Fighting cancer with metals: main focus on Rhemium(I) complexes

[摘要] In recent years, photodynamic therapy (PDT) has aroused significant interest as apotential method of treatment for certain cancers. A non-intrusive treatment, PDTconsequently overcomes various obstacles of currently available treatment methods,notably toxicity. However, PDT is not without its limitations. These include, althoughthey are not limited to, low selectivity and an inability to penetrate deep tissues. Toovercome such shortcomings, a range of rhenium(I) compounds of the type fac-[Re(CO)3(N,N'-bid(X)]n and cis-trans-[Re(CO)2(N,N'-bid)(X)2]n (n = 0, +1) weresynthesised, most of which displayed good yields, ranging from 38.10 to 85.90 % fortricarbonyl and 12.80 to 80.30 % for dicarbonyl complexes, and characterised. Fourbimetallic complexes [(Cl2)Pt(O,O'-phenO2-N,N')-Re(CO)3(Br)], [(Cl2)Pd(O,O'-phenO2-N,N')-Re(CO)3(Br)], [(Cl2)Pt(O,O'-phenO2-N,N')-Ru(bpy)2][PF6]2�?H2O, and[(Cl2)Pd(O,O'-phenO2-N,N')-Ru(bpy)2][PF6]2 �?2H2O were synthesised andcharacterised. However, low yields ranging from 10.66 to 45.52 % were obtained.Two 99mTc complexes, cis-trans-[99mTc(CO)2(bpy)(PPh3)2]+ and cis-trans-[99mTc(CO)2(bpy)(PTA)2]+ were synthesised and isolated with retentiontimes of 16.928 and 11.385 minutes respectively.The crystal structure of fac-[Re(CO)3(bpy)(Br)] was obtained and solved and isreported in this study. The rhenium to nitrogen bond distances (Re1-N1, Re1-N2) arereported as 2.171(4) Å and 2.170(4) Å with a bite-angle (N2-Re1-N1) of 74.95(16)°,while the rhenium to bromido bond distance was 2.6126(15) Å. The rhenium tocarbonyl carbon bond distances range from 1.912(6) Å to 2.008(7) Å. A distortion ofthe octahedral sphere is confirmed by the angles N1-Re1-Br1, N2-Re1-Br1, and C1-Re1-Br1 which are 85.66(11)°, 83.50(11)° and 176.16(15)° respectively. A dihedralangle of 7.028(15)° was reported between the equatorial plane and the plane throughthe 2,2'-bipyridine system. A hydrogen bonding interaction is observed between H6and Br1, while three π-interactions are observed in fac-[Re(CO)3(bpy)(Br)].The photoluminescent properties of eleven rhenium(I) compounds were determinedand emission wavelengths ranging from 604 to 650 nm were found for Re(I)tricarbonyl complexes and 610 to 670 nm in Re(I) dicarbonyl complexes. The highest emission wavelength was obtained from the water soluble complexcis-trans-[Re(CO)2(bpy)(PTA)2][NO3] in CH3OH solution. This emission wassignificantly higher than the same complex in aqueous solution, which displayed anemission wavelength of 642 nm. A second water soluble complex,fac-[Re(CO)3(bpy)(PTA)][NO3], was studied in both CH3OH and aqueous solution.This compound showed a similar trend to cis-trans-[Re(CO)2(bpy)(PTA)2][NO3],namely that the emission of these water soluble complexes is higher in CH3OH thanin aqueous solution.

[发布机构] University of the Free State