Hofmann type complex with property of regulating and controlling fluorescence by light-induced spin state switching, preparation method and application of Hofmann type complex with property of regulating and controlling fluorescence by light-induced spin state switching

Abstract

The invention belongs to the technical field of molecule-based magnetic materials, and discloses a Hofmann type complex with a property of regulating and controlling fluorescence through photo-induced spin state switching, a preparation method and application. The complex is obtained by carrying out coordination self-assembly on a ligand L (N-phenyl-4-(pyridine-4-yl)-N-(4-(pyridine-4-yl) phenyl) aniline), a dicyanosilver building unit KAg (CN) 2 and transition metal Fe II in an ethanol solution. The preparation method comprises the following steps: carrying out coordination self-assembly on the ligand L (N-phenyl-4-(pyridine-4-yl)-N-(4-(pyridine-4-yl) phenyl) aniline) and the dicyanosilver building unit KAg (CN) 2; the crystal is in a C2 / c monoclinic space group, and the chemical formula is {Fe (L) [Ag (CN) 2] 2}. 2EtOH. The complex has the property of regulating and controlling fluorescence emission intensity through spin crossover induced by heat and light, and a valuable strategy and method are provided for designing a function coupled Hofmann type spin crossover material.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular-based magnetic materials, and relates to a Hofmann-type complex with light-induced spin state switching and fluorescence properties, a preparation method and an application thereof, and specifically relates to a three-dimensional Hofmann-type complex with heat- and light-induced spin crossover and fluorescence synergistic coupling, and a preparation method and an application thereof. Background Art

[0002] Spin crossover (SCO) is an extremely attractive bistable material. It is a forward-looking research topic to introduce functional elements into bistable materials, design and synthesize molecular-based magnetic materials that respond to external stimuli, study the relationship between magnetism and dielectric, ferroelectric, fluorescence and other properties, and then realize the construction of functional molecular materials. In recent years, the combination of fluorescence and magnetic bistable materials has attracted the interest of researchers, among which the combination of fluorescence and SCO has been studied more. The intrinsic microscopic changes of spin state, spin state density, bond length, etc. accompanied by the SCO process will cause macroscopic changes such as energy transfer and fluorescence, and then couple with fluorescence. In basic research, the coupling of SCO and fluorescence may bring new phenomena and new mechanisms of action, and bring new insights into the coupling of magnetism with other functions. In terms of application prospects, SCO-fluorescence synergistic materials provide possibilities for the research of molecular devices such as optical switches, bioluminescence imaging and fluorescence thermometry.

[0003] Studies have shown that the fluorescence intensity of SCO complexes can be effectively regulated by switching the metal spin state, and the switching between high-spin state and low-spin state can be regulated by light-induced excited spin state trapping (LIESST) and reverse LIESST (RE-LIESST) effects. Therefore, the SCO unit is expected to provide a simple and easy way to manipulate fluorescence properties through LIESST and RE-LIESST effects without significant conformational changes. Currently, among the reported fluorescent-SCO complexes, only two SCO complexes show fluorescence modulation upon photoinduced spin state switching, but the recovery of fluorescence requires time-consuming thermal treatment. Hofmann complexes have high thermal stability and multifunctional coupling properties, which can be achieved by pre-designing appropriate functional ligands and introducing guest molecules. They are potential candidates for achieving synergistic effects between SCO and fluorescence properties. Therefore, we can study the regulation of fluorescence properties by spin crossover by introducing fluorescent ligands in the Hofmann system. Based on this, we designed and synthesized a Hofmann-type complex with photoinduced spin state switching to regulate fluorescence properties. By studying the changes in fluorescence properties during spin crossover, we can further study the factors affecting magnetic bistability and fluorescence coupling, and summarize the construction strategy of the system, providing a basis for the development and utilization of switchable fluorescent functional molecular materials and magnetic molecular devices. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a Hofmann-type complex with light-induced spin-state switching and fluorescence properties, as well as a preparation method and application thereof. By introducing fluorescent ligands into a three-dimensional Hofmann-type framework, a SCO-MOFs with both spin crossover and fluorescence properties is constructed. By studying the changes in fluorescence properties during the spin crossover process, the influencing factors of magnetic bistability and fluorescence coupling can be further understood, providing a basis for designing more advanced switch-type fluorescent functional molecular materials and magnetic molecular devices.

[0005] The present invention relates to a Hofmann-type complex with light-induced spin-state switching and fluorescence regulation properties, wherein the chemical formula is {Fe(L)[Ag(CN)2]2}·2EtOH (L=N-phenyl-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline), the molecular formula is C 36 H 33 N7O2Ag2Fe. The complex crystallizes at C 2 / c Monoclinic space group, its unit cell parameters are: α =8.9631(4); β =18.8914(2); γ =20.4693(10); Z =4; ρ calc (g / cm 3 )=1.639.

[0006] The present invention relates to a Hofmann-type complex with light-induced spin-state switching and fluorescence regulation properties. The raw materials for its preparation include: KAg(CN)2, N-phenyl-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline, Fe(ClO4)2·6H2O, and ethanol. The preparation method is a solvent diffusion method under room temperature conditions.

[0007] The present invention relates to a Hofmann-type complex with light-induced spin-state switching and fluorescence properties. The preparation method of the complex comprises the following steps: (1) placing 1 mL of 0.02 mmol Fe(ClO4)2·6H2O in EtOH solution on one side of an H tube at room temperature; (2) dissolving an L ligand (0.02 mmol, 7.98 mg) and KAg(CN)2 (0.04 mmol, 7.96 mg) in 2 mL of EtOH solution and placing the solution on the other side of the H tube; (3) slowly adding a buffer layer solvent EtOH in the middle to connect the two ends of the H tube; and (4) sealing the tube with a sealing film, allowing the tube to stand for one month at room temperature to precipitate light yellow block crystals, collecting the crystals, and obtaining the Hofmann-type complex.

[0008] The applicant conducted magnetic research on the Hofmann type complex of the present invention and found that the Fe II An incomplete transition from high-spin to low-spin occurs in the 2-300 K range, with a transition temperature of T 1 / 2 is 161 K.

[0009] The applicant conducted fluorescence emission spectrum testing on the Hofmann-type complex described in the present invention and found that the fluorescence emission intensity of the complex in the spin transition range increases with increasing temperature.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a three-dimensional Hofmann-type complex that has never been reported. The complex has a clear single crystal structure, which is convenient for studying the relationship between the structure and magnetic and fluorescent properties. The free ethanol solvent molecules in the three-dimensional Hofmann complex of the present invention form a weak C–H···O interaction with the triphenylamine group on the ligand, so it has high high-temperature thermal stability and stable chemical properties. At the same time, magnetic and fluorescence tests of the three-dimensional Hofmann-type complex of the present invention show that it has the properties of heat- and light-induced spin crossover and fluorescence synergistic coupling. In addition, the synthetic raw materials of the three-dimensional Hofmann-type complex are low-cost and easy to obtain, the synthesis conditions are mild, the steps are simple, the yield is high, the reproducibility is good, and it is easy to promote on a large scale. Therefore, it has good application and development prospects in the field of switch-type fluorescent functional molecular materials and magnetic molecular devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The three-dimensional Hofmann complex center Fe II Schematic diagram of the coordination environment.

[0012] Figure 2 It is the MOF framework of the three-dimensional Hofmann-type complex of the present invention, forming a [Fe6{Ag(CN)2}6] grid unit. The red dotted line represents the C–H···O weak interaction formed between the solvent molecule ethanol and the framework.

[0013] Figure 3 The figure is the powder X-ray diffraction pattern of the three-dimensional Hofmann type complex of the present invention.

[0014] Figure 4 This is a thermogravimetric analysis diagram of the three-dimensional Hofmann-type complex of the present invention under a nitrogen atmosphere.

[0015] Figure 5 It is a temperature-dependent magnetic susceptibility curve of the three-dimensional Hofmann-type complex of the present invention.

[0016] Figure 6 The three-dimensional Hofmann complex of the present invention is measured at 10 K using 532 nm and 808 nm laser continuous alternating irradiation. χ M T Graph of value changes over time.

[0017] Figure 7 It is the solid temperature variable fluorescence spectrum of the ligand L of the present invention under 398 nm excitation.

[0018] Figure 8 It is the variable temperature solid-state fluorescence emission spectrum of the three-dimensional Hofmann-type complex of the present invention in the range of 80-300 K.

[0019] Fig. 9 The three-dimensional Hofmann complex of the present invention χ M T The fluorescence intensity of the maximum emission peak varies with temperature.

[0020] Fig.10 This is a fluorescence emission spectrum of the three-dimensional Hofmann-type complex of the present invention measured at a temperature of 10 K, an excitation wavelength of 398 nm, and continuous alternating irradiation of 532 nm (green line) and 808 nm (red line) lasers. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific examples to facilitate a better understanding of the content of the present invention, but it is worth noting that the present invention is not limited to the following examples. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0022] Example 1

[0023] The preparation method of the three-dimensional Hofmann-type complex in this embodiment is as follows: (1) at room temperature, place 1 mL of 0.02 mmol Fe(ClO4)2·6H2O in EtOH solution on one side of the H tube; (2) dissolve the L ligand (0.02 mmol, 7.98 mg) and KAg(CN)2 (0.04 mmol, 7.96 mg) in 2 mL of EtOH solution and place them on the other side of the H tube; (3) slowly add buffer solvent EtOH in the middle to connect the two ends of the H tube; (4) seal with a sealing film, let stand at room temperature for one month to precipitate light yellow block crystals, collect the crystals, and obtain the Hofmann-type complex.

[0024] Example 2

[0025] The single crystal structure of the three-dimensional Hofmann-type complex obtained in this example is characterized as follows:

[0026] (1) Single crystal X-ray diffraction data collection and structural analysis. Select a crystal of moderate size without cracks, cover its surface with a thin layer of oil, fix it with a loop and place it under a nitrogen cold flow. The single crystal data involved in the present invention were obtained by Bruker D8 Venture X-ray (Mo-Kα ray, wavelength λ = 0.71073 Å) single crystal diffractometer with adjustable temperature, and the diffraction point data were collected using SMART and SAINT programs. The ShelXT program embedded in Olex2 was used to solve the crystal structure by direct method, and the data were refined by full matrix least squares method. All non-hydrogen atoms were anisotropically treated except for solvents, and hydrogen atoms were determined by electron cloud or theoretical hydrogenation.

[0027] (2) Table 1 shows the crystallographic data and refinement parameters of the three-dimensional Hofmann-type complex obtained in this example. Figure 1 The molecular structure diagram of the three-dimensional Hofmann type complex obtained in this example. Structural analysis shows that the complex crystallizes at C 2 / c Monoclinic space group. In this three-dimensional Hofmann-type complex, each Fe II The center shows a typical [Fe II N6] octahedral coordination configuration, in which the four coordination sites on the equatorial plane are from [Ag(CN)2] − The four cyanide nitrogen atoms of the unit are occupied, and the top positions are occupied by the two nitrogen atoms from the ligand L.

[0028] Table 1. Crystallographic data of the three-dimensional Hofmann-type complex of the present invention at different temperatures.

[0029] Complex <![CDATA[12 60 K ]]> <![CDATA[12 120 K ]]> <![CDATA[12 270 K ]]> Formula <![CDATA[C 36 H 33 N7O2Ag2Fe]]> <![CDATA[C 36 H 33 N7O2Ag2Fe]]> <![CDATA[C 36 H 33 N7O2Ag2Fe]]> FWf 867.28 867.28 867.28 Crystal system Monoclinic Monoclinic Monoclinic Space group 2 / 2 / 2 / , Å 8.8993(6) 8.9631(4) 8.9674(11) , Å 18.8352(12) 18.8914(10) 19.1331(19) , Å 20.4134(16) 20.4693(10) 20.710(2) , ° 90 90 90 , ° 102.59 102.65 102.50 , ° 90 90 90 <![CDATA[ V , Oh 3 ]]> 3339.4(4) 3381.9(3) 3469.0(7) 4 4 4 <![CDATA[ ρ calc (g / cm 3 )]]> 1.659 1.639 1.637 <![CDATA[ R int ]]> 0.0308 0.0556 0.0344 <![CDATA[GOF on F 2 ]]> 1.040 1.040 1.051 <![CDATA[ R 1, [ I ³2 s ( I )]]]> 0.0710 0.0670 0.010 <![CDATA[ wxya 2, [ I ³2 s ( I )]]]> 0.1995 0.1914 0.596 R 1 = Σ (| F o |–| F c |) / Σ | F o |; wxya 2 = [Σ w (| F o | 2 –| F c |2 ) 2 / Σ w ( F o 2 ) 2 ] 1 / 2

[0030] (3) Figure 2 As shown, in the three-dimensional Hofmann-type complex obtained in this embodiment, the building unit [Ag(CN)2] − Unit bridge Fe II ions, forming a three-dimensional Hofmann-type framework with [Fe6{Ag(CN)2}6] grid units, while the ligand L crosses the MOF framework to bridge the Fe II ions. The free ethanol molecules are located in the framework gaps and form weak C–H···O interactions with the triphenylamine groups. At 270 K, Fe1–N L and Fe1–N cyanide The bond lengths of the two species are 2.195(5) Å and 2.131(7)−2.157(5) Å, respectively, which are high-spin Fe II ions. When the temperature is lowered to 120 K, Fe1–N L and Fe1–N cyanide The bond lengths of Fe1–N L and Fe1–N cyanide The bond lengths were shortened by only 0.012 Å and 0.016 Å. These changes in bond lengths indicate that the complexes obtained in this example underwent thermally induced incomplete SCO behavior.

[0031] Example 3

[0032] The three-dimensional Hofmann-type complex obtained in this example was subjected to X-ray powder diffraction test:

[0033] XRD powder diffraction data were obtained by Bruker AXS D8 Advance X-ray powder diffractometer (Cu-K α radiation, λ =0.15418 nm) collected. The X-ray powder diffraction test of the three-dimensional Hofmann-type complex obtained in this example adopts small-angle diffraction conditions, 2 θ The scanning range was 5–50° and the scanning rate was 5° / min. Figure 3 As shown, the experimental spectrum is consistent with the spectrum obtained by fitting the single crystal structure using Mercury software. Figure 1This indicates that the three-dimensional Hofmann-type complex obtained in this example has a higher phase purity.

[0034] Example 4

[0035] The three-dimensional Hofmann-type complex obtained in this example was subjected to thermogravimetric analysis under a nitrogen atmosphere:

[0036] like Figure 4 As shown, the thermogravimetric analysis test results of the three-dimensional Hofmann-type complex obtained in this example under a nitrogen atmosphere show that the complex begins to lose mass at 100°C, and the mass loss at 150°C is 4%, while the calculated molecular structure accounts for 5.31% of ethanol molecules, indicating that the ethanol molecules in the lattice are gradually lost during the heating process, and the molecular structure begins to collapse above 200°C.

[0037] Example 5

[0038] The three-dimensional Hofmann-type complex obtained in this example was subjected to a temperature-dependent magnetic susceptibility test under a DC field:

[0039] Under a 1000 Oe DC magnetic field, the temperature-dependent magnetic susceptibility curve of the polycrystalline sample of the complex obtained in this example was tested in the range of 2-300 K. Figure 5 As shown in Figure 2, at 300 K, the χ M T The value is 3.82 cm 3 mol −1 K, which is high spin Fe II ion( S = 2, g = 2.26). As the temperature decreases χ M T The curve gradually decreases at 20 K. χ M T The value is 1.37 cm 3 mol −1 K, higher than low-spin Fe II The spin-only theoretical value for the ion (0 cm 3 mol −1 K), indicating about 36 % Fe II Still in a high spin state. χ M T The curve drops suddenly below 20 K and at 2 K χ M T The value is 0.73cm3 mol −1 The above results show that the complex obtained in this example undergoes an incomplete transition from high spin to low spin, and the transition temperature T 1 / 2 is 161 K. Considering that the closest distance between Fe···Fe in the framework structure is 10.207 Å (60 K), the antiferromagnetic interaction c M T The influence of the curve is negligible, so below 20 K c M T The sudden drop in the value is mainly attributed to the residual Fe II HS The zero-field splitting of the species. The temperature-dependent magnetic susceptibility curves measured in the heating mode and the cooling mode are the same, indicating that there is no obvious thermal hysteresis.

[0040] Example 6

[0041] The three-dimensional Hofmann-type complex obtained in this example was tested for its light susceptibility at 10 K:

[0042] At 10 K, the complex in the low temperature phase was irradiated with 532 nm laser. χ M T The value increased from 0.56 to 2.36 cm in 90 min. 3 mol −1 K, which indicates that most of the LS-Fe II HS*-Fe transforms into a metastable phase via the LIESST effect II . Then, it was irradiated with 808 nm laser for 90 min. χ M T The value dropped from 2.36 to 0.69 cm 3 mol −1 K, which is due to the RE-LIESST effect from the metastable phase to the low-temperature phase. The three-dimensional Hofmann-type complex obtained in this embodiment was tested cyclically using 532 nm and 808 nm lasers, achieving continuous reversible regulation of its spin state by light.

[0043] Example 7

[0044] The solid temperature variable fluorescence spectrum test of the ligand L obtained in this example was carried out under 398 nm excitation:

[0045] like Figure 7As shown in the figure, the solid-state variable temperature fluorescence spectrum of ligand L in the range of 80–300 K was tested in a temperature rising mode. At 80 K, ligand L was excited by 398 nm excitation light and had a maximum fluorescence emission peak at 471 nm. As the temperature increased, the thermal quenching effect caused the fluorescence intensity to decrease monotonically.

[0046] Example 8

[0047] The three-dimensional Hofmann-type complex obtained in this example was tested for variable temperature solid-state fluorescence emission spectroscopy in the range of 80-300 K:

[0048] At 80 K, the fluorescence emission spectrum of the three-dimensional Hofmann-type complex obtained in this example shows two emission peaks, with peak values ​​at 450 and 480 nm, respectively. As the temperature increases, the emission intensities of the two emission peaks gradually increase and merge into one emission peak, and reach a maximum value at 220 K. The fluorescence emission intensity at 220 K is 1.6 times that at 80 K. Then, as the temperature further increases, the fluorescence emission intensity gradually decreases.

[0049] Example 9

[0050] The three-dimensional Hofmann complex obtained in this example χ M T The fluorescence intensity of the maximum emission peak and the temperature are compared:

[0051] like Fig. 9 As shown, by comparing the magnetic and fluorescence properties, it is found that this abnormal fluorescence enhancement region only occurs in the process of transition from low spin to high spin, indicating that in the range of 80-220 K, the effect of spin crossover on fluorescence is greater than the thermal quenching effect, while in the range of 230-300 K, the thermal quenching effect is dominant. The above results indicate that the three-dimensional Hofmann-type complex obtained in this example exhibits synergistic coupling between fluorescence and SCO.

[0052] Example 10

[0053] The three-dimensional Hofmann-type complex obtained in this example was tested for fluorescence emission spectrum at a temperature of 10 K and an excitation wavelength of 398 nm, with continuous and alternating irradiation of 532 nm (green line) and 808 nm (red line) lasers:

[0054] like Fig.10 As shown, when the excitation light is λ ex= 398 nm, and the fluorescence emission spectra before and after irradiation at 10 K were tested. At 10 K, the complex obtained in this example showed a maximum fluorescence emission peak at about 427 nm. Its fluorescence intensity increased significantly when irradiated with 532 nm laser, and reached saturation after irradiation for 30 min. This is because under 532 nm light irradiation, the LS-Fe II Most of the ions are transformed into the metastable phase HS*-Fe II , which eventually leads to fluorescence enhancement. When the complex in the metastable phase is irradiated by 808 nm laser, its fluorescence intensity decreases and reaches the same intensity as before illumination. The cyclic illumination experiment also confirmed the reversible regulation of the fluorescence intensity of the complex obtained in this example by 532 nm and 808 nm.

[0055] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A Hofmann-type complex with light-induced spin-state switching and fluorescence properties, characterized in that: The chemical formula is {Fe(L)[Ag(CN)2]2}·2EtOH, L = N-phenyl-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline, and the molecular formula is C 36 H 33 N7O2Ag2Fe.

2. The Hofmann-type complex with light-induced spin-state switching and fluorescence properties according to claim 1, characterized in that: The complex is prepared by the following method: Step 1: Place 1 mL of 0.02 mmol Fe(ClO4)2·6H2O in EtOH solution on one side of the H tube at room temperature; Step 2: Dissolve L ligand (0.02 mmol, 7.98 mg) and KAg(CN)2 (0.04 mmol, 7.96 mg) in 2 mL of EtOH solution and place on the other side of the H tube; Step 3: Slowly add buffer solvent EtOH in the middle to connect the two ends of the H tube; Step 4: Seal with sealing film, let stand at room temperature for one month to precipitate light yellow block crystals, collect the crystals to obtain the complex.

3. The Hofmann-type complex with light-induced spin-state switching and fluorescence properties according to claim 1, characterized in that: The unit cell parameters of the complex crystal are: α =8.9631(4); β =18.8914(2); γ =20.4693(10); Z =4; ρ calc (g / cm 3 )=1.

639.

4. The Hofmann-type complex with light-induced spin-state switching and fluorescence properties according to claim 1, characterized in that: The spatial structural characteristics of the complex are Fe ions and linear [Ag(CN)2] − Coordinate with ligand L to form a three-dimensional Hofmann-type MOF framework structure.

5. The Hofmann-type complex with light-induced spin-state switching and fluorescence properties according to claim 1, characterized in that: The complex exhibits synergistic coupling of thermally driven SCO and fluorescence in the spin transition region, and exhibits regulation of fluorescence emission intensity by photoinduced spin state switching at 10 K.

6. The Hofmann-type complex having light-induced spin-state switching and fluorescence properties according to any one of claims 1 to 5, characterized in that: It provides a valuable strategy and method for designing functionally coupled Hofmann-type spin-crossover materials.

Images