PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of actaeInternational Union of Crystallographysearchopen accessarticle submissionjournal home pagethis article
 
Acta Crystallogr Sect E Struct Rep Online. 2009 November 1; 65(Pt 11): o2786.
Published online 2009 October 17. doi:  10.1107/S1600536809041099
PMCID: PMC2970961

2,4-Di-tert-butyl-6-[(2,5-difluorophenyl)iminomethyl]phenol

Abstract

In the title Schiff base, C21H25F2NO, the dihedral angle between the aromatic rings is 27.90(5)° and an intramolecular O—H(...)N hydrogen bond occurs. In the crystal, the molecules are linked by C—H(...)O, C—H(...)N and C—H(...)F interactions.

Related literature

For background on the photochromic behavior of salicyli­dene­anilines, see: Brown (1971 [triangle]); Chemla & Zyss (1987 [triangle]); MacDonald & Whitesides (1994 [triangle]); Cohen et al. (1966 [triangle]). For related compounds, see: Ancın et al. (2007 [triangle]); Kasumov, Köksal & Köseoĝlu (2004 [triangle]); Kasumov, Medjidov, Ya­ylı & Zeren (2004 [triangle]); Çelik et al. (2007 [triangle], 2009 [triangle]). For graph-set notation, see: Bernstein et al. (1995 [triangle]); Etter (1991 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-o2786-scheme1.jpg

Experimental

Crystal data

  • C21H25F2NO
  • M r = 345.42
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-o2786-efi1.jpg
  • a = 6.423 (5) Å
  • b = 17.386 (5) Å
  • c = 17.337 (5) Å
  • β = 90.319 (5)°
  • V = 1936.0 (17) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 293 K
  • 0.20 × 0.20 × 0.20 mm

Data collection

  • Rigaku Rxdiffractometer
  • Absorption correction: multi-scan (Blessing, 1995 [triangle]) T min = 0.983, T max = 0.983
  • 50854 measured reflections
  • 5662 independent reflections
  • 2715 reflections with I > 2σ(I)
  • R int = 0.099

Refinement

  • R[F 2 > 2σ(F 2)] = 0.057
  • wR(F 2) = 0.144
  • S = 0.96
  • 5662 reflections
  • 238 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.11 e Å−3
  • Δρmin = −0.13 e Å−3

Data collection: CrystalClear (Rigaku/MSC, 2005 [triangle]); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 (Farrugia, 1997 [triangle]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 [triangle]) and local programs.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809041099/jh2098sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809041099/jh2098Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

Proton tautomerization plays an important role in many fields of chemistry and biochemistry. The tautomerization in salicylideneanilines has been the subject of particular interest, because it is closely related to thermochromisim and photochromisim. While salicylideneanilines are widely used as a precursor compounds for a design of various type new metal complexes they are also a convenient model compounds for studying theoretical aspects of coordination chemistry and photochemistry, as well as for designing molecular architecture by means of molecular motifs capable of H-bond formation. The existence of photochromic behavior suggests the possibility of using these compounds as elements for constructing the optical switches or optical memory devices (Brown, 1971; Chemla et al., 1987; Cohen et al., 1966; Chemla, et al., 1987; MacDonald, et al., 1994). As part of our interest on electron transfer and complexation behaviors of redox-active salicylaldimines, obtained from bulky di-tertbutylated sterically hindered aminophenols, salicylaldehydes and aryl amines and their complexes (Kasumov et al., 2004; Kasumov et al., 2004), we decided to prepare and structurally investigate the bidentate salicylaldimines derived from 3,5-di-tert-butyl-salicylaldehyde and difluorinated anilines.

In the compound, the difluoroaniline atoms (P1) and benzylidene atoms (P2) are plane and the dihedral angle between P1 and P2 planes is 27.90 (5)°. The maximum deviations from the P1 plane of C3 and P2 plane of C11 are -0.008 Å and 0.002 Å, respectivity. The bond between N and C7 atoms is double bond, whose length is 1.282 (2)Å, and the conformation at this double bond is trans with the torsion angle C1-N-C7-C8 is 178.2 (1)°. The bond lengths are as expected. Similar results are were observed in the study of N-[5- methylisoxazole-amino-3-yl]-3, 5-di-tert-butylsalicylaldimine amino-3-yl]-3,5 -di-tert-butylsalicylaldimine(Çelik et al., 2007), N-[1-(3-Aminopropyl) imidazole]-3,5-di-tertbutylsalicylaldimine(Çelik et al., 2009) and N,N'-bis- (5-methylsalicylidene)-2,2'-diamino-4-4'-di-(trifloromethyl)-diphenyl disulfide (Ancın, et al., 2007).

In Table 2 is given interactions have types of O-H···N, C-H···O, C-H···N and C-H···F. O-H···N hydrogen bond which are intramolecular interaction causes to reversible proton transfer between imine N atom and the hydroxyl O atom. The three intra-molecular interaction have strong effects for molecule. C-H···O hydrogen bond which are intramolecular interaction causes to reversible proton transfer between methyl C atom and the hydroxyl O atom. Similar Schiff bases usually show photochromism and thermocromism because of the above mentioned intramolecular hydrogen bonds. Similar proton transfer has nor been determined in the molecular structure of our compound. The cause of this results may be explained by a steric effect and are effective for the molecular packing of the compound.

Experimental

The pale yellow crystalline the title compound was prepared by using standard procedure involving the condensation of equimolar amount of 3,5-di-tert-butyl-2-hydroxybenzaldehyde with 2,5 difluoroaniline in refluxing ethanol in the presence of catalytic amount of formic acid (3–4 drops). To a stirred and heated (60 °C) solution of 3,5-di-tert-butyl-2-hydroxybenzaldehyde (0.936 g, 4 mmol) in absolute ethanol (80 ml), a solution of 0.516 g (4 mmol) of 2,5-difluoroaniline in 5 ml methanol was added immediately. Then 4 drops of formic acid was added to this solution and refluxed for 24 h. The volume of the reaction mixture was evaporated to 25 ml and after cooling to 15 °C, the yellow crystals were collected and air dried to yield 1.298 g (94%).

Figures

Fig. 1.
ORTEP III diagram of the compound, showing the molecular numbering scheme. Displacement ellipsoids are drawn at 50% probability for all atoms except H.
Fig. 2.
Tautomerism in the title compound.

Crystal data

C21H25F2NOF(000) = 736
Mr = 345.42Dx = 1.185 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 6.423 (5) ÅCell parameters from 5929 reflections
b = 17.386 (5) Åθ = 2.6–30.5°
c = 17.337 (5) ŵ = 0.09 mm1
β = 90.319 (5)°T = 293 K
V = 1936.0 (17) Å3Needle, pale yellow
Z = 40.20 × 0.20 × 0.20 mm

Data collection

Rigaku Rx diffractometer5662 independent reflections
Radiation source: fine-focus sealed tube2715 reflections with I > 2σ(I)
graphiteRint = 0.099
Detector resolution: 10.0000 pixels mm-1θmax = 30.5°, θmin = 2.6°
dtprofit.ref scansh = −9→7
Absorption correction: multi-scan (Blessing, 1995)k = −24→24
Tmin = 0.983, Tmax = 0.983l = −24→24
50854 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.057Hydrogen site location: mixed
wR(F2) = 0.144H atoms treated by a mixture of independent and constrained refinement
S = 0.96w = 1/[σ2(Fo2) + (0.0514P)2] where P = (Fo2 + 2Fc2)/3
5662 reflections(Δ/σ)max < 0.001
238 parametersΔρmax = 0.11 e Å3
0 restraintsΔρmin = −0.13 e Å3
none constraints

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 (Å2)

xyzUiso*/Ueq
F11.34032 (17)−0.06161 (7)0.45693 (7)0.0928 (4)
F20.7822 (2)−0.18169 (7)0.25642 (7)0.1106 (5)
O0.43585 (19)−0.00558 (7)0.19801 (7)0.0716 (3)
N0.7118 (2)−0.03731 (8)0.30481 (8)0.0599 (3)
C10.8873 (2)−0.07788 (9)0.33323 (9)0.0579 (4)
C21.0326 (3)−0.04776 (11)0.38404 (10)0.0632 (4)
C31.2008 (3)−0.09201 (11)0.40566 (10)0.0670 (4)
C41.2353 (3)−0.16381 (13)0.37793 (11)0.0817 (6)
C51.0919 (3)−0.19439 (12)0.32701 (12)0.0887 (6)
C60.9227 (3)−0.15091 (11)0.30581 (10)0.0727 (5)
C70.6290 (3)0.01624 (9)0.34520 (10)0.0571 (4)
C80.4535 (2)0.06101 (9)0.31824 (8)0.0533 (4)
C90.3601 (2)0.04900 (8)0.24564 (9)0.0542 (4)
C100.1864 (2)0.09270 (8)0.22268 (8)0.0531 (4)
C110.1149 (3)0.14730 (9)0.27431 (9)0.0551 (4)
C120.2021 (2)0.16151 (8)0.34774 (9)0.0517 (4)
C130.3714 (2)0.11717 (8)0.36766 (9)0.0543 (4)
C140.0847 (3)0.08127 (9)0.14289 (9)0.0608 (4)
C150.2440 (3)0.10244 (12)0.07964 (10)0.0878 (6)
C160.0150 (3)−0.00280 (10)0.13124 (10)0.0745 (5)
C17−0.1094 (3)0.13131 (11)0.13211 (11)0.0852 (6)
C180.1136 (3)0.22420 (9)0.40007 (9)0.0590 (4)
C190.2129 (3)0.22172 (12)0.48075 (10)0.0835 (6)
C20−0.1214 (3)0.21370 (11)0.40956 (11)0.0767 (5)
C210.1544 (3)0.30292 (10)0.36414 (12)0.0909 (6)
H00.5354−0.02690.21870.107*
H21.018 (3)0.0018 (10)0.4049 (10)0.072 (5)*
H41.3524−0.19160.39290.098*
H51.1096−0.24370.30730.106*
H70.681 (2)0.0293 (9)0.4007 (10)0.071 (5)*
H110.001 (2)0.1785 (8)0.2587 (8)0.054 (4)*
H130.43370.12470.41560.065*
H15A0.36590.07090.08530.132*
H15B0.28200.15560.08460.132*
H15C0.18300.09390.02970.132*
H16A0.1327−0.03630.13740.112*
H16B−0.0422−0.00880.08030.112*
H16C−0.0888−0.01560.16870.112*
H17A−0.16800.12230.08190.128*
H17B−0.07190.18450.13690.128*
H17C−0.21000.11840.17080.128*
H19A0.15440.26170.51210.125*
H19B0.36040.22920.47660.125*
H19C0.18580.17270.50410.125*
H20A−0.17490.25370.44210.115*
H20B−0.14870.16450.43260.115*
H20C−0.18810.21630.35990.115*
H21A0.09820.34230.39680.136*
H21B0.08900.30550.31430.136*
H21C0.30170.31050.35880.136*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
F10.0730 (7)0.1143 (9)0.0908 (8)−0.0059 (6)−0.0254 (6)0.0194 (6)
F20.1241 (10)0.0941 (9)0.1131 (10)0.0261 (7)−0.0420 (8)−0.0405 (7)
O0.0734 (8)0.0773 (8)0.0639 (7)0.0170 (6)−0.0125 (6)−0.0166 (6)
N0.0572 (8)0.0612 (8)0.0613 (8)0.0052 (6)−0.0076 (6)−0.0001 (6)
C10.0557 (9)0.0593 (10)0.0587 (9)0.0053 (8)−0.0012 (7)0.0062 (7)
C20.0598 (10)0.0635 (11)0.0662 (11)−0.0011 (8)−0.0034 (8)0.0075 (8)
C30.0579 (10)0.0824 (12)0.0608 (10)−0.0001 (9)−0.0042 (8)0.0134 (9)
C40.0724 (12)0.0961 (15)0.0766 (13)0.0274 (11)0.0037 (10)0.0123 (11)
C50.1007 (16)0.0829 (13)0.0825 (13)0.0350 (12)−0.0014 (12)−0.0069 (10)
C60.0785 (12)0.0752 (12)0.0644 (11)0.0108 (10)−0.0086 (9)−0.0091 (9)
C70.0557 (9)0.0584 (10)0.0572 (10)−0.0004 (8)−0.0077 (8)0.0019 (7)
C80.0518 (9)0.0542 (9)0.0538 (9)−0.0010 (7)−0.0049 (7)0.0000 (7)
C90.0585 (9)0.0503 (9)0.0536 (9)−0.0021 (7)−0.0026 (7)−0.0037 (7)
C100.0573 (9)0.0521 (8)0.0498 (8)−0.0045 (7)−0.0064 (7)0.0026 (7)
C110.0576 (10)0.0494 (9)0.0582 (9)0.0010 (7)−0.0075 (7)0.0040 (7)
C120.0536 (9)0.0468 (8)0.0546 (8)−0.0063 (7)−0.0038 (7)−0.0004 (6)
C130.0562 (9)0.0540 (9)0.0527 (8)−0.0049 (7)−0.0091 (7)−0.0027 (7)
C140.0723 (11)0.0595 (10)0.0504 (9)−0.0034 (8)−0.0122 (8)0.0013 (7)
C150.1058 (16)0.0983 (15)0.0594 (11)−0.0252 (12)−0.0046 (11)0.0053 (10)
C160.0868 (13)0.0699 (11)0.0667 (11)−0.0099 (10)−0.0171 (9)−0.0068 (8)
C170.0960 (15)0.0814 (13)0.0779 (13)0.0107 (11)−0.0372 (11)0.0014 (10)
C180.0635 (10)0.0500 (9)0.0636 (10)−0.0017 (7)−0.0001 (8)−0.0090 (7)
C190.0862 (13)0.0914 (14)0.0727 (12)0.0044 (11)−0.0081 (10)−0.0281 (10)
C200.0649 (11)0.0869 (13)0.0784 (12)0.0017 (9)0.0046 (9)−0.0107 (10)
C210.1132 (17)0.0543 (11)0.1054 (16)−0.0062 (11)0.0154 (13)−0.0068 (10)

Geometric parameters (Å, °)

F1—C31.365 (2)C2—H20.940 (17)
F2—C61.351 (2)C16—H16A0.9600
O—C91.3503 (18)C16—H16B0.9600
N—C71.282 (2)C16—H16C0.9600
N—C11.416 (2)C19—H19A0.9600
C1—C21.383 (2)C19—H19B0.9600
C1—C61.375 (2)C19—H19C0.9600
C3—C41.356 (3)C17—H17A0.9600
C3—C21.376 (2)C17—H17B0.9600
C4—C51.379 (3)C17—H17C0.9600
C6—C51.372 (3)C20—H20A0.9600
C8—C131.404 (2)C20—H20B0.9600
C8—C91.407 (2)C20—H20C0.9600
C8—C71.445 (2)C4—H40.9300
C10—C111.385 (2)C15—H15A0.9600
C10—C91.405 (2)C15—H15B0.9600
C10—C141.540 (2)C15—H15C0.9600
C11—C121.410 (2)C5—H50.9300
C12—C131.375 (2)C21—H21A0.9600
C12—C181.530 (2)C21—H21B0.9600
C14—C171.531 (2)C21—H21C0.9600
C14—C161.542 (2)C11—H110.948 (14)
C14—C151.548 (3)C13—H130.9300
C18—C211.527 (2)C7—H71.042 (17)
C18—C201.530 (3)O—H00.8200
C18—C191.535 (2)
C7—N—C1120.24 (14)C14—C16—H16C109.5
C11—C10—C9116.96 (14)H16A—C16—H16C109.5
C11—C10—C14121.90 (14)H16B—C16—H16C109.5
C9—C10—C14121.13 (14)C18—C19—H19A109.5
C10—C11—C12124.88 (15)C18—C19—H19B109.5
C13—C8—C9119.32 (14)H19A—C19—H19B109.5
C13—C8—C7118.16 (14)C18—C19—H19C109.5
C9—C8—C7122.50 (14)H19A—C19—H19C109.5
C13—C12—C11116.00 (14)H19B—C19—H19C109.5
C13—C12—C18123.12 (14)C14—C17—H17A109.5
C11—C12—C18120.87 (14)C14—C17—H17B109.5
C12—C13—C8122.39 (14)H17A—C17—H17B109.5
C6—C1—C2117.22 (16)C14—C17—H17C109.5
C6—C1—N118.20 (15)H17A—C17—H17C109.5
C2—C1—N124.49 (16)H17B—C17—H17C109.5
O—C9—C10119.66 (14)C18—C20—H20A109.5
O—C9—C8119.88 (14)C18—C20—H20B109.5
C10—C9—C8120.45 (14)H20A—C20—H20B109.5
C21—C18—C12109.36 (14)C18—C20—H20C109.5
C21—C18—C20108.81 (15)H20A—C20—H20C109.5
C12—C18—C20110.42 (13)H20B—C20—H20C109.5
C21—C18—C19109.01 (15)C3—C4—H4120.9
C12—C18—C19111.50 (14)C5—C4—H4120.9
C20—C18—C19107.68 (14)C14—C15—H15A109.5
N—C7—C8122.66 (15)C14—C15—H15B109.5
C17—C14—C10112.19 (14)H15A—C15—H15B109.5
C17—C14—C16106.69 (15)C14—C15—H15C109.5
C10—C14—C16111.20 (13)H15A—C15—H15C109.5
C17—C14—C15108.64 (15)H15B—C15—H15C109.5
C10—C14—C15109.07 (14)C6—C5—H5120.5
C16—C14—C15108.97 (15)C4—C5—H5120.5
C4—C3—F1118.63 (17)C18—C21—H21A109.5
C4—C3—C2123.19 (18)C18—C21—H21B109.5
F1—C3—C2118.17 (18)H21A—C21—H21B109.5
C3—C2—C1119.19 (18)C18—C21—H21C109.5
F2—C6—C5118.48 (17)H21A—C21—H21C109.5
F2—C6—C1118.27 (16)H21B—C21—H21C109.5
C5—C6—C1123.24 (18)C10—C11—H11117.7 (9)
C3—C4—C5118.17 (18)C12—C11—H11117.4 (9)
C6—C5—C4118.96 (19)C12—C13—H13118.8
C3—C2—H2119.2 (11)C8—C13—H13118.8
C1—C2—H2121.6 (11)N—C7—H7122.0 (9)
C14—C16—H16A109.5C8—C7—H7115.3 (9)
C14—C16—H16B109.5C9—O—H0109.5
H16A—C16—H16B109.5
C9—C10—C11—C12−0.5 (2)C11—C12—C18—C19172.11 (15)
C14—C10—C11—C12−179.12 (14)C1—N—C7—C8178.23 (14)
C10—C11—C12—C130.3 (2)C13—C8—C7—N178.59 (15)
C10—C11—C12—C18178.97 (15)C9—C8—C7—N0.1 (2)
C11—C12—C13—C80.0 (2)C11—C10—C14—C17−4.9 (2)
C18—C12—C13—C8−178.57 (14)C9—C10—C14—C17176.53 (15)
C9—C8—C13—C12−0.2 (2)C11—C10—C14—C16−124.32 (17)
C7—C8—C13—C12−178.68 (14)C9—C10—C14—C1657.1 (2)
C7—N—C1—C6155.18 (17)C11—C10—C14—C15115.49 (18)
C7—N—C1—C2−28.3 (2)C9—C10—C14—C15−63.06 (19)
C11—C10—C9—O179.42 (14)C4—C3—C2—C11.8 (3)
C14—C10—C9—O−2.0 (2)F1—C3—C2—C1−178.84 (14)
C11—C10—C9—C80.3 (2)C6—C1—C2—C3−1.3 (2)
C14—C10—C9—C8178.94 (14)N—C1—C2—C3−177.87 (15)
C13—C8—C9—O−179.09 (14)C2—C1—C6—F2179.66 (16)
C7—C8—C9—O−0.7 (2)N—C1—C6—F2−3.5 (3)
C13—C8—C9—C100.0 (2)C2—C1—C6—C50.6 (3)
C7—C8—C9—C10178.43 (14)N—C1—C6—C5177.43 (17)
C13—C12—C18—C21111.27 (18)F1—C3—C4—C5179.11 (17)
C11—C12—C18—C21−67.3 (2)C2—C3—C4—C5−1.6 (3)
C13—C12—C18—C20−129.03 (17)F2—C6—C5—C4−179.41 (17)
C11—C12—C18—C2052.4 (2)C1—C6—C5—C4−0.4 (3)
C13—C12—C18—C19−9.4 (2)C3—C4—C5—C60.8 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O—H0···N0.821.882.615 (2)149
C16—H16A···O0.962.272.935 (3)126
C15—H15A···O0.962.403.038 (2)123
C7—H7···F1i1.0422.8753.010 (2)87
C16—H16C···Ni0.962.723.643 (3)162
C21—H21B···F2ii0.962.683.498 (3)143

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: JH2098).

References

  • Ancın, N., Çelik, Ö., Öztaş, S. G. & Íde, S. (2007). Struct. Chem.18, 347–352.
  • Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N. L. (1995). Angew. Chem. Int. Ed. Engl.34, 1555–1573.
  • Blessing, R. H. (1995). Acta Cryst. A51, 33–38. [PubMed]
  • Brown, G. H. (1971). Editor. Photochromisim New York: Wiley Interscience.
  • Çelik, Ö., Taş, E., Íde, S. & Ulusoy, M. (2009). Anal. Sci.25, 75–76.
  • Çelik, Ö., Ulusoy, M., Taş, E. & Íde, S. (2007). Anal. Sci.23, 185–186.
  • Chemla, D. S. & Zyss, J. (1987). Nonlinear Optical Properties of Organic Molecules and Crystals, Vols. 1 and 2. Orlando: Academic Press.
  • Cohen, M.D. & Schmidt, J. G. M. (1966). J. Phys. Chem.66, 2442–2445.
  • Etter, M. C. (1991). J. Phys. Chem.95, 4601–4610.
  • Farrugia, L. J. (1997). J. Appl. Cryst.30, 565.
  • Kasumov, V. T., Köksal, F. & Köseoĝlu, R. (2004). J. Coord. Chem.57, 591–603.
  • Kasumov, V. T., Medjidov, A. A., Yaylı, N. & Zeren, Y. (2004). Spectrochim. Acta Part A, 60, 3037–3047. [PubMed]
  • MacDonald, J. & Whitesides, G. M. C. (1994). Chem. Rev.94, 2383–2420.
  • Rigaku/MSC (2005). CrystalClear Rigaku/MSC, The Woodlands, Texas, USA.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography