Anion-Selective Interaction and Colorimeter by an Optical Metalloreceptor Based on Ruthenium(II) 2,2‘-Biimidazole:  Hydrogen Bonding and Proton Transfer

Abstract

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.

Synthesis, characterization, antiproliferative and anti-metastatic properties of two ruthenium–DMSO complexes containing 2,2′-biimidazole

“…The average RueN bond length, 2.135(8) Å, is close to the bond lengths reported for other Ru(II)eH 2 biim complexes [12,26]. The bite angle involving coordinated H 2 biim (77.40 (10) ) is also similar to those found for other Ru(II)e H 2 biim complexes [12,26]. For complex 2 (Fig.…”

“…James and Kennedy have reported the synthesis and in vitro antiproliferative properties of a series of ruthenium(II) complexes containing 4,4 0 -biimidazole [10]. Metal complexes incorporating the heterocyclic ligand, 2,2 0 -biimidazole (H 2 biim), have drawn much attention as they can function as receptors for anions [11,12] and participate in self-assembling processes through hydrogen bonding interactions [13e15]. It has also been suggested that due to the presence of eNH in the ancillary H 2 biim, cobalt(III) mixed ligand complexes can bind to DNA through the groove via hydrogen bonding [16].…”

Binding of fluorine containing anions by new cationic Co(III) complex: Competitive interaction of chloride and hexafluorophosphate with [Co(phen)(H2biim)2]3+

“…In complex salts 1 and 2, 1 H and 13 C NMR chemical shift values are in good agreement with the literature values reported for related complexes [44][45][46]. Doublets in region 9.17-9.13, 7.98-7.93, 7.75-7.72, 7.57-7.53, 6.53-6.49, 6.38-6.37, singlet at 8.52-8.50 and triplet at 8.17-8.14 were assigned to protons H phen 2/9, H phen 4/7, H biim 5 0 ,H biim 5, H biim 4 0 , H biim 4, H phen 5/ 6, and H phen 3/8, respectively.…”

[Ru(tpy)(H4bbdip)]2+ as an anion-selective colorimetric sensor

“…The presence of multiple isosbestic points in the UV-vis adsorption titrations implied that a couple of species coexisted at the equilibrium. Based on the usual behavior of F − and OAc − [8][9][10], we deduced that they might interact with complex 1 via two simultaneous processes: hydrogen bonding and proton transfer on the N\H group of ligand H 4 bbdip to F − and OAc − .…”