Hydrogen-Bonding Research in Photochemistry, Photobiology, and Optoelectronic Materials

Keli Han, Guangjiu Zhao

• Publisher: WSPC (EUROPE)
• Year: 2019
• eBook ISBN: 9781786346094
• Topic: Physical Sciences
• Subtopic: Physical & Theoretical Chemistry

As one of the typical intermolecular interactions, hydrogen-bonding plays a significant role in molecular structure and function. When the hydrogen bond research system is connected with the photon, the hydrogen-bonding effect turns to an excited-state one influencing photochemistry, photobiology, and photophysics. Thus, the hydrogen bond in an excited state is a key topic for understanding the excited-state properties, especially for optoelectronic or luminescent materials.

The approaches presented in this book include quantum chemical calculation, molecular dynamics simulation and ultrafast spectroscopy, which are strong tools to investigate the hydrogen bond. Unlike other existing titles, this book combines theoretical calculations and experiments to explore the nature of excited-state hydrogen bonds. By using these methods, more details and faster processes involved in excited-state dynamics of hydrogen bond are explored.

This highly interdisciplinary book provides an overview of leading hydrogen bond research. It is essential reading for faculties and students in researching photochemistry, photobiology and photophysics, as well as novel optoelectronic materials, fluorescence probes and photocatalysts. It will also guide research beginners to getting a quick start within this field.

Contents:

• Effect of Solute-Solvent Hydrogen-Bonding on Spectral and Photophysical Properties of Aromatic Probes (Ewa Krystkowiak)
• Intramolecular and Intra-Assembly Triplet Energy Transfer (Kepeng Chen and Jianzhang Zhao)
• Elucidating Excited-State Hydrogen-Bonding Dynamics and Proton Transfer Inside Fluorescent Protein Calcium Biosensors (Longteng Tang and Chong Fang)
• Proton-Coupled Electron Transfer (PCET) Mechanism of Identify Hydrogen-Atom Exchange Reaction — Two Transition States in the Vicinity of Conical Intersection (Shmuel Zilberg)
• Probing Dynamics of Nonfluorescent Excited-State Intramolecular Proton Transfer (Ying Shi and Hang Yin)
• Excited-State Dynamics of Intermolecular Dihydrogen Bond in Different Systems (Ningning Wei and Guangjiu Zhao)
• Computational Studies on the Excited-State Intramolecular Proton Transfer in Five-Membered-Ring Hydrogen-Bonded Systems (Renuka Pradhan and Upakarasamy Lourderaj)
• Theoretical Investigation of Excited-State Intramolecular Proton Transfer Mechanism of Flavonoid Derivatives (Zhe Tang, Yi Wang, and Ningjiu Zhao)
• Photophysical Processes of Organic Chromophores with Intramolecular and Intermolecular Hydrogen Bonds (Shuo Chai and Shu-Lin Cong)
• Stronger Hydrogen Bonds of Less Stable Tautomers in the Ground State and Reversed Stability in the First Excited State: The Role of Electronic Excited States in Hydrogen-Bonding (Shmuel Zilberg)
• Effects of Hydrogen Bond and π–π Stacking on the Luminescence of Metal-Organic Frameworks (Lei Liu and Dan Zhao)
• Excited-State Hydrogen-Bonding Dynamics of Polyaniline Complex (Yahong Zhang, Dan Zhao, and Mingxing Zhang)
• Femtosecond Stimulated Raman Spectrocopy (FSRS) Investigation of Excited State Hydrogen-Bonding Dynamics and Photoacidity in Solution (Yanli Wang and Chong Fang)
• TD/DFT Study of Hydrogen-Bonding-Concerned System in the Excited State (Dandan Wang and Peng Li)
• Excited-State Hydrogen-Bonding Dynamics and Coupled Proton Transfer for Luminous Molecules (Mingzhen Zhang, Baiping Ren, and Yi Wang)
• Exploring and Elaborating Excited-State Intramolecular Double-Proton Transfer Mechanisms (Jinfeng Zhao and Yujun Zheng)

Readership: Hydrogen-bonding researchers, including faculties, post-doctors, and graduate students. It will serve as a good reference book for all researchers to gain knowledge about the excited-state hydrogen-bonding information. Hydrogen-Bonding;Photochemistry;Photobiology;Optoelectronic Materials00

Chapter 1

Effect of Solute–Solvent Hydrogen-Bonding on Spectral and Photophysical Properties of Aromatic Probes

Ewa Krystkowiak

Faculty of Chemistry, Adam Mickiewicz University in Poznań,
Umultowska 89b, Poznań, Poland
[email protected]

Abstract

The most important aspects of spectral and photophysical study of aromatic compounds in the solvents capable of forming hydrogen bonds with them are presented. A careful choice of the solvents for the solvatochromic study was emphasized, and 1-chloro-n-alkanes as non-specifically interacting solvents were used. The combination of experimental measurements and theoretical calculations was shown as very important to find out which species are present in a solution at a given electronic state and what are the changes in their concentrations and properties as a result of excitation or deactivation processes.

Keywords: Electronic excited state, hydrogen-bonding, solvato-chromism, spectroscopy, photophysics, ab initio calculations

Introduction

There are many classes of organic compounds whose molecules contain numerous heteroatoms with free electron pairs (e.g., N, O, S) and functional groups with protic hydrogen atoms (e.g., –OH, –NH₂, –NHR), besides aromatic rings. These compounds interact with the solvent molecules forming hydrogen bonds of acceptor or donor type.^1–8 This often leads to formation of stable solute–solvent intermolecular complexes in the ground state (GS) (present also after excitation) and exciplexes in electronic excited states (ESs), and besides, polarity and polarizability of the solvent also affect the spectral and photophysical properties of the solute molecules.^9–15 When the solute molecule is large and has a number of potential sites of hydrogen-bond formation with the solvent molecules it is not easy to characterize the effect of solvent on the absorption and emission spectra as well as photophysical properties of the solute. In view of the above, in order to get information on the solvent effect, it is recommended to perform studies with a solute of simpler structure, comprising chromophores characteristic for more complex structures.

This chapter gives an account of our work on the properties of intermolecular hydrogen bonds made between solutes in the ground and electronic ESs and solvents. In particular, the studies were concerned with the determination of the effect of the solute–solvent hydrogen bonds, especially their energy, on the formation of different species in the ground as well as in electronic ESs, on the spectral, absorption and emission properties of these species and dynamics of processes of their deactivation. The studies were performed for solutes of donor–acceptor properties: 4-aminophthalimide, 4AP,^16,17 4-amino-N-methyl-phthalimide, NM-4AP,¹⁷ 7-aminocoumarines (coumarin-120, C120, and coumarin-151, C151),¹⁸ 6-aminocoumarin, 6AC,^18–22 and selected ketones (thiox-anthone, TX)²³ and thioketones (benzopyranthione, BPT).^24,25 The structures of the solute molecules studied are shown in Figure 1. The above-mentioned compounds are used, e.g., as molecular probes for investigation of the properties of complex systems, e.g., micelles, cyclodextrins, ionic liquids, as model systems or as sensitizers.

Solvent selection — important study point

The solute–solvent interactions are divided into nonspecific — when they are caused by polarity and polarizability — and specific hydrogen bonds. That is why proper interpretation and description of the relation between the spectral and photophysical properties of a given solute and the properties of the solvent requires prior determination of the solvent polarity and polarizability and capability of hydrogen-bond formation.²⁶ The classification of solvents according to polarity and ability of hydrogen-bond formation is usually based on the criteria proposed on the basis of spectral measurements by Kamlet and Taft^27–29 and Catalan.^30–32 The solvents showing the ability of hydrogen-bond formation are acceptors or donors of hydrogen bonds. The acceptor properties of the solvent depend on its ability to accept a hydrogen atom from the solute in order to form a hydrogen bond (β in Kamlet–Taft scale and SB in Catalan scale), while its donor properties depend on its ability to donate a hydrogen atom in order to form a hydrogen bond with the solute (α in Kamlet–Taft scale and SA in Catalan scale). The scale of α values extends from 0.0 for the solvents not able to donate hydrogen atoms to 1.96 for hexafluoroisopropanol (HFIP), while the scale of β extends from 0.0 for the solvents whose molecules have no heteroatoms with a lone electron pair to 1.0 for triamide of hexamethylphosphoric acid (HMPA).³³ The properties of selected solvents are presented in Table 1.

Figure 1.Molecular structures of 6-aminocoumarin (6AC), coumarin-120 (C120), coumarin-151 (C151), 4-aminophthalimide (4AP), 4-amino-N-methyl-phthalimide (NM-4AP), thioxanthone (9H-thioxanthen-9-one, TX), and benzopy-ranthione (4H-1-benzopyrane-4-thione (BPT)).

Table 1.Solvent properties.

Notes: f(ε, n²) = ((ε – 1)/(2ε + 1)) – ((n² – 1)/(2n² + 1)) — solvent polarity function, n — refraction coefficient, ε — relative permittivity, α — Kamlet–Taft’s solvatochromic parameter related to hydrogen-bond donating ability, β — Kamlet–Taft’s solvatochromic parameter related to hydrogen-bond accepting ability.
^aFrom Ref. [33].

The changes in spectral behavior, quantum yields of emission and lifetime in ESs of a given solute observed on changing the solvent are consequences of the specific (hydrogen bonds) and nonspecific interactions between the solute and solvent molecules. If the solute molecules contain donor and/or acceptor groups, correct interpretation of spectral, photophysical, and photochemical data needs separation and independent determination of these two types of interactions. Therefore, the vital aspect ...

Table of contents

• Cover
• Halftitle
• Series Editors
• Title
• Copyright
• Preface
• About the Editors
• Contents
• 1. Effect of Solute–Solvent Hydrogen-Bonding on Spectral and Photophysical Properties of Aromatic Probes
• 2. Intramolecular and Intra-assembly Triplet Energy Transfer
• 3. Elucidating Excited-State Hydrogen-Bonding Dynamics and Proton Transfer inside Fluorescent Protein Calcium Biosensors
• 4. Proton-Coupled Electron Transfer (PCET) Mechanism to Identify Hydrogen-Atom Exchange Reaction — Two Transition States in the Vicinity of Conical Intersection
• 5. Probing Dynamics of Nonfluorescent Excited-State Intramolecular Proton Transfer
• 6. Excited-State Dynamics of Intermolecular Dihydrogen Bond in Different Systems
• 7. Computational Studies on the Excited-State Intramolecular Proton Transfer in Five-Membered-Ring Hydrogen-Bonded Systems
• 8. Theoretical Investigation of Excited-State Intramolecular Proton Transfer Mechanism of Flavonoid Derivatives
• 9. Photophysical Processes of Organic Chromophores with Intramolecular and Intermolecular Hydrogen Bonds
• 10. Stronger Hydrogen Bonds of Less Stable Tautomers in the Ground State and Reversed Stability in the First Excited State: The Role of Electronic Excited States in Hydrogen-Bonding
• 11. Effects of Hydrogen Bond and π–π Stacking on the Luminescence of Metal-Organic Frameworks
• 12. Excited-State Hydrogen-Bonding Dynamics of Polyaniline Complex
• 13. Femtosecond Stimulated Raman Spectroscopy (FSRS) Investigation of Excited-State Hydrogen-Bonding Dynamics and Photoacidity in Solution
• 14. TD/DFT Study of Hydrogen-Bonding-Concerned System in the Excited State
• 15. Excited-State Hydrogen-Bonding Dynamics and Coupled Proton Transfer for Luminous Molecules
• 16. Exploring and Elaborating Excited-State Intramolecular Double-Proton Transfer Mechanisms
• Index