AI Article Synopsis
- - The study explores how the color of the organic material tyraminium violurate can be changed by manipulating its environment (solvatochromic) and different crystal forms (crystallochromic), which exhibit a significant color shift (192 nm) from yellow to dark violet.
- - Tyraminium violurate crystallizes in two forms: red crystals (form I) from water and violet crystals (form II) from methanol, with form I undergoing phase transformations upon heating that also change color.
- - Advanced techniques, including UV-Vis spectroscopy and theoretical calculations, help explain the optical properties and color origins of these materials, highlighting form II's remarkable birefringence and high refractive index.
Article Abstract
Chromic materials are nowadays widely used in various technological applications, however understanding the effect and the possibility of tuning the obtained colour of a material are still challenging. Here a combined experimental and theoretical study is presented on the solvatochromic and crystallochromic effects in the (pseudo)polymorphs of tyraminium violurate. This organic material exhibits a large solvatochromic shift ( 192 nm) associated with broad colour change (from yellow to dark violet). Tyraminum violurate crystallizes as red crystals of form (I) from water as a solvate, and as an unsolvated form [violet crystals of (II)] from methanol solution. Form (I), when heated, undergoes two crystal-to-crystal phase transformations associated with colour change of the crystals. Crystals of (II) show extreme birefringence ( 0.46) and high refractive index ( above 1.90), which can be correlated with preferential orientation of the resultant dipole moments of the ions. Examination of optical effects (UV-Vis spectra) along with theoretical calculations (QTAIM, atomic and bond polarizabilities) enabled the description of the origin of colour in the studied materials.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6400187 | PMC |
| http://dx.doi.org/10.1107/S2052252518017037 | DOI Listing |
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