Thermochromism at Room Temperature in Overcrowded Bistricyclic Aromatic Enes: Closely Populated Twisted and Folded Conformations

Levy, Amalia; Pogodin, Sergey; Cohen, Shmuel; Agranat, Israel

doi:10.1002/ejoc.200700414

Cited by 37 publications

(47 citation statements)

References 48 publications

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“…Thermochromism: Some molecules exhibit the property of changing the color according to the temperature. These molecules comprise spiroheterocyclic compounds, [11,[17][18][19] salicylSchiff bases, [20][21][22][23] overcrowded ethylenes [24][25][26] and phasechange thermochromic materials (PCTM, organic thermochromic mixtures) that include crystal violet lactone and related compounds. [27][28][29][30][31] Thermochromism involving the present flavylium compound is a PCTM sample and was achieved by using EDIPA as a color developer, and different solvents, namely acetonitrile and n-pentadecanonitrile ( Figure 5).…”

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confidence: 99%

Formation of a leuco Spirolactone from 4‐(2‐Carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium: Design of a Phase‐Change Thermochromic System Based on a Flavylium Dye

Gavara

Laia

Parola

et al. 2010

Chemistry A European J

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A phase-change thermochromic system was designed through the reversible transformation of the 4-substituted flavylium dye 4-(2-carboxyphenyl)-7-diethylamino-4'-dimethylamino-1-benzopyrylium into its leuco form, in the presence of a developer (ethyldiisopropylamine) and a suitable solvent (e.g., acetonitrile, n-pentadecanonitrile). The leuco form of the flavylium-based dye is a spirolactone species whose ring opens at low temperature (below the solvent melting point) to form the blue flavylium cation. Decarboxylation of the lactone to give 4-phenyl-7-diethylamino-4'-dimethylamino-1-benzopyrylium was observed upon irradiation of the system with UV light, erasing the thermochromic effect.

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confidence: 99%

Formation of a leuco Spirolactone from 4‐(2‐Carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium: Design of a Phase‐Change Thermochromic System Based on a Flavylium Dye

Gavara

Laia

Parola

et al. 2010

Chemistry A European J

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“…The second synthetic route (Scheme 2) was based on coupling between 9H-fluorene-9-thione (14) (prepared from 9H-fluorene-9-one (15) and LR [26,32]) and di(1-naphthyl)diazomethane (16) in boiling benzene, which gave 5 directly in 60% yield, without isolating the intermediate thiirane 11. Diazo compound 16 was prepared from 10 in two steps according to a literature procedure [25].…”

Section: Synthesis Ofmentioning

confidence: 99%

“…DFT methods are capable of generating a variety of isolated molecular properties quite accurately, especially via the hybrid functionals, and in a cost-effective way [38,39] Recently, the B3LYP hybrid functional was successfully employed to treat overcrowded BAEs [16,40] Enes 5 and 6 and their 2-naphthyl substituted constitutional isomers 7 and 8 were subjected to a systematic computational DFT study of their conformational spaces and of their relative stabilities. The relative B3LYP/6-31G(d) energies of 5-8 and their selected calculated and experimental geometrical parameters are presented in Table 5.…”

Section: Dft Studymentioning

confidence: 99%

“…The bridges X and Y of BAEs have a profound, significant effect on their overcrowding, dynamic stereochemistry, and thermochromic behavior [16,17]. By the same token, the removal of one of the bridges (X or Y) of BAEs, to give x,x-diaryl-tricyclic aromatic enes, e.g., 9-(diphenylmethylene)-9H-fluorene (4) [18], confers more flexibility on these systems and the degree of overcrowding is expected to decrease.…”

Section: Introductionmentioning

confidence: 99%

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Overcrowded naphthologs of mono-bridged tetraarylethylenes: analogs of bistricyclic aromatic enes

et al. 2009

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The naphthalogous mono-bridged tetraarylethylenes 9,9 0 -di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9 0 -di-(1-naphthylmethylene)-9H-xanthene (6), analogs of bifluorenylidene (1) and bixanthenylidene (2), have been synthesized and their molecular and crystal structures have been determined. Ene 5 has been prepared by two alternative synthetic routes. The molecular structures of 5 and 6 show that each of these enes has very small twist around the central double bond, but the two naphthalene rings in both 5 and 6 are highly twisted. According to the NMR study, 5 and 6 in solution adopt conformations which are similar to those found by X-ray crystal structure analysis. The notable upfield shifts of H 1 and H 8 (6.11 and 6.83 ppm, respectively) and H 2 and H 7 (6.70 and 6.44 ppm, respectively) in 5 and 6 are due to the shielding caused by the nearly orthogonally twisted naphthalene rings. The B3LYP/6-31G(d) calculations of 5, 6, and their 2-naphthyl and phenyl analogs have been performed. In the 1-naphthyl series, the more efficient conjugation between the naphthyl substituents and the central C=C and the overcrowding due to the peri-hydrogen atoms lead to higher twists of the naphthyl groups and to lower twists of the central C=C. In the 2-naphthyl series, the opposite effects are noted.

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“…Each conformation represents a compromise between p-delocalization and steric strain. The bridges X and Y play an important role in the relative stability of the three conformations, leading in favorable cases to thermochromism [16][17][18][19]. The stereochemistry of BAEs has very recently been reviewed and analyzed [4].…”

Section: Introductionmentioning

confidence: 99%

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

et al. 2014

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The syntheses, molecular and crystal structures, NMR spectroscopic study, and DFT computational study of naphthologs of mono-bridged (X = -, O, S, Se, and Te) tetraarylethene (BAE-1s) 11-25 with a,a-, b,b-, and a,b-dinaphthalenyl substituents have been reported. The BAE-1s have been prepared by Barton-Kellog twofold extrusion from the respective chalcogenothiones and diazomethylenebisnaphthylenes. Complete assignments of 1 Hand 13 C-NMR spectra of 11-25 have been made through 2-dimensional correlation spectroscopy (DQF-COSY, HSQC, HMBC, and NOESY). The corresponding intermediates, thiiranes 33-47, have been also isolated (except 38), and their molecular and crystal structures have been determined. The molecular structures of BAE-1s 12-15, 20, and 22-25 adopted folded-twisted conformations with considerably folded (u = 30°-57°) tricyclic moieties. The a,a-and a,b-dinaphthalenyl derivatives are more overcrowded than b,b-dinaphthalenyl derivatives. The relief of the steric strain due to the overcrowding around C 9 = C 9 0 caused by the presence of naphthalenyl substituents was achieved by their twisting around the single bonds that connect the a-naphthalenyl and b-naphthalenyl moieties to C 9 0 . The 1 H-NMR spectra have shown shielding of H 2 , H 7 of 11-25 and the pronounced deshielding of H 8 0 , H 8 00 of a,a-dinaphthalenyl-substituted BAE-1s 13-15 in contrast to b,b-dinaphthalenyl-substituted BAE-1s 16-20. The upfield shifts of H 2 , H 7 suggested conformations in which these hydrogens are located above the planes of the opposing naphthalene rings. DFT calculations of 11-20 have been performed at B3LYP/6-31G(d) and B3LYP/ SDD. The results have shown that the global minima of BAE-1s without a chalcogen bridge 11 and 16 are twisted (-sc,-sc)-C 2 -t conformations. The global minima of BAE1s with a chalcogen bridge are folded-twisted (-sc,-ac)-C 1 -ft conformations for a,a-dinaphthalenyl-substituted BAE1s 12-15 and either anti-or syn-(-sc,ac)-C 1 -ft conformations for b,b-dinaphthalenyl-substituted BAE-1s 17-20. The pronounced differences between the a,a-dinaphthalenyl and the b,b-dinaphthalenyl derivatives are noted. Dispersion-corrected B3LYP calculations stabilize significantly the a,a-dinaphthalenyl derivatives versus the b,b-dinaphthalenyl derivatives. The geometrical parameters of BAEs-1 11-15 and 20, derived from their molecular X-ray structures and from their B3LYP-optimized geometries are in a good agreement.

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Thermochromism at Room Temperature in Overcrowded Bistricyclic Aromatic Enes: Closely Populated Twisted and Folded Conformations

Cited by 37 publications

References 48 publications

Formation of a leuco Spirolactone from 4‐(2‐Carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium: Design of a Phase‐Change Thermochromic System Based on a Flavylium Dye

Formation of a leuco Spirolactone from 4‐(2‐Carboxyphenyl)‐7‐diethylamino‐4′‐dimethylamino‐1‐benzopyrylium: Design of a Phase‐Change Thermochromic System Based on a Flavylium Dye

Overcrowded naphthologs of mono-bridged tetraarylethylenes: analogs of bistricyclic aromatic enes

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

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