0.108*	0.43
C5	0.1720 (6)	−0.0312 (2)	0.1463 (2)	0.0406 (8)
C51	0.3171 (7)	−0.1035 (2)	0.1441 (3)	0.0528 (10)
H51A	0.3993	−0.1137	0.2074	0.063*
H51B	0.2192	−0.1480	0.1249	0.063*
O52	0.4755 (6)	−0.09238 (17)	0.0786 (2)	0.0723 (9)
H52	0.5598	−0.1306	0.0792	0.108*
C6	0.2066 (6)	0.0309 (2)	0.0894 (2)	0.0422 (8)
H6	0.3201	0.0285	0.0494	0.051*
O11	0.2154 (5)	0.20163 (14)	−0.03583 (18)	0.0530 (7)
O12	0.2032 (6)	0.29565 (17)	0.0689 (2)	0.0767 (10)
C11	0.2437 (6)	0.2694 (2)	−0.0072 (3)	0.0436 (8)
C12	0.3523 (6)	0.3270 (2)	−0.0752 (3)	0.0463 (9)
Cl1	0.3153 (2)	0.29344 (7)	−0.19483 (8)	0.0776 (4)
Cl2	0.2266 (3)	0.41993 (7)	−0.07418 (10)	0.0905 (5)
Cl3	0.6480 (2)	0.33330 (10)	−0.03478 (11)	0.0981 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0488 (18)	0.0368 (16)	0.0421 (16)	−0.0028 (14)	0.0122 (14)	0.0037 (13)
C2	0.043 (2)	0.0382 (18)	0.0396 (18)	−0.0004 (16)	0.0068 (16)	0.0005 (15)
C21	0.059 (3)	0.048 (2)	0.070 (3)	0.008 (2)	0.020 (2)	0.009 (2)
C3	0.040 (2)	0.044 (2)	0.0379 (18)	−0.0040 (16)	0.0118 (15)	−0.0043 (15)
O3	0.0587 (17)	0.0566 (17)	0.0657 (18)	0.0067 (14)	0.0325 (14)	0.0079 (14)
C4	0.046 (2)	0.0372 (18)	0.0354 (17)	−0.0019 (16)	0.0056 (15)	−0.0001 (14)
C41	0.064 (3)	0.050 (2)	0.057 (2)	0.003 (2)	0.024 (2)	0.0113 (19)
O41	0.071 (6)	0.070 (7)	0.090 (8)	0.004 (4)	0.040 (5)	0.036 (5)
O42	0.108 (12)	0.043 (6)	0.079 (9)	0.001 (6)	0.061 (8)	0.020 (5)
C5	0.043 (2)	0.0397 (19)	0.0397 (18)	−0.0031 (16)	0.0063 (15)	−0.0029 (15)
C51	0.056 (2)	0.043 (2)	0.062 (2)	0.0059 (18)	0.019 (2)	0.0036 (18)
O52	0.081 (2)	0.0550 (18)	0.091 (2)	0.0190 (15)	0.0490 (19)	0.0064 (16)
C6	0.044 (2)	0.0398 (19)	0.046 (2)	−0.0001 (16)	0.0148 (16)	−0.0023 (16)
O11	0.0693 (18)	0.0352 (14)	0.0612 (16)	−0.0001 (12)	0.0321 (14)	0.0019 (12)
O12	0.118 (3)	0.0550 (18)	0.0680 (19)	−0.0143 (17)	0.0530 (19)	−0.0151 (15)
C11	0.045 (2)	0.041 (2)	0.047 (2)	0.0042 (17)	0.0139 (17)	0.0031 (16)
C12	0.045 (2)	0.042 (2)	0.053 (2)	0.0003 (17)	0.0116 (17)	0.0090 (17)
Cl1	0.1067 (10)	0.0787 (8)	0.0521 (6)	−0.0178 (7)	0.0271 (6)	0.0053 (6)
Cl2	0.1338 (12)	0.0476 (6)	0.0919 (9)	0.0246 (7)	0.0218 (8)	0.0187 (6)
Cl3	0.0517 (7)	0.1302 (12)	0.1074 (10)	−0.0239 (7)	−0.0065 (6)	0.0533 (9)

Geometric parameters (Å, º)

N1—C2	1.332 (4)	C41—H42A	0.9700
N1—C6	1.342 (4)	C41—H42B	0.9700
N1—H1	0.8600	O41—H41	0.8200
C2—C3	1.396 (5)	O42—H42	0.8200
C2—C21	1.486 (5)	C5—C6	1.365 (5)
C21—H21A	0.9600	C5—C51	1.505 (5)
C21—H21B	0.9600	C51—O52	1.410 (4)
C21—H21C	0.9600	C51—H51A	0.9700
C3—O3	1.357 (4)	C51—H51B	0.9700
C3—C4	1.390 (5)	O52—H52	0.8200
O3—H3	0.8200	C6—H6	0.9300
C4—C5	1.402 (5)	O11—C11	1.235 (4)
C4—C41	1.502 (5)	O12—C11	1.217 (4)
C41—O42	1.400 (15)	C11—C12	1.570 (5)
C41—O41	1.443 (12)	C12—Cl3	1.750 (4)
C41—H41A	0.9700	C12—Cl2	1.757 (4)
C41—H41B	0.9700	C12—Cl1	1.766 (4)
C2—N1—C6	124.1 (3)	H41A—C41—H42A	29.4
C2—N1—H1	118.0	H41B—C41—H42A	130.2
C6—N1—H1	118.0	O42—C41—H42B	109.6
N1—C2—C3	117.3 (3)	O41—C41—H42B	128.8
N1—C2—C21	119.9 (3)	C4—C41—H42B	109.8
C3—C2—C21	122.8 (3)	H41A—C41—H42B	81.9
C2—C21—H21A	109.5	H41B—C41—H42B	27.7
C2—C21—H21B	109.5	H42A—C41—H42B	108.4
H21A—C21—H21B	109.5	C41—O41—H41	109.5
C2—C21—H21C	109.5	C41—O42—H42	109.5
H21A—C21—H21C	109.5	C6—C5—C4	119.1 (3)
H21B—C21—H21C	109.5	C6—C5—C51	120.0 (3)
O3—C3—C4	124.3 (3)	C4—C5—C51	120.9 (3)
O3—C3—C2	114.7 (3)	O52—C51—C5	109.0 (3)
C4—C3—C2	121.0 (3)	O52—C51—H51A	109.9
C3—O3—H3	109.5	C5—C51—H51A	109.9
C3—C4—C5	118.4 (3)	O52—C51—H51B	109.9
C3—C4—C41	122.7 (3)	C5—C51—H51B	109.9
C5—C4—C41	118.9 (3)	H51A—C51—H51B	108.3
O42—C41—O41	29.2 (6)	C51—O52—H52	109.5
O42—C41—C4	108.5 (7)	N1—C6—C5	120.2 (3)
O41—C41—C4	112.7 (6)	N1—C6—H6	119.9
O42—C41—H41A	133.6	C5—C6—H6	119.9
O41—C41—H41A	109.0	O12—C11—O11	127.1 (3)
C4—C41—H41A	109.0	O12—C11—C12	116.8 (3)
O42—C41—H41B	84.3	O11—C11—C12	116.0 (3)
O41—C41—H41B	109.0	C11—C12—Cl3	107.8 (2)
C4—C41—H41B	109.0	C11—C12—Cl2	111.1 (2)
H41A—C41—H41B	107.8	Cl3—C12—Cl2	109.7 (2)
O42—C41—H42A	110.3	C11—C12—Cl1	111.9 (3)
O41—C41—H42A	82.3	Cl3—C12—Cl1	108.4 (2)
C4—C41—H42A	110.3	Cl2—C12—Cl1	107.9 (2)
C6—N1—C2—C3	1.1 (5)	C41—C4—C5—C6	−178.3 (3)
C6—N1—C2—C21	179.4 (3)	C3—C4—C5—C51	−178.4 (3)
N1—C2—C3—O3	−179.9 (3)	C41—C4—C5—C51	1.7 (5)
C21—C2—C3—O3	1.8 (5)	C6—C5—C51—O52	0.3 (5)
N1—C2—C3—C4	0.5 (5)	C4—C5—C51—O52	−179.6 (3)
C21—C2—C3—C4	−177.8 (3)	C2—N1—C6—C5	−1.3 (5)
O3—C3—C4—C5	178.6 (3)	C4—C5—C6—N1	−0.1 (5)
C2—C3—C4—C5	−1.9 (5)	C51—C5—C6—N1	179.9 (3)
O3—C3—C4—C41	−1.5 (6)	O12—C11—C12—Cl3	80.3 (4)
C2—C3—C4—C41	178.1 (3)	O11—C11—C12—Cl3	−97.6 (3)
C3—C4—C41—O42	−21.0 (8)	O12—C11—C12—Cl2	−40.0 (4)
C5—C4—C41—O42	158.9 (7)	O11—C11—C12—Cl2	142.2 (3)
C3—C4—C41—O41	10.0 (7)	O12—C11—C12—Cl1	−160.6 (3)
C5—C4—C41—O41	−170.1 (5)	O11—C11—C12—Cl1	21.5 (4)
C3—C4—C5—C6	1.6 (5)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O11	0.86	1.91	2.752 (4)	166
O3—H3···O41	0.82	1.83	2.544 (13)	145
O3—H3···O42	0.82	1.81	2.518 (17)	143
O41—H41···O12^i	0.82	1.77	2.577 (13)	166
O42—H42···O12^i	0.82	1.88	2.683 (14)	164
O52—H52···O11^ii	0.82	1.95	2.729 (4)	158

Symmetry codes: (i) −x, y−1/2, −z+1/2; (ii) −x+1, −y, −z.