Photophysical, electrochemical and anion sensing properties of Ru(ii) bipyridine complexes with 2,2′-biimidazole-like ligand

Abstract

A new anion sensor [Ru(bpy)(2)(DMBbimH(2))](PF(6))(2) (3) (bpy is 2, 2'-bipyridine and DMBbimH(2) is 7,7'-dimethyl-2,2'-bibenzimidazole) has been developed. Its photophysical, electrochemical and anion sensing properties are compared with two previously investigated systems, [Ru(bpy)(2)(BiimH(2))](PF(6))(2) (1) and [Ru(bpy)(2)(BbimH(2))](PF(6))(2) (2) (BiimH(2) is 2,2'-biimidazole and BbimH(2) is 2,2'-bibenzimidazole). The high acidity of the N-H fragments in these complexes make them easy to be deprotonated by strong basic anions such as F(-) and OAc(-), and they form N-H···X hydrogen bonds with weak basic anions like Cl(-), Br(-), I(-), NO(3)(-), and HSO(4)(-). Complex 3 displays strong hydrogen bonding with these 5 weak basic anions, with binding constants between 17,000 and 21,000, which are larger than those observed in complex 1, with binding constants between 3300 and 5700, and in complex 2, which shows no hydrogen bonding toward Cl(-), Br(-), I(-), and NO(3)(-), and forms considerable hydrogen bonds with HSO(4)(-) with a binding constant of 11,209. These hydrogen bonding behaviours give different NMR, emission and electrochemical responses. The different anion binding affinity of these complexes may be mainly attributed to their different pK(a1) values, 7.2 for 1, 5.7 for 2, and 6.2 for 3. The additional methyl groups at the 7 and 7' positions of complex 3 may also play an important role in the enhancement of anion binding strength.

Functional Dimming of Pincer‐Shaped Bibenzimidazole‐Ruthenium(II) Complexes with Improved Anion‐Sensitive Luminescence

“…Nonetheless, a considerable rise of luminescence intensity has been demonstrated for unsubstituted complexes of 2,2′-bibenzimidazole, and an improvement of this effect could be achieved through the introduction of a small pocket upon the methylation of the 4,4′-positions. [25] By using the procedure presented by Siegel et al for the synthesis of a wide variety of 4,4′-disubstituted 2,2′-bibenzimidazoles through a Negishi coupling route, we have recently reported the synthesis, photophysical, and structural characterization of new pincer-shaped ruthenium dyes with versatile supramolecular functions. [24] With the ability to introduce aromatic substituents (Scheme 1, R 1 ), a direct spatial influence on the H-bond pocket can be envisaged.…”

Ruthenium Imidazophenanthrolinium Complexes with Prolonged Excited‐State Lifetimes

“…[11][12][13][14] Owing to their remarkably stable photoredox chemistry, many ruthenium polypyridyl complexes are potent chromophores for lightdriven catalysis, [15,16] dye-sensitized solar cells, [17][18][19] and photocatalytic water splitting. [20,21] Crucial factors for their application herein are (1) high chemical stability, (2) intense absorption of visible light, (3) efficient population of a reactive charge-transfer (CT) excited state, and (4) long excitedstate lifetimes (up to the μs range).…”

Detection of NaCN in aqueous media using a calixarene-based fluoroionophore containing ruthenium(ii)-bipyridine as the fluorogenic unit

“…[36][37][38] The redox property of Ru(II) of 1 was investigated by recording cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV) in acetonitrile and the CV and DPV for the region 0.0 to +2.0 V are shown in Fig. S9.…”

“…Moreover the spectroscopic and electrochemical properties of metal ion can also be used for monitoring of the recognition event. [36][37][38] This new experimental procedure is given in the Experimental Section. Compound L was synthesized from compound C and F (scheme 1) in dry acetonitrile using Et 3 N as base under inert atmosphere.…”