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Supplementary Information

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31P NMR Study of the Activated Radioprotection Mechanism of Octylphenyl-N,N-diisobutylcarbamoylmethyl Phosphine Oxide (CMPO) and Analogues

Gregory P. Horne, James J. Kiddle, Christopher A. Zarzana, Cathy Rae, Julie R. Peller, Andrew R. Cook, Stephen P. Mezyk, and Bruce J. Mincher

Dioctyl(phenyl) phosphine oxide (DOPPO) Nitric Acid Complex DFT Structure

Figure S1. Molecular geometry for the [DOPPO•HNO3] complex calculated using the B3LYP functional and the 6-31G(d) basis set. Phosphorous atoms are shown in orange, oxygen in red, nitrogen in blue, carbon in grey, and hydrogen in off white.

Octylphenyl-N,N-diisobutylcarbamoylmethyl Phosphine Oxide (CMPO) 31P NMR Spectra

0.0 0.5 1.0 1.5 2.0 2.5 3.00

2

4

6

8

10

Dd / p

pm

[HNO3](aq) / M

Figure S2. Observed change in 31P NMR chemical chift of CMPO upon complexation with HNO3 as a function of HNO3 concentration. First-order fitted line to guide the eye.

Electronic Supplementary Material (ESI) for Dalton Transactions.This journal is © The Royal Society of Chemistry 2019


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Figure S3. Organic phase 31P NMR spectra for 0.1 M CMPO/n-dodecane pre-equilibrated with 3.0 M aqueous acid (HNO3, DNO3, H2SO4, HCl, and HClO4).

CMPO Organic-Only

CMPO:HNO3

CMPO:DNO3

CMPO:H2SO4

CMPO:HClO4

CMPO:HCl


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Figure S4. Organic phase 31P NMR spectra for 0.1 M CMPO/n-dodecane pre-equilibrated with varying concentrations of HNO3.

CMPO:1.5 M HNO3

CMPO:0.1 M HNO3

CMPO:1.0 M HNO3

CMPO:2.0 M HNO3

CMPO:3.0 M HNO3


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Figure S5. Organic phase 31P NMR spectra for irradiated n-dodecane and post-irradiation equilibrated with 0.1 M CMPO.

300 kGy

100 kGy

0 kGy


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Figure S6. Organic phase 31P NMR spectra for irradiated n-dodecane solution pre-equilibrated with water and post-irradiation equilibrated with 0.1 M CMPO: (A) organic phase only or (B) biphasic solution.

(A)

(B)

0 kGy

100 kGy

300 kGy

0 kGy

100 kGy

300 kGy


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Figure S7. Organic phase 31P NMR spectra for irradiated n-dodecane solution pre-equilibrated with 0.1 M HNO3 and post-irradiation equilibrated with 0.1 M CMPO: (A) organic phase only or (B) biphasic solution.

(B)

0 kGy

100 kGy

300 kGy

0 kGy

100 kGy

300 kGy

(A)


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Figure S8. Organic phase 31P NMR spectra for irradiated n-dodecane solution pre-equilibrated with 3.0 M HNO3 and post-irradiation equilibrated with 0.1 M CMPO: (A) organic phase only or (B) biphasic solution.

(A)

(B)

0 kGy

100 kGy

300 kGy

0 kGy

100 kGy

300 kGy


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Figure S9. Organic phase 31P NMR spectra for formally organic-only CMPO/n-dodecane as a function of absorbed gamma dose.

CMPO 0 kGy

CMPO 100 kGy

CMPO 200 kGy

CMPO 300 kGy

CMPO 400 kGy

CMPO 500 kGy


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Figure S10. Organic phase 31P NMR spectra for formally CMPO/n-dodecane contacted with 0.1 M HNO3 as a function of absorbed gamma dose.

CMPO 0 kGy

CMPO 100 kGy

CMPO 250 kGy

CMPO 300 kGy

CMPO 400 kGy

CMPO 500 kGy


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Figure S11. Organic phase 31P NMR spectra for formally CMPO/n-dodecane contacted with 3.0 M HNO3 as a function of absorbed gamma dose.

CMPO 0 kGy

CMPO 100 kGy

CMPO 200 kGy

CMPO 300 kGy

CMPO 400 kGy

CMPO 500 kGy


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Dioctyl(phenyl) phosphine oxide (DOPPO) 31P NMR Spectra

Figure S12. Organic phase 31P NMR spectra for formally organic-only DOPPO/n-dodecane as a function of absorbed gamma dose.

DOPPO 0 kGy

DOPPO 50 kGy

DOPPO 100 kGy

DOPPO 200 kGy

DOPPO 300 kGy

DOPPO 400 kGy


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Figure S13. Organic phase 31P NMR spectra for formally DOPPO/n-dodecane contacted with 0.1 M HNO3 as a function of absorbed gamma dose.

DOPPO 0 kGy

DOPPO 100 kGy

DOPPO 250 kGy

DOPPO 300 kGy

DOPPO 400 kGy

DOPPO 500 kGy


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Figure S14. Organic phase 31P NMR spectra for formally DOPPO/n-dodecane contacted with 3.0 M HNO3 as a function of absorbed gamma dose.

DOPPO 0 kGy

DOPPO 50 kGy

DOPPO 100 kGy

DOPPO 200 kGy

DOPPO 400 kGy

DOPPO 500 kGy


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Trioctyl phosphine oxide (TOPO) 31P NMR Spectra

Figure S15. Organic phase 31P NMR spectra for formally organic-only TOPO/n-dodecane as a function of absorbed gamma dose.

TOPO 0 kGy

TOPO 50 kGy

TOPO 100 kGy

TOPO 200 kGy

TOPO 400 kGy

TOPO 300 kGy


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Figure S16. Organic phase 31P NMR spectra for formally TOPO/n-dodecane contacted with 0.1 M HNO3 as a function of absorbed gamma dose.

TOPO 0 kGy

TOPO 100 kGy

TOPO 250 kGy

TOPO 300 kGy

TOPO 400 kGy

TOPO 500 kGy


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Figure S17. Organic phase 31P NMR spectra for formally TOPO/n-dodecane contacted with 3.0 M HNO3 as a function of absorbed gamma dose.

TOPO 0 kGy

TOPO 50 kGy

TOPO 100 kGy

TOPO 200 kGy

TOPO 400 kGy

TOPO 500 kGy


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Identification of CMPO Radiolytic Degradation Products using LC-MS

Ultra-high performance liquid chromatography coupled to a mass spectrometer with an electrospray ionization source (LC-ESI-MS) was used to identify the radiolytic degradation products of CMPO. Additionally, the mass spectrometer used here has a mass accuracy of better than 2 millimass units, enabling unambiguous molecular formula for compounds in the mass range of potential CMPO degradation products. Irradiated samples of CMPO were analyzed using a Dionex (now Thermo Fisher Scientific, Waltham, MA, USA) Ultimate 3000 ultra-high-pressure liquid chromatograph (UHPLC) with a Bruker (Billerica, MA, USA) micrOTOF-Q II quadrupole time-of-flight mass spectrometer with electrospray ionization. Separation was achieved using a Phenomenex Kinetex® 1.7 µm XB-C18 column (150 × 2.1 mm) with a flow rate of 600 µL min−1. All solvents used were Sigma Aldrich (St. Louis, MO, USA) Hypergrade for LC-MS LiChrosolv® grade. The aqueous mobile phase component was water with 0.1% (v/v) formic acid, and the organic component was acetonitrile with 0.1% (v/v) formic acid. A gradient elution profile was used. The column was equilibrated at 40% organic for 3 minutes, followed by a ramp to 60% organic over 3 minutes, a ramp to 97% organic over 1 min, and held at 97% organic for 2 minutes, before a 0.5 min ramp back to the initial conditions. The mass spectrometer source and tuning parameters can be found in Table S2. Mass calibration was achieved using sodium formate clusters by infusing a tune mixture during each chromatographic run via a divert valve on the mass spectrometer. Using this mass calibration procedure, the mass spectrometer routinely achieves mass accuracy of ≤ 2 millimass units (mDa). The proposed structured of the two major degradation products identified are based on exact mass measurements and tandem mass spectrometry (MS2) experiments were performed using collision-induced dissociation. It should be noted that with this instrument, especially for low abundance peaks (which for these experiments included Compounds 1 and 2), there can be a slight mass shift for peaks in MS2 mode compared to normal MS1 mode. Exact masses reported in Table S1 correspond to the mass measured in MS1 mode. All other peaks in the chromatograms were assigned to contaminants.

Because standards were not available, the concentrations of the two identified degradation products (Figure S18) could not be quantified as a function of absorbed dose. However, the signals for both compounds did increase with absorbed dose.


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Table S1: Liquid chromatography compound table for irradiated CMPO samples. The R-groups in the structures correspond to octyl (C8H17) groups.

Compound Retention Time (min)

Measured Mass [M+H+] (Da)

Proposed Formula Theoretical Mass [M+H+] (Da)

Mass Error (Da)

Structure

1 1.1 297.160 C16H26O3P 297.161 -0.001

2 2.0 352.240 C20H35NO2P 352.240 -0.000

CMPO 5.3 408.302 C24H43NO2P 408.303 -0.001


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Figure S18. Radiolytic fragmentation scheme for CMPO based on the identified degradation products.


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Figure S19: Collision-induced dissociation fragmentation (MS2) spectrum of CMPO.

50 100 150 200 250 300 350 400 450

0

20

40

60

80

100

130.157

154.158

237.140

278.165

279.153

352.236Rela

tive A

bundance (

%)

m/z

35 eV

408.302

-C4H8

56.066

74.071

-(C4H8+H2O)

129.149

-C8H19N

171.162

-C10H21NO

278.145

-C16H23O2P

254.144

-(C14H21OP+H2O)


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Figure S20: Collision-induced dissociation fragmentation (MS2) spectrum of Compound 1, m/z = 297.160.

200 300

0

20

40

60

80

100237.138

279.149

Re

lative

Ab

und

ance (

%)

m/z

297.155

20 eV

18.006

-H2O

60.017

-C2H4O2


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Figure S21: Collision-induced dissociation fragmentation (MS2) spectrum of Compound 2, m/z = 352.240.

200 300 400

0

20

40

60

80

100

-C6H11N

97.087

255.149

237.139

278.166

Rela

tive A

bundance (

%)

m/z

352.236

35 eV

74.070

-C4H8

115.097

-C6H13NO


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Table S2: Bruker micrOTOF-Q II Instrument Parameters

Source Parameter Value Source Parameter Value

End-Plate Offset: 500 V Nebulizer: 3.0 bar

Capillary: 4500 V Dry Gas: 9.0 L/min

Dry Temp: 220 °C

Tune Parameter Value Tune Parameter Value

Funnel 1: 200.0 Vpp Funnel 2: 200.0 Vpp

Quad Ion Energy: 4.0 eV Low Mass Range: 40.000 m/z

Transfer Time: 80.0 µs Pre-Pulse Storage Time: 5.0 µs

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