2-(benzimidazol-2-yl)-3-hydroxychromone derivatives: spectroscopic properties and a possibile alternative intramolecular proton phototransfer

Abstract

Three2-(benzimidazol-2-yl)-3-hydroxychromonederivativesweresynthesized.Theirspectroscopicandfluorescentproperties,due to excited state intramolecular proton transfer (ESIPT) from OH to carbonyl, were studied. Theoretical possibility of an alternative intramolecularH-bondingandexperimentalevidenceforsuchbehaviorarediscussed. © Versita Warsaw and Springer-Verlag Berlin Heidelberg.

Acidic C–H Bond as a Proton Donor in Excited State Intramolecular Proton Transfer Reactions

“…8,9 Typically, ESIPT reaction is an extremely fast process occurring in the femto-to picosecond time scale. The ultrafast nature of ESIPT accompanied by a large Stokes shift provide numerous opportunities for the use of such compounds in a variety of applications, such as UV-photostabilizers, 10,11,12,13 filtered materials, 14 3 as well as fluorescent solar concentrator, 15,16 laser dyes, 17,18,19 fluorescent sensors, 20,21,22,23,24,25 probes for biological environments, 26 organic light emitting devices, 27,28 etc.…”

Nature of dual fluorescence in 2-(quinolin-2-yl)-3-hydroxychromone: Tuning between concurrent H-bond directions and ESIPT pathways

“…The plate-like orange crystals of Q3HC (C 18 H 11 NO 3 ), obtained for X-ray structure analysis at recrystallization from the DMF solution, were monoclinic: a ¼10.4226 (15) ¼0.095 mm À 1 and F(0 0 0) ¼276. Intensities of 4715 reflections (1059 independent, R int ¼0.0733) were measured on the OxfordDiffraction Xcalibur-3 diffractometer equipped with a 4Mpixel CCD detector Sapphire-3 using monochromated MoKa radiation (l ¼0.71073Å).…”

“…This type of electron density redistribution does not affect the possibility of the ESIPT process, but makes the dipole moment in the ''normal'' excited state lower than that in the ground state. However, substituents with weaker electron accepting ability estimated with the charge transfer numbers comparison [33] (for example, phenyl or benzimidazol-2-yl [15]) determine a positive solvatochromism for the corresponding 3HC derivatives' absorption and fluorescence. Fig.…”

“…Earlier, based on the theoretical modeling and experimental results, we discussed the possibility of an alternative H-bond existence in the molecule of 2-(benzimidazol-2-yl)-3-hydroxychromone, as well as realization of ESIPT along this alternative pathway in this molecule [14,15]. Thus, an alternative hydrogen bond with the nitrogen atom forms a 6-membered ring that should be more favorable than a 5-membered ring in the case of the ''flavonol-like'' H-bond with the carbonyl oxygen.…”

Structure and photoluminescent properties of 2-methyl-6,7-difluoro-8-hydroxyquinoline

“…Depending on specific features of the system, various types of proton transfer occur in the ground or excited state. Most interesting from the theoretical and experimental point of view is the Excited State Intramolecular Proton Transfer (ESIPT) [1,2]. The photoinduced ESIPT is normally observed in organic compounds having both a protic acidic group and a basic center with an intramolecular hydrogen bond [3].…”