organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

1-(4,4′′-Di­fluoro-5′-meth­­oxy-1,1′:3′,1′′-terphenyl-4′-yl)ethanone

aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, bDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri 574 199, India, and cDepartment of Chemistry, P. A. College of Engineering, Nadupadavu, Mangalore 574 153, India
*Correspondence e-mail: hkfun@usm.my

(Received 2 December 2011; accepted 9 December 2011; online 17 December 2011)

In the title compound, C21H16F2O2, the central benzene ring is inclined at dihedral angles of 30.91 (8) and 46.88 (7)° to the two terminal fluoro-substituted rings. The dihedral angle between the two terminal fluoro-subsituted rings is 68.34 (8)°. An intra­molecular C—H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure is stabilized by weak C—H⋯π inter­actions.

Related literature

For a related structure and background to terphenyls, see: Fun, Chia et al. (2011[Fun, H.-K., Chia, T. S., Samshuddin, S., Narayana, B. & Sarojini, B. K. (2011). Acta Cryst. E67, o3390.]); Samshuddin et al. (2011[Samshuddin, S., Narayana, B. & Sarojini, B. K. (2011). Molbank, M745.]). For chalcone derivatives of the title compound, see: Fun, Hemamalini et al. (2011[Fun, H.-K., Hemamalini, M., Samshuddin, S., Narayana, B. & Sarojini, B. K. (2011). Acta Cryst. E67, o3327-o3328.]); Betz et al. (2011a[Betz, R., Gerber, T., Hosten, E., Samshuddin, S., Narayana, B. & Sarojini, B. K. (2011a). Acta Cryst. E67, o2996-o2997.],b[Betz, R., Gerber, T., Hosten, E., Samshuddin, S., Narayana, B. & Yathirajan, H. S. (2011b). Acta Cryst. E67, o3323-o3324.]). For the synthetic procedure, see: Kotnis (1990[Kotnis, A. S. (1990). Tetrahedron Lett. 31, 481-484.]). For hydrogen-bond motifs, see: Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]).

[Scheme 1]

Experimental

Crystal data
  • C21H16F2O2

  • Mr = 338.34

  • Monoclinic, P 21 /c

  • a = 6.0816 (7) Å

  • b = 25.997 (3) Å

  • c = 10.9061 (12) Å

  • β = 100.866 (2)°

  • V = 1693.4 (3) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 296 K

  • 0.74 × 0.31 × 0.10 mm

Data collection
  • Bruker APEXII DUO CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.930, Tmax = 0.990

  • 17519 measured reflections

  • 4923 independent reflections

  • 2883 reflections with I > 2σ(I)

  • Rint = 0.033

Refinement
  • R[F2 > 2σ(F2)] = 0.050

  • wR(F2) = 0.167

  • S = 1.03

  • 4923 reflections

  • 228 parameters

  • H-atom parameters constrained

  • Δρmax = 0.23 e Å−3

  • Δρmin = −0.27 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the C1–C6 ring.

D—H⋯A D—H H⋯A DA D—H⋯A
C14—H14A⋯O2 0.93 2.58 3.188 (2) 124
C19—H19ACg1i 0.96 2.80 3.6432 (19) 147
Symmetry code: (i) [x, -y+{\script{1\over 2}}, z-{\script{3\over 2}}].

Data collection: APEX2 (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2009[Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]).

Supporting information


Comment top

As a part of our ongoing studies on synthesis of terphenyl moiety from 4,4'-difluoro chalcone (Fun, Chia et al., 2011; Samshuddin et al., 2011), the title compound was prepared and its crystal structure is reported. We have used this acetyl terphenyl as a starting material for many chalcones (Fun, Hemamalini et al., 2011; Betz et al., 2011a,b).

The asymmetric unit of the title compound is shown in Fig. 1. The central benzene (C7–C12) ring is inclined at dihedral angles of 30.91 (8) and 46.88 (7)° to the two terminal fluoro-substituted phenyl (C1–C6, C13–C18) rings, respectively. The corresponding angle between the two terminal fluoro-subsituted phenyl rings is 68.34 (8)°.

An intramolecular C—H···O hydrogen bond generates an S(6) (Bernstein et al., 1995) ring motif in the molecule (Fig. 1; Table 1). The crystal structure (Fig. 2) is stabilized by weak C—H···π interactions (Table 1) involving the C1–C6 ring (centroid Cg1).

Related literature top

For a related structure and background to terphenyls, see: Fun, Chia et al. (2011); Samshuddin et al. (2011). For chalcone derivatives of the title compound, see: Fun, Hemamalini et al. (2011); Betz et al. (2011a,b). For the synthetic procedure, see: Kotnis (1990). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Experimental top

The title compound was prepared by the aromatization of the cyclohexenone derivative, (6Z)-3,5-bis(4-fluorophenyl)-6-(1-hydroxyethylidene)cyclo hex-2-en-1-one, using iodine and methanol at reflux condition (Kotnis, 1990). Single crystal of the product was grown from a mixture of ethanol and DMF (1:1 v/v) by slow evaporation method (m.p. 391K).

Refinement top

All hydrogen atoms were positioned geometrically [C–H = 0.93 or 0.96 Å] and were refined using a riding model, with Uiso(H) = 1.2 or 1.5 Ueq(C). A rotating group model was applied to the methyl groups.

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. An ORTEP view of the title compound, showing 30% probability displacement ellipsoids. Intramolecular hydrogen bond is shown by a dashed line.
[Figure 2] Fig. 2. The crystal packing of the title compound viewed along the a axis.
1-(4,4''-Difluoro-5'-methoxy-1,1':3',1''-terphenyl-4'-yl)ethanone top
Crystal data top
C21H16F2O2F(000) = 704
Mr = 338.34Dx = 1.327 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 3484 reflections
a = 6.0816 (7) Åθ = 2.5–24.5°
b = 25.997 (3) ŵ = 0.10 mm1
c = 10.9061 (12) ÅT = 296 K
β = 100.866 (2)°Plate, colourless
V = 1693.4 (3) Å30.74 × 0.31 × 0.10 mm
Z = 4
Data collection top
Bruker APEXII DUO CCD area-detector
diffractometer
4923 independent reflections
Radiation source: fine-focus sealed tube2883 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.033
ϕ and ω scansθmax = 30.1°, θmin = 1.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
h = 88
Tmin = 0.930, Tmax = 0.990k = 3336
17519 measured reflectionsl = 1515
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)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.167H-atom parameters constrained
S = 1.03 w = 1/[σ2(Fo2) + (0.0857P)2 + 0.0565P]
where P = (Fo2 + 2Fc2)/3
4923 reflections(Δ/σ)max = 0.001
228 parametersΔρmax = 0.23 e Å3
0 restraintsΔρmin = 0.27 e Å3
Crystal data top
C21H16F2O2V = 1693.4 (3) Å3
Mr = 338.34Z = 4
Monoclinic, P21/cMo Kα radiation
a = 6.0816 (7) ŵ = 0.10 mm1
b = 25.997 (3) ÅT = 296 K
c = 10.9061 (12) Å0.74 × 0.31 × 0.10 mm
β = 100.866 (2)°
Data collection top
Bruker APEXII DUO CCD area-detector
diffractometer
4923 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2009)
2883 reflections with I > 2σ(I)
Tmin = 0.930, Tmax = 0.990Rint = 0.033
17519 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0500 restraints
wR(F2) = 0.167H-atom parameters constrained
S = 1.03Δρmax = 0.23 e Å3
4923 reflectionsΔρmin = 0.27 e Å3
228 parameters
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
F10.7590 (3)0.93216 (6)0.59950 (13)0.1136 (5)
F20.8096 (2)1.00075 (4)0.25890 (13)0.0932 (4)
O10.0345 (2)0.73907 (4)0.00260 (11)0.0617 (3)
O20.4540 (2)0.77193 (5)0.13608 (13)0.0825 (4)
C10.2502 (3)0.91677 (6)0.37217 (14)0.0527 (4)
H1A0.10610.93020.35450.063*
C20.3999 (3)0.93447 (7)0.47550 (16)0.0647 (5)
H2A0.35690.95920.52790.078*
C30.6109 (4)0.91488 (7)0.49859 (17)0.0705 (5)
C40.6816 (3)0.87831 (8)0.42537 (18)0.0711 (5)
H4A0.82670.86550.44440.085*
C50.5325 (3)0.86066 (6)0.32199 (15)0.0586 (4)
H5A0.57950.83620.27030.070*
C60.3128 (3)0.87898 (5)0.29407 (13)0.0456 (3)
C70.1516 (2)0.85840 (5)0.18611 (13)0.0457 (3)
C80.1709 (3)0.80732 (6)0.14915 (13)0.0502 (4)
H8A0.28190.78630.19350.060*
C90.0255 (3)0.78806 (5)0.04698 (14)0.0493 (3)
C100.1469 (3)0.81858 (5)0.01979 (13)0.0467 (3)
C110.1702 (2)0.86946 (5)0.01721 (13)0.0455 (3)
C120.0200 (2)0.88852 (5)0.12041 (13)0.0465 (3)
H12A0.03540.92230.14570.056*
C130.3440 (2)0.90439 (5)0.05353 (12)0.0454 (3)
C140.5668 (3)0.88925 (6)0.08926 (16)0.0573 (4)
H14A0.61060.85700.06610.069*
C150.7240 (3)0.92160 (7)0.15882 (17)0.0660 (5)
H15A0.87210.91120.18370.079*
C160.6553 (3)0.96922 (7)0.18989 (15)0.0612 (4)
C170.4413 (3)0.98642 (6)0.15416 (16)0.0610 (4)
H17A0.40101.01940.17480.073*
C180.2853 (3)0.95354 (6)0.08626 (14)0.0525 (4)
H18A0.13800.96450.06190.063*
C190.2322 (3)0.70987 (6)0.04690 (18)0.0668 (5)
H19A0.22670.67830.00070.100*
H19B0.24170.70230.13390.100*
H19C0.36120.72930.03590.100*
C200.2837 (3)0.79540 (6)0.13640 (15)0.0548 (4)
C210.1930 (4)0.80270 (11)0.25154 (18)0.0997 (8)
H21A0.26530.77930.31460.150*
H21B0.03480.79610.23440.150*
H21C0.21980.83740.28050.150*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.1147 (10)0.1119 (10)0.0921 (9)0.0152 (8)0.0369 (8)0.0252 (8)
F20.0933 (8)0.0800 (8)0.0952 (9)0.0405 (6)0.0111 (7)0.0045 (6)
O10.0756 (8)0.0373 (6)0.0671 (7)0.0058 (5)0.0004 (6)0.0108 (5)
O20.0853 (9)0.0775 (9)0.0815 (9)0.0340 (7)0.0074 (7)0.0082 (7)
C10.0663 (9)0.0407 (8)0.0495 (8)0.0009 (7)0.0069 (7)0.0013 (6)
C20.0898 (13)0.0491 (9)0.0520 (9)0.0063 (9)0.0056 (9)0.0073 (7)
C30.0818 (12)0.0611 (11)0.0591 (10)0.0144 (9)0.0106 (9)0.0027 (8)
C40.0575 (10)0.0697 (12)0.0788 (12)0.0044 (8)0.0055 (9)0.0030 (10)
C50.0603 (9)0.0524 (9)0.0618 (9)0.0009 (7)0.0084 (8)0.0030 (7)
C60.0576 (8)0.0351 (7)0.0433 (7)0.0028 (6)0.0072 (6)0.0044 (5)
C70.0572 (8)0.0358 (7)0.0439 (7)0.0007 (6)0.0092 (6)0.0012 (5)
C80.0618 (9)0.0367 (7)0.0497 (8)0.0041 (6)0.0046 (7)0.0008 (6)
C90.0628 (9)0.0340 (7)0.0509 (8)0.0001 (6)0.0101 (7)0.0020 (6)
C100.0559 (8)0.0383 (7)0.0458 (7)0.0034 (6)0.0096 (6)0.0011 (6)
C110.0513 (8)0.0387 (7)0.0465 (7)0.0005 (6)0.0095 (6)0.0010 (6)
C120.0578 (8)0.0349 (7)0.0461 (7)0.0025 (6)0.0079 (6)0.0026 (5)
C130.0528 (8)0.0404 (7)0.0440 (7)0.0030 (6)0.0118 (6)0.0010 (6)
C140.0554 (9)0.0489 (9)0.0683 (10)0.0005 (7)0.0137 (8)0.0020 (7)
C150.0510 (9)0.0665 (12)0.0785 (11)0.0080 (8)0.0067 (8)0.0084 (9)
C160.0680 (10)0.0585 (10)0.0543 (9)0.0224 (8)0.0044 (8)0.0016 (8)
C170.0752 (11)0.0441 (9)0.0651 (10)0.0090 (8)0.0171 (9)0.0089 (7)
C180.0545 (8)0.0444 (8)0.0586 (9)0.0012 (6)0.0106 (7)0.0015 (7)
C190.0764 (11)0.0456 (9)0.0781 (12)0.0123 (8)0.0141 (9)0.0103 (8)
C200.0607 (9)0.0445 (8)0.0571 (9)0.0012 (7)0.0057 (7)0.0054 (7)
C210.0960 (16)0.145 (2)0.0591 (11)0.0280 (15)0.0183 (11)0.0237 (13)
Geometric parameters (Å, º) top
F1—C31.360 (2)C10—C201.508 (2)
F2—C161.3610 (19)C11—C121.3997 (19)
O1—C91.3671 (17)C11—C131.4930 (19)
O1—C191.427 (2)C12—H12A0.9300
O2—C201.203 (2)C13—C181.391 (2)
C1—C21.387 (2)C13—C141.394 (2)
C1—C61.399 (2)C14—C151.387 (2)
C1—H1A0.9300C14—H14A0.9300
C2—C31.359 (3)C15—C161.369 (3)
C2—H2A0.9300C15—H15A0.9300
C3—C41.362 (3)C16—C171.362 (3)
C4—C51.385 (2)C17—C181.383 (2)
C4—H4A0.9300C17—H17A0.9300
C5—C61.397 (2)C18—H18A0.9300
C5—H5A0.9300C19—H19A0.9600
C6—C71.483 (2)C19—H19B0.9600
C7—C121.3904 (19)C19—H19C0.9600
C7—C81.399 (2)C20—C211.476 (3)
C8—C91.379 (2)C21—H21A0.9600
C8—H8A0.9300C21—H21B0.9600
C9—C101.404 (2)C21—H21C0.9600
C10—C111.398 (2)
C9—O1—C19117.60 (12)C7—C12—H12A119.1
C2—C1—C6121.04 (16)C11—C12—H12A119.1
C2—C1—H1A119.5C18—C13—C14118.05 (14)
C6—C1—H1A119.5C18—C13—C11120.02 (13)
C3—C2—C1118.57 (17)C14—C13—C11121.93 (13)
C3—C2—H2A120.7C15—C14—C13121.03 (16)
C1—C2—H2A120.7C15—C14—H14A119.5
C2—C3—F1118.96 (19)C13—C14—H14A119.5
C2—C3—C4122.96 (16)C16—C15—C14118.18 (16)
F1—C3—C4118.09 (19)C16—C15—H15A120.9
C3—C4—C5118.56 (18)C14—C15—H15A120.9
C3—C4—H4A120.7F2—C16—C17118.85 (16)
C5—C4—H4A120.7F2—C16—C15118.08 (17)
C4—C5—C6121.13 (16)C17—C16—C15123.08 (15)
C4—C5—H5A119.4C16—C17—C18118.17 (16)
C6—C5—H5A119.4C16—C17—H17A120.9
C5—C6—C1117.73 (14)C18—C17—H17A120.9
C5—C6—C7120.81 (13)C17—C18—C13121.45 (15)
C1—C6—C7121.46 (14)C17—C18—H18A119.3
C12—C7—C8118.78 (13)C13—C18—H18A119.3
C12—C7—C6121.72 (12)O1—C19—H19A109.5
C8—C7—C6119.49 (13)O1—C19—H19B109.5
C9—C8—C7120.08 (14)H19A—C19—H19B109.5
C9—C8—H8A120.0O1—C19—H19C109.5
C7—C8—H8A120.0H19A—C19—H19C109.5
O1—C9—C8124.16 (14)H19B—C19—H19C109.5
O1—C9—C10114.76 (13)O2—C20—C21121.87 (16)
C8—C9—C10121.08 (13)O2—C20—C10122.61 (15)
C11—C10—C9119.45 (13)C21—C20—C10115.52 (15)
C11—C10—C20123.47 (13)C20—C21—H21A109.5
C9—C10—C20116.81 (12)C20—C21—H21B109.5
C10—C11—C12118.71 (13)H21A—C21—H21B109.5
C10—C11—C13121.79 (13)C20—C21—H21C109.5
C12—C11—C13119.44 (12)H21A—C21—H21C109.5
C7—C12—C11121.86 (13)H21B—C21—H21C109.5
C6—C1—C2—C31.0 (3)C20—C10—C11—C12173.84 (14)
C1—C2—C3—F1179.78 (16)C9—C10—C11—C13177.29 (14)
C1—C2—C3—C40.5 (3)C20—C10—C11—C133.5 (2)
C2—C3—C4—C50.7 (3)C8—C7—C12—C111.3 (2)
F1—C3—C4—C5179.64 (17)C6—C7—C12—C11178.96 (14)
C3—C4—C5—C61.3 (3)C10—C11—C12—C70.4 (2)
C4—C5—C6—C11.7 (2)C13—C11—C12—C7176.95 (13)
C4—C5—C6—C7177.57 (15)C10—C11—C13—C18131.38 (16)
C2—C1—C6—C51.6 (2)C12—C11—C13—C1845.89 (19)
C2—C1—C6—C7177.70 (14)C10—C11—C13—C1448.3 (2)
C5—C6—C7—C12149.43 (15)C12—C11—C13—C14134.44 (16)
C1—C6—C7—C1231.3 (2)C18—C13—C14—C152.0 (2)
C5—C6—C7—C830.9 (2)C11—C13—C14—C15177.66 (14)
C1—C6—C7—C8148.36 (15)C13—C14—C15—C161.0 (3)
C12—C7—C8—C91.9 (2)C14—C15—C16—F2179.55 (15)
C6—C7—C8—C9178.40 (14)C14—C15—C16—C171.0 (3)
C19—O1—C9—C814.0 (2)F2—C16—C17—C18178.69 (14)
C19—O1—C9—C10166.16 (14)C15—C16—C17—C181.8 (3)
C7—C8—C9—O1178.61 (14)C16—C17—C18—C130.7 (2)
C7—C8—C9—C101.5 (2)C14—C13—C18—C171.1 (2)
O1—C9—C10—C11179.55 (13)C11—C13—C18—C17178.55 (14)
C8—C9—C10—C110.6 (2)C11—C10—C20—O293.9 (2)
O1—C9—C10—C205.3 (2)C9—C10—C20—O292.1 (2)
C8—C9—C10—C20174.82 (15)C11—C10—C20—C2187.0 (2)
C9—C10—C11—C120.0 (2)C9—C10—C20—C2187.0 (2)
Hydrogen-bond geometry (Å, º) top
Cg1 is the centroid of the C1–C6 ring.
D—H···AD—HH···AD···AD—H···A
C14—H14A···O20.932.583.188 (2)124
C19—H19A···Cg1i0.962.803.6432 (19)147
Symmetry code: (i) x, y+1/2, z3/2.

Experimental details

Crystal data
Chemical formulaC21H16F2O2
Mr338.34
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)6.0816 (7), 25.997 (3), 10.9061 (12)
β (°) 100.866 (2)
V3)1693.4 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.74 × 0.31 × 0.10
Data collection
DiffractometerBruker APEXII DUO CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2009)
Tmin, Tmax0.930, 0.990
No. of measured, independent and
observed [I > 2σ(I)] reflections
17519, 4923, 2883
Rint0.033
(sin θ/λ)max1)0.705
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.050, 0.167, 1.03
No. of reflections4923
No. of parameters228
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.23, 0.27

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top
Cg1 is the centroid of the C1–C6 ring.
D—H···AD—HH···AD···AD—H···A
C14—H14A···O20.93002.58003.188 (2)124.00
C19—H19A···Cg1i0.96002.80003.6432 (19)147.00
Symmetry code: (i) x, y+1/2, z3/2.
 

Footnotes

Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

HKF and MH thank the Malaysian Government and Universiti Sains Malaysia for the Research University grant No. 1001/PFIZIK/811160. MH also thanks Universiti Sains Malaysia for a post-doctoral research fellowship. BN thanks the UGC for financial assistance through the SAP and BSR one-time grant for the purchase of chemicals. SS thanks Mangalore University for research facilities.

References

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