Gryl Marlena, Rydz Agnieszka, Wojnarska Joanna, Krawczuk Anna, Kozieł Marcin, Seidler Tomasz, Ostrowska Katarzyna, Marzec Monika, Stadnicka Katarzyna Marta
Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland.
Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
IUCrJ. 2019 Jan 24;6(Pt 2):226-237. doi: 10.1107/S2052252518017037. eCollection 2019 Mar 1.
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.
如今，铬材料在各种技术应用中被广泛使用，然而，了解材料所产生颜色的影响以及调节颜色的可能性仍然具有挑战性。本文对紫尿酸酪胺（pseudo）多晶型物中的溶剂化显色和晶体显色效应进行了实验和理论相结合的研究。这种有机材料表现出较大的溶剂化显色位移（192 nm），伴随着广泛的颜色变化（从黄色到深紫色）。紫尿酸酪胺从水溶剂中结晶为红色的晶型（I），从甲醇溶液中结晶为非溶剂化形式[晶型（II）的紫色晶体]。晶型（I）加热时会发生两次与晶体颜色变化相关的晶型间相变。晶型（II）的晶体表现出极高的双折射（0.46）和高折射率（高于1.90），这与离子的合成偶极矩的优先取向有关。通过对光学效应（紫外-可见光谱）以及理论计算（QTAIM、原子和键极化率）的研究，得以描述所研究材料中颜色的来源。
