CN109020805B

CN109020805B - Fluorescent color-changing eutectic material under ultrahigh pressure condition and preparation method thereof

Info

Publication number: CN109020805B
Application number: CN201810878899.5A
Authority: CN
Inventors: 闫东鹏; 路博
Original assignee: Beijing Normal University
Current assignee: Beijing Normal University
Priority date: 2018-08-03
Filing date: 2018-08-03
Publication date: 2020-11-03
Anticipated expiration: 2038-08-03
Also published as: CN109020805A

Abstract

The invention discloses a fluorescent color-changing eutectic material under an ultrahigh pressure condition and a preparation method thereof, belonging to the field of molecular solid luminescent materials. The invention selects a plurality of polyfluoro-substituted organic micromolecules as a co-assembly unit, and adopts a plurality of methods such as a solvent auxiliary grinding method, a solvent volatilization method, ultrasonic synthesis and the like to prepare the novel multi-component molecular co-crystallized compound. The cyano-substituted p-phenylene vinylene type molecules and the co-assembled small molecules are mutually identified through non-covalent acting forces such as multiple hydrogen bonds, pi-pi acting forces and the like to form a supermolecular structure with an ordered structure, so that the self-stacking molecular configuration and the spatial arrangement of the original cyano-substituted p-phenylene vinylene type molecules are changed, and a certain modulation effect is further achieved on the photophysical properties of the original cyano-substituted p-phenylene vinylene type molecules. The novel eutectic crystal prepared by the invention can generate different fluorescent color-changing behaviors under the condition of ultrahigh pressure, and is a first example of eutectic system with fluorescent color-changing under the condition of ultrahigh pressure. Has application prospect in the fields of novel optical sensors, pressure sensitive materials and the like.

Description

Fluorescent color-changing eutectic material under ultrahigh pressure condition and preparation method thereof

Technical Field

The invention belongs to the technical field of molecular solid luminescent materials, and particularly relates to a fluorescent color-changing eutectic material under an ultrahigh pressure condition and a preparation method thereof.

Background

High pressure chemistry refers to a cross-science of studying the composition, properties, structure and rules of change of substances under high pressure environmental conditions. Under extreme conditions of ultra-high pressure, the structure and properties of many well-known substances can vary greatly. For example, in 2013 Bignonia and the like, sodium chloride crystals are reported to have various crystal forms under high pressure conditions, and the stoichiometric ratio of sodium ions to chloride ions in the crystals obtained through experiments is 1:3 or 3:1, rather than 1:1 under normal pressure conditions, which is well known. In situ testing of high pressure conditions is an effective way to reveal material composition, phase transitions, and the nature of chemical bonds. In recent years, the research on the piezochromism of organic molecular materials with single components under the extreme conditions of high pressure has made certain progress and breakthrough. However, the research on the self-assembly behavior and the stacking aggregation mechanism of the multi-component organic supermolecular system under high pressure condition still remains a blank, and the application thereof is also a challenge.

A molecular eutectic material is generally considered to be a crystalline material formed by two or more organic molecules according to a certain stoichiometric ratio under the action of intermolecular non-covalent bond force. Based on the selection diversity of the supramolecular synthon, the non-covalent action mode among different component molecules has adjustability, thereby regulating and controlling the configuration of the molecules, the accumulation form of molecular aggregates and the spatial arrangement orientation, finally realizing the effect of effectively regulating the optical property of the chromophore molecules, and even obtaining the special optical performance which each single component does not have.

Cyano-substituted p-phenylenevinylenes are a typical fluorescent material, and have great pi conjugation degree, easy electron delocalization and high quantum yield, so the cyano-substituted p-phenylenevinylenes are attractive in the field of organic photoelectrons. However, the luminescence property of p-phenylene ethylene type compounds is not only dependent on the properties of single molecules, but also influenced by factors such as molecular configuration, molecular stacking and arrangement, aggregate particle size and the like in the aggregates, so that the solid fluorescence color of the compounds has certain unpredictability. Therefore, how to reasonably control the optical performance of the organic solid-state light-emitting material by controlling the intrinsic interaction mode and stacking arrangement mode of the organic molecular solid is one of the important challenges in the field of organic solid-state light-emitting materials.

The invention is based on the ideas of supermolecule chemistry and crystal engineering, selects a cyano-substituted p-phenylene ethylene type compound as a host molecule for preparing a light-function supermolecule crystal, and introduces different small organic molecules as co-assembled object molecules. Mutual recognition between the two molecules is realized through non-covalent bond actions such as multiple hydrogen bonds, pi-pi acting force and the like, so that the space arrangement structure of the main body molecule is controllably modulated to a certain extent, and the design space and the preparation range of the crystalline material formed by the main body chromophore molecule are greatly expanded. Two eutectic materials based on cyano-substituted p-phenylene ethylene are prepared by utilizing the technologies of solvent-assisted grinding, ultrasonic heating-assisted dissolution, solvent volatilization and the like. Compared with a pure host compound, the two eutectic compounds have the characteristic of adjustable photophysical properties (including fluorescence color, fluorescence lifetime, quantum yield and the like), especially show the characteristic of fluorescence stimulation response under the conditions of extreme high pressure, alkaline steam fumigation and the like, and provide theoretical premises and application basis for developing novel optical sensors and fluorescent anti-counterfeiting materials based on the solid compounds.

Disclosure of Invention

The invention aims to provide a p-phenylene vinylene type multi-component molecular crystalline material with a fluorescent color-changing characteristic under an ultrahigh pressure condition and a preparation method thereof, so as to realize the fluorescent emission modulation of the material under different static pressures and provide a new thought and feasible solution for developing the design and synthesis of a novel organic piezochromic fluorescent color-changing crystalline material.

The invention relates to a multi-component molecular-based crystal material formed by organic small molecules such as series of halogenated benzene, halogenated phenol, halogenated benzoic acid, halogenated naphthalene and the like and cyano-substituted p-phenylene ethylene compounds, namely, a novel molecular-based crystalline solid material is generated through intermolecular hydrogen bonds, pi-pi interaction and the like. By introducing the co-assembly unit with specific halogen atoms or functional groups, the molecular configuration and the spatial stacking arrangement mode of the stilbene organic molecules substituted by the cyano group of the chromophore molecule are effectively changed, so that the chromophore molecule has a relatively remarkable piezochromic effect. In addition, compared with the condition that the main molecules of the raw materials have no obvious fluorescence response to alkaline steam, the novel multi-component crystal material which generates fluorescence quenching to the alkaline steam is obtained through reasonable design.

The preparation method of the fluorescent color-changing eutectic material under the ultrahigh pressure condition comprises the following steps:

1) weighing the main substance A in an amount of 0.002-5 mol; weighing the amount of the substance of the co-assembly substance B to be 0.004-25 mol;

2) preparing a eutectic material:

a. ball mill grinding method:

fully mixing the substance A and the substance B, adding or adding 1-100 mL of organic solvent, and then placing the mixture in a ball mill for grinding to obtain powder;

b. ultrasonic or heat-assisted dissolution:

directly mixing the substance A and the substance B without grinding by a ball mill or respectively dissolving the powder obtained by grinding in the step a into 10-1000 mL of solvent C, and dissolving under the condition of ultrasonic oscillation or heating in an auxiliary manner, wherein the liquid is turbid, then adding 5-200 mL of solvent D, and continuing ultrasonic oscillation or heating until the liquid is clear, transparent and uniform; finally, volatilizing the solvent for 2-3 weeks at room temperature under the condition of keeping out of the sun, and obtaining the single crystal of the target binary component co-crystallized substance, namely the fluorescent color-changing eutectic material under the condition of ultrahigh pressure.

The substance A is cyano-substituted p-phenylene ethylene; the substance B is a compound containing carboxyl, hydroxyl or halogenated condensed ring; the solvent C is any one of dichloromethane, trichloromethane, acetonitrile and tetrahydrofuran, and the solvent D is methanol or ethanol.

The substance B is any one of 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid, 2,3,5, 6-tetrafluoro hydroquinone and octafluoronaphthalene.

The ball mill is a German RETSCH ball mill (MM 200), the frequency of the ball mill is set to be 10-20 Hz, and the grinding time is set to be 5-60 min.

The ultrasonic time is 5-60 min, and the heating temperature is 50-90 ℃.

Mixing the above prepared materials:

1. the powder XRD characterization and the single crystal XRD characterization show that the generated eutectic compound has obvious changes in the molecular configuration, the distortion degree, the spatial stacking arrangement and other structural properties compared with the cyano stilbene molecule.

2. Fluorescence series characterization tests show that the cocrystallized material has the characteristics of different degrees of spectral red shift, prolonged fluorescence life, reduced quantum yield and other photophysical property changes relative to the replacement of a raw material cyano group for a styrene molecule.

3. The characterization of in-situ spectral test by applying hydrostatic pressure shows that the emission wavelength of the series of eutectic materials gradually red shifts with the increase of pressure, and the emission position of the materials has certain difference with the fluorescence emission position before no pressure is applied in the pressure relief process.

4. The stimulation response characteristic representation shows that the fluorescence color or the luminous intensity of the series of eutectic materials can be obviously changed under the action of external ammonia fumigation; however, the material did not respond significantly to this.

The invention has the advantages that: through mutual recognition of a series of hydroxyl, carboxyl and halogen atom substituted phenyl and naphthyl organic small molecules and a cyano stilbene organic substance through various non-covalent bond interactions (hydrogen bonds, pi-pi interactions and the like), the molecular configuration, the twisted structure and the arrangement state of the cyano substituted p-phenylene ethylene molecules are effectively changed, so that the optical function of the cyano substituted p-phenylene ethylene organic substance is controllably modulated to a certain extent, and fluorescence response can be generated to external condition changes (such as high pressure and steam fumigation) to change the corresponding emission wavelength and the corresponding luminous intensity. The novel molecular eutectic material with fluorescent color-changing response under the conditions of ultrahigh pressure, alkaline steam fumigation and the like is prepared. And the corresponding relation between the space structure and the optical property of the binary component organic molecular crystal based on the cyano-substituted p-phenylene ethylene is constructed. The preparation idea and the application field of the multi-component organic molecular crystal are widened. Provides certain reference and reference significance for developing and designing novel pressure-induced fluorescence color-changing materials with high-quality optical characteristics, harmful gas fluorescence sensing materials and the like, and is the first example of a eutectic system with fluorescence color change under the condition of ultrahigh pressure. Provides a new design idea and a feasible scheme for the design and synthesis of the fluorescent color-changing and alkaline gas chemical sensing material under the high-pressure condition.

Drawings

FIG. 1 is a schematic diagram showing the crystal structure and intermolecular forces of cocrystallization of cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluorohydroquinone;

FIG. 2 is a schematic diagram showing the crystal structure and intermolecular forces of a cocrystal of cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid;

FIG. 3 shows fluorescence spectra of a raw material of cyano-substituted p-phenylene vinylene, a co-crystal of cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-hydroquinone, and a co-crystal of cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid;

FIG. 4 is a diagram showing the variation of in-situ luminescence spectrum of a cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluorohydroquinone cocrystallized material with pressure;

FIG. 5 is a diagram showing the variation of in-situ luminescence spectrum of a cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid co-crystal material with pressure;

FIG. 6 is a graph showing the variation of the maximum emission wavelength of a co-crystallized material (graph A, co-crystallized cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid; graph B, co-crystallized cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid) with applied pressure and unloaded pressure;

FIG. 7 is a graph showing the change of fluorescence spectrum of a cocrystallized material (FIG. A, cocrystallized by cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid; FIG. B, cocrystallized by cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid) before and after being fumigated with ammonia gas.

Detailed Description

Example 1

1. 0.0664g of 1, 4-bis (1-cyano-2-phenylvinyl) benzene and 0.1821g of 2,3,5, 6-tetrafluorohydroquinone were weighed out;

2. mixing the two materials uniformly, placing the mixture in an MM200 ball mill, adding 3 drops of chloroform by using a dropper, and then placing the mixture in the ball mill for ball milling for 20 minutes under the condition of 20 Hz;

3. dissolving about 0.1g of ground powder by using 10mL of chloroform, placing the powder at room temperature, and waiting for the solvent to slowly volatilize to obtain a binary eutectic monocrystal product;

the product was characterized by the presence of a catalyst,

from single crystal X-ray diffraction analysis, cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluorohydroquinone form a bi-cyclic co-crystallized product through intermolecular multiple hydrogen bond interactions, as shown in fig. 1.

As can be seen from the fluorescence spectrum, the maximum emission of the novel cocrystal material is about 498nm, which is more remarkable than that of the raw material cyano-substituted p-phenylene ethylene. The novel cocrystallized material was fumigated with ammonia gas volatilized from 13mol/L concentrated ammonia water, and it was found that the fluorescence intensity was greatly reduced and blue-shifted less, as shown in FIG. 7A.

As can be seen from the high-pressure test in-situ spectrum, the fluorescence emission of the novel cocrystallization material is gradually red-shifted along with the increase of the pressure, and when the pressure reaches 0.79Gpa, the emission wavelength is suddenly changed from 497nm to 522 nm. When the pressure gradually exceeded 2.49Gpa, the emission wavelength gradually returned to linearity with the change in pressure without significant abrupt changes. When the pressure was increased to 10GPa, the emission wavelength of the fluorescence red shifted to 609nm, compared to 112nm when no pressure was applied. In the process of pressure relief, the emission wavelength of the novel cocrystallization material gradually shifts blue along with the reduction of pressure, and when the pressure is restored to normal pressure, the emission wavelength is not restored as before, as shown in fig. 4 and fig. 6A.

Example 2

1. 0.0332g of 1, 4-bis (1-cyano-2-phenylvinyl) benzene and 0.0420g of 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid are weighed and dissolved in 6mL of chloroform solvent, and the chloroform solvent is dissolved as far as possible by means of ultrasonic or heating, and at the moment, the liquid gradually becomes light blue-green turbid liquid;

2. dropwise adding a methanol solvent into the light blue-green turbid liquid until the solution is clear and transparent, wherein the volume of the added methanol is about 0.5-1 mL, and then continuing to perform ultrasonic treatment or heating to uniformly mix the solution and fully dissolve a solute;

3. standing for 1-2 weeks under a natural volatilization condition to obtain a cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid eutectic compound;

the product was characterized by the presence of a catalyst,

it is known from single crystal X-ray diffraction analysis that cyano-substituted p-phenylene vinylene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid generate a two-component co-crystal product with a layered structure through intermolecular multiple hydrogen bond interactions, as shown in fig. 2.

From the fluorescence spectrum, it is shown that the maximum emission of the novel cocrystallized material is about 458nm, and the emission is red-shifted relative to the cyano-substituted p-phenylene ethylene as the raw material, as shown in FIG. 3. The novel cocrystallized material was fumigated with ammonia gas volatilized from 13mol/L concentrated ammonia water, and it was found that the fluorescence intensity was greatly reduced and there was a certain red shift, as shown in FIG. 7B.

As can be seen from the high-pressure test in-situ spectrum, the fluorescence emission of the novel cocrystallization material gradually shifts in red along with the increase of the pressure, and when the pressure reaches 1.98Gpa, the emission wavelength suddenly changes and increases from 487nm to 525 nm. When the pressure gradually exceeded 2.49Gpa, the emission wavelength gradually returned to linearity with the change in pressure without significant abrupt changes. When the pressure was increased to 10GPa, the emission wavelength of the fluorescence red shifted to 657nm, which was close to 202nm compared to when no pressure was applied. In the process of pressure relief, the emission wavelength of the novel eutectic material gradually shifts blue with the reduction of pressure, and when the pressure is restored to normal pressure, the emission wavelength is not restored as before, as shown in fig. 5 and 6B.

Claims

1. A preparation method of a fluorescent color-changing eutectic material under an ultrahigh pressure condition is characterized by comprising the following specific operation steps:

1) 0.0664g of 1, 4-bis (1-cyano-2-phenylvinyl) benzene and 0.1821g of 2,3,5, 6-tetrafluorohydroquinone were weighed out;

2) mixing the two materials uniformly, placing the mixture in an MM200 ball mill, adding 3 drops of chloroform by using a dropper, and then placing the mixture in the ball mill for ball milling for 20 minutes under the condition of 20 Hz;

3) dissolving 0.1g of ground powder by using 10mL of chloroform, placing the powder at room temperature, and waiting for the solvent to slowly volatilize to obtain a binary eutectic monocrystal product, namely the fluorescent discoloration eutectic material under the ultrahigh pressure condition.

2. A preparation method of a fluorescent color-changing eutectic material under an ultrahigh pressure condition is characterized by comprising the following specific operation steps:

1) 0.0332g of 1, 4-bis (1-cyano-2-phenylvinyl) benzene and 0.0420g of 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid were dissolved in 6mL of chloroform solvent, and the solution was dissolved by ultrasonic wave or heating, and at this time, the solution gradually changed to a pale blue-green turbid solution;

2) dropwise adding a methanol solvent into the light blue-green turbid liquid until the solution is clear and transparent, adding 0.5-1 mL of methanol, and continuing to perform ultrasonic treatment or heating to uniformly mix the solution and fully dissolve a solute;

3) under the condition of natural volatilization, after standing for 1-2 weeks, an eutectic compound of 1, 4-bis (1-cyano-2-phenyl vinyl) benzene and 2,3,5, 6-tetrafluoro-4-hydroxybenzoic acid, namely the fluorescent color-changing eutectic material under the condition of ultrahigh pressure, can be obtained.