Solvothermal Preparation of Copper(II) Porphyrin Sensitized Mesoporous TiO2Composites: Enhanced Photocatalytic Activity and Stability in Degradation of 4-Nitrophenol

Xiao Liu, Mimi Yu, Zengqi Zhang, Xin Zhao,Jun Li*

Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi’an, Shaanxi 710069, PR China

*Correspondence author Tel: +0086 29 88302604; Fax: +0086 29 88303798

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The synthesis of H2Pp (1, 2, 3, 4)

The synthesis routes to the porphyrins are shown in SchemeS1.

5[4-(carboethoxymethyleneoxy)phenyl]-10,15,20-tri(4-Butylphenyl) porphyrinH2Pp (1)

The steps to H2Pp(1) were described as follows: firstly ethyl chloroacetate in the presence of anhydrous potassium carbonate and dry acetone was reacted with commercially available 4-hydroxy-benzaldehyde. Then we can obtain the (4-formyl-phenoxy)-acetic acid ethyl ester (76% yield)[1]. Secondly,p-Tertbutyl Benzaldehyde, (4-formyl-phenoxy)-acetic acid ethyl ester (3.1g, 15 mmol·L-1)and pyrrole(1.0 mL, 15 mmol·L-1) were added in a three-necked bottle according to the appropriate proportion in 150 mL CH3CH2COOH. The mixture was heated to reflux for 1h and then the solvent was removed under reduced pressure. Finally, the crude products were purified by column chromatography on silica gel with dichloromethane as eluent. A purple solid of H2Pp (1) was obtained.

H2Pp(1).Yield:23%.Mp:>250°C, Anal. Calcd. for C60H60N4O3 (Mol. Wt: 884.47), %: C 81.40(81.42), H 6.84(6.83), N 6.32(6.33); MS: m/z 885.47([M+H]+)amu.UV-Vis (CH2Cl2) λmax/nm, 419 (Soret band), 517, 550, 592, 647 (Qbands); 1H NMR (400MHz, CDCl3): δ (ppm) = 8.88-8.84 (m, 8H, β–H), 8.15 (d, 8H, Ar), 7.77-7.30 (d, 8H, Ar), 4.93 (s, 2H, –OCH2CO–), 4.42 (m, 2H, –COOCH2–), 1.62 (s, 22H, t-but –CH3), 1.42 (t, 3H, –COOCH2CH3 ), 1.26 (d, 5H, t-but –CH3), -2.75 (s, 2H, NH). FT–IR: υcm-1, 3446, 2960, 2360, 1745, 1608, 1466, 1270, 1197, 1078, 965, 804, 736.

5,15-di[4-(carboethoxymethyleneoxy)phenyl]-10,20-di(4-Butylphenyl) porphyrin H2Pp(2)

The prepared process to the H2Pp(2) followed the procedure: Firstly, a solution of 4-tert-butylbenzaldehyde (1.7ml, 0.01mol) in pyrrole (36mL, 0.043 mol) was distilled before using under N2 was stirred and kept in a dark place for the whole process. After 15 minutes, a few drops of BF3·Et2O was added to the miscible liquids. When the mixture was celandine green, the mixture was diluted with 30ml CH2Cl2. Secondly anhydrous Na2SO4 was added to remove the water. After filtration and distillation, a brown oil liquid was gained and purified by chromatography on a silica gel column with CH2Cl2 as eluant. We obtained2,2′-[[4-(1,1-dimethylethyl)phenyl]methylene](Compound1). Finally the Compound1 was refluxed in 150 mL CH3CH2COOH for 1h. As a resultwe received H2Pp (2).

H2Pp(2).Yield: 13%. Mp: >250°C, Anal. Calcd. for C60H58N4O6 (Mol. Wt: 931.13),%:C 77.40 (77.39), H 6.26 (6.28), N 6.01 (6.02); MS: m/z 932.13([M+H]+)amu. UV-Vis (CH2Cl2) λmax/nm: 420 (Soret band), 517, 551, 592, 648 (Q bands);1H NMR (400MHz, CDCl3): δ (ppm) = 8.89-8.85 (m, 8H, β–H), 8.15 (d, 4H, Ar), 7.78 (d, 4H, Ar), 7.32-7.28 (m, 8H, Ar), 4.94 (s, 4H, –OCH2), 4.43 (d, 4H, –COOCH2–), 1.63-1.57 (s, 18H, t-but –CH3), 1.43 (t, 6H, –COOCH2CH3 ), -2.77 (s, 2H, NH). FT–IR:υcm-1, 3446, 2960, 2360, 1760, 1601, 1507, 1479, 1384, 1176, 972, 800, 735.

5,10,15-tri[4-(carboethoxymethyleneoxy)phenyl]-20-(4-Butylphenyl) porphyrinH2Pp(3)

The synthetic route to the H2Pp(3) was the same as H2Pp(1) except for the different proportion of (4-formyl-phenoxy)-acetic acid ethyl ester,p-Tertbutyl Benzaldehydeand pyrrole.

H2Pp(3).Yield: 20%. Mp: >250°C, Anal. Calcd. for C60H56N4O9 (Mol. Wt: 977.11), %: C 73.56 (73.65), H 5.76 (5.78), N 5.69 (5.73); MS: m/z 978.11 ([M+H]+)amu. UV-Vis (CH2Cl2) λmax/nm: 421 (Soret band), 516, 553, 592, 648 (Q bands); 1H NMR (400MHz, CDCl3): δ (ppm) = 8.89-8.84 (m, 8H, β–H), 8.56-8.48 (m, 5H, Ar), 8.13 (d, 9H, Ar), 7.76 (d, 2H, Ar), 4.92 (s, 6H, –OCH2), 4.44-4.39 (m, 6H, –COOCH2–), 1.62 (s, 9H, t-but –CH3), 1.42 (t, 9H, –COOCH2CH3 ), -2.75 (s, 2H, NH). FT–IR: υcm-1, 3446, 2968, 2360, 1759, 1508, 1384, 1176, 798, 728.

5,10,15,20-tetrakis[4-(carboethoxymethyleneoxy)phenyl]porphyrinH2Pp (4)

H2Pp(4) were synthesized and purified according to the literature [2].

The H2Pp(4) was prepared by thestepsbelow. Firstly, involved the synthesis of the (4-formyl-phenoxy)-acetic acid ethyl ester starting material from commercially available 4-hydroxy-benzaldehyde, by reacting the latter with ethyl chloroacetate in the presence of anhydrous potassium carbonate and dry acetone. Secondly, (4-formyl-phenoxy)-acetic acid ethyl ester (3.1g, 15 mmol·L-1)was reacted with an equivalent amount of pyrrole (1.0 mL, 15 mmol·L-1)in a refluxing propionicacid (80 mL) for 1 h and then the solvent was removed under reduced pressure. Finally, the residue was purified by column chromatography on silica gel with dichloromethane as eluent, We can get a purple solid of H2Pp(4).

H2Pp(4).Yield: 11%. Mp: >250°C. Anal. Calcd (found) for C60H54N4O12 (Mol.Wt:1023.09), %: C 70.32(70.44); H 5.30(5.32); N 5.46(5.48). MS:m/z 1024.09 ([M+H]+) amu. UV-vis (CH2Cl2) λmax/nm, 421 (Soret band), 518, 554, 591, 649 (Q-bands). FT–IR: υcm-1, 3447, 2922, 2361, 1759, 1506, 1202, 1080, 974,800, 731. 1H NMR (400MHz, CDCl3): δ (ppm)= 8.86 (s, 8H, β–H), 8.13 (d, 8H, Ar), 7.25 (d, 8H, Ar), 4.90 (s, 8H, –OCH2), 4.42-4.37 (q, 8H,–COOCH2–), 1.42 (t, 12H, –CH3),-2.75 (s, 2H, NH).

Scheme S1Synthesis of the porphyrins

BET analysis

Fig. S1Nitrogen adsorption–desorption isotherm and pore size distributions (inset)of the mesoporous TiO2

Fig. S2Nitrogen adsorption–desorption isotherm and pore size distributions (inset)of the mesoporous CuPp(1)/TiO2

Fig. S3Nitrogen adsorption–desorption isotherm and pore size distributions (inset)of the mesoporous CuPp(2)/TiO2

Fig. S4Nitrogen adsorption–desorption isotherm and pore size distributions (inset)of the mesoporous CuPp(3)/TiO2

Fig. S5Nitrogen adsorption–desorption isotherm and pore size distributions (inset)of the mesoporous CuPp(4)/TiO2

Fig. S6Degradation of 4-NP vs. dark time with mesoporous TiO2 and CuPp(1, 2, 3, 4)/TiO2 composites

References

[1]T.V Duncan, S.PWu, M.JTherien,J. Am. Chem. Soc. 128(2006)10423–10435.

[2] X.QSu, J.Li,J. Alloy. Compd.626(2015)252–259.