Thermochromism.

Day, Jesse H.

doi:10.1021/cr60221a005

Cited by 285 publications

(148 citation statements)

References 90 publications

(143 reference statements)

Supporting

Mentioning

143

Contrasting

Order By: Relevance

“…The phenomenon of thermochromism [1][2][3] in overcrowded bistricyclic aromatic enes (BAEs, 1; thermochromic ethylenes [3a] ) was discovered almost one hundred years ago. [4] Meyer reported that the yellow solutions of 9,9'-bi-9(10H)-anthracenylidene-10,10'-dione (bianthrone, 2) reversibly turn dark green upon heating.…”

Section: Introductionmentioning

confidence: 99%

“…[23] Thermochromism is a reversible, temperature-dependent change of color. [1] In BAEs, the phenomenon is based on a unimolecular [24] equilibrium [25,26] between a colorless or yellow ambient-temperature form A and a deep-blue or deep-green high-temperature form B: [27] A kT ! B Although A absorbs in the UV region (and close to it), the thermochromic form has a new absorption band at l = 600-700 nm.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Polymorphism Versus Thermochromism: Interrelation of Color and Conformation in Overcrowded Bistricyclic Aromatic Enes

Biedermann

Stezowski

Agranat

2006

Chemistry A European J

View full text Add to dashboard Cite

The nature of the thermochromic form of overcrowded bistricyclic aromatic enes (BAEs) has been controversial for a century. We report the single-crystal X-ray structure analysis of the deep-purple and yellow polymorphs of 9-(2,7-dimethyl-9H-fluoren-9-ylidene)-9H-xanthene (11), which revealed the molecules in a twisted and a folded conformation, respectively. Therefore, the deeply colored thermochromic form B of BAEs is identified as having a twisted conformation and the ambient-temperature form A as having a folded conformation. This relationship between the color and the conformation is further supported by the X-ray structures of the deep-purple crystals of the twisted 9-(9H-fluoren-9-ylidene)-9H-xanthene (10), and of the yellow crystals of the folded 9-(11H-benzo[b]fluoren-11-ylidene)-9H-xanthene (12). Based on this conclusive crystallographic evidence, eleven previously proposed rationales of thermochromism in BAEs are refuted. In the twisted structures, the tricyclic moieties are nearly planar and the central double bond is elongated to 1.40 A and twisted by 42 degrees . In the folded structures, the xanthylidene moieties are folded by 45 degrees and the fluorenylidene moieties by 18-20 degrees . Factors stabilizing the twisted and folded conformations are discussed, including twisting of formal single or double bonds, intramolecular overcrowding, and the significance of a dipolar aromatic "xanthenylium-fluorenide" push-pull structure.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Polymorphism Versus Thermochromism: Interrelation of Color and Conformation in Overcrowded Bistricyclic Aromatic Enes

Biedermann

Stezowski

Agranat

2006

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…1). [17][18][19] This spectral change was reversible: upon warming the solution, it became colourless again. The transition temperature was dependent on the host-guest combination, the solvent and the molar ratio of phenol to amine.…”

Section: Effects Of Structures Of Phenols and Amines On Thermochromismmentioning

confidence: 98%

Hydrogen-bonding-based thermochromic phenol-amine complexes

Mizutani

Takagi

Ueno

et al. 1998

J. Phys. Org. Chem.

View full text Add to dashboard Cite

Variable-temperature UV-vis, 13 C NMR and IR studies showed that proton-transferred complexes were formed between phenols and amines in apolar solvents at low temperature. Upon cooling a solution of pnitrophenol and diisopropylamine in toluene, the colour of the solution changed from colourless to yellow. This thermochromism was ascribed to the proton transfer in the hydrogen-bonding complex. Under UV-vis conditions, butylamine and imidazole also caused similar thermochromism upon complexation with p-nitrophenol, while triethylamine, quinuclidine and pyridine did not. The thermochromic behaviour was particularly dependent on the stoichiometry of the amine and the phenol: a solution of 3,3'-dibromo-5,5'-dinitro-2,2'-biphenyldiol and diisopropylamine with a molar ratio of 1:1 showed no thermochromism, while solutions with 1:2 or higher ratios showed thermochromism, indicating that excess amine is required to obtain the proton-transferred species. These results revealed that the proton-transferred species forms in apolar solvents at low temperature if an appropriate hydrogen-bonding network between the phenol and the amine can stabilize it.

show abstract

“…Reversible dependence of colour on temperature is known as thermochromism (Day, 1963). Such change in colour is often associated with temperaturedependent changes in the coordination geometry of the chromophore (Grenthe, Paoletti, SandstriSm & Glikberg, 1979).…”

Section: Commentmentioning

confidence: 99%