Chuandong Jia

An Electrochemical and Optical Anion Chemosensor Based on Tripodal Tris(ferrocenylurea)

A neutral tripodal tris(ferrocenylurea) anion receptor has been designed that can electrochemically and optically recognize sulfate and phosphate anions. The binding of the tetrahedral anion induced distinct cathodic shifts of the ferrocene/ferrocenium redox couple in chloroform, whereas the UV/Vis spectrum of the receptor showed an increase in the d-d transition band upon addition of sulfate ions. Furthermore, the anion complexes (TBA)2 · [SO4 ⊂L] · H2O (1) and TBA[F⊂L] (2; TBA = tetrabutylammonium ion) were isolated. Crystal structural analyses showed that the receptor in the two 1:1 (host/guest) complexes encapsulated sulfate or fluoride ions in the tripodal cavity through multiple hydrogen bonds. (1)H NMR spectroscopic and ESI mass-spectrometric analysis revealed strong sulfate and fluoride binding in solution.

Chloride Coordination by Oligoureas: From Mononuclear Crescents to Dinuclear Foldamers

A series of acyclic oligourea receptors which closely resemble the scaffolds and coordination behavior of oligopyridines have been synthesized. Assembly of the receptors with chloride ions afforded mononuclear anion complexes or dinuclear foldamers depending on the number of the urea groups.

A Colorimetric and Ratiometric Fluorescent Chemosensor for Fluoride Based on Proton Transfer

N-Phenyl-N’-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially 1H and 19F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (Rmax/Rmin = 2620) to fluoride. Taking H+ as the “recovering reagent”, the sensor can be reversibly “used” and “recovered” for several cycles with only a slight decay of the response ability.

Metallomacrocycle or helix: Supramolecular isomerism in bis(pyridylurea) metal complexes

Self-assembly of a flexible ligand, butylene bis(3-(3-pyridyl)urea) (L), with ZnCl2 in the presence of different guests results in a metallomacrocycle or a helical chain, the former entrapping a guest molecule in its cavity.

Coordination polymers derived from a flexible bis(pyridylurea) ligand: conformational change of the ligand and structural diversity of the complexes

The assembly of a bis(pyridylurea) ligand, N,N′-ethane-1,2-diylbis(3-pyridin-4-ylurea) (L), with Zn(AcO)2, CdCl2, CdSO4 or CuSO4 led to four coordination polymers, {[Zn(AcO)2L]·H2O·CH3OH}n (1), {[CdCl2L2]·2DMF}n (2), {[CdSO4L(H2O)3]·3H2O}n (3), and {[CuSO4L(H2O)2]·2H2O}n (4). Compound 1 is an infinite 1D zigzag chain with alternate Zn(AcO)2 units and L molecules. The cadmium(II) dichloro complex 2 features a corrugated sheet structure with a (4,4) net topology, while the sulfato complex 3 shows a unique 1O/2U interwoven 3D structure assembled from zigzag chains. The copper(II) complex 4 is an exceptional diamondoid network with an unusual 12-fold [6 + 6] interpenetration mode. Interestingly, the ligand shows the expected flexibility in the formation of the coordination polymers. In 1, 3 and 4, the central ethylene spacer adopts the anti conformations and is roughly linear, whereas in 2 it assumes a gauche form and exists as a V-shaped linker. The structural variation of these coordination polymers as well as the conformational change of the ligand in the presence of different counter anions and metal ions is discussed.

Sulphate binding by a quinolinyl-functionalised tripodal tris-urea receptor

A quinolinyl-functionalised tripodal tris(urea) receptor (L) has been designed for sulphate binding. The neutral receptor formed the 1:1 binding mode with sulphate ion (as tetrabutylammonium salt). However, when L interacted with H2SO4, a 2:1 (host/guest) complex (HL)2SO4·EtOH·12.5H2O (1) was isolated. Crystal structural analysis showed that the tertiary amine N atom of L is protonated, and the sulphate ion is located outside the receptor rather than inside the tripodal cleft. 1H NMR studies revealed that the 2:1 binding ratio was persistent in solution. Interestingly, the protonated receptor displayed an unusual enhanced binding for sulphate ion in aqueous environments because of the stronger electrostatic effect in the presence of water.

One-dimensional coordination polymers of a flexible bis(pyridylurea) ligand

The assembly of a bis(pyridylurea) ligand, N,N′-ethane-1,2-diylbis(3-pyridin-4-ylurea) (L), with Cu(AcO)2, CuCl2 or CoSO4 led to four 1D coordination polymers, {[Cu2(AcO)3(OH)L]·2.6H2O}n (1), {[CuL2(H2O)2]·2AcO·3CH3OH}n (2), {[CuL2(DMF)2]·2Cl·2H2O}n (3), and {[Co2L3(H2O)4(CH3OH)2]·2SO4·6H2O}n (4). The ligand exhibits the expected flexibility in the formation of the coordination polymers. Compounds 1, 2 and 3 are infinite 1D ribbon-like polymers with metal nodes and flexible ligands in bent/gauche (V-shaped) conformations, while complex 4 shows a 1D ladder structure. Interestingly, the ligand molecules show two different conformations (roughly linear GAG and V-shaped GAA; G = gauche, A = anti) in 4. The tetranuclear copper(II) complex 1 is analyzed by temperature-dependent magnetic measurements, and represents a rare example of a six-coordinate copper complex with an endohedral hydroxide anion.

CCDC 823696: Experimental Crystal Structure Determination

Related Article: Biao Wu, Chuandong Jia, Xiaolei Wang, Shaoguang Li, Xiaojuan Huang, Xiao-Juan Yang|2012|Org.Lett.|14|684|doi:10.1021/ol2031153