title: Synthesis and X-ray crystal structure of isomeric pyridine-based leuco-TAM dyes, 2,2-(2-(pyridinyl)propane-1,3-diylidene)bis(5-chloro-1,3,3-trimethyl indoline) derivatives and unusual stability of 4-pyridinyl compound.
abstract: The solid-state structures and unequivocal stereochemistries of isomeric pyridine-based leuco-triarylmethane (LTAM) dyes 2,2'-(2-(pyridin-4 or 3-yl)propane-1,3-diylidene)bis(5-chloro-1,3,3-trimethylindoline) derivatives were established by X-ray crystallography. Surprisingly, the EE isomer was formed for the 4-pyridinyl compound, whereas the 3-pyridinyl compound formed ZE isomers. In addition, the latter have a so-called three-bladed propeller conformation, whereas the former possess a Y-shaped conformation. These pyridine-based LTAM compounds stack to form a dimer, adopting either an orthorhombic, with Pcmn space group, or monoclinic crystal system with P21/n space group in the crystal unit cell.
authors.affiliation: Department of Advanced Materials Chemistry, Korea University, Se-Jong Campus, Jochiwon 339-700, South Korea.
authors.forename: So-Young
authors.initials: SY
authors.lastname: Ma
authors.forename: Sam-Rok
authors.initials: SR
authors.lastname: Keum
mesh_terms: D004396:Coloring Agents / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019281:Dimerization; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004396:Coloring Agents; D011725:Pyridines; C023666:pyridine
keywords: Monoclinic crystal; Orthorhombic crystal; Pyridine-based leuco-TAM molecules; Stereoselective formation; Three-bladed propeller conformation; Y-shaped conformation