Rationalization of the Color Properties of Fluorescein in the Solid State: A Combined Computational and Experimental Study.
Fluorescein is known to exist in three tautomeric forms defined as quinoid, zwitterionic, and lactoid. In the solid state, the quinoid and zwitterionic forms give rise to red and yellow materials, respectively. The lactoid form has not been crystallized pure, although its cocrystal and solvate forms exhibit colors ranging from yellow to green. An explanation for the observed colors of the crystals is found using a combination of UV/Vis spectroscopy and plane-wave DFT calculations. The role of cocrystal coformers in modifying crystal color is also established. Several new crystal structures are determined using a combination of X-ray and electron diffraction, solid-state NMR spectroscopy, and crystal structure prediction (CSP). The protocol presented herein may be used to predict color properties of materials prior to their synthesis.
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
Mihails
http://orcid.org/0000-0003-1150-3108
M
Arhangelskis
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
Mark D
MD
Eddleston
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
David G
DG
Reid
School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.
Graeme M
http://orcid.org/0000-0001-8396-2771
GM
Day
Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.
Dejan-Krešimir
http://orcid.org/0000-0001-6393-276X
DK
Bučar
Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK.
Andrew J
http://orcid.org/0000-0001-7453-5698
AJ
Morris
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK. wj10@cam.ac.uk.
William
http://orcid.org/0000-0002-4690-4852
W
Jones
density functional calculations; fluorescein; optical spectroscopy; surface analysis; tautomerism