A study of the competitive multiple hydrogen bonding effect and its associated excited-state proton transfer tautomerism

Abstract

1,8-Dihydroxynaphthalene-2,7-dicarbaldehyde (DHDA) has been strategically designed and synthesized with the aim to study the competitive multiple hydrogen bonding (H-bonding) effect and the associated excited-state intramolecular proton transfer reaction (ESIPT). In nonpolar solvents such as cyclohexane, equilibrium exists between the two H-bonding isomers DHDA-23_OO and DHDA-23_OI, both of which possess double intramolecular H-bonds. In polar, aprotic solvents such as CHCl, DHDA-23_OO becomes the predominant species. Due to various degrees of H-bond induced changes of electronic configuration each isomer reveals a distinct absorption feature and excited-state behavior, in which DHDA-23_OI in cyclohexane undergoes double ESIPT in a stepwise manner, giving the first and second proton-transfer tautomer emissions maximized at ∼500 nm and 660 nm, respectively. As for DHDA-23_OO both single and double ESIPT are prohibited, resulting in an intense normal 450 nm emission band. In a single crystal DHDA-23_OI is the dominant species, which undergoes excited state double proton transfer, giving intense emission bands at 530 nm and 650 nm. The mechanism associated with competitive multiple H-bonding energetics and ESIPT was underpinned by detailed spectroscopy/dynamics and computational approaches.

Dynamic Excited-State Intramolecular Proton Transfer Mechanisms of Two Novel 3-Hydroxyflavone-Based Chromophores in Two Different Surroundings

“…Accordingly, the double-ESIPT reaction exerts a tremendous fascination on researchers due to their important features in materials and biological fields. During the past few decades, an army of typical and excellent organic compounds with two intramolecular HBs (i.e., double proton) has been designed and synthesized in experiment; − meanwhile, the double-ESIPT mechanisms widely have been explored by combined experimental time-resolved spectroscopies and theoretical calculations. − To date, the reaction pathways of the double-ESIPT processes can be outlined as follows: stepwise and simultaneous reaction pathways. − Nevertheless, the previous research mainly has poured attention into the symmetric ESIPT compounds, but rarely has attempted to the asymmetric.…”

Investigation of the hydrogen bond donating ability of 1,8-naphthalenediol by NMR spectroscopy and its use as a hydrogen bonding catalyst

“…35 OH OMe While the X-ray structure of 1,8-naphthalenediol (7) has not been reported, the crystal structure of compound 9 was shown to display an intramolecular hydrogen bond between the two -OH groups of the 1,8naphthalenediol core ( Figure 2). 36 Due to all these reasons, 1,8-naphthalenediol (7) was expected to be a good candidate for an effective hydrogen bonding catalyst because of the increased hydrogen bond donating strength of the phenol groups.…”

Selective Synthesis and Photoluminescence Study of Pyrazolopyridopyridazine Diones and N-Aminopyrazolopyrrolopyridine Diones

“…Therefore, the solvent polarity modulation of fluorescence was quite interesting. It was well studied that amide tautomer of pyrazolopyridopyridazine dione 6a was efficiently produced in toluene, THF, EA, and CH 2 Cl 2 solvents [39][40][41][42][43][44]. In alcoholic (protic) and DMSO solvent, there exists competition between intermolecular bonding of the nearest hydrogen with the hydroxyimine tautomer of 6-hydroxypyrazolopyridopyridazin-9-one 6a.…”