title: Crystal engineering approach to design colorimetric indicator array to discriminate positional isomers of aromatic organic molecules.
abstract: Discriminating by color: A 2D colorimetric indicator array has been designed by a crystal engineering approach (NH-O hydrogen bonding and charge-transfer complexation) involving solid-state co-grinding for the visual discrimination of positional isomers of dihydroxynaphthalene. Factors governing the close packing of pi planes, and hence color of the complex, were determined by single-crystal X-ray analysis, allowing fine tuning by crystal engineering. A 2D colorimetric indicator array to discriminate isomers of dihydroxynaphthalene has been designed by using a crystal engineering concept combined with solid-state co-grinding and charge-transfer complexation. The NH-O supramolecular synthon between the pyridyl N atom of the probe and hydroxy group of the analyte has been observed in all reported single-crystal X-ray structures of resultant CT complexes. Solid-state co-grinding with aromatic solids easily provided the highly concentrated solvent-free conditions required to promote the formation of charge-transfer complexes with brighter color changes. Probe D (N,N'-bis-(4-pyridyl)pyromellitic diimide) showed an excellent ability to discriminate eight isomers of dihydroxynaphthalene with a wide variety of colors of the resultant CT complexes.
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan.
authors.forename: Darshak R
authors.initials: DR
authors.lastname: Trivedi
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Fujiki
authors.forename: Norifumi
authors.initials: N
authors.lastname: Fujita
authors.forename: Seiji
authors.initials: S
authors.lastname: Shinkai
authors.forename: Kazuki
authors.initials: K
authors.lastname: Sada