organic compounds
2-[(3,3-Dimethylindolin-2-ylidene)methyl]-4-[(3,3-dimethyl-3H-indol-1-ium-2-yl)methylidene]-3-oxocyclobut-1-en-1-olate chloroform disolvate
aScience and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia, and bExilica Limited, The Technocentre, Puma Way, Coventry CV1 2TT, England
*Correspondence e-mail: g.smith@qut.edu.au
In the title squaraine dye solvate, C26H24N2O2·2CHCl3, the dye molecule is essentially planar, except for the methyl groups, having a maximum deviation over the 26-membered delocalized bond system of 0.060 (2) Å. It possesses crystallographic twofold rotational symmetry with the indole ring systems adopting a syn conformation. The molecular structure features intramolecular N—H⋯O hydrogen bonds enclosing conjoint S7 ring motifs about one of the dioxocyclobutene O atoms, while the two chloroform solvent molecules are linked to the second O atom through C—H⋯O hydrogen bonds.
Related literature
For the first report of bis(indolenine)squaraine dyes with alkyl substituents on the N-atom of each of the indolenine rings, see: Sprenger Von & Ziegenbein (1967). For background to bis(indolenine)squaraine dyes as biomarkers, see: Patsenker et al. (2011); Sameiro & Gonçalves (2009). For the structures of some analogues of the parent dye, see: Kobiyashi et al. (1986); Natsukawa & Nakazumi (1993); Tong & Peng (1999); Lynch & Byriel (1999); Lynch (2002); Arunkumar et al. (2007); Matsui et al. (2012); Lynch et al. (2012).
Experimental
Crystal data
|
|
Data collection: CrysAlis PRO (Agilent, 2012); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON.
Supporting information
https://doi.org/10.1107/S1600536813010386/su2588sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813010386/su2588Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536813010386/su2588Isup3.cml
Squaric acid (200 mg, 1.75 mmol) was added to 2.0 molar equivalents of 2,3,3-trimethylindolenine (0.56 g, 3.5 mmol) and quinoline (0.45 g, 3.5 mmol) in a 1:1 v/v mix of 1-butanol:toluene (30 ml) and the mixture was then refluxed for 16 h using a Dean and Stark apparatus. Upon cooling, metallic green crystals were collected in vacuo, washed with petroleum ether (60/40), and were used without further purification [Yield: 0.31 g (45%)]. Spectroscopic data are available in the archived
For the X-ray large green-black lustrous crystal prisms of the title compound were obtained from the room temperature evaporation of a solution of the dye in chloroform. A cleaved crystal specimen was used for the actual analysis.The H atom of the N—H group was located in a difference Fourier but was subsequently refined as a riding atom: N-H = 0.88 Å with Uiso(H) = 1.2Ueq(N). C-bound H atoms were included in calculated positions and refined as riding atoms: C—H = 0.93 Å (aromatic or ethylenic), 0.96 Å (methyl) or 0.98 Å (methine) with Uiso(H) = 1.5Ueq(C-methyl) and = 1.2Ueq(C) for other H atoms.
Bis(indolenine)squaraine dyes, in which there is an alkyl substituent on the N-atom of each of the indolenine rings, were first reported on by Sprenger Von & Ziegenbein (1967) and have been studied since then for a range of opto-electronic applications such as long-wavelength protein-sensitive bioprobes (Lynch et al., 2012; Patsenker et al., 2011; Sameiro & Gonçalves, 2009). However, the parent dye compound 2,4-[(3,3-dimethyl-2-indolylidene)methyl]cyclobutenediylio-1,3-diolate, which has no N-alkyl substituent (R) on the indolenine ring, has remained relatively untouched in the literature, including reporting of the
The crystal structures of a number of analogues with such substituents have been reported; for e.g. R = methyl (Kobiyashi et al., 1986), ethyl (Natsukawa & Nakazumi, 1993), isopropyl (Tong & Peng, 1999), n-butyl (Matsui et al., 2012), n-hexyl (Lynch & Byriel, 1999) and n-octyl (Lynch, 2002).Evaporation of a solution of the dye in chloroform gave the title compound solvate as large green-black crystal prisms and its
is reported on herein. The dye molecule adopts the uncommon syn-conformation with respect to the indolenine rings, having crystallographic twofold rotational symmetry (Fig. 1). The structures of all other members of this series of N-alkyl-substituted squaraine dyes have the inversion-related anti-conformation.The planarity of the delocalized 26-membered linked ring system in the overall molecule is indicated by maximum deviations of 0.059 (2) (C6 and C6i) and 0.060 (2) (C4 and C4i) from the least-squares plane [symmetry code (i): -x, y, -z + 3/2]. This planarity is further stabilized by the intramolecular N—H···O hydrogen bonds to O2 of the dioxocyclobutene ring (Table 1), closing conjoint S7 ring motifs.
Inter-species C—H···O hydrogen-bonding interactions link the two chloroform molecules to the second O-atom (O1). Although chloroform is a common solvent for the crystallization of squaraine dyes, chloroform solvates are uncommon with only three such structures reported on previously (Natsukawa & Nakazumi, 1993; Lynch & Byriel, 1999; Arunkumar et al., 2007).
For the first report of bis(indolenine)squaraine dyes with alkyl substituents on the N-atom of each of the indolenine rings, see: Sprenger Von & Ziegenbein (1967). For background to bis(indolenine)squaraine dyes as biomarkers, see: Patsenker et al. (2011); Sameiro & Gonçalves (2009). For the structures of some analogues of the parent dye, see: Kobiyashi et al. (1986); Natsukawa & Nakazumi (1993); Tong & Peng (1999); Lynch & Byriel (1999); Lynch (2002); Arunkumar et al. (2007); Matsui et al. (2012); Lynch et al. (2012).
Data collection: CrysAlis PRO (Agilent, 2012); cell
CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009).C26H24N2O2·2CHCl3 | F(000) = 1304 |
Mr = 635.21 | Dx = 1.416 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2690 reflections |
a = 20.4270 (11) Å | θ = 3.3–28.8° |
b = 13.5433 (5) Å | µ = 0.61 mm−1 |
c = 11.4259 (5) Å | T = 200 K |
β = 109.561 (5)° | Prism, green |
V = 2978.5 (3) Å3 | 0.40 × 0.22 × 0.20 mm |
Z = 4 |
Oxford Diffraction Gemini-S CCD-detector diffractometer | 2926 independent reflections |
Radiation source: Enhance (Mo) X-ray source | 2415 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.027 |
Detector resolution: 16.077 pixels mm-1 | θmax = 26.0°, θmin = 3.5° |
ω scans | h = −22→25 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | k = −16→16 |
Tmin = 0.794, Tmax = 0.888 | l = −13→14 |
10054 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.044 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.112 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.047P)2 + 4.0361P] where P = (Fo2 + 2Fc2)/3 |
2926 reflections | (Δ/σ)max < 0.001 |
176 parameters | Δρmax = 0.54 e Å−3 |
0 restraints | Δρmin = −0.50 e Å−3 |
C26H24N2O2·2CHCl3 | V = 2978.5 (3) Å3 |
Mr = 635.21 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 20.4270 (11) Å | µ = 0.61 mm−1 |
b = 13.5433 (5) Å | T = 200 K |
c = 11.4259 (5) Å | 0.40 × 0.22 × 0.20 mm |
β = 109.561 (5)° |
Oxford Diffraction Gemini-S CCD-detector diffractometer | 2926 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | 2415 reflections with I > 2σ(I) |
Tmin = 0.794, Tmax = 0.888 | Rint = 0.027 |
10054 measured reflections |
R[F2 > 2σ(F2)] = 0.044 | 0 restraints |
wR(F2) = 0.112 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.54 e Å−3 |
2926 reflections | Δρmin = −0.50 e Å−3 |
176 parameters |
Experimental. Spectroscopic details of the as synthesized metallic green crystals of the title dye: UV/Vis (CHCl3), recorded on a Nicolet 205 F T—IR spectrometer: λmax (log ε): 665(5.54). IR (KBr, cm-1) recorded on a Unicam UV-4 spectrometer: λmax: 1623 (C—O). Electrospray mass spectra recorded in the the positive (ES+) ion mode: 397.1 [M+H]+, 460.1 [M+Na+MeCN]+, 815.3 [2M+Na]+, 1211.6 [3M+Na]+. |
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 e.s.d.'s 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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.00000 | 0.35895 (15) | 0.75000 | 0.0420 (8) | |
O2 | 0.00000 | 0.02418 (14) | 0.75000 | 0.0330 (7) | |
N1 | 0.08460 (9) | 0.01681 (12) | 0.60326 (15) | 0.0292 (5) | |
C1 | 0.00000 | 0.2681 (2) | 0.75000 | 0.0308 (9) | |
C2 | 0.03058 (10) | 0.19196 (14) | 0.69306 (18) | 0.0283 (6) | |
C3 | 0.00000 | 0.1172 (2) | 0.75000 | 0.0273 (8) | |
C4 | 0.07197 (11) | 0.19354 (15) | 0.61835 (19) | 0.0300 (6) | |
C5 | 0.09788 (10) | 0.11037 (14) | 0.57941 (18) | 0.0272 (6) | |
C6 | 0.14808 (11) | 0.10979 (15) | 0.50618 (19) | 0.0298 (6) | |
C7 | 0.19200 (12) | −0.05112 (17) | 0.4256 (2) | 0.0364 (7) | |
C8 | 0.18945 (12) | −0.15368 (18) | 0.4251 (2) | 0.0400 (8) | |
C9 | 0.15195 (12) | −0.20386 (17) | 0.4872 (2) | 0.0390 (7) | |
C10 | 0.11502 (12) | −0.15347 (15) | 0.55071 (19) | 0.0333 (7) | |
C11 | 0.11792 (11) | −0.05144 (15) | 0.54957 (18) | 0.0278 (6) | |
C12 | 0.15568 (10) | −0.00001 (15) | 0.48861 (18) | 0.0293 (6) | |
C13 | 0.21729 (12) | 0.15545 (17) | 0.5872 (2) | 0.0397 (7) | |
C14 | 0.11833 (13) | 0.16552 (17) | 0.3829 (2) | 0.0400 (8) | |
Cl1 | 0.10014 (5) | 0.46856 (7) | 0.50703 (7) | 0.0756 (3) | |
Cl2 | 0.09549 (5) | 0.60290 (5) | 0.70002 (8) | 0.0724 (3) | |
Cl3 | 0.17949 (4) | 0.42725 (6) | 0.76203 (7) | 0.0650 (3) | |
C15 | 0.10219 (14) | 0.47904 (18) | 0.6610 (2) | 0.0444 (8) | |
H1 | 0.05820 | 0.00030 | 0.64720 | 0.0350* | |
H4 | 0.08300 | 0.25470 | 0.59290 | 0.0360* | |
H7 | 0.21760 | −0.01770 | 0.38450 | 0.0440* | |
H8 | 0.21330 | −0.18910 | 0.38230 | 0.0480* | |
H9 | 0.15150 | −0.27250 | 0.48640 | 0.0470* | |
H10 | 0.08950 | −0.18680 | 0.59210 | 0.0400* | |
H131 | 0.23420 | 0.12070 | 0.66480 | 0.0600* | |
H132 | 0.21030 | 0.22370 | 0.60240 | 0.0600* | |
H133 | 0.25060 | 0.15050 | 0.54490 | 0.0600* | |
H141 | 0.15020 | 0.16100 | 0.33750 | 0.0600* | |
H142 | 0.11160 | 0.23360 | 0.39920 | 0.0600* | |
H143 | 0.07460 | 0.13680 | 0.33480 | 0.0600* | |
H15 | 0.06270 | 0.44250 | 0.66990 | 0.0530* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0502 (14) | 0.0225 (10) | 0.0651 (15) | 0.0000 | 0.0351 (12) | 0.0000 |
O2 | 0.0396 (12) | 0.0231 (10) | 0.0439 (12) | 0.0000 | 0.0240 (10) | 0.0000 |
N1 | 0.0351 (9) | 0.0247 (9) | 0.0344 (9) | 0.0005 (7) | 0.0203 (8) | 0.0024 (7) |
C1 | 0.0302 (15) | 0.0265 (15) | 0.0392 (16) | 0.0000 | 0.0161 (13) | 0.0000 |
C2 | 0.0261 (10) | 0.0252 (10) | 0.0342 (11) | −0.0004 (8) | 0.0111 (9) | 0.0009 (8) |
C3 | 0.0260 (14) | 0.0265 (15) | 0.0304 (14) | 0.0000 | 0.0108 (12) | 0.0000 |
C4 | 0.0336 (11) | 0.0229 (10) | 0.0377 (11) | −0.0023 (8) | 0.0176 (9) | 0.0028 (8) |
C5 | 0.0268 (10) | 0.0281 (10) | 0.0272 (10) | −0.0018 (8) | 0.0099 (8) | 0.0017 (8) |
C6 | 0.0315 (11) | 0.0308 (11) | 0.0310 (10) | −0.0012 (9) | 0.0156 (9) | 0.0018 (8) |
C7 | 0.0336 (12) | 0.0442 (13) | 0.0349 (11) | 0.0034 (10) | 0.0162 (10) | 0.0003 (9) |
C8 | 0.0399 (13) | 0.0444 (14) | 0.0373 (12) | 0.0119 (11) | 0.0150 (10) | −0.0059 (10) |
C9 | 0.0432 (13) | 0.0337 (12) | 0.0375 (12) | 0.0079 (10) | 0.0102 (10) | −0.0026 (9) |
C10 | 0.0392 (12) | 0.0288 (11) | 0.0325 (11) | −0.0001 (9) | 0.0127 (9) | 0.0009 (8) |
C11 | 0.0291 (10) | 0.0295 (10) | 0.0254 (9) | 0.0031 (8) | 0.0098 (8) | 0.0002 (8) |
C12 | 0.0272 (10) | 0.0315 (11) | 0.0303 (10) | 0.0004 (9) | 0.0110 (8) | 0.0009 (8) |
C13 | 0.0350 (12) | 0.0408 (13) | 0.0477 (13) | −0.0062 (10) | 0.0196 (11) | −0.0029 (10) |
C14 | 0.0524 (15) | 0.0354 (12) | 0.0366 (12) | 0.0007 (11) | 0.0206 (11) | 0.0076 (9) |
Cl1 | 0.0984 (7) | 0.0894 (6) | 0.0439 (4) | −0.0101 (5) | 0.0303 (4) | −0.0026 (4) |
Cl2 | 0.0981 (6) | 0.0384 (4) | 0.0764 (5) | −0.0049 (4) | 0.0234 (5) | −0.0064 (3) |
Cl3 | 0.0658 (5) | 0.0531 (4) | 0.0653 (5) | −0.0084 (4) | 0.0077 (4) | 0.0035 (3) |
C15 | 0.0548 (15) | 0.0384 (13) | 0.0436 (13) | −0.0135 (12) | 0.0214 (12) | −0.0011 (10) |
Cl1—C15 | 1.751 (2) | C7—C8 | 1.390 (3) |
Cl2—C15 | 1.753 (3) | C8—C9 | 1.384 (3) |
Cl3—C15 | 1.760 (3) | C9—C10 | 1.389 (3) |
O1—C1 | 1.230 (3) | C10—C11 | 1.383 (3) |
O2—C3 | 1.260 (3) | C11—C12 | 1.387 (3) |
N1—C5 | 1.343 (3) | C4—H4 | 0.9300 |
N1—C11 | 1.405 (3) | C7—H7 | 0.9300 |
N1—H1 | 0.8800 | C8—H8 | 0.9300 |
C1—C2i | 1.466 (3) | C9—H9 | 0.9300 |
C1—C2 | 1.466 (3) | C10—H10 | 0.9300 |
C2—C4 | 1.388 (3) | C13—H133 | 0.9600 |
C2—C3 | 1.453 (3) | C13—H131 | 0.9600 |
C4—C5 | 1.380 (3) | C13—H132 | 0.9600 |
C5—C6 | 1.525 (3) | C14—H141 | 0.9600 |
C6—C12 | 1.516 (3) | C14—H142 | 0.9600 |
C6—C13 | 1.537 (3) | C14—H143 | 0.9600 |
C6—C14 | 1.533 (3) | C15—H15 | 0.9800 |
C7—C12 | 1.380 (3) | ||
C5—N1—C11 | 111.84 (18) | C6—C12—C7 | 131.1 (2) |
C11—N1—H1 | 124.00 | C6—C12—C11 | 109.10 (18) |
C5—N1—H1 | 124.00 | C2—C4—H4 | 118.00 |
C2—C1—C2i | 90.59 (19) | C5—C4—H4 | 118.00 |
O1—C1—C2i | 134.70 (11) | C8—C7—H7 | 121.00 |
O1—C1—C2 | 134.70 (11) | C12—C7—H7 | 121.00 |
C1—C2—C3 | 88.88 (16) | C7—C8—H8 | 119.00 |
C1—C2—C4 | 134.41 (18) | C9—C8—H8 | 120.00 |
C3—C2—C4 | 136.70 (18) | C8—C9—H9 | 119.00 |
O2—C3—C2 | 134.18 (11) | C10—C9—H9 | 119.00 |
C2—C3—C2i | 91.64 (19) | C9—C10—H10 | 122.00 |
O2—C3—C2i | 134.18 (11) | C11—C10—H10 | 122.00 |
C2—C4—C5 | 124.33 (19) | C6—C13—H131 | 109.00 |
N1—C5—C4 | 125.4 (2) | C6—C13—H132 | 110.00 |
N1—C5—C6 | 108.97 (17) | C6—C13—H133 | 109.00 |
C4—C5—C6 | 125.59 (18) | H131—C13—H132 | 110.00 |
C5—C6—C12 | 101.26 (16) | H131—C13—H133 | 110.00 |
C12—C6—C13 | 111.12 (18) | H132—C13—H133 | 109.00 |
C12—C6—C14 | 112.84 (17) | C6—C14—H141 | 109.00 |
C13—C6—C14 | 110.92 (18) | C6—C14—H142 | 109.00 |
C5—C6—C13 | 108.62 (17) | C6—C14—H143 | 109.00 |
C5—C6—C14 | 111.66 (19) | H141—C14—H142 | 109.00 |
C8—C7—C12 | 118.5 (2) | H141—C14—H143 | 109.00 |
C7—C8—C9 | 121.0 (2) | H142—C14—H143 | 110.00 |
C8—C9—C10 | 121.2 (2) | Cl1—C15—Cl2 | 110.82 (13) |
C9—C10—C11 | 117.0 (2) | Cl1—C15—Cl3 | 109.94 (16) |
N1—C11—C12 | 108.72 (17) | Cl2—C15—Cl3 | 110.12 (13) |
C10—C11—C12 | 122.6 (2) | Cl1—C15—H15 | 109.00 |
N1—C11—C10 | 128.7 (2) | Cl2—C15—H15 | 109.00 |
C7—C12—C11 | 119.8 (2) | Cl3—C15—H15 | 109.00 |
C11—N1—C5—C4 | 179.2 (2) | C4—C5—C6—C12 | −178.6 (2) |
C11—N1—C5—C6 | −2.7 (2) | C4—C5—C6—C13 | 64.3 (3) |
C5—N1—C11—C10 | −177.9 (2) | C4—C5—C6—C14 | −58.3 (3) |
C5—N1—C11—C12 | 0.8 (2) | C5—C6—C12—C7 | 177.2 (2) |
O1—C1—C2—C3 | 180.00 (2) | C5—C6—C12—C11 | −2.8 (2) |
O1—C1—C2—C4 | 0.9 (3) | C13—C6—C12—C7 | −67.6 (3) |
C2i—C1—C2—C3 | 0.00 (12) | C13—C6—C12—C11 | 112.4 (2) |
C2i—C1—C2—C4 | −179.1 (2) | C14—C6—C12—C7 | 57.7 (3) |
C2—C1—C2i—C3 | 0.02 (16) | C14—C6—C12—C11 | −122.3 (2) |
C1—C2—C3—O2 | 180.00 (1) | C12—C7—C8—C9 | −0.6 (3) |
C1—C2—C3—C2i | 0.00 (11) | C8—C7—C12—C6 | −179.9 (2) |
C4—C2—C3—O2 | −0.9 (3) | C8—C7—C12—C11 | 0.1 (3) |
C4—C2—C3—C2i | 179.1 (3) | C7—C8—C9—C10 | 0.8 (4) |
C1—C2—C4—C5 | 176.79 (19) | C8—C9—C10—C11 | −0.4 (3) |
C3—C2—C4—C5 | −1.9 (4) | C9—C10—C11—N1 | 178.4 (2) |
C2—C4—C5—N1 | 3.0 (3) | C9—C10—C11—C12 | −0.1 (3) |
C2—C4—C5—C6 | −174.8 (2) | N1—C11—C12—C6 | 1.5 (2) |
N1—C5—C6—C12 | 3.3 (2) | N1—C11—C12—C7 | −178.52 (19) |
N1—C5—C6—C13 | −113.77 (19) | C10—C11—C12—C6 | −179.7 (2) |
N1—C5—C6—C14 | 123.59 (19) | C10—C11—C12—C7 | 0.2 (3) |
Symmetry code: (i) −x, y, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2 | 0.88 | 1.96 | 2.7835 (18) | 156 |
C15—H15···O1 | 0.98 | 2.13 | 3.075 (3) | 161 |
Experimental details
Crystal data | |
Chemical formula | C26H24N2O2·2CHCl3 |
Mr | 635.21 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 200 |
a, b, c (Å) | 20.4270 (11), 13.5433 (5), 11.4259 (5) |
β (°) | 109.561 (5) |
V (Å3) | 2978.5 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.61 |
Crystal size (mm) | 0.40 × 0.22 × 0.20 |
Data collection | |
Diffractometer | Oxford Diffraction Gemini-S CCD-detector diffractometer |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2012) |
Tmin, Tmax | 0.794, 0.888 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10054, 2926, 2415 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.112, 1.02 |
No. of reflections | 2926 |
No. of parameters | 176 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.54, −0.50 |
Computer programs: CrysAlis PRO (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2 | 0.88 | 1.96 | 2.7835 (18) | 156 |
C15—H15···O1 | 0.98 | 2.13 | 3.075 (3) | 161 |
Acknowledgements
The authors acknowledge financial support from the Australian Research Council and the Science and Engineering Faculty and the University Library, Queensland University of Technology. John Langley (Southampton University, England) is thanked for the collection of electrospray
data.References
Agilent (2012). CrysAlis PRO. Agilent Technologies Ltd, Yarnton, England. Google Scholar
Arunkumar, E., Sudeep, P. K., Kamat, P. V., Noll, B. C. & Smith, B. D. (2007). New J. Chem. 31, 677–683. Web of Science CSD CrossRef CAS PubMed Google Scholar
Kobiyashi, Y., Goto, M. & Kurahashi, M. (1986). Bull. Chem. Soc. Jpn, 59, 311–312. Google Scholar
Lynch, D. E. (2002). Acta Cryst. E58, o1025–o1027. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lynch, D. E. & Byriel, K. A. (1999). Cryst. Eng. 2, 225–239. CSD CrossRef CAS Google Scholar
Lynch, D. E., Kirkham, V. B., Chowdhury, M. Z. H., Wane, E. S. & Heptinstall, J. (2012). Dyes Pigments, 60, 393–402. Web of Science CSD CrossRef Google Scholar
Matsui, M., Fukushima, M., Kubota, Y., Funabiki, K. & Shiro, M. (2012). Tetrahedron, 68, 1931–1935. Web of Science CSD CrossRef CAS Google Scholar
Natsukawa, K. & Nakazumi, H. (1993). Sangyo Gij. Sogo Kenk. Hokuku, 6, 16–21. CAS Google Scholar
Patsenker, L. D., Tatarets, A. L., Povrozin, Y. A. & Terpetschnig, E. A. (2011). Bioanal. Rev. 3, 115–137. CrossRef Google Scholar
Sameiro, M. & Gonçalves, T. (2009). Chem. Rev. 109, 190–212. PubMed Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sprenger Von, H.-E. & Ziegenbein, W. (1967). Angew. Chem. 79, 581–582. Google Scholar
Tong, L. & Peng, B.-X. (1999). Dyes Pigments, 43, 73–76. CSD CrossRef Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Bis(indolenine)squaraine dyes, in which there is an alkyl substituent on the N-atom of each of the indolenine rings, were first reported on by Sprenger Von & Ziegenbein (1967) and have been studied since then for a range of opto-electronic applications such as long-wavelength protein-sensitive bioprobes (Lynch et al., 2012; Patsenker et al., 2011; Sameiro & Gonçalves, 2009). However, the parent dye compound 2,4-[(3,3-dimethyl-2-indolylidene)methyl]cyclobutenediylio-1,3-diolate, which has no N-alkyl substituent (R) on the indolenine ring, has remained relatively untouched in the literature, including reporting of the crystal structure. The crystal structures of a number of analogues with such substituents have been reported; for e.g. R = methyl (Kobiyashi et al., 1986), ethyl (Natsukawa & Nakazumi, 1993), isopropyl (Tong & Peng, 1999), n-butyl (Matsui et al., 2012), n-hexyl (Lynch & Byriel, 1999) and n-octyl (Lynch, 2002).
Evaporation of a solution of the dye in chloroform gave the title compound solvate as large green-black crystal prisms and its crystal structure is reported on herein. The dye molecule adopts the uncommon syn-conformation with respect to the indolenine rings, having crystallographic twofold rotational symmetry (Fig. 1). The structures of all other members of this series of N-alkyl-substituted squaraine dyes have the inversion-related anti-conformation.
The planarity of the delocalized 26-membered linked ring system in the overall molecule is indicated by maximum deviations of 0.059 (2) (C6 and C6i) and 0.060 (2) (C4 and C4i) from the least-squares plane [symmetry code (i): -x, y, -z + 3/2]. This planarity is further stabilized by the intramolecular N—H···O hydrogen bonds to O2 of the dioxocyclobutene ring (Table 1), closing conjoint S7 ring motifs.
Inter-species C—H···O hydrogen-bonding interactions link the two chloroform molecules to the second O-atom (O1). Although chloroform is a common solvent for the crystallization of squaraine dyes, chloroform solvates are uncommon with only three such structures reported on previously (Natsukawa & Nakazumi, 1993; Lynch & Byriel, 1999; Arunkumar et al., 2007).