Sulfur-Based Intramolecular Hydrogen-Bond: Excited-State Hydrogen-Bond On/Off Switch with Dual Room-Temperature Phosphorescence

Abstract

We report O−H----S hydrogen-bond (Hbond) formation and its excited-state intramolecular H-bond on/off reaction unveiled by room-temperature phosphorescence (RTP). In this seminal work, this phenomenon is demonstrated with 7-hydroxy-2,2-dimethyl-2,3-dihydro-1Hindene-1-thione (DM-7HIT), which possesses a strong polar (hydroxy)-dispersive (thione) type H-bond. Upon excitation, DM-7HIT exhibits anomalous dual RTP with maxima at 550 and 685 nm. This study found that the lowest lying excited state (S 1 ) of DM-7HIT is a sulfur nonbonding (n) to π* transition, which undergoes O−H bond flipping from S 1 (nπ*) to the non-H-bonded S′ 1 (nπ*) state, followed by intersystem crossing and internal conversion to populate the T′ 1 (nπ*) state. Fast H-bond on/off switching then takes place between T′ 1 (nπ*) and T 1 (nπ*), forming a pre-equilibrium that affords both the T′ 1 (nπ*, 685 nm) and T 1 (nπ*, 550 nm) RTP. The generality of the sulfur H-bond on/off switching mechanism, dubbed a molecule wiper, was rigorously evaluated with a variety of other H-bonded thiones, and these results open a new chapter in the chemistry of hydrogen bonds.

Diphenolic acid-modified PAMAM/chlorinated butyl rubber nanocomposites with superior mechanical, damping, and self-healing properties

“…(1) The hydrogen bonds formed by G2 PAMAM-H in CIIR were thermally expanded during heating, and thus the hydrogen bonds became longer [42,43]. 2During the heating process, the hydrogen bonds were broken and the energy of these special functional groups became high, and thus the structure was unstable and blue shift occurred.…”

Recent developments in molecular docking technology applied in food science: a review

“…The acting forces between molecules include hydrogen bonding, van der Waals forces, hydrophobic interaction, electrostatic interaction, p-p stacking and salt bonding (Zhu et al, 2018;Wang et al, 2019c;Wu et al, 2019b;Yasrebi et al, 2019). Hydrogen bonding is produced by the covalent bonding of hydrogen atoms with more electronegative atoms, such as oxygen, nitrogen and sulphur (Cleland, 2010;Liu et al, 2019;van der Lubbe & Fonseca Guerra, 2019). The formation of hydrogen bonding is an interatomic interaction and is generally included in all molecular docking.…”

Perylene Bisimide and Naphthyl‐Based Molecular Dyads: Hydrogen Bonds Driving Co‐planarization and Anomalous Temperature‐Response Fluorescence

“…A strategy to solve the problem, to our viewpoint, is to introduce weak but sufficient interactions to improve the stability of the conjugated structures via hindering the rotation. To realize such a design, H‐bonding seems to be a case in point, which has been used in the fixation of certain conformations of molecular systems …”