Luminescent probes for indole-binding proteins derived from ruthenium(II) polypyridine complexes |
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| Authors: | Kenneth Kam-Wing Lo Terence Kwok-Ming Lee Kenneth Yin Zhang |
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| Institution: | Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, PR China |
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| Abstract: | We report here the synthesis, characterisation, electrochemical, photophysical and protein-binding properties of four luminescent ruthenium(II) polypyridine indole complexes Ru(bpy)2(L1)](PF6)2 (1), Ru(bpy)2(L2)](PF6)2 (2), Ru(L1)3](PF6)2 (1a), and Ru(L2)3](PF6)2 (2a) (bpy = 2,2′-bipyridine; L1 = 4-(N-(2-indol-3-ylethyl)amido)-4′-methyl-2,2′-bipyridine; L2 = 4-(N-(6-N-(2-indol-3-ylethyl)hexanamidyl)amido)-4′-methyl-2,2′-bipyridine). Their indole-free counterparts, Ru(bpy)2(L3)](PF6)2 (3) and Ru(L3)3](PF6)2 (3a) (L3 = 4-(N-(ethyl)amido)-4′-methyl-2,2′-bipyridine), have also been synthesised for comparison purposes. Cyclic voltammetric studies revealed ruthenium-based oxidation at ca. +1.3 V versus SCE and diimine-based reductions at ca. −1.20 to −2.28 V. The indole moieties of complexes 1, 2, 1a and 2a displayed an irreversible wave at ca. +1.1 V versus SCE. All the ruthenium(II) complexes exhibited intense and long-lived orange-red triplet metal-to-ligand charge-transfer 3MLCT (dπ(Ru) → π*(L1-L3)) luminescence upon visible-light irradiation in fluid solutions at 298 K and in alcohol glass at 77 K. The binding of the indole-containing complexes to bovine serum album (BSA) has been studied by quenching experiments and emission titrations. |
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| Keywords: | Bovine serum albumin Emission quenching Indole Luminescence Ruthenium(II) complexes |
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