Anion-selective interaction and colorimeter by an optical metalloreceptor based on ruthenium(II) 2,2'-biimidazole: hydrogen bonding and proton transfer.
A new anion sensor [Ru(bpy)2(H2biim)](PF6)2 (1) (bpy = 2,2'-bipyridine and H2biim = 2,2'-biimidazole) has been developed, in which the Ru(II)-bpy moiety acts as a chromophore and the H2biim ligand as an anion receptor via hydrogen bonding. A systematic investigation shows that 1 is an eligible sensor for various anions. It donates protons for hydrogen bonding to Cl-, Br-, I-, NO3-, HSO4-, H2PO4-, and OAc- anions and further actualizes monoproton transfer to the OAc- anion, changing color from yellow to orange brown. The fluoride ion has a high affinity toward the N-H group of the H2biim ligand for proton transfer, rather than hydrogen bonding, because of the formation of the highly stable HF2- anion, resulting in stepwise deprotonation of the two N-H fragments. These processes are signaled by vivid color changes from yellow to orange brown and then to violet because of second-sphere donor-acceptor interactions between Ru(II)-H2biim and the anions. The significant color changes can be distinguished visually. The processes are not only determined by the basicity of anion but also by the strength of hydrogen bonding and the stability of the anion-receptor complexes. The design strategy and remarkable photophysical properties of sensor 1 help to extend the development of anion sensors.
Cui
Ying
Y
MOE Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, China.
Mo
Hao-Jun
HJ
Chen
Jin-Can
JC
Niu
Yan-Li
YL
Zhong
Yong-Rui
YR
Zheng
Kang-Cheng
KC
Ye
Bao-Hui
BH
D000838:Anions; D003124:Colorimetry / Q000379:methods*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D008968:Molecular Conformation; D055095:Optics and Photonics; D010777:Photochemistry / Q000379:methods; D011522:Protons; D012428:Ruthenium / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
D000838:Anions; D007093:Imidazoles; D008024:Ligands; D011522:Protons; C065541:2,2'-biimidazole; D012428:Ruthenium