Crystal structure of a host–guest complex between mephedrone hydrochloride and a tetraphosphonate cavitand

A new supramolecular complex (I) between the tetraphosphonate cavitand Tiiii[C3H7,CH3,C6H5] [systematic name: 2,8,14,20-tetrapropyl-5,11,17,23-tetramethyl-6,10:12,16:18,22:24,4-tetrakis(phenylphosphonato-O,O′)resorcin[4]arene] and mephedrone hydrochoride {C11H16NO+·Cl−; systematic name: methyl[1-(4-methylphenyl)-1-oxopropan-2-yl]azanium chloride} has been obtained and characterized both in solution and in the solid state. The complex of general formula (C11H16NO)@Tiiii[C3H7,CH3,C6H5]Cl·CH3OH or C11H16NO+·Cl−·C68H68O12P4·CH3OH, crystallizes in the monoclinic space group P21/c with one lattice methanol molecule per cavitand, disordered over two positions with occupancy factors of 0.665 (6) and 0.335 (6). The mephedrone guest interacts with the P=O groups at the upper rim of the cavitand through two charge-assisted N—H...O hydrogen bonds, while the methyl group directly bound to the amino moiety is stabilized inside the π basic cavity via cation...π interactions. The chloride counter-anion is located between the alkyl legs of the cavitand, forming C—H...Cl interactions with the aromatic and methylenic H atoms of the lower rim. The chloride anion is also responsible for the formation of a supramolecular chain along the b-axis direction through C—H...Cl interactions involving the phenyl substituent of one phosphonate group. C—H...O and C—H...π interactions between the guest and adjacent cavitands contribute to the formation of the crystal structure

Chemoselective recognition with phosphonate cavitands: the ephedrine over pseudoephedrine case

Complete discrimination of ephedrine and pseudoephedrine, both in solution and in the solid state, was achieved with a phosphonate cavitand receptor. The molecular origin of the epimer discrimination was revealed by the crystal structure of the respective complexes

Fully Reversible Guest Exchange in Tetraphosphonate Cavitand Complexes Probed by Fluorescence Spectroscopy

We report here the monitoring of reversible guest inclusion in phosphonate cavitands through a large increase in luminescence intensity caused by the modulation of the exoergonicity of an electron-transfer reaction

Cavitands Endow All-Dielectric Beads With Selectivity for Plasmon-Free Enhanced Raman Detection of <i>N</i>_ε‑Methylated Lysine

SiO₂/TiO₂ microbeads (T-rex) are promising materials for plasmon-free surface-enhanced Raman scattering (SERS), offering several key advantages in biodiagnostics. In this paper we report the combination of T-rex beads with tetraphosphonate cavitands (Tiiii), which imparts selectivity toward <i>N</i>_ε<i>-</i>methylated lysine. SERS experiments demonstrated the efficiency and selectivity of the T-rex-Tiiii assays in detecting methylated lysine hydrochloride (<i>N</i>_ε<i>-</i>Me-Lys-Fmoc) from aqueous solutions, even in the presence of the parent Lys-Fmoc hydrochloride as interferent. The negative results obtained in control experiments using TSiiii ruled out any other form of surface recognition or preferential physisorption. MALDI-TOF analyses on the beads exposed to <i>N</i>_ε<i>-</i>Me-Lys-Fmoc revealed the presence of the Tiiii•<i>N</i>_ε<i>-</i>Me-Lys-Fmoc complex. Raman analyses based on the intensity ratio of <i>N</i>_ε<i>-</i>Me-Lys-Fmoc and cavitand-specific modes resulted in a dose–response plot, which allowed for estimating the concentration of <i>N</i>_ε<i>-</i>methylated lysine from initial solutions in the 1 × 10^–3 to 1 × 10^–5 M range. These results can set the basis for the development of new Raman assays for epigenetic diagnostics

Cavitand-Grafted Silicon Microcantilevers as a Universal Probe for Illicit and Designer Drugs in Water

The direct, clean, and unbiased transduction of molecular recognition into a readable and reproducible response is the biggest challenge associated to the use of synthetic receptors in sensing. All possible solutions demand the mastering of molecular recognition at the solid–liquid interface as prerequisite. The socially relevant issue of screening amine-based illicit and designer drugs is addressed by nanomechanical recognition at the silicon–water interface. The methylamino moieties of different drugs are all first recognized by a single cavitand receptor through a synergistic set of weak interactions. The peculiar recognition ability of the cavitand is then transferred with high fidelity and robustness on silicon microcantilevers and harnessed to realize a nanomechanical device for label-free detection of these drugs in water

An electrochemiluminescent-supramolecular approach to sarcosine detection for early diagnosis of prostate cancer.

Monitoring Prostate Cancer (PCa) biomarkers is an efficient way to the early diagnosis of this disease, since it improves therapeutic success rate and suppress PCa patients mortality: for this reason a powerful analytical technique such as Electrochemiluminescence (ECL) is already used for this application, but its widespread usability is still hampered by the high cost of commercial ECL equipment. We describe an innovative approach for the selective and sensitive detection of the PCa biomarker sarcosine, obtained by a synergistic ECL-supramolecular approach, in which the free base form of sarcosine acts as co-reagent in a Ru(bpy)3 2+-ECL process. We used magnetic micro-beads decorated with a supramolecular tetraphosphonate cavitand (Tiiii) for the selective capture of sarcosine hydrochloride in a complex matrix like urine. Sarcosine determination was then obtained with ECL measurements thanks to the complexation proprieties of Tiiii, with a protocol involving simple pH changes - to drive the capturing-releasing process of sarcosine from the receptor - and magnetic micro-beads technology. With this approach we were able to measure sarcosine in the \u3bcM-mM window, a concentration range that encompasses the diagnostic urinary value of sarcosine in healthy subject and PCa patients, respectively. These results indicate how this ECL-supramolecular approach is extremely promising for the detection of sarcosine and for PCa diagnosis and monitoring, and toward the development of portable and more affordable devices

An electrochemiluminescence-supramolecular approach to sarcosine detection for early diagnosis of prostate cancer

Monitoring Prostate Cancer (PCa) biomarkers is an efficient way to diagnosis this disease early, since it improves the therapeutic success rate and suppresses PCa patient mortality: for this reason a powerful analytical technique such as electrochemiluminescence (ECL) is already used for this application, but its widespread usability is still hampered by the high cost of commercial ECL equipment. We describe an innovative approach for the selective and sensitive detection of the PCa biomarker sarcosine, obtained by a synergistic ECL-supramolecular approach, in which the free base form of sarcosine acts as co-reagent in a Ru(bpy)32+-ECL process. We used magnetic micro-beads decorated with a supramolecular tetraphosphonate cavitand (Tiiii) for the selective capture of sarcosine hydrochloride in a complex matrix like urine. Sarcosine determination was then obtained with ECL measurements thanks to the complexation properties of Tiiii, with a protocol involving simple pH changes – to drive the capture–release process of sarcosine from the receptor – and magnetic micro-bead technology. With this approach we were able to measure sarcosine in the mM to mM window, a concentration range that encompasses the diagnostic urinary value of sarcosine in healthy subjects and PCa patients, respectively. These results indicate how this ECL-supramolecular approach is extremely promising for the detection of sarcosine and for PCa diagnosis and monitoring, and for the development of portable and more affordable devices

Rapid screening and identification of illicit drugs by IR absorption spectroscopy and gas chromatography

Analytical instruments based on InfraRed Absorption Spectroscopy (IRAS) and Gas Chromatography (GC) are today available only as bench-top instrumentation for forensic labs and bulk analysis. Within the 'DIRAC' project funded by the European Commission, we are developing an advanced portable sensor, that combines miniaturized GC as its key chemical separation tool, and IRAS in a Hollow Fiber (HF) as its key analytical tool, to detect and recognize illicit drugs and key precursors, as bulk and as traces. The HF-IRAS module essentially consists of a broadly tunable External Cavity (EC) Quantum Cascade Laser (QCL), thermo-electrically cooled MCT detectors, and an infrared hollow fiber at controlled temperature. The hollow fiber works as a miniaturized gas cell, that can be connected to the output of the GC column with minimal dead volumes. Indeed, the module has been coupled to GC columns of different internal diameter and stationary phase, and with a Vapour Phase Pre-concentrator (VPC) that selectively traps target chemicals from the air. The presentation will report the results of tests made with amphetamines and precursors, as pure substances, mixtures, and solutions. It will show that the sensor is capable of analyzing all the chemicals of interest, with limits of detection ranging from a few nanograms to about 100-200 ng. Furthermore, it is suitable to deal with vapours directly trapped from the headspace of a vessel, and with salts treated in a basic solution. When coupled to FAST GC columns, the module can analyze multi-components mixes in less than 5 minutes

Toward street detection of amphetamines

A portable, advanced IR sensor in a hollow fiber matched to a silicon-micromachined fast gas chromatography column can analyze illegal stimulants and precursors with nanogram-level sensitivity