2,4-Bis(3,3-dimethyl-1-octylindolin-2-ylidenemethyl)cyclobutenediylio-1,3-diolate

Abstract

The structure of the title compound, C42H56N2O2, comprises a centrosymmetric mol­ecule, with only half of the mol­ecule in the asymmetric unit and with an inversion centre in the middle of the squarate ring. The squaraine moiety is planar and extensively delocalized, with the dihedral angle between the squarate and indoline planes being 3.9 (2)°.

Croconaine Dyes – the Lesser Known Siblings of Squaraines

“…[80] Eur. This is particularly evident for the indolinylidene squaraines (the squaraine equivalent of a type 4 molecule) that majorly adopt the trans configuration [86] (R 1 ≠ H; Figure 3), while the parent molecule (R = H) adopts the cis configuration. Org.…”

“…The vast majority of squaraine molecules with known crystal structures are symmetrical molecules, both crystallographically and chemically, that adopt a trans configuration. This is particularly evident for the indolinylidene squaraines (the squaraine equivalent of a type 4 molecule) that majorly adopt the trans configuration [86] (R 1 ≠ H; Figure 3), while the parent molecule (R = H) adopts the cis configuration. [87] For anilinium squaraines (equivalent of type 13 croconaines), a similar tendency can be observed if there are asymmetric substituents on either or both of the phenyl rings or on the N atom, and a cis/trans ratio in solution can be determined from the 1 H NMR spectra.…”

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

“…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…”

“…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).…”

Crystal structures of a benzoselenazole-derived squarylium cyanine dye and three derivatives substituted at the central squaric ring

“…Additionally, the largely extended p-conjugated systems in squarylium dyes that promote the formation of long-range slip-stacked charge-transfer columns often yield very thin planar single crystals unsuitable for diffraction studies. 4 The majority of crystal structures of squarylium dyes described in the literature belong to compounds bearing an Nalkyl derivative of 3,3-dimethylindolenine [9][10][11][12][13] as the terminal nuclei. The crystal structures of some squarylium dyes derived from benzothiazole, 8,10 quinoline 14 and aniline [15][16][17][18][19] have also been determined.…”