Two-Arm Ferrocene Amide Compounds:  Synclinal Conformations for Selective Sensing of Dihydrogen Phosphate Ion

Abstract

[structure: see text] Ferrocene compounds bearing multiple amido groups selectively bind with the H(2)PO(4)(-) ion over other anions. The one-arm receptors form 1:1 complexes with the H(2)PO(4)(-) ion, whereas the two-arm receptors can accommodate two H(2)PO(4)(-) ions. The complexation modes and binding strengths are deduced from the NMR, calorimetry, fluorescence, and cyclic voltammetry studies. The two-arm ferrocene hexamide receptors likely exist in synclinal conformations to incorporate tetrahydrofuran molecules and H(2)PO(4)(-) ions.

Syntheses and Characterisation of Diurea Molecular Tweesors for the Recognition of Anion

“…Urea -NHCONH-protons are seen as two doublets at 8.71 and 8.64 ppm. Urea, NHCONH protons for compound (11) seem to be more upfield than urea protons for compound (12).…”

“…For compound (11), the urea NH protons resonate as two singlets downfield at 8.706 ppm and 8.635 ppm. For compound (12) these two urea -NHCONH protons resonate at 8.614 ppm.Urea protons for compound (11) seems to be more upfield than that for compound (12). Methylene CH 2 protons show singlet resonance at 3.873 ppm and 3.859 ppm for (11) and (12) respectively, suggesting that there is no conformational rotation about the CH 2 unit of the 3,3' methylene dianiline scaffold on the NMR timescale.…”

“…Methylene CH 2 protons show singlet resonance at 3.873 ppm and 3.859 ppm for (11) and (12) respectively, suggesting that there is no conformational rotation about the CH 2 unit of the 3,3' methylene dianiline scaffold on the NMR timescale. For compound (11), aromatic protons resonate in the region 6.837 ppm to 7.464 ppm whereas for compound (12) this is seen at 6.847 to 7.462 ppm.…”

“…For compound (12), five sets of aromatic resonances were seen. Protons on ring C and D, H-8 and H-9 are seen as two sets of doublets.…”

“…Both symmetrical and unsymmetrically substituted derivatives can be synthesised. Neutral receptors of urea, thiourea and amides are of further significance because the transport of anions such as phosphate, PO 4 3 -anion through cell membranes is regulated by neutral binding proteins [9][10][11][12][13][14][15]. Also, neutral anion receptors, especially those of the amido type exploit hydrogen bonding interactions with anions and are found in biological systems.…”