Cobalt complex taking bis (tetradipyridyl) as ligand as well as synthesis method and application of cobalt complex
By designing and synthesizing the cobalt complex biqpyCo(ClO4)2 with bitetrapyridine as a ligand as a catalyst, the problem of low catalytic efficiency of existing catalysts when reducing carbon dioxide is solved, and the effect of efficient reduction of carbon dioxide at a low overpotential is achieved.
Patent Information
- Application Number
- CN202510149520.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-11
- Publication Date
- 2025-05-13
AI Technical Summary
Existing catalysts are not catalytic efficiency when reducing carbon dioxide and require low overpotential reduction and catalysts that contribute to electron transfer are difficult to develop.
The cobalt complex biqpyCo(ClO4)2 with bitetrapyridine as ligand was designed and synthesized as a catalyst. Through photo/electrocatalytic reduction of carbon dioxide reaction, the electronic structure of the cobalt complex was adjusted to improve catalytic activity.
It realizes efficient reduction of carbon dioxide at low overpotential conditions, the Faraday efficiency of HCOO-generating can be as high as 124%, and CO2 is reduced to HCOO- under light conditions, with a maximum conversion of 376 and a selectivity of up to 97%.
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Figure CN119977952A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of metal complexes, and in particular relates to a cobalt complex using bis-quadrupyridine as a ligand, a synthesis method and application thereof. Background Art
[0002] In recent years, with the continuous increase in energy demand and the rapid development of the global economy, the search for economic and renewable energy has become one of the main challenges facing mankind in the 21st century (Reichstein M, Bahn M, Ciais P, et al. Climate extremes and the carbon cycle [J]. Nature, 2013, 500 (7462): 287-295.). Fossil fuels account for 85% of the energy currently used by people. Humans have carried out large-scale mining of non-renewable fossil fuels, making them more expensive and difficult to obtain; in addition, the combustion of fossil fuels has caused serious environmental pollution and released a large amount of CO2. CO2 is a greenhouse gas that will cause global warming and threaten the sustainable development of human society. Therefore, it is particularly important to make full use of renewable energy to reduce CO2 to fuel or high-value-added chemicals. However, in thermodynamics, CO2 is extremely stable, and directly converting CO2 into CO2 with one electron is not easy. ·-It is very difficult and requires a very negative redox potential to achieve (Francke R, Schille B, Roemelt M. Homogeneously catalyzed electroreduction of carbondioxide—methods, mechanisms, and catalysts [J]. Chemical Reviews, 2018, 118 (9): 4631-4701.); Another relatively easy method is to reduce CO2 by proton-assisted multi-electron transfer, so that CO2 can be reduced to formic acid (HCOOH), carbon monoxide (CO), acetic acid (H2C2O4), formaldehyde (HCHO), methanol (CH3OH) and methane (CH4) at a relatively positive redox potential (Wang WH, Himeda Y, Muckerman JT, et al. CO2 hydrogenation to formate and methanol as an alternative to photo-and electrochemical CO2 reduction [J]. Chemical Reviews, 2015, 115 (23): 12936-12973.). At the same time, the thermodynamically favorable proton reduction reaction can also compete with CO2 reduction. Therefore, it is particularly important to develop catalysts that can reduce CO2 and facilitate electron transfer under low overpotential conditions. Ideally, the energy required to reduce CO2 can come from solar energy and electrical energy converted from solar energy. Therefore, in recent decades, scientists have shown great interest in designing efficient, highly selective, and long-lived photo / electrocatalytic CO2 reduction catalysts. At present, many transition metal photo / electrocatalytic CO2 reduction catalysts have been developed, but the catalytic efficiency of many of them is not high. Therefore, it is particularly important to design and synthesize efficient molecular catalysts and to improve the catalytic efficiency by optimizing the reaction conditions. In view of this, this patent application is hereby filed. Summary of the invention
[0003] The purpose of the present invention is to provide a cobalt complex with bis-quadrupyridine as a ligand, a synthesis method thereof and an application thereof in carbon dioxide reduction.
[0004] To achieve the above object, the present invention adopts the following technical solution:
[0005] A cobalt complex with biquadrupyridine as a ligand, wherein the molecular formula of the cobalt complex is biqpyCo(ClO4)2; wherein biqby represents the ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-oxanthene-4,5-diyl)di-2,2':6',2":6",2"'-tetrapyridine.
[0006] The method for synthesizing a cobalt complex using bis-quadrupyridine as a ligand comprises the following steps: dissolving a ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene-4,5-diyl)di-2,2':6',2":6",2"'-quadrupyridine in a mixed solvent, then adding a cobalt salt, stirring the obtained mixture for reaction, filtering to remove insoluble matter after the reaction is completed, then removing the organic solvent, washing the obtained solid with water, ethanol and dichloromethane in sequence, and drying the obtained solid to prepare the cobalt complex using bis-quadrupyridine as a ligand.
[0007] Preferably, the mixed solvent consists of methanol and dichloromethane.
[0008] Preferably, the cobalt salt is selected from one of cobalt perchlorate, cobalt chloride, cobalt bromide, cobalt nitrate or cobalt sulfate.
[0009] Preferably, the stirring reaction conditions are: the reaction temperature is room temperature, and the reaction time is 24 hours.
[0010] The application of the aforementioned cobalt complex with bis-quadrupyridine as a ligand in the electrocatalytic reduction of carbon dioxide specifically comprises the following steps: adding an electrolyte containing the cobalt complex with bis-quadrupyridine as a ligand into an electrolytic cell, and then blowing carbon dioxide into the electrocatalytic reduction of carbon dioxide.
[0011] Preferably, the electrolytic cell is a three-electrode system, wherein the working electrode is a glassy carbon electrode, the counter electrode is a platinum wire electrode, and the reference electrode is a calomel electrode.
[0012] The application of the aforementioned cobalt complex with bis-quadrupyridine as a ligand in the photocatalytic reduction of carbon dioxide specifically comprises the following steps: dissolving the catalyst, photosensitizer, sacrificial agent and additive, sealing the resulting solution, blowing carbon dioxide into it, and then irradiating it with a light source to carry out the photocatalytic reduction of carbon dioxide reaction.
[0013] Preferably, the catalyst is biqpyCo(ClO4)2; wherein biqby represents the ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-oxanthene-4,5-diyl)di-2,2':6',2":6",2"'-tetrapyridine.
[0014] Preferably, the light source is a blue LED lamp with a wavelength of 460 nm.
[0015] The principle of the present invention is as follows:
[0016] The method provided by the present invention first couples xanthene with a tetrapyridine ligand to obtain a biqpy ligand, and then uses the biqpy ligand to react with a cobalt salt to synthesize a cobalt complex biqpyCo(ClO4)2 as a catalyst for photo / electrocatalytic reduction of carbon dioxide. Among them, the principle of using the cobalt complex biqpyCo(ClO4)2 as a catalyst for electrocatalytic reduction of carbon dioxide may be: the self-designed ligand biqpy provided by the present invention can adjust the electronic structure of the synthesized cobalt complex biqpyCo(ClO4)2. Specifically, the biqpy ligand can significantly increase the electron density of the central metal cobalt center, thereby enhancing its interaction with the CO2 intermediate, thereby improving the catalytic activity. The specific principle of using the cobalt complex biqpyCo(ClO4)2 as a catalyst for the photocatalytic reduction of carbon dioxide may be: under light, the photosensitizer is excited to an excited state, and when oxidative quenching occurs, the photosensitizer in the excited state is quenched by the photocatalyst [biqpyCo Ⅱ ] 2+ Oxidation to the oxidized state, while forming a strongly reducing biqpyCo 0 , which then combines with CO2 to form the active intermediate biqpyCo 0 CO2, with the help of protons, releases HCOO - , forming [biqpyCo Ⅱ ] 2+ for the next catalytic cycle.
[0017] The beneficial effects of the present invention are as follows:
[0018] 1) The catalyst synthesis method provided by the present invention has mild reaction conditions, does not require high temperature and high pressure, does not require special equipment, and is suitable for large-scale industrial production.
[0019] 2) The cobalt complex synthesized by the present invention with bis-quadrupyridine as ligand is used as a catalyst for electrocatalytic carbon dioxide reduction and shows good catalytic activity to generate HCOO - The Faradaic efficiency can be as high as 124%.
[0020] 3) The cobalt complex synthesized by the present invention with bis-quadrupyridine as ligand is used as a catalyst, 4CzIPN is used as a photosensitizer, base TEA and a small amount of BIH are used as a sacrificial agent, and a non-precious metal photocatalytic system can be formed in NMP solution; after 11 hours of light irradiation (λ>460nm), CO2 is photocatalytically reduced to HCOO - , HCOO - The conversion number can reach up to 376, and the selectivity can be as high as 97%.
[0021] 4) The method provided by the present invention can realize the recycling of carbon dioxide and the rational utilization of energy, and provides an ideal artificial photosynthesis simulation system for reference, which has good potential application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 The present invention provides a reaction formula for synthesizing the biquadrupyridine biqpy ligand.
[0023] Figure 2 The present invention provides a reaction formula for synthesizing the cobalt complex biqpyCo(ClO4)2 using bis-quadrupyridine as a ligand.
[0024] Figure 3 The mass spectrum of the cobalt complex biqpyCo(ClO4)2 synthesized by the present invention with biquadrupyridine as a ligand. DETAILED DESCRIPTION
[0025] The present invention is further described in detail below with reference to the accompanying drawings and examples. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. The specific mass, reaction time, temperature, process parameters, etc. in the examples are only examples within the appropriate range. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention.
[0026] The specific synthesis steps of the biquadrupyridine biqpy ligand used in the examples of the present invention are as follows (all operations are carried out under Ar atmosphere protection, the reaction formula is as follows Figure 1 shown):
[0027] (1) According to the literature method (Guo Z, Chen G, Cometto C, et al. Selectivity control of CO versus HCOO -Production in the visible-light-driven catalytic reduction of CO2 with two cooperative metal sites[J].Nature Catalysis,2019,2(9):801-808.) Synthesis of 4-bromo-2,2':6',2":6",2"'-tetrapyridine: 6-bromo-2,2':6',2"-terpyridine (0.57 g, 1.80 mmol), hexamethyltin (0.60 g, 1.84 mmol) and Pd(PPh3)4 (0.10 g, 0.08 mmol) were placed in 25 mL of dry dimethyl ether and heated at 80 °C for 24 h. After evaporating the solvent, it was pumped under vacuum for 12 h. Then, 2,4-dibromopyridine (1.76 g, 5.4 mmol), LiCl (0.16 g, 3.4 mmol), Pd(PPh3)4 (0.15 g, 0.12 mmol) and 40 mL of dry toluene were added and refluxed under Ar conditions for 48 hours. After removing the solvent, the mixture was purified and separated by alumina column chromatography using dichloromethane / petroleum ether (1:2) as the eluent to obtain 4-bromo-2,2':6',2":6",2"'-tetrapyridine as a white solid;
[0028] (2) 4-bromo-2,2':6',2":6",2"'-tetrapyridine (78 mg, 0.2 mmol), 2,7-di-tert-butyl-9,9-dimethylxanthene-4,5-diboronic acid (41 mg, 0.1 mmol), Pd(PPh3)4 (24 mg, 0.01 mmol) and Na2CO3 (106 mg, 1.0 mmol) prepared in step (1) were placed in a i PrOH / PhMe / H2O (10 mL, 10:10:1), refluxed under Ar conditions for 16 hours. After evaporation of the solvent, the product was purified and separated by alumina column chromatography using dichloromethane / petroleum ether (2:1) as the eluent to obtain a white solid 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene-4,5-diyl)di-2,2':6',2":6",2"'-tetrapyridine.
[0029] The chemical structure of the photosensitizer 4CzIPN used in the examples of the present invention is as follows:
[0030]
[0031] The chemical structure of the photosensitizer Ru(phen)3Cl2 used in the examples of the present invention is as follows:
[0032]
[0033] The chemical structure of the photosensitizer Ru(bpy)3Cl2·6H2O used in the examples of the present invention is as follows:
[0034]
[0035] The chemical structure of the photosensitizer Cu(PhOHphen)(xantphos)PF6 used in the examples of the present invention is as follows:
[0036]
[0037] The chemical structure of the sacrificial agent BIH used in the embodiments of the present invention is as follows:
[0038]
[0039] Embodiment 1:
[0040] The specific synthesis steps of the cobalt complex biqpyCo(ClO4)2 with bis(quadrupyridine) as ligand are as follows (reaction formula: Figure 2 shown):
[0041] Biqpy (94 mg, 1.0 mmol) and Co(ClO4)2·6H2O (36 mg, 1.0 mmol) were placed in 10 mL MeOH / CH2Cl2 (v / v, 1 / 2) and stirred at room temperature for 24 hours. After the solvent was removed by rotary evaporation, the obtained solid was washed with water (5 mL), isopropanol (5 mL) and dichloromethane (5 mL) in sequence, and the washed solid was dried to obtain the cobalt complex.
[0042] The cobalt complex biqpyCo(ClO4)2 was dissolved in MeOH and characterized by electrospray ionization mass spectrometry. Figure 3 Shown: ESI-MS (MeOH) results of biqpyCo(ClO4)2: The peak at m / z=498.7 corresponds to [biqpyCoCl] 2+ ; The peak at m / z = 1096.2 corresponds to [biqpyCo(ClO4)] + .
[0043] Embodiment 2:
[0044] The experimental steps for the electrocatalytic reduction of carbon dioxide using the cobalt complex biqpyCo(ClO4)2 with bis(quadrupyridine) as a ligand are as follows:
[0045] Cyclic voltammetry (CV) was performed using a Shanghai Chenhua 760E instrument. 2), a platinum wire counter electrode (CHI 115) and a saturated calomel reference electrode (SCE, CHI 150) formed a three-electrode system. The working electrode was polished with α-Al2O3 (0.3, 0.1 and 0.05 μm, 1 min each time) and thoroughly rinsed with H2O and ethanol. The solution was blown with argon or CO2 and tested. The potentials in this application are all relative to SCE.
[0046] The performance test of controlled potential coulometry was carried out using the Energylab XM electrochemical workstation of AMETEK, UK. The three-electrode system consists of a glassy carbon working electrode (1cm×1cm), a platinum wire counter electrode (CHI 115) and a saturated calomel reference electrode (SCE, CHI150). The working electrode was polished with α-Al2O3 and rinsed thoroughly with H2O and ethanol. CO2 was bubbled into the electrolyte for 30 minutes, and it was strictly sealed. CV was measured first to determine the electrolysis potential, and then electrolysis was performed; the composition of the electrolyte was as follows: biqpyCo(ClO4)2 and Bu4NPF6 were added to an acetonitrile solution containing 25% triethylamine to ensure that the concentration of biqpyCo(ClO4)2 was 0.5mM;
[0047] The concentration of Bu4NPF6 is 0.1M; the electrolysis potential is -1.3V.
[0048] The Faraday efficiency (FE) is used to evaluate the electrocatalytic performance of the catalyst; in the electrocatalytic CO2 reduction process, the actual amount of product substance is compared to the percentage of the theoretical product. The calculation formula of Faraday efficiency (FE) is as follows:
[0049] FE(%)=n 实际 / n 理论 =2n 实际 F / Q;
[0050] Among them, 2 represents the number of electrons transferred to catalyze the reduction of CO2 to products; F is the Faraday constant, F = 96485.3C / mol; Q is the amount of electricity transferred during the reaction.
[0051] The catalytic results are shown in Table 1.
[0052] Embodiment 3-5:
[0053] The experimental steps for the electrocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 2, except that the electrolysis potential is changed to -1.5V, -1.7V and -1.9V in sequence; the catalytic results are shown in Table 1.
[0054] Embodiment 6:
[0055] The experimental steps for the electrocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 2, except that the electrolysis potential is changed to -1.5V and the concentration of triethylamine in the electrolyte is changed to 0; the catalytic results are shown in Table 1.
[0056] Embodiment 7:
[0057] The experimental steps for the electrocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 2, except that the electrolysis potential is changed to -1.7V and the solvent acetonitrile in the electrolyte is changed to N-methylpyrrolidone; the catalytic results are shown in Table 1.
[0058] Table 1 Faraday efficiency of biqpyCo(ClO4)2 as an electrocatalyst for electrolysis of CO2 to produce reduction products.
[0059]
[0060] Reaction conditions: CO2 saturated solvent, 0.5 mM biqpyCo(ClO4)2, 0.1 M Bu4NPF6, electrolysis for 1.5 hours.
[0061] Embodiment 8:
[0062] The experimental steps for the photocatalytic reduction of carbon dioxide using the cobalt complex biqpyCo(ClO4)2 with bis(quadrupyridine) as a ligand are as follows:
[0063] The catalyst biqpyCo(ClO4)2, the photosensitizer 4CzIPN and the sacrificial agent BIH were added to 2mL of acetonitrile MeCN solution containing 40% triethylamine to form a photocatalytic system, wherein the concentration of biqpyCo(ClO4)2 was 0.05mM, the concentration of 4CzIPN was 0.2mM, and the concentration of BIH was 0.025M; the obtained photocatalytic system was stirred evenly and placed in a 12.3mL glass tube sealed with a rubber stopper and tape, and CO2 was blown into it for 30 minutes to fill the tube with CO2. Then, the glass tube was placed in a constant temperature water bath glass bottle wrapped with a blue LED lamp (460nm) for illumination for 11 hours. The gas products on the upper part of the glass tube were analyzed by gas chromatography, and the liquid products in the glass tube were analyzed by ion chromatography.
[0064] The photocatalytic performance of the catalyst was evaluated by turnover number (TON) and selectivity. The catalytic results are shown in Table 2.
[0065] Table 2 Effect of different photosensitizers on photocatalytic CO2 reduction.
[0066]
[0067] Reaction conditions: MeCN solution containing 0.05 mM biqpyCo(ClO4)2, 0.005 M BIH, 40% TEA and saturated CO2 was illuminated under blue LED light for 11 hours.
[0068] Embodiment 9-11:
[0069] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 8, except that the photosensitizer 4CzIPN is replaced with Ru(phen)3Cl2, Ru(bpy)3Cl2·6H2O and Cu(PhOHphen)(xantphos)PF6 in sequence; the catalytic results are shown in Table 2.
[0070] Embodiment 12:
[0071] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with bis(quadrupyridine) as a ligand refer to Example 8, except that acetonitrile is replaced with N-methylpyrrolidone; the catalytic results are shown in Table 3.
[0072] Embodiment 13:
[0073] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as the ligand refer to Example 8, except that acetonitrile is replaced with N-methylpyrrolidone; the concentration of the catalyst biqpyCo(ClO4)2 is changed to 0; and the catalytic results are shown in Table 3.
[0074] Embodiment 14:
[0075] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 8, except that acetonitrile is replaced with N-methylpyrrolidone; the concentration of the photosensitizer 4CzIPN is changed to 0; the catalytic results are shown in Table 3.
[0076] Embodiment 15:
[0077] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 8, except that acetonitrile is replaced with N-methylpyrrolidone; the concentration of triethylamine is changed to 0; the catalytic results are shown in Table 3.
[0078] Embodiment 16:
[0079] The experimental steps for the photocatalytic reduction of carbon dioxide by the cobalt complex biqpyCo(ClO4)2 with biquadrupyridine as a ligand refer to Example 8, except that acetonitrile is replaced with N-methylpyrrolidone; the concentration of the sacrificial agent BIH is changed to 0; and the catalytic results are shown in Table 3.
[0080] Table 3 Effect of different conditions on photocatalytic CO2 reduction
[0081]
Claims
1. A cobalt complex with bis-quadrupyridine as a ligand, characterized in that: The molecular formula of the cobalt complex is biqpyCo(ClO4)2, wherein biqby represents the ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-oxanthene-4,5-diyl)di-2,2':6',2":6",2"'-tetrapyridine.
2. The method for synthesizing a cobalt complex with bis-quadrupyridine as a ligand according to claim 1, characterized in that: The method comprises the following steps: dissolving a ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-oxanthene-4,5-diyl)di-2,2':6',2":6",2"'-quadrupyridine in a mixed solvent, then adding a cobalt salt, stirring the obtained mixture for reaction, filtering to remove insoluble matter after the reaction, then removing the organic solvent, washing the obtained solid with water, ethanol and dichloromethane in sequence, and drying the obtained solid to prepare the cobalt complex with bis-quadrupyridine as a ligand.
3. The synthesis method using bis-quadrupyridine as a ligand according to claim 2, characterized in that: The mixed solvent consists of methanol and dichloromethane.
4. The synthesis method using bis-quadrupyridine as a ligand according to claim 2, characterized in that: The cobalt salt is selected from one of cobalt perchlorate, cobalt chloride, cobalt bromide, cobalt nitrate or cobalt sulfate.
5. The synthesis method using bis-quadrupyridine as a ligand according to claim 2, characterized in that: The stirring reaction conditions are: the reaction temperature is room temperature, and the reaction time is 24 hours.
6. Use of the cobalt complex with bis-quadrupyridine as ligand according to claim 1 or the cobalt complex prepared by the preparation method according to claims 2-5 in electrocatalytic carbon dioxide reduction, characterized in that: The method specifically comprises the following steps: adding an electrolyte containing the cobalt complex with bis-quadrupyridine as a ligand into an electrolytic cell, and then blowing carbon dioxide into the electrocatalytic reduction reaction of carbon dioxide.
7. The use of the cobalt complex with bis-quadrupyridine as ligand in electrocatalytic carbon dioxide reduction according to claim 6, characterized in that: The electrolytic cell is a three-electrode system, wherein the working electrode is a glassy carbon electrode, the counter electrode is a platinum wire electrode, and the reference electrode is a calomel electrode.
8. Use of the cobalt complex with bis-quadrupyridine as ligand according to claim 1 or the cobalt complex prepared by the preparation method according to claims 2-5 in photocatalytic carbon dioxide reduction, characterized in that: The method specifically comprises the following steps: dissolving the catalyst, photosensitizer, sacrificial agent and additive, sealing the obtained solution, blowing carbon dioxide into it, and then irradiating it with a light source to carry out a photocatalytic reduction of carbon dioxide reaction.
9. The use of the cobalt complex with bis-quadrupyridine as ligand in photocatalytic carbon dioxide reduction according to claim 8, characterized in that: The catalyst is biqpyCo(ClO4)2; wherein biqby represents the ligand 4,4""-(2,7-di-tert-butyl-9,9-dimethyl-9H-oxanthene-4,5-diyl)di-2,2':6',2":6",2"'-tetrapyridine.
10. The use of the cobalt complex with bis-quadrupyridine as ligand in photocatalytic carbon dioxide reduction according to claim 8, characterized in that: The light source is a blue LED lamp with a wavelength of 460nm.