Publication | Closed Access
Synthesis, characterization, kinetic investigation and biological evaluation of Re(<scp>i</scp>) di- and tricarbonyl complexes with tertiary phosphine ligands
24
Citations
57
References
2019
Year
Rhenium(i) di- and tri-carbonyl complexes of the form fac-[Re(CO)<sub>3</sub>(L,L'-Bid)X] and [Re(CO)<sub>2</sub>(L,L'-Bid)X<sub>2</sub>], where X = aqua (H<sub>2</sub>O), methanol (CH<sub>3</sub>OH), triphenylphosphine (PPh<sub>3</sub>), 1,3,5-triaza-7-phosphaadamantane (PTA), tricyclohexylphosphine (PCy<sub>3</sub>) and L,L'-Bid = O,O' bidentate ligands (tropolone = TropH and 3-hydroxyflavone = FlavH) and N,O bidentate ligands (8-hydroxyquinoline = QuinH, 5,7-chloro-8-hydroxyquinoline = diCl-QuinH and quinoline-2,4-dicarboxylic acid = QuinH<sub>2</sub>), were synthesized and unambiguously characterized by <sup>1</sup>H-, <sup>13</sup>C-and <sup>31</sup>P-NMR, IR, UV/Vis and micro-analysis. The crystal structures of four complexes, namely fac-[Re(CO)<sub>3</sub>(QuinH)(H<sub>2</sub>O)]·H<sub>2</sub>O (5), fac-[Re(CO)<sub>3</sub>(Quin)(PPh<sub>3</sub>)] (11), fac-[Re(CO)<sub>3</sub>(diCl-Quin)(PPh<sub>3</sub>)] (12) and [Re(CO)<sub>2</sub>(Trop)(PPh<sub>3</sub>)<sub>2</sub>]·2C<sub>6</sub>H<sub>5</sub>CH<sub>3</sub> (20) were obtained. Re-P bonding distances for 11 and 12 are 2.4948(8) and 2.4908(8) Å, respectively, indicating the effect of the electron-withdrawing substituents of the diCl-Quin<sup>-</sup> ligand. The second-order rate constants for the substitutions of methanol at 25.1 °C in fac-[Re(CO)<sub>3</sub>(L,L'-Bid)(CH<sub>3</sub>OH)] (L,L'-Bid = Trop, Flav and QuinH) type complexes by different entering phosphine ligands (PPh<sub>3</sub>, PCy<sub>3</sub>, and PTA) varied between 7.23(7) × 10<sup>-5</sup> and 1.32(3) × 10<sup>-3</sup> M<sup>-1</sup> s<sup>-1</sup> and were found to depend on the coordinated bidentate ligand (in general k<sub>1</sub> (QuinH) < k<sub>1</sub> (Trop) < k<sub>1</sub> (Flav)). The toxicity of fac-[Re(CO)<sub>3</sub>(QuinH)(PTA)], fac-[Re(CO)<sub>3</sub>(Trop)(PTA)], fac-[Re(CO)<sub>3</sub>(Trop)(PPh<sub>3</sub>)] and fac-[Re(CO)<sub>3</sub>(Flav)(PPh<sub>3</sub>)] on the cervical cancer HeLa and epithelial RPE-1 cell lines was then evaluated. Complex fac-[Re(CO)<sub>3</sub>(Flav)(PPh<sub>3</sub>)] (16) and fac-[Re(CO)<sub>3</sub>(Trop)(PPh<sub>3</sub>)] (13) displayed the highest cytotoxicity with IC<sub>50</sub> values of 12.21 ± 0.17 μM and 13.35 ± 0.94 μM, respectively in HeLa cells. Interestingly, a small selectivity towards cancer over non-cancerous cells was observed for these compounds (IC<sub>50</sub> = 18.41 ± 3.16 μM and >25 μM in RPE-1 cells).
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