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Acta Cryst. (2009). E65, o566-o567    [ doi:10.1107/S1600536809004978 ]

9-(Methylsulfanyl)acridinium trifluoromethanesulfonate

B. Zadykowicz, D. Trzybinski, A. Sikorski and J. Blazejowski

Abstract top

In the crystal structure of the title compound, C14H12NS+·CF3SO3-, N-H...O hydrogen bonds link cations and anions into ion pairs. Inversely oriented ion pairs form stacks through multidirectional [pi]-[pi] interactions among the acridine units. The crystal structure features a network of C-H...O interactions among stacks and also long-range electrostatic interactions among ions. In the packing of the molecules, the acridine units are nearly parallel in stacks or inclined at an angle of 33.07 (2)° in the four adjacent stacks with which they interact via weak C-H...O interactions. The methylsulfanyl group is twisted through an angle of 60.53 (2)° with respect to the acridine ring.

Comment top

Acridinium cations containing various substituents at position 9 and alkyl substitutes at the endocyclic N atom (position 10) are susceptible to oxidation by H2O2 or other oxidants in alkaline media, leading to the formation of electronically excited 10-alkyl-9-acridinones capable of emitting light with a quantum yield of several percent (Zomer & Jacquemijns, 2001; Wróblewska et al., 2004). The chemiluminescence phenomenon described above is governed by the features of the substituent at position 9. In the search for derivatives that could exhibit enhanced chemiluminescence, we turned our attention to compounds in which the C atom at position 9 is bound to the S atom. The simplest compound that we were able to synthesize was 9-(methylthio)acridinium trifluoromethanesulfonate. It was obtained by the reaction of 9-thioacridinone (Berny et al., 1992) with methyl trifluoromethanesulfonate, which usually leads to quarternarization of the endocyclic N atom (Sato, 1996). The cation of the reaction product has a protonated endocyclic N atom, enabling it to react with oxidants, thereby facilitating the investigation of chemiluminescence phenomena. This paper presents the crystal structure of the title compound. This is, to our knowledge, only the second report on the crystal structure of an acridine derivatives S-substitued at position 9 (for the first one, see Mrozek et al., 2002).

In the cations of the title compound (Fig. 1), the bond lenghts and angles characterizing the geometry of the acridine skeleton are typical of acridine-based derivatives (Storoniak et al., 2000; Meszko et al., 2002; Mrozek et al., 2002). The C9–S15 and S15–C16 bond lengths (1.754 (3) Å and 1.807 (4) Å, respectively) correlate well with those reported for 9-(thio-2'-methyl-4'-nitrophenyl)acridine (Mrozek et al., 2002). The C9–S15–C16 fragment and the acridine ring system, with an average deviation from planarity of 0.037 (4) Å, are oriented at 60.53 (2)° to each other. The acridine units in the lattice are either parallel (within stacks) or inclined at an angle of 33.07 (2)° (in four adjacent stacks with which they interact via C–H···O hydrogen bonds).

In the crystal structure, N–H···O hydrogen bonds (Aakeröy et al., 1992) link cations and anions in ion pairs (Table 1, Fig. 1). Inversely oriented ion pairs form stacks in which the central ring (Cg1) and the aromatic rings (Cg2 and Cg3) are involved in multidirectional π-π interactions (Table 2, Fig. 2) of an attractive nature (Hunter et al., 2001). The crystal structure is stabilized by a network of C–H···O hydrogen type bonding interactions (Steiner, 1991; Bianchi et al., 2004) between neighbouring stacks (Figs 2 and 3) as well as by long-range electrostatic interactions between ions.

Related literature top

For general background, see: Wróblewska et al. (2004); Zomer & Jacquemijns (2001). For related structures, see: Meszko et al. (2002); Mrozek et al. (2002); Storoniak et al. (2000). For molecular interactions, see: Aakeröy et al. (1992); Bianchi et al. (2004); Hunter et al. (2001); Spek (2009); Steiner (1991). For the synthesis, see: Berny et al. (1992); Sato (1996).

Experimental top

9-(Methylthio)acridinium trifluoromethanesulfonate was synthesized in two steps. First, 9-thioacridinone was synthesized by heating with stirring a mixture of 9(10H)-acridinone, tetraphosphorus decasulfide and freshly distilled pyridine at 100°C for 1 h (Berny et al., 1992). The reactant mixture was subsequently poured into 30% aq ammonia and the resulting precipitate of 9-thioacridinone filtered off. This compound was then treated with a fivefold molar excess of methyl triluoromethanesulfonate dissolved in dichloromethane for 3 h (Ar athmosphere, room temperature) (Sato, 1996). The crude 9-(methylthio)acridinium trifluoromethanesulfonate thus formed was dissolved in a small amount of ethanol, filtered, and again precipitated with a 25 v/v excess of diethyl ether (yield: 87%). Yellow crystals suitable for X-ray investigations were grown from absolute ethanol solution (m.p. 421–423 K).

Refinement top

H atoms involved in C–H···O interactions were located in a difference map and refined without constrains. H atoms involved in N–H···O interaction were located in a difference map and refined using the N—H distance restraint of 0.86 (2) Å. Other H atoms were positioned geometrically, with C—H = 0.93 Å (aromatic) and 0.96 Å (methyl), and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(C) (aromatic) or Uiso(H) = 1.5Ueq(C) (methyl).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 25% probability level and H atoms are shown as small spheres of arbitrary radius. The N10–H10···O19 hydrogen bond is represented by a dashed line. Cg1, Cg2 and Cg3 denote the ring centroids.
[Figure 2] Fig. 2. The arrangement of the ions in the crystal structure. The N–H···O and C–H···O hydrogen bonds are represented by dashed lines, the π-π contacts by dotted lines. H atoms not involved in the interactions have been omitted. [Symmetry codes: (i) -x + 1, y + 1/2, -z + 3/2; (ii) -x, -y + 2, -z + 1; (iii) -x + 1, -y + 2, -z + 1.]
[Figure 3] Fig. 3. Stacks of the ion pairs in the crystal structure viewed along the a axis. The N–H···O and C–H···O interactions are represented by dashed lines. H atoms not involved in interactions have been omitted.
9-(Methylsulfanyl)acridinium trifluoromethanesulfonate top
Crystal data top
C14H12NS+·CF3SO3−F(000) = 768
Mr = 375.40Dx = 1.557 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5491 reflections
a = 7.2992 (2) Åθ = 3.1–29.2°
b = 17.3090 (6) ŵ = 0.38 mm−1
c = 13.0582 (4) ÅT = 295 K
β = 103.910 (3)°Block, yellow
V = 1601.42 (9) Å30.45 × 0.4 × 0.2 mm
Z = 4
Data collection top
Oxford Diffraction Gemini R Ultra Ruby CCD
diffractometer		1944 reflections with I > 2σ(I)
Radiation source: Enhance (Mo) X-ray SourceRint = 0.028
graphiteθmax = 25.1°, θmin = 3.1°
Detector resolution: 10.4002 pixels mm-1h = −8→8
ω scansk = −20→20
13308 measured reflectionsl = −15→15
2841 independent reflections
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) = 0.161H atoms treated by a mixture of independent and constrained refinement
S = 1.06 w = 1/[σ2(Fo2) + (0.1054P)2]
where P = (Fo2 + 2Fc2)/3
2841 reflections(Δ/σ)max = 0.001
226 parametersΔρmax = 0.51 e Å−3
1 restraintΔρmin = −0.35 e Å−3
Crystal data top
C14H12NS+·CF3SO3−V = 1601.42 (9) Å3
Mr = 375.40Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.2992 (2) ŵ = 0.38 mm−1
b = 17.3090 (6) ÅT = 295 K
c = 13.0582 (4) Å0.45 × 0.4 × 0.2 mm
β = 103.910 (3)°
Data collection top
Oxford Diffraction Gemini R Ultra Ruby CCD
diffractometer		1944 reflections with I > 2σ(I)
13308 measured reflectionsRint = 0.028
2841 independent reflectionsθmax = 25.1°
Refinement top
R[F2 > 2σ(F2)] = 0.050H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.161Δρmax = 0.51 e Å−3
S = 1.06Δρmin = −0.35 e Å−3
2841 reflectionsAbsolute structure: ?
226 parametersFlack parameter: ?
1 restraintRogers parameter: ?
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C1−0.0169 (4)1.03470 (19)0.2103 (2)0.0567 (7)
H1−0.07401.08240.19160.068*
C2−0.0343 (4)0.9785 (2)0.1374 (2)0.0702 (9)
H2−0.10390.98790.06900.084*
C30.0508 (5)0.9058 (2)0.1626 (3)0.0751 (10)
H30.04040.86840.11030.090*
C40.1478 (4)0.8897 (2)0.2624 (3)0.0630 (8)
H40.20230.84140.27910.076*
C50.3767 (3)0.9596 (2)0.6240 (2)0.0577 (8)
H50.41900.90920.63800.069*
C60.4067 (4)1.0138 (2)0.7023 (2)0.0657 (9)
H60.47170.99980.77000.079*
C70.3425 (4)1.0895 (2)0.6832 (3)0.0670 (9)
H70.380 (4)1.127 (2)0.742 (3)0.079 (10)*
C80.2485 (4)1.11202 (18)0.5862 (2)0.0573 (7)
H80.20701.16280.57500.069*
C90.1176 (3)1.07880 (15)0.3956 (2)0.0442 (6)
N100.2546 (3)0.93052 (14)0.44086 (19)0.0478 (6)
H100.300 (4)0.8858 (12)0.462 (2)0.071 (10)*
C110.0877 (3)1.02193 (16)0.3156 (2)0.0453 (6)
C120.1652 (3)0.94706 (16)0.3405 (2)0.0455 (6)
C130.2116 (3)1.05863 (16)0.49974 (19)0.0438 (6)
C140.2796 (3)0.98202 (16)0.5208 (2)0.0441 (6)
S150.03215 (12)1.17329 (5)0.36941 (8)0.0731 (3)
C160.1546 (5)1.2067 (2)0.2729 (3)0.0770 (10)
H16A0.10991.25720.24880.116*
H16B0.13141.17160.21420.116*
H16C0.28771.20890.30440.116*
S170.36383 (10)0.71528 (5)0.50824 (6)0.0577 (3)
O180.4183 (4)0.6911 (2)0.6130 (2)0.1215 (12)
O190.4246 (4)0.79237 (14)0.4965 (3)0.1040 (10)
O200.1780 (3)0.6955 (2)0.4545 (2)0.1045 (10)
C210.5109 (6)0.6611 (3)0.4413 (4)0.0960 (13)
F220.4700 (5)0.6751 (3)0.3414 (3)0.193 (2)
F230.4819 (6)0.5867 (2)0.4487 (4)0.2000 (19)
F240.6911 (3)0.67460 (17)0.4790 (3)0.1366 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0519 (15)0.068 (2)0.0489 (15)0.0013 (14)0.0100 (12)0.0050 (15)
C20.0620 (18)0.096 (3)0.0504 (17)−0.0082 (18)0.0092 (14)−0.0036 (18)
C30.0695 (19)0.092 (3)0.067 (2)−0.0095 (19)0.0227 (17)−0.031 (2)
C40.0542 (16)0.059 (2)0.077 (2)0.0015 (14)0.0176 (15)−0.0158 (16)
C50.0438 (14)0.070 (2)0.0586 (18)−0.0061 (13)0.0101 (13)0.0162 (16)
C60.0537 (16)0.095 (3)0.0466 (17)−0.0186 (17)0.0077 (13)0.0052 (17)
C70.0646 (18)0.086 (3)0.0510 (18)−0.0206 (18)0.0156 (15)−0.0155 (18)
C80.0582 (16)0.0533 (19)0.0639 (19)−0.0093 (13)0.0218 (14)−0.0097 (14)
C90.0383 (12)0.0407 (16)0.0555 (16)0.0005 (11)0.0151 (11)0.0019 (12)
N100.0417 (11)0.0395 (14)0.0618 (15)0.0004 (10)0.0118 (10)0.0048 (12)
C110.0379 (12)0.0494 (17)0.0499 (15)0.0018 (11)0.0129 (11)0.0016 (12)
C120.0375 (12)0.0475 (17)0.0534 (16)−0.0055 (11)0.0144 (11)−0.0059 (13)
C130.0400 (12)0.0448 (16)0.0496 (15)−0.0082 (11)0.0166 (11)−0.0039 (12)
C140.0353 (12)0.0488 (17)0.0489 (15)−0.0069 (11)0.0113 (11)0.0023 (12)
S150.0800 (6)0.0507 (6)0.0909 (7)0.0178 (4)0.0248 (5)0.0059 (4)
C160.083 (2)0.056 (2)0.087 (2)−0.0126 (17)0.0096 (19)0.0185 (17)
S170.0620 (5)0.0550 (5)0.0527 (5)−0.0016 (3)0.0070 (3)0.0084 (3)
O180.124 (2)0.173 (3)0.0551 (15)−0.023 (2)−0.0018 (15)0.0306 (16)
O190.1003 (18)0.0507 (16)0.172 (3)0.0158 (13)0.0536 (18)0.0300 (16)
O200.0605 (14)0.159 (3)0.0864 (18)−0.0124 (15)0.0026 (13)−0.0175 (17)
C210.077 (3)0.081 (3)0.122 (4)0.005 (2)0.007 (2)−0.023 (3)
F220.144 (3)0.345 (6)0.097 (2)0.028 (3)0.044 (2)−0.063 (3)
F230.177 (3)0.085 (2)0.331 (6)−0.001 (2)0.047 (3)−0.088 (3)
F240.0666 (14)0.132 (2)0.199 (3)0.0187 (13)0.0096 (15)−0.057 (2)
Geometric parameters (Å, °) top
C1—C21.346 (4)C9—C111.414 (4)
C1—C111.421 (4)C9—S151.754 (3)
C1—H10.9300N10—C121.347 (3)
C2—C31.407 (5)N10—C141.351 (3)
C2—H20.9300N10—H100.860 (18)
C3—C41.354 (4)C11—C121.420 (4)
C3—H30.9300C13—C141.419 (4)
C4—C121.407 (4)S15—C161.807 (4)
C4—H40.9300C16—H16A0.9600
C5—C61.365 (5)C16—H16B0.9600
C5—C141.417 (4)C16—H16C0.9600
C5—H50.9300S17—O181.393 (3)
C6—C71.394 (5)S17—O201.411 (2)
C6—H60.9300S17—O191.426 (3)
C7—C81.346 (4)S17—C211.803 (5)
C7—H71.00 (4)C21—F221.289 (6)
C8—C131.433 (4)C21—F231.312 (5)
C8—H80.9300C21—F241.310 (5)
C9—C131.412 (4)
C2—C1—C11120.6 (3)C9—C11—C1124.0 (3)
C2—C1—H1119.7C12—C11—C1117.1 (2)
C11—C1—H1119.7N10—C12—C4119.6 (3)
C1—C2—C3121.4 (3)N10—C12—C11119.4 (2)
C1—C2—H2119.3C4—C12—C11121.1 (3)
C3—C2—H2119.3C9—C13—C14119.0 (2)
C4—C3—C2120.5 (3)C9—C13—C8123.7 (3)
C4—C3—H3119.7C14—C13—C8117.3 (2)
C2—C3—H3119.7N10—C14—C13119.4 (2)
C3—C4—C12119.2 (3)N10—C14—C5119.9 (3)
C3—C4—H4120.4C13—C14—C5120.8 (3)
C12—C4—H4120.4C9—S15—C16102.83 (15)
C6—C5—C14118.5 (3)S15—C16—H16A109.5
C6—C5—H5120.7S15—C16—H16B109.5
C14—C5—H5120.7H16A—C16—H16B109.5
C5—C6—C7121.7 (3)S15—C16—H16C109.5
C5—C6—H6119.2H16A—C16—H16C109.5
C7—C6—H6119.2H16B—C16—H16C109.5
C8—C7—C6120.9 (3)O18—S17—O20115.38 (19)
C8—C7—H7121 (2)O18—S17—O19111.4 (2)
C6—C7—H7117 (2)O20—S17—O19117.40 (19)
C7—C8—C13120.8 (3)O18—S17—C21104.9 (2)
C7—C8—H8119.6O20—S17—C21104.20 (19)
C13—C8—H8119.6O19—S17—C21101.4 (2)
C13—C9—C11119.5 (2)F22—C21—F23105.0 (5)
C13—C9—S15119.1 (2)F22—C21—F24108.3 (4)
C11—C9—S15121.4 (2)F23—C21—F24108.2 (4)
C12—N10—C14123.7 (2)F22—C21—S17111.9 (3)
C12—N10—H10124 (2)F23—C21—S17110.5 (4)
C14—N10—H10112 (2)F24—C21—S17112.7 (3)
C9—C11—C12118.9 (2)
C11—C1—C2—C3−0.4 (5)S15—C9—C13—C8−2.4 (3)
C1—C2—C3—C42.2 (5)C7—C8—C13—C9−178.6 (2)
C2—C3—C4—C12−1.0 (5)C7—C8—C13—C14−0.6 (4)
C14—C5—C6—C70.8 (4)C12—N10—C14—C13−1.0 (4)
C5—C6—C7—C8−0.2 (5)C12—N10—C14—C5−179.6 (2)
C6—C7—C8—C130.1 (4)C9—C13—C14—N100.7 (3)
C13—C9—C11—C12−4.4 (3)C8—C13—C14—N10−177.4 (2)
S15—C9—C11—C12178.03 (18)C9—C13—C14—C5179.3 (2)
C13—C9—C11—C1175.3 (2)C8—C13—C14—C51.2 (3)
S15—C9—C11—C1−2.3 (3)C6—C5—C14—N10177.3 (2)
C2—C1—C11—C9177.8 (3)C6—C5—C14—C13−1.3 (4)
C2—C1—C11—C12−2.5 (4)C13—C9—S15—C16120.7 (2)
C14—N10—C12—C4179.4 (2)C11—C9—S15—C16−61.7 (2)
C14—N10—C12—C11−1.4 (4)O18—S17—C21—F22177.1 (4)
C3—C4—C12—N10177.3 (3)O20—S17—C21—F2255.5 (4)
C3—C4—C12—C11−1.9 (4)O19—S17—C21—F22−66.9 (4)
C9—C11—C12—N104.2 (4)O18—S17—C21—F2360.6 (4)
C1—C11—C12—N10−175.6 (2)O20—S17—C21—F23−61.0 (4)
C9—C11—C12—C4−176.7 (2)O19—S17—C21—F23176.6 (4)
C1—C11—C12—C43.6 (4)O18—S17—C21—F24−60.6 (4)
C11—C9—C13—C142.0 (3)O20—S17—C21—F24177.8 (4)
S15—C9—C13—C14179.63 (17)O19—S17—C21—F2455.4 (4)
C11—C9—C13—C8−180.0 (2)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C7—H7···O18i0.99 (4)2.38 (4)3.315 (5)158 (3)
N10—H10···O190.86 (2)1.86 (2)2.712 (4)172 (3)
Symmetry codes: (i) −x+1, y+1/2, −z+3/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C7—H7···O18i0.99 (4)2.38 (4)3.315 (5)158 (3)
N10—H10···O190.86 (2)1.86 (2)2.712 (4)172 (3)
Symmetry codes: (i) −x+1, y+1/2, −z+3/2.
Table 2
π–π Interactions (Å,°). top
CgICgJCg···CgDihedral angleInterplanar distanceOffset
Cg1Cg1ii3.827 (2)0.03.468 (2)1.618 (2)
Cg1Cg3ii3.634 (2)1.443.474 (2)1.066 (2)
Cg1Cg3iii3.810 (2)1.443.412 (2)1.695 (2)
Cg2Cg3ii3.830 (2)3.963.492 (2)1.573 (2)
Cg3Cg1ii3.634 (2)1.443.483 (2)1.037 (2)
Cg3Cg1iii3.810 (2)1.443.386 (2)1.747 (2)
Cg3Cg2ii3.830 (2)3.963.449 (2)1.665 (2)
Symmetry codes: (ii) -x, -y+2, -z+1; (iii) -x+1, -y+2, -z+1. Notes: Cg1, Cg2 and Cg3 are the centroids of the C9/N10/C11–C14, C1–C4/C11/C12 and C5–C8/C13/C14 rings, respectively. Cg···Cg is the distance between ring centroids. The dihedral angle is that between the planes of the rings CgI and CgJ. The interplanar distance is the perpendicular distance of CgI from ring J. The offset is the perpendicular distance of ring I from ring J.
Acknowledgements top

This study was financed by the State Funds for Scientific Research (grant No. N204 123 32/3143, contract No. 3143/H03/2007/32 of the Polish Ministry of Research and Higher Education) for the period 2007–2010. BZ expresses her gratitude for the fellowship from the European Social Fund, the Polish State Budget and the Budget of the Province of Pomerania within the framework of the Priority VIII Human Capital Operational Programme, action 8.2, subaction 8.2.2 'Regional Innovation Strategy', of the 'InnoDoktorant' project of the Province of Pomerania - fellowships for PhD students, 1st edition.

references
References top

Aakeröy, C. B., Seddon, K. R. & Leslie, M. (1992). Struct. Chem. 3, 63–65.

Berny, H., Bsiri, N., Charbit, J. J., Galy, A. M., Soyfer, J. C., Galy, J. P., Barbe, J., Sharples, D., Mesa Valle, C. M., Mascaro, C. & Osuna, A. (1992). Arzneim. Forsch. Drug Res. 42, 674–679.

Bianchi, R., Forni, A. & Pilati, T. (2004). Acta Cryst. B60, 559–568.

Hunter, C. A., Lawson, K. R., Perkins, J. & Urch, C. J. (2001). J. Chem. Soc. Perkin Trans. 2, pp. 651–669.

Johnson, C. K. (1976). ORTEPII. Report ORNL-5138. Oak Ridge National Laboratory, Tennessee, USA.

Meszko, J., Sikorski, A., Huta, O. M., Konitz, A. & Błażejowski, J. (2002). Acta Cryst. C58, o669–o671.

Mrozek, A., Karolak-Wojciechowska, J., Amiel, P. & Barbe, J. (2002). Acta Cryst. E58, o1065–o1067.

Oxford Diffraction. (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.

Sato, N. (1996). Tetrahedron Lett. 37, 8519–8522.

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

Spek, A. L. (2009). Acta Cryst. D65, 148–155.

Steiner, T. (1991). Chem. Commun. pp. 313–314.

Storoniak, P., Krzymiński, K., Dokurno, P., Konitz, A. & Błażejowski, J. (2000). Aust. J. Chem. 53, 627–633.

Wróblewska, A., Huta, O. M., Midyanyj, S. V., Patsay, I. O. & Błażejowski, J. (2004). J. Org. Chem. 69, 1607–1614.

Zomer, G. & Jacquemijns, M. (2001). Chemiluminescence in Analytical Chemistry, edited by A. M. Garcia-Campana & W. R. G. Baeyens, pp. 529–549. New York: Marcel Dekker.