Selective Recognition of Cyanide Anion via Formation of Multipoint NH and Phenyl CH Hydrogen Bonding with Acyclic Ruthenium Bipyridine Imidazole Receptors in Water

Abstract

Five imidazole-based anion receptors A-E are designed for cyanide anion recognition via hydrogen bonding interaction in water. Only receptors A [Ru(bpy)(2)(mpipH)](ClO(4))(2) (bpy is bipyridine and mpipH is 2-(4-methylphenyl)-imidazo[4,5-f]-1,10-phenanthroline) and E [Ru(2)(bpy)(4)(mbpibH(2))](ClO(4))(4) (mbpibH(2) is 1,3-bis([1,10]-phenanthroline-[5,6-d]imidazol-2-yl)benzene) selectively recognize CN(-) from OAc(-), F(-), Cl(-), Br(-), I(-), NO(3)(-), HSO(4)(-), ClO(4)(-), H(2)PO(4)(-), HCO(3)(-), N(3)(-), and SCN(-) anions in water (without organic solvent) at physiological conditions via formation of multiple hydrogen bonding interaction with binding constants of K(A(H2O)) = 345 ± 21 and K(E(H2O)) = 878 ± 41, respectively. The detection limits of A and E toward CN(-) in water are 100 and 5 μM, respectively. Receptor E has an appropriate pK(a2)* value (8.75) of N-H proton and a C-shape cavity structure with three-point hydrogen bonding, consisting of two NH and one cooperative phenyl CH hydrogen bonds. Appropriate acidity of N-H proton and multipoint hydrogen bonding are both important in enhancing the selectivity and sensitivity toward CN(-) in water. The phenyl CH···CN(-) hydrogen bonding interaction is observed by the HMBC NMR technique for the first time, which provides an efficient approach to directly probe the binding site of the receptor toward CN(-). Moreover, CN(-) induced emission lifetime change of the receptor has been exploited in water for the first time. The energy-optimized structure of E-CN adduct is also proposed on the basis of theoretical calculations.

Iodide Recognition and Sensing in Water by a Halogen‐Bonding Ruthenium(II)‐Based Rotaxane

“…44 Such an outer‐sphere anion coordination approach (with respect to the ruthenium metal centre) has previously been utilized for halide‐ and oxo anion‐sensing in organic solvents5 and for the sensing of phosphate45 and cyanide46 anions in aqueous media. But to the best of our knowledge, the detection of halide anions in 100 % water using this approach has not been reported.…”

Design and Synthesis of Some Imidazolyl Derivatives: Photophysical Studies and Application in the Detection of Anions

“…Thus, clearly suggested about the dual mode of interaction wherein, first Michael adduct was formed due to the nucleophile addition of cyanide at the dicyanovinyl fragment. The new entity so formed then further establish an interaction with -NH fragment of phenanthroimidazolyl was established [26,35] through the -N…CN…H type of hydrogen bonding leading to typical deprotonation of the N-H function [19 -29].…”

Synthesis and characterization of ruthenium(II) complexes incorporating 4′-phenyl-terpyridine and triphenylphosphine

“…They are used as light harvesters in dye-sensitized solar cells [2][3][4], luminescent emitters in light-emitting electrochemical cells [5][6][7], potential anticancer and imaging agents in phototherapy [8][9][10], sensors for ions [11][12][13][14][15][16] and small molecules [17,18], photocatalysts for water splitting [19,20], hydrogen production [21][22][23][24], CO 2 reduction [21,23,25], and many other chemical reactions [23,[26][27][28][29], components in mixed valence systems [30][31][32][33][34][35], light upconversion systems [36][37][38][39] and molecular memory devices [40][41][42].…”