Synthesis and Characterization of Novel Acyclic, Macrocyclic, and Calix[4]arene Ruthenium(II) Bipyridyl Receptor Molecules That Recognize and Sense Anions

Abstract

The Lewis acidic redox-active and photoactive ruthenium(II) bipyridyl moiety in combination with amide (CO−NH) groups has been incorporated into acyclic, macrocyclic, and lower rim calix[4]arene structural frameworks to produce a new class of anion receptor with the dual capability of sensing anionic guest species via electrochemical and optical methodologies. Single-crystal X-ray structures of (1)Cl and (11)H2PO4 reveal the importance of hydrogen bonding to the overall anion complexation process. In the former complex, six hydrogen bonds (two amide and four C−H groups) stabilize the Cl- anion and three hydrogen bonds (two amide and one calix[4]arene hydroxyl) effect H2PO4 - complexation with 11. Proton NMR titration investigations in deuterated DMSO solutions reveal these receptors form strong and, in the case of the macrocyclic 5 and calix[4]arene-containing receptor 11, highly selective complexes with H2PO4 -. Cyclic and square-wave voltammetric studies have demonstrated these receptors to electrochemically recognize Cl-, Br-, H2PO4 -, and HSO4 - anions. The calix[4]arene anion receptor 11 selectively electrochemically senses H2PO4 - in the presence of 10-fold excess amounts of HSO4 - and Cl-. Fluorescence emission spectral recognition of H2PO4 - in DMSO solutions is displayed by 3, 5, and 11.

New insights into dihydrogenphosphate recognition with dirhenium(i) tricarbonyl complexes bridged by a thiourea moiety

“…Recently both Blažek et al 14 and Amendola et al 61 have also shown that the binding of phosphate to urea provides additional stability though the formation of secondary hydrogen bonds between the two phosphates groups. In addition a study by Gale and co-workers with a diindolylurea complex has also shown an anomalous interaction with [63][64][65] In the case of ligand L1, where only solution phase behaviour is available to us, and basing this on the previous observations, it is proposed that in solution, the second phosphate "piggy backs" on the first formally bonded anion (Figure 7b). This interaction, with a partial transfer of a proton from the thiourea to the anions then encourages one of the protons from the dihydrogenphosphate from the first anion onto the second, enhancing the anionic character of the formally bound anion thereby strengthening its interaction explaining the observed cooperativity, and the high binding constants.…”

Synthesis, X-ray Structure and Anion Binding Properties of the Novel Urea Derivatives of Calix[4]arene Dimer

“…Bridging reaction was carried out with the treatment of aminocalix [4]arene 1 11 with its isocyanate 2 which was prepared by treating 1 with TCF(trichloromethylformate) in 1,4-dioxane and used without separation. Bridge urea calix [4]arene dimer 3 was obtained in 40% yield from the column purification.…”

Structural Effects on the Langmuir Monolayers of Calix[4]arene Induced by Lower Rim Aromatic Substitution

“…Reduction with LiAlH 4 subsequently led to the amino derivative. 22,23 Then the lower rim calix [4]arene diamine was acylated by carboxylic acids directly with N,N'-dicyclohexylcarbodiimide (DCC) as an accelerator. 24 Thus, 0.2 mmol of DCC was added into a flask containing 3-5 mL of CHCl 3 and 0.2 mmol of RCO 2 H with stirring and cooled by an ice-water bath.…”