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Subcomponent self-assembly relies on cation coordination whereas the roles of anions often only emerge during the assembly process. When sites for anions are instead pre-programmed, they have the potential to be used as orthogonal elements to build up structure in a predictable and modular way. We explore this idea by combining cation (M + ) and anion (X − ) binding sites together and show the orthogonal and modular build up of structure in a multi-ion assembly. Cation binding is based on a ligand (L) made by subcomponent metal-imine chemistry (M + = Cu + , Au + ) while the site for anion binding (X − = BF 4 − , ClO 4 − ) derives from the inner cavity of cyanostar (CS) macrocycles. The two sites are connected by imine condensation between a pyridyl-aldehyde and an aniline-modified cyanostar. The target assembly [LM-CS-X-CS-ML], + generates two terminal metal complexation sites (LM and ML) with one central anion-bridging site (X) defined by cyanostar dimerization. We showcase modular assembly by isolating intermediates when the primary structure-directing ions are paired with weakly coordinating counter ions. Cation-directed (Cu + ) or anion-bridged (BF 4 − ) intermediates can be isolated along either cation–anion or anion–cation pathways. Different products can also be prepared in a modular way using Au + and ClO 4 − . This is also the first use of gold( i ) in subcomponent self-assembly. Pre-programmed cation and anion binding sites combine with judicious selection of spectator ions to provide modular noncovalent syntheses of multi-component architectures. 

The supramolecular recognition of anions is increasingly harnessed to achieve the self‐assembly of supramolecular architectures, ranging from cages and polymers to (pseudo)rotaxanes. The cyanostar (CS) macrocycle has previously been shown to form 2 : 1 complexes with organophosphate anions that can be turned into [3]rotaxanes by stoppering. Here we achieved steric control over the assembly of pseudorotaxanes comprising the cyanostar macrocycle and a thread that is based, for the first time, on organo‐pyrophosphonates. Subtle differences in steric bulk on the threads allowed formation of either [3]pseudorotaxanes or [2]pseudorotaxanes. We demonstrate that the threading kinetics are governed by the steric demand of the organo‐pyrophosphonates and in one case, slows down to the timescale of minutes. Calculations show that the dianions are sterically offset inside the macrocycles. Our findings broaden the scope of cyanostar‐anion assemblies and may have relevance for the design of molecular machines whose directionality is a result of relatively slow slipping.

 

We report the magnetic and magnetostrictive behaviors of the pseudobinary ferrimagnetic spinel oxide system (1−x)CoFe2O4–xCoAl2O4 [Co(Fe1−xAlx)2O4], with one end-member being the ferrimagnetic CoFe2O4 and the other end-member being CoAl2O4 that is paramagnetic above 9.8 K. The temperature spectra of magnetization and magnetic susceptibility were employed to detect the magnetic transition temperatures and to determine the phase diagram of this system. Composition dependent and temperature dependent magnetostrictive behaviors reveal an exotic phase boundary that separates two ferrimagnetic states: At room temperature and under small magnetic fields (∼500 Oe), Fe-rich compositions exhibit negative magnetostriction while the Al-rich compositions exhibit positive magnetostriction though the values are small (<10 ppm). Moreover, the compositions around this phase boundary at room temperature (x = 0.35, 0.4, 0.45, 0.5) exhibit near-zero magnetostriction and enhanced magnetic susceptibility, which may be promising in the applications for magnetic cores, current sensors, or magnetic shielding materials. 

Phosphate oxyanions play central roles in biological, agricultural, industrial, and ecological processes. Their high hydration energies and dynamic properties present a number of critical challenges limiting the development of sensing technologies that are cost‐effective, selective, sensitive, field‐deployable, and which operate in real‐time within complex aqueous environments. Here, a strategy that enables the fabrication of an electrolyte‐gated organic field‐effect transistor (EGOFET) is demonstrated, which overcomes these challenges and enables sensitive phosphate quantification in challenging aqueous environments such as seawater. The device channel comprises a composite layer incorporating a diketopyrrolopyrrole‐based semiconducting polymer and a π‐conjugated penta‐t‐butylpentacyanopentabenzo[25]annulene “cyanostar” receptor capable of oxyanion recognition and embodies a new concept, where the receptor synergistically enhances the stability and transport characteristics via doping. Upon exposure of the device to phosphate, a current reduction is observed, consistent with dedoping upon analyte binding. Sensing studies demonstrate ultrasensitive and selective phosphate detection within remarkably low limits of detection of 178 × 10⁻¹²m(17.3 parts per trillion) in buffered samples and stable operation in seawater. This receptor‐based doping strategy, in conjunction with the versatility of EGOFETs for miniaturization and monolithic integration, enables manifold opportunities in diagnostics, healthcare, and environmental monitoring.