supplementary materials


su2560 scheme

Acta Cryst. (2013). E69, m157-m158    [ doi:10.1107/S160053681300425X ]

(1RS,2RS)-4,4'-(1-Azaniumyl-2-hydroxyethane-1,2-diyl)dipyridinium tetrachloridoplatinate(II) chloride

J. J. Campos-Gaxiola, J. L. Almaral-Sanchez, A. Cruz-Enríquez, H. Höpfl and M. Parra-Hake

Abstract top

The title compound, (C12H16N3O)[PtCl4]Cl, consists of a 4,4'-(1-azaniumyl-2-hydroxyethane-1,2-diyl)dipyridinium trication, a square-planar tetrachloridoplatinate(II) dianion and a chloride ion. In the cation, the pyridinium rings attached to the central 1-azaniumyl-2-hydroxyethane fragment have an anti conformation, as indicated by the central C-C-C-C torsion angle of -166.5 (6)°, and they are inclined to one another by 63.5 (4)°. In the crystal, the cations and anions are linked through N-H...Cl and O-H...Cl hydrogen bonds. There are also [pi]-[pi] contacts [centroid-centroid distances = 3.671 (4) and 3.851 (4) Å] and a number of C-H...Cl interactions present, consolidating the formation of a three-dimensional supramolecular structure.

Comment top

Hydrogen bond based organic–inorganic hybrid materials are receiving continuous interest because of their structural, magnetic, optical and electrical properties (Yao et al. 2010; Sanchez et al. 2011; Pardo et al. 2011 and Piecha et al. 2012). An interesting approach for the preparation of such materials consists in the utilization of supramolecular synthons containing charge-assisted N+–H···-Cl hydrogen bonds, through which organic cations and anionic metal complexes are linked to form crystalline organic–inorganic hybrid solids (Fusi et al. 2012; Adarsh et al. 2010; Campos-Gaxiola et al. 2010, and Adams et al. 2005). As a further contribution we report herein the crystal structure of the title compound.

The molecular structure of the title compound is illustrated in Fig. 1. The asymmetric unit consists of one threefold charged organic cation in a general position, one independent [PtCl4]2- dianion, and one chloride atom (Fig 1). In the cation, the pyridinium rings attached to the central 2-ammoniumethanol fragment show anti conformation, as indicated by the C8—C1—C2—C3 torsion angle of -166.5 (6)°. The pyridinium rings form a dihedral angle of 63.5 (4)°. The Pt atom is embedded in a square-planar coordination environment with Pt—Cl distances ranging from 2.2999 (17) to 2.3127 (18) Å.

In the crystal, the cations and anions are linked by charge-assisted N+—H···-Cl, O—H···-Cl hydrogen bonds (Table 1). There are also a number of C—H···Cl contacts and ππ interactions present, consolidating the formation of the three-dimensional supramolecular structure (Table 1 and Fig 2). The ππ interactions are parallel slipped interactions involving inversion related pyridinium rings, Cg1 = N2/C8-C12 and Cg2 = N3/C3-C7 [Cg1···Cg1i = 3.851 (4); normal distance 3.487 (3) Å; slippage 1.634 Å; symmetry code: (i) -x, -y+2, -z: Cg2···Cg2ii = 3.671 (4) Å; normal distance 3.460 (3) Å; slippage 1.225 Å; symmetry code: (ii) -x, -y+1, -z].

Related literature top

For potential applications of organic-inorganic hybrid materials with magnetic, optical and electrical properties, see: Yao et al. (2010); Sanchez et al. (2011); Pardo et al. (2011); Piecha et al. (2012). For related tetrachloroplatinate(II) compounds, see: Fusi et al. (2012); Adarsh et al. (2010); Campos-Gaxiola et al. (2010); Adams et al. (2005). For the synthesis of the title ligand, see: Campos-Gaxiola et al. (2012).

Experimental top

The organic entities in the title compound are a product of partial hydrolysis starting from 2,4,5-tris(pyridin-4-yl)-4,5-dihydro-1,3-oxazole, which was synthesized according to a previously reported procedure (Campos-Gaxiola et al., 2012). For the preparation of the platinum compound, a solution of 2,4,5-tris(pyridin-4-yl)-4,5-dihydro-1,3-oxazole (0.05 g, 0.16 mmol) in methanol and concentrated HCl (37%, 3 ml) was added dropwise to a stirring solution of potassium tetrachloroplatinate (0.06 g, 0.16 mmol) in water (5 ml). The resulting yellow solution was stirred for 40 Min at 323 K, whereupon the solution was left to evaporate slowly at room temperature. After two weeks, yellow crystals were isolated [Yield: 45%]. Spectroscopic and other analytical data for the title compound are available in the archived CIF.

Refinement top

The N—H and O—H hydrogen atoms were localized in difference Fourier maps. They were refined with distance restraints: O-H = 0.84 (1) Å, N-H = 0.86 (1) (NH3+) and 0.84 (1) Å (pyN-H+), with Uiso(H) = 1.5 Ueq(O, N). C-bound H atoms were positioned geometrically and refined using a riding-model approximation: aryl C—H = 0.93 Å, alkyl C—H = 0.98 Å with Uiso(H) = 1.2 Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus-NT (Bruker 2001); data reduction: SAINT-Plus-NT (Bruker 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. Perspective view of a fragment of the three-dimensional supramolecular network with O—H···Cl, N—H···Cl and C—H···Cl hydrogen bonds (dashed lines; see Table 1 for details).
(1RS,2RS)-4,4'-(1-Azaniumyl-2-hydroxyethane-1,2-diyl)dipyridinium tetrachloridoplatinate(II) chloride top
Crystal data top
(C12H16N3O)[PtCl4]ClZ = 2
Mr = 590.62F(000) = 560
Triclinic, P1Dx = 2.326 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.636 (2) ÅCell parameters from 926 reflections
b = 8.082 (2) Åθ = 2.7–27.5°
c = 14.599 (4) ŵ = 9.12 mm1
α = 88.689 (4)°T = 100 K
β = 84.240 (4)°Rectangular prism, orange
γ = 70.148 (4)°0.50 × 0.26 × 0.12 mm
V = 843.1 (4) Å3
Data collection top
Bruker SMART CCD area-detector
diffractometer
2911 independent reflections
Radiation source: fine-focus sealed tube2726 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.043
phi and ω scansθmax = 25.0°, θmin = 2.7°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 89
Tmin = 0.092, Tmax = 0.408k = 89
5093 measured reflectionsl = 1716
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.091H atoms treated by a mixture of independent and constrained refinement
S = 1.05 w = 1/[σ2(Fo2) + (0.043P)2]
where P = (Fo2 + 2Fc2)/3
2911 reflections(Δ/σ)max < 0.001
217 parametersΔρmax = 2.34 e Å3
6 restraintsΔρmin = 1.98 e Å3
Crystal data top
(C12H16N3O)[PtCl4]Clγ = 70.148 (4)°
Mr = 590.62V = 843.1 (4) Å3
Triclinic, P1Z = 2
a = 7.636 (2) ÅMo Kα radiation
b = 8.082 (2) ŵ = 9.12 mm1
c = 14.599 (4) ÅT = 100 K
α = 88.689 (4)°0.50 × 0.26 × 0.12 mm
β = 84.240 (4)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
2911 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
2726 reflections with I > 2σ(I)
Tmin = 0.092, Tmax = 0.408Rint = 0.043
5093 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.038H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.091Δρmax = 2.34 e Å3
S = 1.05Δρmin = 1.98 e Å3
2911 reflectionsAbsolute structure: ?
217 parametersFlack parameter: ?
6 restraintsRogers parameter: ?
Special details top

Experimental. Spectroscopic and other analytical data for the title compound: IR (KBr, cm-1): 3409, 3198, 3071, 2882, 2825, 1706, 1620, 1500, 1417, 1331, 1295, 1232, 1031, 857 and 693. TGA: Calcd. for HCl: 4.32. Found: 4.75% (310–398 K); Calcd. for 2HCl: 8.65. Found: 8.23% (398–498 K).

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

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 (Å2) top
xyzUiso*/Ueq
O10.0077 (7)0.6320 (7)0.1932 (4)0.0269 (17)
N10.3686 (8)0.5578 (8)0.1506 (4)0.0204 (17)
N20.0968 (8)1.1792 (8)0.0449 (4)0.0209 (19)
N30.2400 (9)0.3227 (9)0.4748 (4)0.025 (2)
C10.2559 (9)0.7175 (9)0.2054 (5)0.018 (2)
C20.0855 (10)0.6886 (9)0.2597 (5)0.021 (2)
C30.1431 (9)0.5553 (9)0.3366 (5)0.019 (2)
C40.2175 (10)0.5946 (10)0.4125 (5)0.023 (2)
C50.2658 (10)0.4784 (10)0.4820 (5)0.024 (2)
C60.1694 (11)0.2782 (10)0.4047 (5)0.027 (3)
C70.1181 (10)0.3947 (9)0.3338 (5)0.022 (2)
C80.1965 (9)0.8788 (9)0.1453 (5)0.019 (2)
C90.0633 (10)1.0334 (9)0.1822 (5)0.022 (2)
C100.0133 (10)1.1822 (9)0.1300 (5)0.022 (2)
C110.2254 (10)1.0358 (9)0.0076 (5)0.022 (2)
C120.2759 (10)0.8818 (9)0.0559 (5)0.020 (2)
Pt10.63165 (3)0.09264 (3)0.31275 (2)0.0146 (1)
Cl10.6085 (3)0.1851 (2)0.32558 (12)0.0222 (6)
Cl20.4705 (3)0.1426 (2)0.18394 (12)0.0226 (5)
Cl30.6558 (2)0.3685 (2)0.30103 (12)0.0192 (5)
Cl40.8053 (3)0.0399 (2)0.43690 (13)0.0259 (6)
Cl50.2607 (2)0.4569 (2)0.96236 (11)0.0201 (5)
H10.334500.737900.249900.0210*
H1'0.117 (5)0.650 (12)0.218 (5)0.0400*
H1A0.317 (10)0.528 (10)0.107 (4)0.0310*
H1B0.480 (4)0.560 (11)0.137 (5)0.0310*
H1C0.407 (11)0.467 (6)0.185 (4)0.0310*
H20.002000.801000.286800.0250*
H2'0.071 (11)1.280 (4)0.022 (5)0.0320*
H3'0.273 (11)0.258 (9)0.520 (4)0.0370*
H40.234800.702700.416000.0270*
H50.315200.505500.532900.0290*
H60.154200.169000.403000.0320*
H70.066700.364900.284200.0270*
H90.008401.035500.242200.0260*
H100.078101.284700.153800.0270*
H110.281601.039400.051600.0270*
H120.363100.780100.028900.0240*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.026 (3)0.035 (3)0.023 (3)0.015 (3)0.001 (2)0.001 (2)
N10.020 (3)0.021 (3)0.018 (3)0.005 (3)0.001 (3)0.002 (3)
N20.022 (3)0.013 (3)0.027 (4)0.006 (3)0.000 (3)0.002 (3)
N30.020 (3)0.029 (4)0.020 (4)0.003 (3)0.004 (3)0.005 (3)
C10.015 (3)0.019 (4)0.018 (4)0.005 (3)0.002 (3)0.000 (3)
C20.021 (4)0.021 (4)0.019 (4)0.004 (3)0.002 (3)0.000 (3)
C30.018 (4)0.024 (4)0.011 (3)0.006 (3)0.006 (3)0.000 (3)
C40.027 (4)0.022 (4)0.019 (4)0.010 (3)0.005 (3)0.007 (3)
C50.025 (4)0.032 (4)0.016 (4)0.012 (3)0.001 (3)0.006 (3)
C60.036 (5)0.023 (4)0.023 (4)0.016 (4)0.008 (3)0.003 (3)
C70.029 (4)0.026 (4)0.014 (4)0.012 (3)0.002 (3)0.004 (3)
C80.020 (4)0.022 (4)0.017 (4)0.011 (3)0.001 (3)0.005 (3)
C90.026 (4)0.020 (4)0.020 (4)0.010 (3)0.004 (3)0.000 (3)
C100.030 (4)0.018 (4)0.017 (4)0.007 (3)0.004 (3)0.003 (3)
C110.032 (4)0.022 (4)0.016 (4)0.013 (3)0.002 (3)0.002 (3)
C120.021 (4)0.020 (4)0.018 (4)0.007 (3)0.003 (3)0.003 (3)
Pt10.0164 (2)0.0135 (2)0.0136 (2)0.0049 (1)0.0005 (1)0.0017 (1)
Cl10.0271 (10)0.0188 (9)0.0244 (10)0.0119 (8)0.0050 (7)0.0010 (7)
Cl20.0248 (10)0.0238 (9)0.0193 (9)0.0077 (8)0.0047 (7)0.0010 (7)
Cl30.0255 (9)0.0136 (8)0.0182 (9)0.0068 (7)0.0000 (7)0.0018 (6)
Cl40.0365 (11)0.0214 (9)0.0243 (10)0.0127 (8)0.0144 (8)0.0043 (7)
Cl50.0198 (9)0.0204 (9)0.0201 (9)0.0076 (7)0.0006 (7)0.0024 (7)
Geometric parameters (Å, º) top
Pt1—Cl22.303 (2)C3—C41.384 (11)
Pt1—Cl32.2999 (17)C3—C71.377 (10)
Pt1—Cl12.3127 (18)C4—C51.358 (11)
Pt1—Cl42.300 (2)C6—C71.378 (10)
O1—C21.428 (10)C8—C121.386 (10)
O1—H1'0.84 (6)C8—C91.394 (10)
N1—C11.484 (9)C9—C101.370 (10)
N2—C111.324 (9)C11—C121.372 (10)
N2—C101.335 (9)C1—H10.9800
N3—C61.314 (10)C2—H20.9800
N3—C51.346 (10)C4—H40.9300
N1—H1B0.86 (5)C5—H50.9300
N1—H1C0.86 (5)C6—H60.9300
N1—H1A0.86 (7)C7—H70.9300
N2—H2'0.84 (4)C9—H90.9300
N3—H3'0.84 (6)C10—H100.9300
C1—C21.539 (11)C11—H110.9300
C1—C81.517 (10)C12—H120.9300
C2—C31.529 (10)
Cl3—Pt1—Cl489.28 (6)C3—C7—C6119.8 (7)
Cl1—Pt1—Cl490.27 (7)C9—C8—C12118.2 (6)
Cl1—Pt1—Cl290.20 (6)C1—C8—C9119.2 (6)
Cl1—Pt1—Cl3179.55 (7)C1—C8—C12122.6 (6)
Cl2—Pt1—Cl390.24 (6)C8—C9—C10119.9 (7)
Cl2—Pt1—Cl4177.33 (8)N2—C10—C9119.6 (7)
C2—O1—H1'105 (5)N2—C11—C12120.3 (7)
C10—N2—C11122.4 (6)C8—C12—C11119.6 (7)
C5—N3—C6123.5 (7)C8—C1—H1108.00
C1—N1—H1C112 (4)N1—C1—H1108.00
H1A—N1—H1B117 (7)C2—C1—H1108.00
C1—N1—H1A117 (5)C3—C2—H2109.00
H1B—N1—H1C93 (8)O1—C2—H2109.00
C1—N1—H1B109 (5)C1—C2—H2109.00
H1A—N1—H1C107 (7)C3—C4—H4119.00
C11—N2—H2'125 (5)C5—C4—H4119.00
C10—N2—H2'112 (5)N3—C5—H5121.00
C6—N3—H3'124 (5)C4—C5—H5121.00
C5—N3—H3'113 (5)C7—C6—H6120.00
N1—C1—C8111.6 (6)N3—C6—H6120.00
N1—C1—C2110.4 (6)C3—C7—H7120.00
C2—C1—C8111.2 (6)C6—C7—H7120.00
O1—C2—C1105.6 (6)C8—C9—H9120.00
O1—C2—C3112.3 (6)C10—C9—H9120.00
C1—C2—C3111.8 (6)C9—C10—H10120.00
C2—C3—C7121.2 (7)N2—C10—H10120.00
C2—C3—C4120.9 (6)N2—C11—H11120.00
C4—C3—C7118.0 (7)C12—C11—H11120.00
C3—C4—C5121.3 (7)C11—C12—H12120.00
N3—C5—C4118.0 (7)C8—C12—H12120.00
N3—C6—C7119.5 (7)
C11—N2—C10—C91.2 (12)C1—C2—C3—C468.4 (9)
C10—N2—C11—C121.0 (12)C1—C2—C3—C7113.4 (8)
C6—N3—C5—C40.6 (12)C2—C3—C4—C5178.7 (7)
C5—N3—C6—C70.1 (12)C7—C3—C4—C50.4 (12)
N1—C1—C2—O153.4 (7)C2—C3—C7—C6179.2 (7)
N1—C1—C2—C369.1 (7)C4—C3—C7—C60.9 (11)
C8—C1—C2—O171.1 (7)C3—C4—C5—N30.3 (12)
C8—C1—C2—C3166.5 (6)N3—C6—C7—C30.7 (12)
N1—C1—C8—C9168.8 (7)C1—C8—C9—C10177.5 (7)
N1—C1—C8—C1214.3 (10)C12—C8—C9—C100.5 (11)
C2—C1—C8—C945.1 (9)C1—C8—C12—C11175.3 (7)
C2—C1—C8—C12138.1 (7)C9—C8—C12—C111.6 (11)
O1—C2—C3—C4173.2 (7)C8—C9—C10—N21.9 (12)
O1—C2—C3—C75.1 (10)N2—C11—C12—C82.4 (12)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···Cl1i0.84 (6)2.49 (7)3.250 (6)152 (6)
N1—H1A···Cl5ii0.86 (7)2.32 (6)3.148 (6)162 (7)
N1—H1B···Cl5iii0.86 (5)2.30 (6)3.097 (7)154 (7)
N1—H1C···Cl20.86 (5)2.50 (5)3.214 (6)141 (6)
N1—H1C···Cl30.86 (5)2.58 (7)3.242 (6)134 (6)
N2—H2···Cl5iv0.84 (4)2.45 (7)3.088 (6)134 (7)
N2—H2···Cl5v0.84 (4)2.69 (6)3.272 (6)128 (7)
N3—H3···Cl1vi0.84 (6)2.50 (6)3.275 (6)155 (6)
N3—H3···Cl4vi0.84 (6)2.72 (7)3.286 (7)127 (7)
C1—H1···Cl1vii0.982.713.660 (8)163
C5—H5···Cl3iii0.932.713.604 (8)162
C10—H10···Cl3i0.932.733.459 (8)136
C10—H10···Cl5v0.932.743.308 (7)120
C11—H11···Cl2viii0.932.643.449 (8)145
Symmetry codes: (i) x1, y+1, z; (ii) x, y, z1; (iii) x+1, y+1, z+1; (iv) x, y+1, z1; (v) x, y+2, z+1; (vi) x+1, y, z+1; (vii) x, y+1, z; (viii) x+1, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1'···Cl1i0.84 (6)2.49 (7)3.250 (6)152 (6)
N1—H1A···Cl5ii0.86 (7)2.32 (6)3.148 (6)162 (7)
N1—H1B···Cl5iii0.86 (5)2.30 (6)3.097 (7)154 (7)
N1—H1C···Cl20.86 (5)2.50 (5)3.214 (6)141 (6)
N1—H1C···Cl30.86 (5)2.58 (7)3.242 (6)134 (6)
N2—H2'···Cl5iv0.84 (4)2.45 (7)3.088 (6)134 (7)
N2—H2'···Cl5v0.84 (4)2.69 (6)3.272 (6)128 (7)
N3—H3'···Cl1vi0.84 (6)2.50 (6)3.275 (6)155 (6)
N3—H3'···Cl4vi0.84 (6)2.72 (7)3.286 (7)127 (7)
C1—H1···Cl1vii0.982.713.660 (8)163
C5—H5···Cl3iii0.932.713.604 (8)162
C10—H10···Cl3i0.932.733.459 (8)136
C10—H10···Cl5v0.932.743.308 (7)120
C11—H11···Cl2viii0.932.643.449 (8)145
Symmetry codes: (i) x1, y+1, z; (ii) x, y, z1; (iii) x+1, y+1, z+1; (iv) x, y+1, z1; (v) x, y+2, z+1; (vi) x+1, y, z+1; (vii) x, y+1, z; (viii) x+1, y+1, z.
Acknowledgements top

This work was supported financially by the Universidad Autónoma de Sinaloa (PROFAPI 2012/032).

references
References top

Adams, C. J., Paul, C. C., Orpen, A. G., Podesta, T. J. & Salt, B. (2005). Chem. Commun. pp. 2457–2458.

Adarsh, N. N., Krishna Kumar, D. & Dastidar, P. (2010). Acta Cryst. E66, m270.

Bruker (2000). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.

Bruker (2001). SAINT-Plus-NT. Bruker AXS Inc., Madison, Wisconsin, USA.

Campos-Gaxiola, J. J., Höpfl, H., Aguirre, G. & Parra-Hake, M. (2012). Acta Cryst. E68, o1873.

Campos-Gaxiola, J. J., Vega-Paz, A., Román-Bravo, P., Höpfl, H. & Sánchez-Vázquez, M. (2010). Cryst. Growth Des. 10, 3182–3190.

Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.

Fusi, V., Giorgi, L., Macedi, E., Paoli, P. & Rossi, P. (2012). Acta Cryst. E68, m1323–m1324.

Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470.

Pardo, R., Zayat, M. & Levy, D. (2011). Chem. Soc. Rev. 40, 672–687.

Piecha, A., Bialoríska, A. & Jakubas, R. (2012). J. Mater. Chem. 22, 333–336.

Sanchez, C., Belleville, P., Popall, M. & Lionel, N. (2011). Chem. Soc. Rev. 40, 696–753.

Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.

Yao, H. B., Gao, M. R. & Yu, S. H. (2010). Nanoscale, 2, 323–334.