Themed collection Hydrogen bonding in electronically excited states

This Perspective article examines the effect of hydrogen bonding on excited state guests included within molecular hosts in solutions, and the impacts on inclusion complex stability and guest fluorescence.

Possible photochemical and photophysical processes following (n,π*) excitation of azines.

We review spectroscopic investigations that have been used to study the excited state dynamics and catalytic mechanism of protochlorophyllide oxidoreductase.

In the condensed phase H-bond strengthening promotes the formation of the ICT state, in the gaseous phase it may be the H-bond breaking.

The principal photophysics and applications of ESIPT in fluorescent molecular probes and white light-emitting materials are summarized.

Hydrogen bonding directs the formation of photoactive fullerene ribbons in the solid-state crystal structure of a fullerene derivative resulting in photopolic behaviour.

Ab initio studies of 3-hydroxychromones show that their proton transfer (ESIPT) can be controlled thermodynamically or kinetically by H-bonding.

A series of the 2-pyridyl-pyrazole derivatives 1–4 possessing five-membered ring hydrogen bonding configuration are synthesized, the structural flexibility of which is strategically tuned to be in the order of 1 > 2 > 3 > 4.

Via a systematic design and synthesis of the excited-state intramolecular proton-transfer system, the proton-transfer emission can be extensively tuned from 450 nm (HPI) to 630 nm (HPNO).

Potential energy profiles are compared for potentially competing photoinduced processes in the hydrogen-bonded guanine–cytosine base pair, including nonradiative decay in each base and proton transfer between the bases.

Propofol–phenol clusters are characterised as a model system of the propofol–tyrosine interaction with the GABA_A receptor.

The hydrogen bonding structures and proton transfer in both the electronic excited and ground states were studied for the hydration complexes of alizarin as a model system for acid–base indicators.

Phenol clusters of various complexities were studied both experimentally and theoretically revealing the solvation effects on their photochemistry.

Excited state proton transfer in HBT–water clusters showing triple proton transfer.

Ground- and excited-state proton transfer was studied by pump–dump–probe spectroscopy combined with target analysis, and super-resolution microscopy application is discussed.

Hydrogen-bonding to the phenolic OH dramatically decelerates the trans to cis isomerization rate of methyl 4-hydroxycinnamate (OMpCA). The isomerization barrier height of the OMpCA–water complex is estimated to be ∼500 cm⁻¹.

The S₀ and S₁ permanent dipoles of the indole–NH₃ complex reveal a substantial contribution from local hydrogen bonding effects, as evidenced by the large induced dipole measured for each electronic state.

Femtosecond-resolved spectroscopy reveals that a water wire plays a catalytic role in aqueous acid–base reactions.

Electron transfer study inside bio-mimicking organized media like niosome helps understanding various chemical reactions occurring in natural biological systems.

TD-DFT computations confirm barrier-less Electron-Driven Proton Transfer in an Adenine–Thymine Watson–Crick complex in the gas phase, suggesting also that both EDPT and the possible radiation-less deactivation to the ground state are strongly influenced by environmental effects.

Two hydrogen-bonded Rydberg type species are located on the lowest excited singlet PES. The Rydberg center shift (RCS) mechanism proposed that the Rydberg orbital could be located on either the pyrrole or the ammonia components of the cluster. The proton shift is escorted by a shift of the Rydberg orbital, according to the new proton location.

Different H-bonded network rearrangements are observed in the S₀, S₁ and D₀ states of neutral and cationic p-cresol(H₂O)(NH₃) complexes.

The ultrafast kinetics and temperature dependence of the excited-state proton transfer (ESPT) of the “super” photoacid N-methyl-6-hydroxyquinolinium was studied and compared with those of another “super”photoacid 5,8-dicyano-2-naphthol.

Hydrogen bonding in the ground and electronically excited singlet states of thioketone.

The present study reports the binding interaction of an ESIPT drug with a model transport protein BSA with insights into structure, functionality of the protein and drug binding pharmacokinetics behavior.

Photophysical diagram proposed to describe the behaviour of the normal molecular structure of methylsalycilate.

The rate constant of excited-state deuteron relay along a hydrogen-bonded blended-alcohol chain is determined mostly by the acidity of the alcohol molecule participating directly in the rate-determining step.