4 aminophenol

The DOPO compound, specifically 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, was acquired from Chemos GmbH in Altdorf, Germany. Prior to its utilization, it underwent a fresh dehydration. Vanilin, phenylphosphonic dichloride, 4-aminophenol, N-methyl-2-pyrrolidone (NMP), triethylamine (Et₃N), 4,4′-diaminodiphenylsulfone (DDS) and AgNO₃ were provided by Sigma-Aldrich (St. Louis, MO, USA) and used without further purification. The bisphenol A diglycidyl ether-based epoxy resin, having the epoxy equivalent weight (EEW) of 0.53 equiv. per 100 g (Mn ~ 377 g/mol), was acquired from Sigma-Aldrich. Bis(4-formyl-2-metoxyphenyl) phenylphosphonate was prepared via a condensation reaction of vanillin with phenylphosphonic dichloride, as described in the literature [51 (link)].

All the chemicals and reactants used in this study were of analytical grade. Methanol, Benzoin, vanillin, picric acid, 4-amino phenol, dichlorophenol, 4-hydroxy benzaldehyde, tyrosin, thymol, alpha-naphthol, and beta-naphthol were purchased from Sigma Chemicals (St. Louis, MO, USA). DPPH (2, 2-diphenyl-1-picrylhydrazyl) and salicylic acid were purchased from Merck (Darmstadt, Germany). 2-(N-((2′-(2H-tetrazole-5-yl)-[1,1′-biphenyl]-4yl)-methyl)-pentanamido)-3-methyl butanoic acid (96%, USP grade) was obtained from Highnoon laboratories Pvt. Ltd., Lahore, Pakistan. Using the Gallen Kamp melting point apparatus, melting points were recorded. 1H and 13C nuclear magnetic resonance analysis was performed. The cary630 FTIR spectrophotometer was used to generate a Fourier transform infrared (FTIR) spectrum using the KBr pellet press technique. The glassware was dried in a UN55 (Memmert) oven at 200 °C. In 1.0 mM of each reactant, the % yields of derivatives are provided.

Cadmium oxide (Aldrich, 99.99%), sulphur (99.9% powder, Anachemia Chemicals Ltd.), selenium (Aldrich), tributylphosphine oxide (Aldrich), octadecylamine (Aldrich, ODA), zinc oxide (Alfa Aesar), ODE (1-octadecene, Aldrich, 90%), oleic acid (Aldrich), tri-n-octylphosphine (Aldrich), tributylphosphine (Aldrich, TBP), stearic acid (Aldrich, SA) and oleic acid (Aldrich, OA). To complete this research, the toxic chemicals such as 3,4-diaminotoluene, 3-chlorophenol, 3-methoxyphenol, 4-aminophenol, 4-nitrophenyhydrazine, acetonitrile, benzylchloride, chlorobenzene, p-nitrophenol and toluene were obtained from the sigma Aldrich supplier and used directly without any refinement. To execute the electrochemical investigation, a Keithly Electrometer was used to analyze into electrochemical cell by electrochemical investigation.

9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was purchased from Chemos GmbH, Germany, and it was freshly dehydrated before use. Phenylphosphonic dichloride, 4-hydroxybenzaldehyde, 4-aminophenol, N,N-dimethylformamide (DMF), triethylamine (Et₃N), BaTiO₃ nanoparticles (cubic crystalline phase, <100 nm particle size (BET)), and 4,4′-diphenylsulfone (DDS) were provided by Sigma-Aldrich and used as received. Epoxy resin based on bisphenol A diglycidyl ether, with an epoxy equivalent weight (EEW) of 0.53 equiv. per 100 g (Mn~377 g/mol), was purchased from Sigma Aldrich. A hyperbranched Cu phthalocyanine polymer (HPc) was synthesized starting from 4,4′-bis(3,4-dicyanophenoxy)biphenyl and CuCl, following a method adapted from a previously reported procedure [32 (link)]. The chemical structure of HPc is shown in Figure 1.
Aromatic dialdehyde, bis(4-formylphenyl) phenylphosphonate, was prepared by the reaction of phenyl phosphonic dichloride and 4-hydroxybenzaldehyde according to a method previously described [27 (link)].

Silica gel, furfural, 4-aminophenol, 2-aminophenol, 3-glycidoxypropyl trimethoxysilane, sodium (Na), ethanol, methanol, toluene, acetic acid, tetrahydrofurane (THF), dimethylformamide (DMF), sodium hydroxide (NaOH), hydrochloric acid (HCl) and Cu(NO₃)₂·2H₂O were purchased from Sigma Aldrich. Silica gel with a particle size in the range of 70–230 mesh, surface area of 470–530 m² g⁻¹, pore diameter of 52–73 Å, and pore volume of 0.7–0.85 cm³ g⁻¹ was activated before use by heating at 120 °C for 24 h. The silylating agent 3-glycidoxypropyltrimethoxysilane was used without purification.

Recombinant proteins were expressed as GST fusion proteins and in Escherichia coli BL21 codon plus strain. Proteins were purified using the Sepharose beads affinity method (Glutathione Sepharose 4B; GE Healthcare).
The activity was measured using a modified end-point method previously described^{51 (link)}. In brief, the samples were incubated in a reaction mixture (total volume of 600 µl) that consisted of 200 mM McIlvaine buffer (100 mM citric acid and 200 mM Na₂HPO₄) pH 7.4, 500 μM 2,6-dichlorophenol indophenol (DCPIP; Sigma) as electron acceptor and different concentrations of N⁶-(2-isopentenyl)adenine (iP; Sigma) as substrate. The volume of the enzyme sample used for the assay was adjusted based on the enzyme activity. The incubation time at 37 °C was 1 h. The enzymatic reaction was stopped after incubation by adding 300 µl of 40% trichloroacetic acid (TCA), then 200 µl 2% 4-aminophenol (Sigma) (in 6% TCA) was added and the sample was centrifuged at 20,000 × g for 5 min to remove protein precipitate. 200 µl supernatant was used to measure the absorption spectrum from 352 to 500 nm to determine the concentration of produced Schiff base with ε352 = 15.2 mM⁻¹ cm⁻¹ using a plate reader.

4-aminophenol and paraformaldehyde were purchased from Sigma-Aldrich (St. Louis, MO, USA). Hydrogen peroxide (H₂O₂), sodium hydroxide (NaOH), dimethyl sulfoxide (DMSO), ethanol, polyvinylidene fluoride (PVDF), and N, N-dimethylformamide (DMF) were purchased from Duksan Chemicals Co., Ltd. (Gyeonggi-do, Republic of Korea). All chemicals were used without further purification.