Triazole appending ruthenium(ii) polypyridine complex for selective sensing of phosphate anions through C-H-anion interaction and copper(ii) ions via cancer cells

A new ruthenium(ii) polypyridine-based complex, [Ru-II(bpy)(2)(Btb)] 2PF(6)(-) (Rbtb) {bpy = 2,2 '-bipyridine and Btb = 2-((1-([2,2 '-bipyridin]-4-yl)-1H-1,2,3-triazol-4-yl)methoxy)-1,3-benzothiazole}, was constructed using a 1,2,3-triazole linker holding a benzothiazole moiety. The complex was confirmed by FT-IR, H-1 NMR, C-13 NMR, and mass spectroscopy. The detection properties were thoroughly checked with various anions and cations. The emission spectrum revealed that luminescence is enhanced by H2PO4-/H2P2O72- anions by similar to 2.3/1.9-fold in CH3CN and quenched (nearly 80%) by Cu2+ ions in CH3CN/10 mM HEPES buffer (pH = 7.4; 9/1 v/v). The H-1 NMR titration result exhibits basic H2PO4-/H2P2O72- anions interacting with acidic triazole C-H, as observed from the downfield shift. The increase and decrease of lifetime obeys the emission result, along with disturbance of the probe structural motif upon binding with anions (mainly by C-HMIDLINE HORIZONTAL ELLIPSISanion interaction) and cations (photoinduced electron transfer), respectively. Better detection limit and binding constant values were obtained for Rbtb upon treatment with H2PO4-/H2P2O72- anions (0.22/0.31 mu M and 7.7/4.2 x 10(4) M-1) and Cu2+ ions (0.7 mu M and 5.11 x 10(4) M-1). The generation of a new separate redox couple was noticed at 0.94 V and 0.45 V due to the interaction of H2PO4-/H2P2O72- anions and Cu2+ ions, respectively. The 1 : 1 binding ratio of Cu2+ ion with Rbtb was established by mass spectrum, and square-based geometry of Rbtb-Cu2+ was identified according to the EPR spectrum (g(||) > g(perpendicular to) > 2.0023 and A(||) = 134 x 10(-4) cm(-1)). Consequently, the luminescence intensity of Ru(bpy)(3) core is further tuned even with the disturbance of the acidic C-H proton of 1,2,3-triazole by H2PO4-/H2P2O72- anions. Here, 1,2,3-triazole could not coordinate primarily to ruthenium(ii), but bonded directly to the 4th position of 2,2 '-bipyridine in the primary ruthenium complex core. Rbtb exhibited low cytotoxicity against MCF-7 cell lines and was used for live-cell imaging of Cu2+ ion. The biological study shows that the complex stained the cytoplasm and nuclear membrane of the cells and specifically binds with the metal ion.