TY - JOUR

T1 - New insights into dihydrogenphosphate recognition with dirhenium(I) tricarbonyl complexes bridged by a thiourea moiety

AU - Blackburn, Anna L.

AU - Baker, Naomi C. A.

AU - Fletcher, Nicholas C.

PY - 2014

Y1 - 2014

N2 - Three thiourea bridged 2,2'-bipyridine ligands bearing either a single thiourea group (L1), or two units separated by either a para (L2) or meta-substituted (L3) aromatic spacer, along with the corresponding bis(fac-tricarbonylrhenium(I)) complexes are reported. The three ligands all show the anticipated binding to acetate. However H-1 NMR titrations reveal an unusual cooperative binding to, and selectivity for, two dihydrogenphosphate ions. The rhenium(I) complexes similarly demonstrate unusual sigmoidal titration curves, and in the case of {Re(CO)(3)Br}(2)(mu-L1) a surprisingly strong interaction to two anions. These were further exemplified in the emissive behaviour leading to the conclusion that there is an unusual interaction with dihydrogenphosphate, giving an initial increase in the emission, followed by a decrease and a blue shift in wavelength possibly as a result of partial deprotonation. It appears that dihydrogenphosphate binds cooperatively, with the addition of a second anion enhancing the interaction of the first, probably by proton transfer; this could explain the remarkable selectivity for phosphate seen with many reported anion receptors.

AB - Three thiourea bridged 2,2'-bipyridine ligands bearing either a single thiourea group (L1), or two units separated by either a para (L2) or meta-substituted (L3) aromatic spacer, along with the corresponding bis(fac-tricarbonylrhenium(I)) complexes are reported. The three ligands all show the anticipated binding to acetate. However H-1 NMR titrations reveal an unusual cooperative binding to, and selectivity for, two dihydrogenphosphate ions. The rhenium(I) complexes similarly demonstrate unusual sigmoidal titration curves, and in the case of {Re(CO)(3)Br}(2)(mu-L1) a surprisingly strong interaction to two anions. These were further exemplified in the emissive behaviour leading to the conclusion that there is an unusual interaction with dihydrogenphosphate, giving an initial increase in the emission, followed by a decrease and a blue shift in wavelength possibly as a result of partial deprotonation. It appears that dihydrogenphosphate binds cooperatively, with the addition of a second anion enhancing the interaction of the first, probably by proton transfer; this could explain the remarkable selectivity for phosphate seen with many reported anion receptors.

KW - ANION-BINDING

KW - TETRAHEDRAL OXOANIONS

KW - RHENIUM(I) COMPLEXES

KW - DINUCLEAR RHENIUM(I)

KW - CRYSTALLINE CAPSULES

KW - SELECTIVITY TRENDS

KW - EXCITED-STATES

KW - RECEPTORS

KW - RUTHENIUM(II)

KW - BIPYRIDYL

U2 - 10.1039/c4ra00912f

DO - 10.1039/c4ra00912f

M3 - Journal article

VL - 4

SP - 18442

EP - 18452

JO - RSC Advances

JF - RSC Advances

SN - 2046-2069

IS - 35

ER -