Towards a stronger halogen bond involving At – Investigation of halogen-bonded adducts of AtI and Bu3PO Lu Liu, Ning Guo, Julie Champion, Jérôme Graton, Gilles Montavon, Nicolas Galland, Rémi Maurice SUBATECH laboratory, Nantes, France [email protected] July 11th, 2019 1. Astatine Background Astatine << astatos (αστατος) Radioelement 2. No long-lived isotope (T1/2 ≤ 8.1h) Motivations Rarest naturally-occurring element Difficult to study Production of its isotopes limited by a cyclotron 3. Available at ultra-trace concentrations Methodology No spectroscopic tool applicable At-211: a promising candidate for nuclear medicine 4. Results Production At-211 in Nantes: E=28 MeV 4 209 211 2He + 83Bi → 85At + 2n 5. Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Conclusions Segrè are recognized that discovered and isolated astatine & at the University of California, Berkeley in 1940. 2 Perspectives 1. Halogen bonds involving At Background σ-hole Halogen bond: 2. Motivations 1 Halogen bond strength: the basicity scale with diiodine (pKBI2) 퐾 c p퐾 = log 퐾 B + I2 ՞ B ⋯ I − I BI2 c Et S 4 2 Bu SO Halogen bonds involving astatine 2 2 3. Ph3PS 3 Methodology (BuO)3PO 2 (EXP) Me(EtO) PO 2 Et2O BAtI ? K 1 Me6Ph log 4. 0 PrCOOEt Results log KBAtI = 1.56(22) pKBI2 MePh r2 = 0.86312 -1 -1 0 1 2 3 4 pKBI2 5. 푲퐁퐀퐭퐈 Objective : 퐀퐭퐈 + 퐁ഥ 퐁 ⋯ 퐀퐭퐈 Conclusions Stronger halogen-bond acceptors for AtI & 1. Laurence, C. et al. J. Chem. - A Eur. J. 2011, 17 (37), 10431. Perspectives 2. N. Guo et al., Nat. Chem., 2018, 10 (4), 1–7. 3 1. Background Methodology 5 Bu PO Et S 3 2 (expected) 4 Bu SO Lewis base: tri-n-butylphosphine oxide (Bu3PO) 2 Ph PS 3 2. 3 (BuO) PO Nucleophilic region 3 Motivations BAtI 2 K Me(EtO) PO log K =4.29 expected 2 BAtI Et2O o log 1 Me6Ph PrCOOEt 0 log K = 1.56(22) pK BAtI BI2 3. MePh r2 = 0.86312 1 Methodology pKBI2=2.75 -1 -1 0 1 2 3 4 Method: liquid/liquid competition pKBI2 Principle: change of distribution coefficient of astatine (D)change of astatine speciation 4. Results Information of the stoichiometry and the D equilibrium constant 5. Conclusions [L] & Perspectives 1. Laurence, C. et al. J. Chem. - A Eur. J. 2011, 17 (37), 10431. 4 1. Experimental protocol Background Organic phase: Cyclohexane with changing concentration of Bu3PO 2. Aqueous phase: 0.05M HClO4, [NaI]fixed = 0.01 M, 0.05 M, 0.07M, 0.1M and 0.2 M and At-211 Motivations 2 h shaking Cyclohexane 3. with Bu3PO Methodology 0.05 M HClO4 with NaI and At- 211 푉aq × 퐴org 퐷 = 푉 × 퐴 Change of Bu3PO concentration org aq 4. Results 5. Conclusions & 5 Perspectives 1. Experimental protocol Background Organic phase: Cyclohexane with changing concentration of Bu3PO 2. Aqueous phase: 0.05M HClO4, [NaI]fixed = 0.01 M, 0.05 M, 0.07M, 0.1M and 0.2 M and At-211 Motivations pH=1.35±0.1, E=0.55±0.05 vs. NHE - AtI2 3. Methodology 퐁퐮ퟑ퐏퐎 퐀퐭퐈 4. Results Pourbaix diagram of astatine in non- - 4 complexing aqueous medium 1-3 Speciation of At(+Ι) in function of [I ] 퐀퐭퐈 − 퐀퐭퐈ퟐ Only AtI is possible to interact with Bu3PO in the organic phase 퐈− 5. 1. J. Champion et al., J. Phys. Chem. A, 2010, 114 (1), 576–582. Conclusions 2. J. Champion et al., J. Phys. Chem. A, 2013, 117 (9), 1983–1990. & 3. D. C. Sergentu et al., Chem. - A Eur. J., 2016, 22 (9), 2964–2971. Perspectives 4. N. Guo et al., Angew. Chemie - Int. Ed., 2016, 55 (49), 15369–15372. 5 1. Model of experimental results Background Take the example of [I-]=0.1M Model 퐾 2. − − AtI + I ՞ AtI2 Motivations 3 10 퐷1 - -1 AtI ՞ AtI [I ] = 0.1 mol L 2 퐷2 10 B ՞ Bഥ 3. 퐾BAtI 101 AtI + Bഥ BAtI Methodology 퐁ഥ 퐀퐭퐈 0 10 퐁퐀퐭퐈 D -1 10 4. Results -2 퐀퐭퐈 10 − 퐀퐭퐈ퟐ 퐈− 10-3 퐁 10-6 10-5 10-4 10-3 10-2 10-1 5. Conclusions [Bu PO] / mol.L-1 3 & 6 Perspectives 1. Model of experimental results Background Take the example of [I-]=0.1M Model 퐾 2. − − AtI + I ՞ AtI2 Motivations 3 10 퐷1 AtI ՞ AtI [I-] = 0.1 mol L-1 2 퐷2 10 B ՞ Bഥ 3. 퐾BAtI 101 AtI + Bഥ BAtI Methodology 퐁ഥ 퐾 퐀퐭퐈 0 ഥ B2AtI 10 AtI + 2B B2AtI 퐁퐀퐭퐈 D 퐁 퐀퐭퐈 -1 ퟐ 10 4. Results -2 퐀퐭퐈 10 − 퐀퐭퐈ퟐ 퐈− 10-3 퐁 10-6 10-5 10-4 10-3 10-2 10-1 5. -1 Conclusions [Bu3PO] / mol L & 6 Perspectives 1. Model of experimental results Background Take the example of [I-]=0.1M Model 퐾 2. − − AtI + I ՞ AtI2 Motivations 3 10 퐷1 AtI ՞ AtI [I-] = 0.1 mol L-1 2 퐷2 10 B ՞ Bഥ 3. 퐾BAtI 101 AtI + Bഥ BAtI Methodology 퐁ഥ 퐾 퐀퐭퐈 0 ഥ B2AtI 10 AtI + 2B B2AtI 퐁퐀퐭퐈 D 퐁 퐀퐭퐈 -1 ퟐ 10 4. Results -2 퐀퐭퐈 10 − 퐀퐭퐈ퟐ 퐈− 10-3 퐁 10-6 10-5 10-4 10-3 10-2 10-1 5. -1 Conclusions [Bu3PO] / mol L & 6 Perspectives 1. Model of experimental results Background Take the example of [I-]=0.1M Model 퐾 2. − − AtI + I ՞ AtI2 Motivations 3 10 퐷1 - -1 AtI ՞ AtI [I ] = 0.1 mol L 퐷2 102 B ՞ Bഥ 3. 퐾BAtI 101 AtI + Bഥ BAtI Methodology 퐁ഥ 퐾B2AtI 퐀퐭퐈 0 ഥ 10 AtI + 2B B2AtI 퐁퐀퐭퐈 D 퐷3 퐁ퟐ퐀퐭퐈 -1 10 BAtI ՞ BAtI 4. 퐷4 Results -2 B2AtI ՞ B2AtI 퐀퐭퐈 10 − 퐀퐭퐈ퟐ − -3 퐈 퐁 10 퐁퐀퐭퐈 10-6 10-5 10-4 10-3 10-2 10-1 5. 퐁 퐀퐭퐈 -1 ퟐ Conclusions [Bu3PO] / mol.L & 6 Perspectives 1. Model of experimental results Background Take the example of [I-]=0.1M Model 퐾 2. − − AtI + I ՞ AtI2 Motivations 3 10 퐷1 - -1 AtI ՞ AtI [I ] = 0.1 mol L 퐷2 102 B ՞ Bഥ 3. 퐾BAtI 101 AtI + Bഥ BAtI Methodology 퐁ഥ 퐾B2AtI 퐀퐭퐈 0 ഥ 10 AtI + 2B B2AtI 퐁퐀퐭퐈 D 퐷3 퐁ퟐ퐀퐭퐈 -1 10 BAtI ՞ BAtI 4. 퐷4 Results -2 B2AtI ՞ B2AtI 퐀퐭퐈 10 − 퐀퐭퐈ퟐ 퐈− 10-3 퐁 -6 -5 -4 -3 -2 -1 퐁퐀퐭퐈 10 10 10 10 10 10 log KBAtI = 4.16±0.34 5. 퐁ퟐ퐀퐭퐈 Conclusions [Bu PO] / mol.L-1 3 log KB2AtI = 8.02±0.66 & 6 Perspectives 1. 1:1 complex: a stronger halogen bond Background 퐾 ഥ BAtI log K = 4.16±0.34 퐈퐀퐭 ⋯ 퐁 ？ AtI + B BAtI BAtI 2. 179.5° 5 Motivations Et S 2 Bu3PO 4 Bu SO 2 2.606 Å log KBAtI Ph3PS 3 (BuO) PO Experimental 4.16±0.34 3 BAtI BAtI 2 Me(EtO)2PO K 1 K Et O 3. dhf-SVPD-2c 4.54 2 log log 1 Methodology PrCOOEt Me Ph m-aug-cc-pVDZ-PP 1 4.37 6 0 log KBAtI = 1.56(22) pKBI2 MePh r2 = 0.86312 -1 -1 0 1 2 3 4 pKBI2 Good agreement with theoretical calculations 4. The most stable conformer of BAtI Results Follow the tendency of previous study Nearly directional interaction in the calculated structure 퐈퐀퐭 ⋯ 퐁 A stronger halogen bond involving astatine than we found before 5. Conclusions 1. Two-component B3LYP calculations in conjunction with dhf-SVPD-2c and aug-cc-pVDZ-PP (AVDZ) basis set. By Nicolas Galland (CEISAM) & 2. Calculated structures at the B3LYP/pVDZ level of theory for the most stable conformer specie corresponding to the interaction between AtI and Bu3PO. Perspectives By Nicolas Galland (CEISAM) 7 1. 1:2 complex: what it is ? Background 퐾B2AtI AtI + 2Bഥ B AtI log KB2AtI = 8.02±0.66 퐁 ⋯ 퐀퐭퐈 ⋯ 퐁 ? 2 2. Motivations 3. Methodology 4. Results 1 MEP of a) BAtI and b) AtI The most stable conformer of B2AtI Formation of a halogen bond deactivated the electrophilic site of iodine atom 5. 2 2 hydrogen bonds between two Bu3PO molecules in B2AtI 퐈퐀퐭 ⋯ ퟐ퐁 Conclusions 1. Molecular electrostatic potential calculated at the B3LYP/AVDZ level of theory. By Nicolas Galland (CEISAM) & 2. Calculated structures at the B3LYP/pVDZ level of theory for the most stable conformer specie corresponding to the interaction between AtI and Bu3PO. Perspectives By Nicolas Galland (CEISAM) 8 1. Conclusions and perspectives Background Conclusions 2. Motivations Two equilibria between AtI and Bu3PO were evidenced 퐾BAtI AtI + Bഥ BAtI, log KBAtI = 4.16±0.34 → A stronger halogen bond involving astatine 3. 퐾 ഥ B2AtI Methodology AtI + 2B B2AtI, log KB2AtI = 8.02±0.66 → First 1:2 complex between AtI and Lewis base but only one halogen bond involved in Perspectives 4. Results Stronger halogen bond acceptors for AtI Possibility to form B ⋯ AtI ⋯ B complex with Lewis base Interaction between AtX and Lewis bases with X = Br or Cl 5. Conclusions & 9 Perspectives Nicolas Galland Ning Guo Rémi Maurice Gilles Montavon Thanks for your attention! Julie Champion Jérôme Graton.