Vapochromism of Organic Crystals Based on Macrocyclic Compounds and Inclusion Complexes

Abstract

Vapochromic materials, which change color and luminescence when exposed to specific vapors and gases, have attracted considerable attention in recent years owing to their potential applications in a wide range of fields such as chemical sensors and environmental monitors. Although the mechanism of vapochromism is still unclear, several studies have elucidated it from the viewpoint of crystal engineering. In this mini-review, we investigate recent advances in the vapochromism of organic crystals. Among them, macrocyclic molecules and inclusion complexes, which have apparent host–guest interactions with analyte molecules (specific vapors and gases), are described. When the host compound is properly designed, its cavity size and symmetry change in response to guest molecules, influencing the optical properties by changing the molecular inclusion and recognition abilities. This information highlights the importance of structure–property relationships resulting from the molecular recognition at the solid–vapor interface.

Multistimuli-Responsive Squaraine Dyad Exhibiting Concentration-Controlled Vapochromic Luminescence

“…Stimuli-responsive organic materials (SOMs) with intriguing luminescence switching properties have been widely studied for both fundamental research and practical applications in the areas of sensing, data security, memory, display devices, and anticounterfeiting. − The photophysical properties of SOMs are usually closely correlated with the interactions between the component molecules and can be readily tuned by external stimuli such as shear force, heat, and exposure to vapor, which are known as mechanochromism, thermochromism, and vapochromism, respectively. − Vapochromic materials, whose color or fluorescence is responsive to certain gases or volatile organic compounds (VOCs), are promising candidates for portable gas sensors for use in diagnosis, safety inspection, and toxic gas detection − and for smart inks used in anticounterfeiting and confidential data encryption. − The reported vapochromic mechanisms can be mainly classified into three types according to the role of the vapor molecules during the luminescence switching process: accelerating the rearrangement of luminophores from an unstable or metastable state to a stable state as a catalyst, − inserting into the cavity or crystal lattice of the luminophores as guests, − and reacting with luminophores as reactants. , In most cases, each organic solvent vapor plays only one of these roles and results in only one color change response during the vapochromic process (Scheme ). Therefore, examples exhibiting two color change responses induced by one solvent vapor are very limited.…”

Multistimuli-responsive materials based on a zinc(ii) complex with high-contrast and multicolor switching

“…[1][2][3][4][5][6] According to the type of stimulus, these intelligent materials can be further divided into photochromic, electrochromic, mechanochromic and acidochromic materials. [5][6][7][8][9] They have been receiving considerable attention due to their promising applications in optical storage, chemical sensors, security systems, and biomedical imaging. [10][11][12][13][14][15][16][17][18] Nowadays, the synthesis of organic compounds, metal complexes and polymers has gradually enriched the family of stimulus-responsive luminescent materials.…”

Chromogenic detection of xylene isomers and luminogenic chemosensing of o-xylene employing a new macrocyclic cobalt complex: synthesis, and X-ray crystallographic, spectroscopic and computational studies

“…They are good alternatives due to the rapid electron and energy transfer employed in these methods or due to the induction of a colour change in the presence of the xylene to afford a fast response alongside a high accuracy towards the particular chemosensor molecule. [5][6][7][8][9][10][11][12][13][14] Table S1 (ESI †) [10][11][12][13][14][15][16][17][18][19][20][21] presents some important fluorescent materials that have been designed for xylene sensing. While some colourimetric sensor arrays are designed for xylene detection in the gas phase, no colourimetric sensors have been reported to detect and distinguish xylene isomers in the liquid phase.…”