Supporting Information
Ruthenium complexes with Lumazine derivatives: Structural, Electrochemical, Computational and Radical Scavenging Studies
Abimbola Adebisi,a Irvin Noel Booysen*,a Matthew Piers Akermana, Bheki Xulua
a School of Chemistry and Physics, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, Pietermaritzburg, South Africa.
N-1-[1,3,7-trimethyllumazine]benzohydride (bzlmz)
The synthetic procedure of the title compound was adopted from a method previously reported [1]. The condensation reaction of benzohydrazide (0.11 g; 0.81 mmol) and 6-acetyl-1,3,7-trimethyllumazine (almz) (0.20 g; 0.81 mmol) was conducted in ethanol (20 ml). The resultant reaction mixture was heated until reflux for 6 hours in the presence of a few drops of glacial acetic acid. A pale yellow solid formed which was filtered and washed with diethyl ether. Yield = 0.23 g (78%); M.P = 258 - 260˚C; IR (νmax/cm-1): ν(N-H)amide 3226 (w), υ(C=O)lumazine 1694 (br, s), υ(C=O)amide 1652 (br, s), υ(C=N)lumazine 1547 (m), ν(C-N)amide 1268 (m); 1H NMR (295K/ppm): 11.00 (s, 1H, N6-H), 9.36 (br, s, 2H, H14, H18), 7.72 – 7.40 (m, 3H, H15, H16, H17), 3.57 (s, 3H, C8-H3), 2.82 (s, 3H, N1-CH3), 2.65 (s, 3H, N2-CH3), 2.09 (s, 3H, C11-H3); UV-Vis (DCM, (λmax (ε, M-1cm-1))): 309 nm (17700); 351 nm (14400).
6-(hydroxyimino)ethyl)-1,3,7-trimethyllumazine (ohlmz)
The reaction of hydroxylamine hydrochloride (0.07 g; 1.01 mmol) and 6-acetyl-1, 3, 7-trimethyllumazine (almz) (0.20 g; 0.81 mmol) was carried out in 20 ml of ethanol under reflux for 6 hours in the presence of a few drops of glacial acetic acid from a method previously reported [2] . Slow evaporation of the solution gave a pale purple crystalline material. Yield = 0.17 g (81%); M.P = 240 - 242˚C; IR (νmax/cm-1): ν(N-H) 3440 (m), ν(O-H) 2901 (br, m), ν(C=O)lumazine 1707 (s), 1648 (vs, sh), ν(C=O)amide 1640 (br, s), ν(C=N)lumazine 1549 (s); 1H NMR (295 K/ppm): 11.68 (s, 1H, OH), 3.55 (s, 3H, C8-H3), 3.32 (d, 6H, N1-CH3, N2-CH3), 2.36 (s, 3H, C11-H3); UV-Vis (DCM, (λmax (ε, M-1cm-1))): 347 nm (8800).
Figure S1: 1H NMR spectrum of the free-ligand bzlmz in the region of 7.21 and 11.52 ppm.
Figure S2: 1H NMR spectrum of ohlmz. Inset: The methyl signals of ohlmz. The non-integrated signals are associated with deuterated dimethylsulphoxide.
Figure S3: Low resolution structure of complex 2.
Figure S4: Overlay IR spectra of complex 1 and its free-ligand, bzlmz in the region of 380 to 2000 cm-1.
Figure S5: Comparison between experimental- (a) and simulated (b) spectrum of 1.
Figure S6: Overlay IR spectra of complex 2 and its free-ligand, olmz in the region of 380 and 2000 cm-1.
This instrinsic molecular transformation of ohlmz is inititiated by Beckmann rearrangement of the oxime ohlmz (refer to Step A) [3], see Scheme S1. In step B, the resultant intermediate undergoes deacetylation which is accompanied by a reaction between the acetate group and acetic acid. In addition, ruthenium catalyzed demethylation of the diketonic aliphatic compound occurs [4]. Thereafter, the amido nitrogen undergoes ruthenium catalyzed oxidation to form a nitroso group, see Step C [5]. Subsequently, the nitroso oxygen is protonated and the methyl group bonds covalently to the aliphatic nitrogen, see Step D.
Scheme S1: A proposed synthetic route for Holmz.
Figure S7: 1H NMR spectrum of complex 1 in the region of 6.99 and 11.14 ppm.
Figure S8: 31P NMR spectrum of complex 1.
Figure S9: Overlay UV-Vis spectra of complex 1 and its free-ligand, bzlmz.
Figure S10: Overlay UV-Vis spectra of complex 2 and its free-ligand, ohlmz.
Figure S11: Solid state EPR spectrum of complex 2 at 298K.
Figure S12: Low resolution mass spectrum of complex 1. The mass spectrum indicates that the compound is highly ionisable which leads to an intricate fragmentation pattern. The [M-H2O-C7H8]+ peak of 1 is observed at m/z 799.1.
Figure S13: Low resolution mass spectrum of complex 2. The mass spectrum indicates that the compound is highly ionisable which leads to an intricate fragmentation pattern. The [M]+ peak of 1 is observed at m/z 684.0.
Figure S14: Overlay cyclic voltammograms of complexes 1 and 2 at 100 mV/s.
Figure S15: Overlay CVs of complex 2 at incrementing scan rates illustrating the diffusion-controlled behaviour of its redox couple.
Figure S16: A perspective view of the hydrogen-bonding occurring in 1; O4-HA····Cl2 = 2.22(5) Å [A] and O4-HB····N3 = 2.15(7) Å [B]. N6-H44····O4 = 2.02(4) Å [C].
Figure S17: A perspective view of the inter- and intramolecular interactions stabilizing the crystal lattice of 1.
References:
[1] Jiménez-Pulido SB, Linares-Ordóñez FM, Martínez-Martos JM, Moreno-Carretero MN, Quirós-Olozábal M, Ramírez-Expósito MJ (2008) J Inorg Biochem 102: 1677-1683.
[2] Jiménez-Pulido SB, Hueso-Ureña F, Fernández-Liencres MP, Fernández-Gómez M, Moreno-Carretero MN (2013) Dalton Trans 42: 530-541.
[3] Owston NA, Parker AJ, Williams JMJ (2007) Org Lett 9: 3599-3601.
[4] Leising RA, Ohman JS, Acquaye JH, Takeuchi KJ (I989) J Chem Soc Chem Commun 905-906; Older CM, Stryker JM (1998) Organometallics 17: 5596-5598.
[5] Jain SL, Sain B(2002) Chem Commun 1040-1041.
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