CN112630283B - Application of (E, E)-1,1′-bis(2-pyridylvinyl)ferrocene as an electrochemical sensor - Google Patents

Abstract

The invention discloses (E,E)-1,1'-bis(2-pyridylvinyl)ferrocene as an organic phase protic acid electrochemical sensor and its application, specifically: (E,E)- 1,1'-bis(2-pyridylvinyl)ferrocene and supporting electrolyte (tetra-n-butylammonium perchlorate) are dissolved in an organic solvent in proportion to obtain a kit; add the test solution to the kit, And insert the reference electrode, working electrode and auxiliary electrode, under the condition of three electrodes, use the electrochemical workstation to measure the test system in the voltage range of -0.2-1.3V by cyclic voltammetry, differential pulse voltammetry, etc. The experiment found that when (E,E)-1,1'-bis(2-pyridylvinyl)ferrocene was used as an electrochemical sensor for the detection of protic acids in the organic phase, it was affected by Ca ²⁺ , Mg ² in the organic phase ⁺ , Mn ²⁺ , Co ²⁺ , Ni ²⁺ , Cd ²⁺ and other cations have little interference. The electrochemical sensor of the present invention is used to make an electrochemical cell for the detection of the concentration of protic acids in the organic phase. It is simple to make, easy to use, and requires no Professional operation, especially suitable for rapid on-site detection of protonic acid content determination.

Description

(E, E)-1,1′-bis(2-pyridylvinyl)ferrocene as an electrochemical sensor application

technical field

The invention belongs to the technical field of rapid detection and analysis, and in particular relates to the application of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as a proton electrochemical sensor, especially for organic phase protic acid Rapid detection of concentration.

Background technique

Due to the huge potential application of ferrocene derivatives in supramolecular chemistry, electron transport materials and nonlinear optical materials, the design, synthesis and property research of ferrocene derivatives are increasingly prosperous.

In the study of supramolecular chemistry, the introduction of ferrocene groups to the appropriate parts of substrate molecules and ion-binding fragments can enable the host molecule to use the good redox properties of the ferrocene center to electrochemically recognize specific guest substrates . The conjugated structure containing ferrocenyl groups provides the possibility of electron transfer between terminal groups, which makes these compounds exhibit excellent electron transport capabilities. Although a large number of ferrocenyl host compounds with various functional groups have been reported for the recognition and detection of various metal ions and anions, there are still few reports on the host compounds in which the binding unit is directly connected to the ferrocene fragment through an ethylenic bond.

When the guest combines with the host molecule, it will cause the change of the molecular microenvironment of the host compound, triggering the electrochemical response of the electrochemical response group, usually in response to the change of the potential or current value of the group. Beer et al. ([1] PD Beer, PA Gale, GZ Chen, J. Chem. Soc., Dalton Trans., (1999) 1897.) showed that the effect of the bonded guest on the redox active center of the host molecule is mainly It works in the following ways: (1) electrostatic perturbation in space; (2) transfer through the conjugated group connecting the redox active center and the bonding site; (3) the complexed guest and the ring structure component Direct interaction between metal ions in redox active centers. These binding information can be detected macroscopically through the expression of ferrocenyl, using electrochemical instruments and techniques, so as to achieve the purpose of identification. The commonly used electrochemical monitoring methods include cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV), electrical impedance method, etc. In the oxidation-reduction process before and after the guest is added to the host compound and the binding and dissociation process between the host and the guest, K _red is the binding stability constant between the neutral host and the guest, and K _ox is the complexation stability between the host molecule and the guest in the oxidized state Constants, E ⁰ _H , E ⁰ _HG are redox peak potentials of free host molecules and host-guest conjugates, respectively. It has the following relationship

ΔE ⁰ = E ⁰ _HG －E ⁰ _H = (RT/nF)×ln (K _red /K _ox )

It can be expected that when a positively charged guest is added, K _ox should be less than K _red due to the steric repulsion between the host ^and the guest. The reason for the potential anode movement; here, the value of ΔE ⁰ directly reflects the change of the binding ability between the host molecule and the guest molecule before and after the oxidation of the ferrocene center, which is of great significance for the development of molecular switching devices.

In the host-guest interaction cyclic voltammetry (CV) curve, larger ΔE ⁰ (usually greater than 100 mV) values often give the double-wave behavior of the CV curve, in 1986, Saji (T. Saji, J. Kinoshita, J . Chem. Soc., Chem.Commun., 1986, 716.) The ferrocene-containing macrocyclic crown ether ligand reported as an example, in the reported example, its interaction with the cation Na ⁺ will cause Fc ⁺ /Fc moves to the anode of the redox potential, and with the addition of Na ⁺ , a new peak appears in the higher potential region and the original redox peak fades; when 1 equivalent of Na ⁺ is added, the original The peak disappears, and the new peak in the anodic direction is fully developed; in the presence of 0.5 equivalent Na ⁺ , its cyclic voltammetry shows a remarkable double-wave behavior.

In the accompanying drawing 8 of the present application, it can be seen that with the addition of perchloric acid, a new redox peak appears in the higher potential region and is accompanied by the disappearance of the redox peak of the original host molecule; as the amount of perchloric acid increases The larger the new peak at the higher potential gradually develops, the redox peak of the original host molecule will gradually disappear. The redox peaks completely disappeared. This is similar to the results of cyclic voltammetry behavior curves of macrocyclic crown ethers for Na ⁺ recognition reported by Saji. When the ΔE ⁰ of the system is greater than 100mV, the redox peaks corresponding to free host molecules and host-guest conjugates have a good resolution during electrochemical detection, which provides a basis for accurate determination of the peak currents of the corresponding redox peaks. Possibly, such systems can be used to develop amperometric sensors for electrochemical recognition and content detection of guest particles.

This application designs (E, E)-1,1'-bis (2-pyridine Vinyl) ferrocene, in this two-arm type ferrocene compound, due to the good basicity of the pyridine nitrogen atom in the molecule, it is easy to combine with the proton of the organic phase protic acid to protonate, which leads to The change of the whole molecule can be expected due to the existence of ethylenic bonds, so that the ferrocene group and pyridine constitute a huge conjugated system, and the change of the electronic state of the pyridine ring caused by the protonation of the pyridine nitrogen atom will inevitably pass through The electron transfer of the conjugated structure is fed back to the ferrocene center, thereby changing the redox potential of the ferrocene, and then realizing the output of the electrochemical signal of the proton binding process through electrochemical detection. The combination of the proton of the guest protic acid and the host molecule (E,E)-1,1'-bis(2-pyridylvinyl)ferrocene can be monitored by electrochemical methods such as cyclic voltammetry and DPV. Use it as an organic phase protic acid electrochemical sensor for rapid electrochemical detection of organic phase protic acid [H] ⁺ , record the corresponding redox peak current obtained from electrochemical detection, and make the acid concentration and peak current relationship curve, and obtain The sensor detects the standard curve of the acid concentration, mixes the test solution with the prepared kit in proportion, records the redox peak-peak current obtained by electrochemical detection, and converts the acid value of the test solution through the standard curve. (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is used as a proton electrochemical sensor for the determination of the concentration of protic acids in organic phases. The titration operation has a large human influence, high operating skills for the operator, large error or even undetectable problems at low concentrations.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, to provide a kind of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as a proton electrochemical sensor for organic phase protic acid (such as for The rapid detection of the concentration of toluenesulfonic acid, or perchloric acid, etc.) has the advantages of high sensitivity, simple production, and convenient use. It solves the shortcomings of traditional titration operations such as large human influence, large errors at low concentrations, and even undetectable defects.

To achieve the above object, the present invention adopts the following technical solutions:

The application of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as an organic phase protic acid electrochemical sensor, the (E, E)-1,1'-bis(2 The structural formula of -pyridine vinyl) ferrocene is as follows:

。

.

Specifically, the (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is prepared through the following steps:

1) Add potassium iodide, 1,1'-ferrocenyldimethanol and triphenylphosphine into a round-bottomed flask filled with water, chloroform and glacial acetic acid, heat and reflux for 30-40 h; evaporate the organic solvent under reduced pressure , to obtain a yellow solid, which was washed and dried in vacuo to obtain ferrocene bis-methylene triphenylphosphonium iodide salt;

2) Weigh ferrocenebismethylenetriphenylphosphonium iodide salt and potassium tert-butoxide in a round bottom flask, add anhydrous THF (tetrahydrofuran) under the condition of avoiding light and stirring under nitrogen atmosphere at room temperature, and add after 20-40min Anhydrous THF solution containing ₂ -pyridinecarbaldehyde, react at room temperature for 1-3h, then react under reflux for 10-14h, distill off the organic solvent under reduced pressure, add saturated saline to the residue, extract with _CH2C12 , organic phase Dry it with anhydrous Na ₂ SO ₄ , distill off the solvent under reduced pressure, separate and purify the product.

The application of the above-mentioned (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as an organic phase protic acid electrochemical sensor, specifically, (E, E)-1,1' - Bis(2-pyridylvinyl)ferrocene and supporting electrolyte tetra-n-butylammonium perchlorate are dissolved in an organic solvent in proportion to obtain a kit.

Further, in the kit, the concentration of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is 2×10 ^{- 2} mol/L-2×10 ^-5 mol/L, The concentration of the supporting electrolyte tetra-n-butylammonium perchlorate is 2×10 ^-1 mol/L. The role of tetra-n-butylammonium perchlorate is that it has good solubility in organic solvents, provides a conductive medium for electrochemical detection, and can better eliminate the possible interference of common electrolyte cations and anions on the test system.

Further preferably, the organic solvent is one or a mixture of two or more of acetonitrile, dichloromethane, methanol, ethanol, and dimethylformamide. The role of the solvent is: as a dissolving reagent for (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene, and using the better miscibility of this type of solvent with the sample to be tested, it is used for Determination of organic phase protic acid test solution. The purity of the solvent was analytically pure.

The above-mentioned (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is used as an organic phase protic acid electrochemical sensor. During detection, the sample solution to be tested is mixed with the kit, and inserted into the Reference electrode, working electrode and auxiliary electrode, under the condition of three-electrode system, use electrochemical workstation to measure the test system by cyclic voltammetry or differential pulse voltammetry in the voltage range of -0.2-1.3V. Record the oxidation or reduction peak current corresponding to the electrochemical detection, and calculate the concentration of the organic phase protic acid (such as p-toluenesulfonic acid, or perchloric acid, etc.) in the sample solution to be tested according to the standard curve.

The standard curve is made as follows: prepare a standard solution of p-toluenesulfonic acid or perchloric acid with accurate concentration, take a certain amount of standard solution and mix it with the kit, use the three-electrode system to test, record the peak current corresponding to the redox peak obtained by electrochemical detection, Draw the relationship curve between acid concentration and peak current to obtain the standard curve of acid concentration detected by the sensor; add the sample solution to be tested into the kit, measure under the same conditions, record the peak current corresponding to the redox peak obtained by electrochemical detection, and bring it into The standard curve obtains the organic phase protonic acid concentration in the sample solution to be tested.

In the application of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as an organic phase protic acid electrochemical sensor, when the protic acid is added gradually, its CV curve shows a good The double-wave behavior (see Figures 8 and 10); and the larger formula potential shift value makes (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as an amperometric sensor It is possible to realize the quantitative detection of protic acid. This application uses the DPV method with high accuracy to conduct system experiments in the presence of protic acids with different equivalents, and the results are shown in Figures 3 and 9. In the DPV curve, the relationship between the peak current value and the ratio of the added protic acid to the ligand is drawn. It can be seen from the relationship curve that with the addition of the protic acid, the change value of the peak current has a good correlation with the amount added. , until the protic acid and (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene reached 2:1 equivalent peak current reached the maximum.

In the present invention, (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is an organic phase protic acid electrochemical sensor, and its combination with organic phase protonic acid can generate ferrocene The change of redox potential and redox peak current of iron, the content of acid in the system and the change of redox peak peak current have a good linear relationship, so as to realize the determination of protic acid content.

The present invention adopts (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene as an electrochemical sensor, and utilizes the positive oxidation-reduction potential of the ferrocene center caused by the protonation of the N atom of the pyridine ring in the molecule. As the degree of protonation increases, the redox peak current of the original ferrocene center gradually decreases, while the peak current of the new peak obtained at a higher potential position gradually increases until the protonation is completely completed, at which point it reaches Protonic acid concentration detection limit, the detection limit is limited by the sensor (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene concentration, the higher the sensor concentration is, the higher the detection limit is, and the smaller the sensor concentration is, the detection sensitivity higher. In use, a gradient solution of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene 10 ^-2 mol/L-10 ^{- 5} mol/L can be configured, and the sample solution to be tested is first Mix the test with a low-concentration sensor solution. If only the redox peak at the corresponding protonated potential is observed, it means that the detection limit of the concentration has been reached. Further change to a higher concentration sensor kit until double waves appear, and record the new peak-to-peak current And the old peak current at low potential. At this time, make a standard curve of the relationship between the standard acid concentration and the peak current at this concentration, and the concentration of the protonic acid in the sample solution to be tested can be obtained by drawing a graph. Compared with the prior art, the beneficial effects of the present invention are as follows:

The detection kit is simple to make, easy to use, has a wide range of tests, does not require professional operation, and is especially suitable for the determination of the content of protonic acids in organic phase systems. In the given example, the lower limit of detection concentration of protonic acid reaches 2.4×10 ^-6 mol/L, which can be well used for the concentration determination of protonic acid in organic phase. In the measurement environment, K ⁺ , Ca ²⁺ , Mg ²⁺ , which are 50 times the acid concentration, and Mn ²⁺ , Co ²⁺ , Ni ²⁺ , Cd ²⁺ , which are 10 times the acid concentration, do not interfere with the determination of the acid concentration. The invention solves the problems that the traditional titration operation is greatly influenced by human beings, has high operating skills for operators, and has large errors or even undetectable problems at low concentrations, and has important application value in the application field of rapid detection of the content of protic acids in organic phases.

Description of drawings

Figure 1 is the hydrogen nuclear magnetic resonance spectrum of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig);

Figure 2 is the cyclic voltammetry of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) under 4 equivalents of different metal ions, p-toluenesulfonic acid and perchloric acid ( CV) test results comparison chart;

Figure 3 shows the test results of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) under different equivalents of perchloric acid by differential pulse voltammetry (DPV);

Fig. 4 is the relationship curve between the peak current of differential pulse voltammetry (DPV) (lig) peak and the concentration of _HClO4 ;

Figure 5 is a scatter diagram of the relationship between the peak current of the differential pulse voltammetry (DPV) (lig+HClO ₄ ) peak and the concentration of HClO ₄ ;

Figure 6 is the relationship curve between the peak current of differential pulse voltammetry (DPV) (lig+HClO ₄ ) peak and the concentration of HClO ₄ ;

Figure 7 is the differential pulse voltammetry (DPV) of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene to 5ml of HClO ₄ solution with a concentration of 3.2×10 ^-3 mol/L Test Results;

Figure 8 shows the test results of cyclic voltammetry (CV) of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) under different equivalents of perchloric acid;

Figure 9 shows the differential pulse voltammetry (DPV) test results of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) under different equivalents of p-toluenesulfonic acid (TSOH) ;

Figure 10 shows the test results of cyclic voltammetry (CV) of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) under different equivalents of p-toluenesulfonic acid (TSOH).

detailed description

The technical solutions of the present invention will be further described in detail below in conjunction with the examples, but the protection scope of the present invention is not limited thereto.

In the following examples, (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene can be prepared by the following method:

Add 16.6 g of potassium iodide, 4.92 g of 1,1'-ferrocenyldimethanol and 17.6 g of triphenylphosphine into a 250 mL round-bottomed flask filled with 20 mL of water, 60 mL of chloroform and 30 mL of glacial acetic acid, and heat Refluxed for 36 h, a large amount of yellow crystals precipitated in the reaction flask, and the organic solvent was evaporated under reduced pressure to obtain a large amount of yellow solid, which was filtered with suction, and the filter cake was successively washed with 3 × 20 mL of secondary water, 3 × 10 mL of absolute ethanol, and 3 × Wash with 10 mL of anhydrous ether and dry in vacuo to obtain 19.2 g of yellow crystals of ferrocene bismethylene triphenylphosphonium iodide salt (yield 97%).

In a glove box at room temperature, weigh 6.0 g of ferrocenebismethylenetriphenylphosphonium iodide and 1.5 g of potassium tert-butoxide in a 100 mL round-bottomed flask. Add 40 mL of anhydrous THF to the system (the reaction solution is dark red), and after 30 min, add the anhydrous THF solution containing 13.5 mmol 2-pyridinecarbaldehyde to the reaction system dropwise, and react at room temperature for 2 h after the dropwise addition, and then Under the reaction overnight (12h). _The organic solvent was evaporated from the reaction liquid under reduced pressure, saturated brine was added to the residue, extracted with _CH2C12 , the organic phase was dried overnight with _{anhydrous Na2SO4} , and the solvent was evaporated under reduced pressure to obtain a deep red viscous substance, which was obtained as CH ₂ Cl ₂ /CH ₃ COOC ₂ H ₅ (V/V= 5:1) mixed solvent was used as eluent for silica gel column chromatography to obtain the target product; dark red powder crystal 0.823g, Yield: 35%; Mp : 160-162 ºC; HRMS: Cacld for C ₂₄ H ₂₁ FeN ₂ [M + H] ⁺ 393.1054, found 393.1052; IR ν _max (KBr): 1632, 1582, 1469,1427, 963, 768 cm ^-1 ; ¹ H NMR (400 MHz): 4.32(t, J=1.7 Hz, 4H, Cp-H), 4.50(t, J=1.7 Hz, 4H, Cp-H), 6.65(d, J=16.0 Hz, 2H, olefinic H), 7.01-7.07(m, 4H, Ar-H), 7.21(d, J=16.2 Hz, 2H, olefinic H), , 7.42-7.46 (m, 2H, Ar-H), 8.45(d,2H , J= 4.4 Hz, Ar-H); ¹³ C NMR (100 MHz): 68.60, 70.75, 83.15, 120.98, 120.99, 126.06, 130.75, 136.35, 149.26, 155.82; ESI-MS: [M + H] ⁺ : 393.1, [M + Na] ⁺ : 415.0. See Figure 1 for the H NMR spectrum.

Metal ion recognition and competition experiments:

Add the acetonitrile solution (1×10 ^-3 M) of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene prepared in the electrolytic cell, metal ions (with its perchloric acid salt form) in acetonitrile solution (0.2 M) was added from a microinjector in an amount of 4 equivalents of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene; electrochemical test Measured with CHI-650A comprehensive electrochemical workstation (Shanghai Chenhua Company), three-electrode system, the working electrode is a Φ3 mm glassy carbon electrode, the auxiliary electrode is a platinum wire, and the reference electrode is a 232-type calomel electrode; the working electrode is at Grind and polish to the mirror surface with 0.05 μm A1 ₂ O ₃ polishing powder before use, and then use 0.1 M NaOH, 1:1 volume of concentrated HNO ₃ , water, absolute ethanol, and double distilled water to ultrasonically clean; The potential range was determined by cyclic voltammetry under the condition of a potential scan rate of 100 mV/s.

The results showed that except Ca ²⁺ and Mg ²⁺ had almost no response, when Mn ²⁺ , Co ²⁺ , Zn ²⁺ , and Cd ²⁺ were added to (E, E)-1,1'-bis(2-pyridine In the acetonitrile solution of vinyl) ferrocene, the selected transition metal ^ions have changed the redox properties of the ferrocene center (see Figure 2), resulting in the anode Move, and the pair still shows good reversibility. Although Mn ²⁺ , Co ²⁺ , Zn ²⁺ , and Cd ²⁺ have a certain electrochemical response, their Fc/Fc ⁺ electron pair type potential change value is significantly smaller than that of protic acid perchloric acid and p-toluenesulfonic acid to Fc The influence value of /Fc ⁺ electricity on the stoichiometric potential. When (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene 2 equivalents of perchloric acid and 100 equivalents of Ca ²⁺ or Mg ²⁺ are added at the same time, the redox peak shape Still behaves the same as in the presence of 2 equivalents of perchloric acid. When (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene 2 equivalents of perchloric acid and 20 equivalents of Mn ²⁺ , Co ²⁺ , Zn ²⁺ or Cd ²⁺ , the redox peak shape still behaves the same as that in the presence of 2 equivalents of perchloric acid, which indicates that (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene has the same effect on the tested metal ions In the presence of , selectively recognize protic acids.

Its recognition and detection results for perchloric acid and p-toluenesulfonic acid in acetonitrile solution are shown in the following examples.

Example 1:

An organic phase protic acid electrochemical sensor and its detection method:

Preparation of sensor (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) solution: using acetonitrile as solvent, prepare 2×10 ^-1 mol/L tetra-n-butyl perchlor ammonium nitrite and 2×10 ^-3 mol/L lig solution; bottle the prepared solution in 5mL as a kit for testing;

Acetonitrile standard solution of perchloric acid: 0 mol/L, 5×10 ^-4 mol/L, 1×10 ^-3 mol/L, 1.5×10 ^-3 mol/L, ² ×10 ^-3 mol/L, 2.5×10 ^-3 mol/L, 3×10 ^-3 mol/L, 3.5×10 ^-3 mol/L, 4×10 ^-3 mol/L, 4.5×10 ^-3 mol/L, 5×10 ^-3 mol/L, respectively take 5mL and bottle it for the calibration standard curve;

The electrochemical test was determined by CHI-650A comprehensive electrochemical workstation (Shanghai Chenhua Company), three-electrode system, the working electrode was a Φ3 mm glassy carbon electrode, the auxiliary electrode was a platinum wire, and the reference electrode was a 232-type calomel electrode; Before use, the working electrode was ground and polished to a mirror surface with 0.05 μm A1 ₂ O ₃ polishing powder, and then ultrasonically cleaned with 0.1 M NaOH, concentrated HNO ₃ with a volume of 1:1, water, absolute ethanol, and double distilled water.

Within the potential range of 0.00 to 0.90 V, mix equal volumes of the prepared 5ml kit and 5ml perchloric acid acetonitrile standard solution, and use differential pulse voltammetry (DPV, the operating parameters are shown in the right column of Figure 3 ) to measure the response of the sensor to different concentrations of perchloric acid. The result is shown in Figure 3. It can be seen from Figure 3 that in the DPV curve, with the increase of the amount of perchloric acid and the increase of the degree of protonation, the redox peak current of the original ligand ferrocene center gradually decreases, while at higher The peak current of the new peak obtained at the potential position gradually increases until the protonation is completed when the acid and ligand are 2:1 equivalent. At this time, the redox peak corresponding to the original ligand ferrocene center completely disappears, reaching the concentration detection upper limit.

Further, the obtained DPV test results were processed to correspond to (E, E)-1,1'-bis( ₂ - ^pyridylvinyl )di The peak current of the ferrocene (lig) peak (peak at low potential) is the ordinate, and the concentration of HClO ₄ is the abscissa. Figure 4 is obtained. It can be seen from Figure 4 that in this concentration range, the corresponding lig The peak current of the peak has a good linear relationship with the concentration of perchloric acid.

In the range of HClO ₄ concentration 2×10 ^-3 -5×10 ^-3 mol/L, to correspond to the addition of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene to HClO ₄ The peak current of the compound (lig+HClO ₄ ) peak (peak at high potential) is the ordinate, and the concentration of HClO ₄ is the abscissa, and a scatter diagram is obtained - Figure 5. It can be seen from Figure 5 that when the concentration of perchloric acid reaches 4×10 ^-3 mol/L, in this state, (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) has completely formed a stable adduct with perchloric acid and reached the upper limit of the test. Higher acid concentrations cannot further significantly increase the peak current.

In the range of HClO ₄ concentration 0-4×10 ^-3 mol/L, take the peak current of (lig+HClO ₄ ) peak (peak at high potential) as the ordinate, and the HClO ₄ concentration as the abscissa, draw a graph, Figure 6. It can be seen from Figure 6 that in this concentration range, the peak current corresponding to the (lig+HClO ₄ ) peak has a good linear relationship with the concentration of perchloric acid.

Further, this application prepares 5ml of HClO ₄ solution with a concentration of 3.2×10 ^-3 mol/L, and then mixes it with a 5ml kit in equal volume, and uses differential pulse voltammetry (DPV) to measure the sensor's response to the concentration of perchloric acid , the result is shown in Figure 7; record the peak current 2.647E-05, and substitute it into the linear relational formula (y=0.0091x-3E-06) of the standard curve shown in Figure 6 to calculate, and the detected concentration result is 3.24× 10 ^-3 mol/L, the deviation is 1.25%, the result is satisfactory.

Example 2:

An organic phase protic acid electrochemical sensor and its detection method:

Preparation of sensor (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) solution: using acetonitrile as solvent, prepare 2×10 ^-1 mol/L tetra-n-butyl perchlor ammonium nitrite and 2×10 ^-3 mol/L lig solution; bottle the prepared solution in 5mL as a kit for testing;

Prepare acetonitrile standard solution of perchloric acid 0 mol/L, 5×10 ^-4 mol/L, 1×10 ^-3 mol/L, 1.5×10 ^-3 mol/L, 2×10 ^-3 mol/L, 2.5 ×10 ^-3 mol/L, 3×10 ^-3 mol/L, 3.5×10 ^-3 mol/L, 4×10 ^-3 mol/L, take 5mL bottle for calibration standard curve;

The electrochemical test was determined by CHI-650A comprehensive electrochemical workstation (Shanghai Chenhua Company), three-electrode system, the working electrode was a Φ3 mm glassy carbon electrode, the auxiliary electrode was a platinum wire, and the reference electrode was a 232-type calomel electrode; Before use, the working electrode was ground and polished to a mirror surface with 0.05 μm A1 ₂ O ₃ polishing powder, and then ultrasonically cleaned with 0.1 M NaOH, concentrated HNO ₃ with a volume of 1:1, water, absolute ethanol, and double distilled water.

Within the potential range of 0.00 to 0.90 V, mix equal volumes of the configured 5ml kit and 5ml perchloric acid acetonitrile standard solution, and use cyclic voltammetry (CV, operating parameters as shown in the right column of Figure 8) to conduct Determination of sensor response to different perchloric acid concentrations. The result is shown in Figure 8. It can be seen from Figure 8 that in the CV curve, with the increase of the amount of perchloric acid and the increase of the protonation degree, the peak current of the redox peak of the original ligand ferrocene center gradually decreases, while in the more The peak current of the new redox peak obtained at the high potential position gradually increases until the protonation is completely completed when the acid and the ligand are 2:1 equivalent. At this time, the redox peak corresponding to the original ligand ferrocene center completely disappears. The upper detection limit of the protonic acid concentration was reached.

Further, the applicant configures 5ml of HClO ₄ solution with a concentration of 3.0×10 ^-3 mol/L, and then mixes it with a 5ml kit in equal volume, uses cyclic voltammetry to measure the response of the sensor to the concentration of perchloric acid, and records the corresponding The peak current of the oxidation peak of the [lig+HClO ₄ ] redox pair was calculated using the linear relational formula of the standard curve, and the detected concentration was 2.92×10 ^-3 mol/L, with a deviation of 2.67%. Can.

Example 3:

An organic phase protic acid electrochemical sensor and its detection method:

Preparation of sensor (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene (lig) solution: using acetonitrile as solvent, prepare 2×10 ^-1 mol/L tetra-n-butyl perchlor ammonium nitrite and 2×10 ^-3 mol/L lig solution; bottle the prepared solution in 5mL as a kit for testing;

Prepare acetonitrile standard solution of p-toluenesulfonic acid (TSOH): 0×10 ^-3 mol/L, 2×10 ^-3 mol/L, 2.5×10 ^-4 mol/L, ^{3×10 -3 mol} /L, 3.5 ×10 ^-3 mol/L, 4×10 ^-3 mol/L, respectively take 5mL bottles for calibration standard curve;

The electrochemical test was determined by CHI-650A comprehensive electrochemical workstation (Shanghai Chenhua Company), three-electrode system, the working electrode was a Φ3 mm glassy carbon electrode, the auxiliary electrode was a platinum wire, and the reference electrode was a 232-type calomel electrode; Before use, the working electrode was ground and polished to a mirror surface with 0.05 μm A1 ₂ O ₃ polishing powder, and then ultrasonically cleaned with 0.1 M NaOH, concentrated HNO ₃ with a volume of 1:1, water, absolute ethanol, and double distilled water.

Within the potential range of 0.00 to 0.90 V, mix equal volumes of the prepared 5ml kit and 5ml acetonitrile standard solution of p-toluenesulfonic acid, and use differential pulse voltammetry (the operating parameters are shown in the right column of Figure 9) A measurement of the sensor's response to different p-toluenesulfonic acid (TSOH) concentrations was performed. The result is shown in Figure 9. It can be seen from Figure 9 that in the DPV curve, as the amount of acid increases, the redox peak current of the original ligand ferrocene center gradually decreases, and the peak current of the new peak obtained at a higher potential position The current gradually increases until the protonation is completed when the acid and ligand are 2:1 equivalent. At this time, the redox peak corresponding to the original ligand ferrocene center completely disappears, reaching the detection limit of the protonic acid concentration.

Example 4:

An organic phase protic acid electrochemical sensor and its detection method:

Preparation of sensor (E, E)-1,1'-bis(2-pyridine vinyl) ferrocene (lig) solution: using acetonitrile as solvent, prepare 2×10 ^-1 mol/L tetra-n-butyl A solution of ammonium perchlorate and 2×10 ^-3 mol/L lig; take 5 mL of the prepared solution and bottle it for testing;

Prepare acetonitrile standard solutions of p-toluenesulfonic acid (TSOH) 0 mol/L, 2×10 ^-3 mol/L, 2.5×10 ^-4 mol/L, 3×10 ^-3 mol/L, 3.5×10 ^-3 mol /L, 4×10 ^-3 mol/L, take 5mL bottles for calibration standard curve;

The electrochemical test was determined by CHI-650A comprehensive electrochemical workstation (Shanghai Chenhua Company), three-electrode system, the working electrode was a Φ3 mm glassy carbon electrode, the auxiliary electrode was a platinum wire, and the reference electrode was a 232-type calomel electrode; Before use, the working electrode was ground and polished to a mirror surface with 0.05 μm A1 ₂ O ₃ polishing powder, and then ultrasonically cleaned with 0.1 M NaOH, concentrated HNO ₃ with a volume of 1:1, water, absolute ethanol, and double distilled water.

Within the potential range of 0.00 to 0.90 V, mix equal volumes of the configured 5ml kit and standard 5ml acetonitrile standard solution of p-toluenesulfonic acid, and use cyclic voltammetry (operating parameters are shown in the right column of Figure 10) to conduct Determination of sensor response to different p-toluenesulfonic acid (TSOH) concentrations. The results are shown in Figure 10. It can be seen from Figure 10 that in the CV curve, as the amount of acid increases and the degree of protonation increases, the redox peak current of the original ligand ferrocene center gradually decreases, while at a higher potential position The peak current of the new peak obtained gradually increases until the protonation is completely completed when the acid and ligand are 2:1 equivalent. At this time, the redox peak corresponding to the original ligand ferrocene center completely disappears, reaching the detection limit of the protonic acid concentration.

In the present invention, (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is an organic phase protic acid electrochemical sensor, and the concentration of the organic phase protic acid is measured in the range of the upper detection limit concentration. With the increase of the proton concentration of the system to be tested, the increase of the protonation degree increases the redox peak current of the original ferrocene center gradually decreases, while the peak current of the new peak obtained at a higher potential position gradually increases until the protonation is completely Complete, by recording the standard curve of the relationship between the standard acid concentration and the peak current at different concentrations, the protonic acid concentration of the unknown test sample can be obtained through detection and drawing. The invention has the advantages of high sensitivity, simple manufacture and convenient use, and solves the problems of large artificial influence in traditional titration operation, high operating skills for operators, large error and even undetectable problems at low concentrations.

The above-mentioned specific embodiments are only exemplary, and are for better understanding of this patent by those skilled in the art, and should not be understood as limiting the scope of protection of this patent; as long as any equivalent changes or Modifications all fall within the scope of this patent.

Claims (6)

1. The application of (E, E)-1,1'-bis(2-pyridine vinyl) ferrocene as an organic phase protic acid electrochemical sensor, characterized in that the (E, E)-1, The structural formula of 1'-bis(2-pyridylvinyl)ferrocene is as follows:

. 2. as claimed in claim 1 (E, E)-1,1 '-bis (2-pyridine vinyl) ferrocene as the application of organic phase protonic acid electrochemical sensor, it is characterized in that, described (E , E)-1,1'-bis(2-pyridylvinyl)ferrocene was prepared by the following steps: 1) Add potassium iodide, 1,1'-ferrocenyldimethanol and triphenylphosphine into a round-bottomed flask filled with water, chloroform and glacial acetic acid, heat and reflux for 30-40 h; evaporate the organic solvent under reduced pressure , to obtain a yellow solid, which was washed and dried in vacuo to obtain ferrocene bis-methylene triphenylphosphonium iodide salt; 2) Weigh ferrocenebismethylenetriphenylphosphonium iodide salt and potassium tert-butoxide in a round bottom flask, add anhydrous THF under the condition of avoiding light, stirring under nitrogen atmosphere at room temperature, and add 2- Anhydrous THF solution of pyridine formaldehyde, react at room temperature for 1-3h, then react under reflux for 10-14h, evaporate the organic solvent under reduced pressure, add saturated saline to the residue, extract with CH ₂ C1 ₂ , and use anhydrous Dry over Na ₂ SO ₄ , distill off the solvent under reduced pressure, separate and purify to obtain the final product. 3. as claimed in claim 2 (E, E)-1,1 '-bis (2-pyridylvinyl) ferrocene as the application of organic phase protonic acid electrochemical sensor, it is characterized in that (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene and supporting electrolyte tetra-n-butylammonium perchlorate are dissolved in an organic solvent in proportion to obtain a kit. 4. as claimed in claim 3 (E, E)-1,1 '-bis (2-pyridylvinyl) ferrocene as the application of the organic phase protic acid electrochemical sensor, it is characterized in that, in the test kit, The concentration of (E, E)-1,1'-bis(2-pyridylvinyl)ferrocene is 2×10 ^-2 mol/L-2×10 ^-5 mol/L, and the supporting electrolyte is tetra-n-butyl The concentration of ammonium chlorate is 2×10 ^-1 mol/L. 5. as claimed in claim 3 or 4 (E, E)-1,1 '-bis (2-pyridine vinyl) ferrocene is as the application of organic phase protonic acid electrochemical sensor, it is characterized in that, the The organic solvent is one or a mixture of two or more of acetonitrile, dichloromethane, methanol, ethanol and dimethylformamide. 6. as claimed in claim 5 (E, E)-1,1 '-bis (2-pyridylvinyl) ferrocene as the application of organic phase protic acid electrochemical sensor, it is characterized in that, the sample to be tested Mix the solution with the kit, and insert the reference electrode, working electrode and auxiliary electrode. Under the condition of the three-electrode system, use the electrochemical workstation to use the cyclic voltammetry or differential pulse voltammetry in the voltage range of -0.2-1.3V To measure.

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