Synthesis of Novel Silicon Porphyrins

Novel Silicon porphyrins synthesized in this work are;

a) trans-dihydroxy[5, 10, 15, 20-tetrakis(2,4,6-trimethylphenyl)porphyrinato]

silicon (IV) : SiTMP(OH)2

b) trans-dihydroxo [-tetracarboxyl phenyl porphyrinate] silicon (IV):SiTCPP(OH)2

c) trans-dihydroxo [tetrakis(4trifluoromethylphenyl)porphyrinate] silicon (IV) : SiTFMP(OH)2

d) trans-dihydroxo [-tetra pyridyl porphyrinate] silicon (IV) : SiTPyP(OH)2

e) trans-dihydroxo [tetra methyl pyridinium porphyrin sulphate] silicon (IV) : SiTMPyP(OH)2

Figure 26 Structure of Novel Silicon Porphyrins investigated in this work

All new silicon porphyrins were synthesised based on method developed by Lemke et.al.

however instead of a step wise multi pot synthesis we used a step wise single pot strategy for synthesis. The synthesis, monitoring the reaction and characterisation of each molecule is described in detail in coming sections.

N N N NSi

OH O O

H O

O H

O

OH O OH

OH

N N N NSi

CF₃ F₃C

F₃C

CF₃ OH

OH

N

N N N NSi

N N

N

OH

OH

N⁺

N N N NSi

N⁺ N⁺

N⁺

OH

OH

CH₃

CH₃ C

H₃ C H₃

N N

N NSi O H

OH

CH

3

CH

3

C H

3

C H

3

CH

3

CH

3

CH

3

CH

3

C H

3

CH

3

C H

3

C H

3

a) b)

c) d)

e)

- 28 -

Synthesis of trans-dihydroxy[5, 10, 15, 20-tetrakis(2,4,6-trimethylphenyl)porphyrinato]

silicon (IV) : Si(IV)TMP(OH)2

Figure 27 Scheme of synthesis of trans-dihydroxy[5, 10, 15, 20-tetrakis(2,4,6-trimethylphenyl)porphyrinato] silicon (IV)

Materials

5,10,15,20-Tetrakis(2,4,6-trimethylphenyl)porphyrin(H2TMP)was synthesized and purified according to literature methods. DME (purchased from TCI chemicals) was stored over molecular sieves (4A), and dried over Na and vacuum transferred immediately prior to use Lithium bis(trimethylsilyl)amide (LHMDS) solid purchased from Aldrich and stored in dry condition Trichloro silane (HSiCl3) was purchased from TCI chemicals AgOTf (Silver trifluoromethanesulfonate) was purchased from TCI chemicals.

Synthesis

Tetra(2, 4, 6-trimethyl)phenylporphyrinatosilicon (SiTMP) as a new compound was synthesized from the free base tetramesitylporphyrin through four steps of lithiation, insertion of silicon, dechlorination, and hydrolysis of axial ligands. The synthesis was carried out as a multi-step single pot synthesis till step 3 as shown in Scheme 1. The free base tetramesitylporhyrin (H2TMP: 399 mg, 0.51 mmoles) was taken in a reaction pot and kept under vacuum for 30 minutes. 80 ml of dimethoxyethane (DME) was vacuum transferred to the reaction vessel and stirred at 80ᴼC for 1 hour under nitrogen atmosphere.

To the solution, lithium bis(trimethylsilyl)amide (LHMDS: 350 mg, 2.1mmoles) was added and stirred under 80ᴼC for 3 hour. The completion of step 1 was confirmed by a

N NH N

HN

1. LHMDS / Dimethoxy ethane 80^C 3 hour 2. HSiCl₃ / Dimethoxy ethane -25^C 1hour 3. AgOTf / Dimethoxy ethane 25^C 12 hour

N

N N

N Si

OTf

OTf

N

N N

N Si

OH

OH

4. NaOH / CH₂Cl₂ 50^C 48hrs

- 29 -

red shift in UV-Vis spectrum (416nm to 436 nm) of reaction mixture measured in dry DME. The reaction mixture is then cooled to -20ᴼC and then HSiCl3 (0.1 ml, 0.99 mmoles) was added carefully and stirred under the same condition for 1 hour. The reaction mixture was then slowly warmed up to room temperature and stirred under room temperature for 12 hr. The completion of step 2 was confirmed by a blue shift in UV-Vis spectrum (436 nm to 432 nm) of the reaction mixture. Then a little excess amount of silver trifluoromethanesulfonate (AgOTf: 1800 mg, 7 mmoles) was added to the reaction mixture and stirred for one overnight at 80ᴼC. The completion of step 3 was confirmed by a blue shift in UV-Vis spectrum (432 nm to 415 nm) of the reaction mixture. The reaction mixture was then filtered through PTFE membrane (pore size: 0.1μm) and celite successively to remove solid inorganic impurities. The purple colored solution thus obtained was vacuum dried to get purple powder which was then dissolved in 100ml of dichloromethane (DCM). Water (100 ml) was further added and the mixture was kept stirring for 48hrs. The completion of Step 4 was confirmed by a red shift in UV-Vis spectrum (415 nm to 422 nm). The organic layer was then separated and purified by passing through SiO2 column using 1:3 ethyl acetate/ hexane as eluent to get pure SiTMP as purple crystal (295 mg, 68% yield). The Si porphyrin synthesized was identified as SiTMP(OH)2 which have two hydroxyl groups as axial ligands on the central Si atom.

Figure 28 a) Assigning the ¹³C NMR values; b) ²⁹Si-NMR of SiTMP (OH)2 in CDCl3

Characterisation:

Elemental analysis: Observed. C 77.97%, H 7.17%, N 5.55 %, Calculated for [Si (IV)TMP(OH)2]( ½ H2O . C6H14. ¼ CH2Cl2), C 77.92 %, H 7.30 %, N 5.84 %.

1H-NMR in ppm (CDCl3): 8.63 (s, 8H), 7.18 (s, 8H), 2.54 (s, 12H), 1.85(s, 24H), -3.04 (s, 1.4H).

13C-NMR in ppm (CDCl3): 21.36 (s)a, 21.60 (s)b, 115.17(s)c, 127.77(s)d, 131.16(s)e, 136.23(s)f, 137.92(s)g, 139.30(s)h, 142.48(s)i.

N

N N

N Si ^OH

HO a

b

e f c

g d

h i

δ / ppm

TMS -202.77

a) b)

- 30 -

29Si-NMR in ppm (CDCl3):  -202.77(s).

IR in cm^-1 (KBr Method): 720¬850 C-Hoop (aromatic), 1050 S-OH stretching, 1375 – 1450 CH3 (bend/ rock), 1600 C=C stretching 2850¬3000 C-H stretching, 3400 O-H stretching

UV-vis: 5.06 x 10⁵ M^-1dm^-3 (max = 422.5 nm in CHCl3).

ESI-MS (negative mode in methanol): m/z = 842.29 (SiTMP(OH)2)

Synthesis of trans-dihydroxo [5, 10, 15, 20-tetra(4-carboxylphenyl)porphyrinato] silicon (IV) : Si(IV)TCPP(OH)2

Figure 29 Scheme of synthesis of trans-dihydroxo [-tetracarboxyl phenyl porphyrinate]

silicon(IV)

Materials

meso-Tetra(4-carboxyphenyl)porphine tetramethyl ester was purchased from Frontier scientific. DME (purchased from TCI chemicals) was stored over molecular sieves (4A), and dried over Na and vacuum transferred immediately prior to use . Lithium bis(trimethylsilyl)amide (LHMDS) solid purchased from Aldrich and stored in dry condition. Trichloro silane (HSiCl3) was purchased from TCI chemicals . AgOTf (Silver trifluoromethanesulfonate) was purchased from TCI chemicals.

Synthesis

In a typical method 50ml DME was added to 150mg of free base H2TCPPMeESTER and stirred at 80^oC for 30 minute. To this a little excess of LHMDS (Lithium

N NH N

HN

1. LHMDS / Dimethoxy ethane 80^C 3 hour 2. HSiCl₃ / Dimethoxy ethane -25^C 1hour 3. AgOTf / Dimethoxy ethane 25^C 12 hour COOCH₃

COOCH₃ H₃COOC

COOCH₃

N

N N

N

COOCH₃

COOCH₃ H₃COOC

COOCH₃

Si

OTf

OTf

N

N N

N

COOH

COOH HOOC

COOH

Si

OH

OH

4. NaOH / CH₂Cl₂ 50^C 48hrs

- 31 -

bis(trimethylsilyl)amide) was added and stirred at 80^oC for 3 hours. After 3hours UV visible spectrum of the reaction mixture was analyzed, a red shift of soret band to 442nm from 416nm indicated the completion of reaction to form the Lithium salt of pophyrin dianion (Li2(TCPPMeESTER) . The reaction mixture is then cooled to -25^oC and kept at that temperature for 1 hour and to this approx. 20μL of HSiCl3 was added and stirred at -25^oC for 30 minutes. The reaction pot was then slowly warmed to room temperature and stirred for 1hour. After 1hour. UV-Vis spectrum was measured, a blue shift of soret band to 434nm from 442nm indicated the completion of reaction to form SiCl2TCPPMeESTER.

The reaction mixture is then slowly warmed to 25^oC and excess of AgOTf was added.

The reaction mixture was kept for one overnight and UV visible spectrum is recorded a blue shift of soret band to 418 nm from 434nm indicated the formation of Si(OTf)2TCPPMeESTER. The reaction mixture was then filtered through 0.1μm PTFE;

the red-purple filtrate was then dried. The red purple solid was then stirred for 3days in a 1:1 mixture of DCM: NaOH(1M) . The aqueous layer was separated and acidified to get pink precipitate of SiTCPP(OH)2. The precipitate was then separated by filtration through 0.1μm PTFE and washed with hot HCl and water several times to get pure SiTCPP(OH)2.

Figure 30 a) Assigning the ¹³C NMR values; b) ²⁹Si-NMR of SiTCPP (OH)2 in D2O

Characterisation:

Elemental Analysis: Observed C 65.99%, H 3.91%, N 6.22 %, Calculated for [Si (IV)TCPP(OH)2]( H2O), C 66.35%, H 3.71 %, N 6.45 %

1H-NMR (D2O, pH=12): 9.06 (s, 8H), 8.24 (d, J = 6.36Hz, 8H), 8.21 (d, J = 6.36Hz, 8H)

13C-NMR (D2O, pH=12):  115.17(s)a, 127.50(s)b, 131.86(s)c, 134.10(s)d, 143.59(s)e, 161.73(s)f, 175.65(s)g

29Si-NMR (D2O, pH=12):  -204.92(s)

N

N N

N

COO

-COO --OOC

COO

-Si

OH

OH

a b

c ed

f g

150430_SiTCPP_SiNMR_D2O_DSS_NaOD.002.esp

100 50 0 -50 -100 -150 -200 -250 -300

Chemical Shift (ppm) -0.2

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Normalized Intensity -204.92

-71.36

Si – 29 NMR of SiTCPP in D₂O – DSS

DSS -204.92

δ/ ppm

a) b)

- 32 -

IR in cm^-1 (KBr Method): 805 C-Hoop (aromatic), 1010 Si¬OH stretching, 1401-1243 C=C stretching 1607 C-O stretching, 1695 C=O stretching, 3064 C-H stretching, 3424 O-H stretching

UV-vis: 5.07 x 10⁵ M^-1dm^-3 (max = 417.5 nm in H2O, pH =11), 1.76 x 10⁴ M^-1dm³(

= 550nm in H2O, pH=11)

ESI-MS (positive mode in methanol): m/z = 847.32 (SiTCPP(OH)2)

Synthesis of trans-dihydroxo [5, 10, 15, 20-tetra(4-trifluoromethylphenyl)porphyrinato]

silicon (IV) : Si(IV)TFMPP(OH)2

Figure 31 Scheme of synthesis of trans-dihydroxo [5, 10, 15, 20-tetra(4-trifluoromethylphenyl)porphyrinato] silicon (IV)

Materials

5,10,15,20-Tetrakis(4-trifluoromethylphenyl)porphyrin(H2TFMPP)was purchased from Frontier scientific. DME (purchased from TCI chemicals) was stored over molecular sieves (4A), and dried over Na and vacuum transferred immediately prior to use. Lithium bis(trimethylsilyl)amide (LHMDS) solid purchased from Aldrich and stored in dry condition. Trichloro silane (HSiCl3) was purchased from TCI chemicals. AgOTf (Silver trifluoromethanesulfonate) was purchased from TCI chemicals

Synthesis

50 ml of DME was added to 100mg of free base 5, 10, 15, 20-tetra(4-trifluoromethylphenyl)porphyrin (H2TFMPP) and stirred at 80^oC for 30 minute. To the solution 40 mg of LHMDS was added and stirred at 80^oC for 3 hours. After 3hours UV

N NH N

HN

1. LHMDS / Dimethoxy ethane 80^C 3 hour 2. HSiCl3 / Dimethoxy ethane -25^C 1hour 3. AgOTf / Dimethoxy ethane 25^C 12 hour CF3

CF₃ F3C

CF₃

N

N N

N

CF3

CF₃ F3C

CF₃

Si

OTf

OTf

N

N N

N

CF3

CF₃ F₃C

CF₃

Si

OH

OH

4. NaOH / CH2Cl2 50^C 48hrs

- 33 -

visible spectrum of the reaction mixture was measured to confirm a red shift of Soret band to 436nm from 414nm, indicating the completion of reaction to form the lithium salt of pophyrin dianion (Li2TFMPP). The reaction mixture was then cooled down to -25^oC and kept at that temperature for 1 hour. To the reaction mixture 0.2ml of HSiCl3 was added and stirred at -25^oC for 30 minutes. The reaction pot was then slowly warmed up to room temperature and stirred for 1hour. An UV-Vis spectrum was measured to confirm a blue shift of Soret band to 431nm from 436nm indicating the completion of reaction to form SiTFMPP(Cl2). The reaction mixture is then slowly warmed to 25^oC and excess amount (144 mg) of AgOTf was added. The reaction mixture was kept for one overnight and UV visible spectrum measured. A blue shift of Soret band to 418.4 nm from 431nm indicated the formation of SiTFMPP(OTf)2). The reaction mixture was then filtered through 0.1μm PTFE to collect red-purple solid and subsequently be dried. The crude crystal was further stirred for 48hrs in a 1:1 mixture of DCM: aqueous solution of NaOH(1M). The aqueous layer was separated and purified by silica gel column chromatography using DCM as an eluent.

Figure 32 a) Assigning the ¹³C NMR values; b) ¹⁹F-NMR of SiTFMP (OH)2 in CDCl3

Characterisation

1H-NMR (CDCl3): 8.88 (s, 8H), 8.26 (d, J = 5.0Hz, 8H), 8.03 (d, J = 5.0Hz, 8H).

13C-NMR (CDCl3):  116.53(s)a, 124.21(s)b, 128.82(s)c, 134.19(s)d, 134.89(s)e, 143.28(s)f, 167.75(s)g.

19F-NMR (D2O): -62.23(s).

19F-NMR (CDCl3):  -62.23(s, 12F)

29Si-NMR (CDCl3):  -200.83(s).

N N N

N

CF₃

CF₃ F₃C

CF₃

Si

OH

OH

a b

d c

e f g

141117_SiT(PF)PP_CDCl3_19F.002.esp

-45 -50 -55 -60 -65 -70 -75 -80

Chemical Shift (ppm) 0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Normalized Intensity

12.00

-62.23

-62.23

δ/ ppm

a) b)

- 34 -

UV-vis: 4.57 x 10⁵ M^-1dm^-3 (max = 420 nm in acetone), 1.77 x 10⁴ M^-1dm^-3( = 552 nm in acetone).

ESI-MS (negative mode): m/z = 946.17.

Synthesis of trans-dihydroxo [-tetra pyridyl porphyrinate] silicon (IV) : SiTPyP(OH)2

Figure 33 Scheme of synthesis trans-dihydroxo [-tetra pyridyl porphyrinate] silicon (IV) : SiTPyP(OH)2

Materials

5,10,15,20-Tetrakis(tetra(4-pyridyl))porphyrin(H2TPyP)was purchased from TCI chemicals. DCM (purchased from TCI chemicals) was stored over molecular sieves (4A) and one overnight in K2CO3, and dried over CaH2 and vacuum transferred immediately prior to use. Lithium bis(trimethylsilyl)amide (LHMDS) solid purchased from Aldrich and stored in dry condition. Trichloro silane (HSiCl3) was purchased from TCI chemicals.

AgOTf (Silver trifluoromethanesulfonate) was purchased from TCI chemicals

Synthesis

The synthesis was carried out as a multi-step single pot synthesis till step 3 as shown in scheme 1.H2TPyP (160 mg, 0.25 mMol) was taken in reaction pot and kept under vacuum for 30 minutes, and then N2 was purged. 25 ml of DCM vacuum transferred to the reaction vessel and stirred under room temperature for 1 hour. To this LHMDS (85 mg, 0.5mMol)

N NH N

HN

N N

N

N

1. LHMDS / Dimethoxy ethane 80^C 3 hour 2. HSiCl3 / Dimethoxy ethane -25^C 1hour 3. AgOTf / Dimethoxy ethane 25^C 12 hour

N

N N

N

N N

N

N Si

OTf

OTf

N

N N

N

N N

N

N Si

OH

OH

4. NaOH / CH₂Cl₂ 50^C 48hrs

- 35 -

was added and stirred under room temperature for an overnight. The completion of step 1 was confirmed by a red shift in UV spectrum (414 nm to 432 nm) of reaction mixture.

The reaction mixture is then cooled to -30ºC and then TEA (0.1ml) HSiCl3 (25μl, 0.25 mMol) was added carefully. The reaction mixture was then slowly warmed to room temperature and stirred under room temperature for 12 hr. The completion of step 2 was confirmed by a blue shift in UV spectrum (432 nm to 427 nm) of reaction mixture. Then little excess of AgOTf was added to reaction mixture and stirred for one overnight under room temperature. The completion of step 3 was confirmed by a blue shift in UV spectrum (427 nm to 418 nm) of reaction mixture. The reaction mixture was then filtered through 0.1μm PTFE and celite to remove solid inorganic impurities.

Figure 34 a) Assigning the ¹³C NMR values; b) ¹³C-NMR of SiTPyP (OH)2 in CD3OH c) Axially Coordinated methanol peak in ¹³C-NMR

Characterisation:

Elemental Analysis: Observed C 67.77%, H 4.58%, N 14.92 %, Calculated for [Si (IV)TPyP(OH)2](2CH3OH), C 67.91%, H 4.61 %, N 15.08 %

1H-NMR (D2O): 9.00 (d, J = 5Hz, 8H), 8.97 (s, 8H), 8.15 (d, J = 5Hz, 8H)

13C-NMR (D2O):  115.15(s)a, 129.18(s)b, 131.88(s)c, 142.84.10(s)d, 147.90(s)e, 148.92(s) f, 149.43(s)g, -1.45(s)h.

29Si-NMR (CD3OH):  -200.37(s)

IR in cm^-1 (KBr Method): 794C-Hoop (aromatic), 1011 Si¬OH stretching, 1406 C=C stretching 1593 C=N stretching, 3000 C-H stretching, 3400 O-H stretching

UV-vis: 4.54 x 10⁵ M^-1dm^-3 (max = 419 nm in H2O in ethanol), 1.80 x 10⁴ M^-1dm³(

= 550nm in ethanol)

N

N N

N

N N

N

N Si OCH3

OCH3

a b c

d e h f g

δ/ ppm

a) b)

150301_SiTPyP_13C.002.esp

145 140 135 130 125 120 115

Chemical Shift (ppm) 0

0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055 0.060 0.065 0.070

Normalized Intensity 115.01115.15

129.11129.18

131.58131.88

142.84142.90

147.72147.86

148.92149.43

150301_SiTPyP_13C.002.esp

1 0 -1 -2 -3 -4 -5 -6 -7

Chemical Shift (ppm) -0.0005

0 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035

Normalized Intensity -1.44

c)

δ/ ppm

- 36 -

ESI-MS (positive mode in methanol): m/z = 661 (SiTPyP(OH))

Synthesis of trans-dihydroxo [tetra methyl pyridinium porphyrin sulphate]silicon (IV) : SiTMPyP(OH)2

Figure 35 Scheme of synthesis trans-dihydroxo [tetra methyl pyridinium porphyrin sulphate]silicon (IV)

Materials

trans-dihydroxo [-tetra pyridyl porphyrinate] silicon (IV) was synthesised in lab. DMF dry was purchased from Kanto chemicals. Dimethyl sulfate was purchased from TCI chemicals.

Synthesis

SiTMPyP was synthesised by the quaternisation of SiTPyP. SiTPyP (30 mg, 0.04mM) was taken in a reaction pot. 1 ml of DMF was added to reaction pot and refluxed at 100

oC for 1hour to this 0.1ml of dimethyl sulfate was added to reaction mixture and refluxed for one overnight the completion of reaction was confirmed by red shift of soret band from 415 nm to 423 nm. The reaction mixture then filtered through 0.1µm PTFE then dissolved in methanol and reprecipitated in ethanol and filtered to a get pure SiTMPyP as violet powder.

Figure 36 a) Assigning the ¹³C NMR values; b) ¹H-NMR of SiTMPyP (OH)2 in D2O

N NH N

HN

N N

N

N

DMF / Dimethyl Sulphate 120^C 12 hour

N N N

N

N N

N

N Si

OH

OH

N

N N

N

N N

N

N

Si CH₃

CH₃

H₃C

CH3 OH HO

a b

e

f g c

d

150531_SiTMPyP.esp

9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5

Chemical Shift (ppm) 0.0005

0.0010 0.0015

Normalized Intensity

12.46 7.98

7.95 8.35

o-Py Pyrrole

m-Py

Me-Py M01(d) M02(d)

4.61

8.708.71

9.069.13

a) b)

- 37 - Characterisation:

Elemental Analysis: Observed C 42.92%, H 3.77%, N 8.97 %, Calculated for [Si (IV)TMPyP(OH)2](4HSO4-), C 43.13%, H 3.62 %, N 9.15 %

1H-NMR (D2O): 9.13 (d, J = 6.36Hz, 8H), 9.06 (s, 8H), 8.71 (d, J = 6.36Hz, 8H), 4.61(s,12H)

13C-NMR (D2O):  48.32(s)a, 112.05(s)b, 132.11(s)c, 132.57(s)d, 133.27(s)e, 141.49(s)f, 144.40(s)g.

UV-vis: 3.13 x 10⁵ M^-1dm^-3 (max = 427 nm in H2O calculated for SiTMPyP(OH)2), 1.71 x 10⁴ M^-1dm³( = 550nm in H2O calculated for SiTMPyP(OH)2)

ESI-MS (positive mode in methanol): m/z = 448 [(SiTMPyP(SO42-)2)]²⁺/2

Figure 37 ESI MS of SiTMPyP in methanol

100 200 300 400 500 600 700 800 900 1000 0

200 400 600 800 1000 1200 1400

306.5

448.2

Intensity

m/z

448.0 448.5 449.0 449.5 450.0 450.5

0 200 400 600 800 1000 1200 1400 1600

450.2 449.7 449.2 448.7 448.2

Intensity

m/z

896/2

^N

N N

N N N

N

N

Si CH3

CH₃

H3C

CH3 SO₄

2-SO₄ 2-2⁺

2⁺

- 38 -

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