Smartphone-Based Sensing of Cortisol by Functionalized Rhodamine Probes.

During a stress condition, the human body synthesizes catecholamine neurotransmitters and specific hormones (called "stress hormones"), the most important of which is cortisol. The monitoring of cortisol levels should be extremely important to control the stress levels, and for this reason, it shows important medical applications. The common analytical methods (HPLC, GC-MS) cannot be used in real life, due to the bulky size of the instruments and the necessity of specialized personnel. Molecular probes solve these problems due to their fast and easy use. The synthesis of new fluorescent rhodamine probes, able to interact by non-covalent interactions with cortisol, the recognition properties in solution as well as in solid state by Strip Test, using a smartphone as detector, are here reported. DFT calculations and FT-IR measurements suggest the formation of supramolecular complexes through hydrogen bonds as main non-covalent interaction. The present study represents one of the first sensor, based on synthetical chemical receptors, able to detect cortisol in a linear range from 1 mM to 1 pM, based on non-covalent molecular recognition and paves the way to the realization of practical point-of-care device for the monitoring of cortisol in real live.

Aryl Boronic Acids in Columnar Stacked Co-crystalline Materials: Key-Factors Governing the Assembly with Quinones.

The assembly of aryl boronic acids B with quinones Q into columnar mixed stacked materials, as previously observed in the solid-state, has been here subjected to a detailed theoretical analysis focusing on the properties of the isolated synthons (HOMO-LUMO energies, electron affinity, ionization potential, reorganization hole/electron energies, partial Hirshfeld atomic charges and conformation stabilities) as well as those of the 1 : 1 adducts (Hirshfeld analysis, IRI surfaces, Hirshfeld atomic charges, hydrogen bond and slipped stacked π-π contributions). The overall picture obtained throught this study shows an intricate pattern of interconnected factors contributing to the formation and stability of the Bx Qy adducts, and it unveils the importance of parameters such as HOMO-LUMO gap, polarization and charge transfer, in addition to the more evident hydrogen bond and slipped-stacked π-π interactions in the formation of 1 : 1 adducts. An explanation has been also given for the presence in some Bx Qy adducts of the rare anti-anti conformation for the BO-H group with respect to the most studied and common anti-syn conformation.

Highly Selective Radical Monoreduction of Dihalides Confined to a Dynamic Supramolecular Host.

Reduction of alkyl dihalide guests (2-5 and 7) with trialkylsilanes (R3 SiH) was performed in water-soluble host 1 to investigate the effects of confinement on fast radical reactions (k≥103 m-1 s-1 ). High selectivity (>95 %) for mono-reduced products was observed for primary and secondary dihalide guests under mild conditions. The results highlight the importance of host-guest complexation rates to modulate the product selectivity in radical reactions.

Radical Reactions in Cavitands Unveil the Effects of Affinity on Dynamic Supramolecular Systems.

Radical reduction of alkyl halides and aerobic oxidation of alkyl aromatics are reported using water-soluble container compounds (1 and 2). The reductions involve α,ω-dihalides (4-8 and 10) with radical initiators in cavitand hosts with varied binding affinities. Product distributions lead to general guidelines for the use of dynamic supramolecular systems with fast reactions. The binding of guest substrates in the hosts must show high affinities (Ka > 103 M-1) to ensure that the reactions take place under confinement in the containers.

Binding orientation and reactivity of alkyl α,ω-dibromides in water-soluble cavitands.

Host-guest complexation of long chain α,ω-dibromides was evaluated in deep water-soluble cavitands 1 and 2. The bound dibromides (C7-C12) tumble rapidly on the NMR timescale and averaged signals were observed. The complexation allows mono hydrolysis of dibromides in aqueous solution. The arrangement of the products in the host-guest complex was fixed in an unsymmetrical manner that protects the guest from further reaction. Up to 93% yields of the mono-alcohols were obtained. The α,ω-dibromides formed a capsule with cavitand 2 and remained unreactive to hydrolysis.

Lipophilic N-Hydroxyphthalimide Catalysts for the Aerobic Oxidation of Cumene: Towards Solvent-Free Conditions and Back.

A new class of lipophilic N-hydroxyphthalimide (NHPI) catalysts designed for the aerobic oxidation of cumene in solvent-free conditions was synthesized and tested. The specific strategy proposed for the introduction of lipophilic tails on the NHPI moiety leads to lipophilic catalysts that-while completely preserving the activity of the precursor-allow the catalytic oxidation to be conducted in neat cumene, for the first time. The corresponding cumyl hydroperoxide is obtained in good yields (28-52 %) and with high selectivity (95-97 %), under mild conditions. Importantly, the presence of a polar solvent is no longer required to guarantee complete solubilization of the catalyst. On the other hand, the oxidation conducted in neat cumene reveals the unexpected necessity of using small amounts of acetonitrile to fully promote the hydrogen atom transfer process and prevent the catalyst from detrimental hydrogen-bond (HB) driven aggregation.

Functionalization of Cyclodextrins with N-Hydroxyphthalimide Moiety: A New Class of Supramolecular Pro-Oxidant Organocatalysts.

N-hydroxyphthalimide (NHPI) is an organocatalyst for free-radical processes able to promote the aerobic oxidation of a wide range of organic substrates. In particular, NHPI can catalyze the hydroperoxidation of polyunsaturated fatty acids (PUFA). This property could be of interest for biological applications. This work reports the synthesis of two ß-cyclodextrin derivatives (CD5 and CD6) having a different degree of methylation and bearing a NHPI moiety. These compounds, having different solubility in water, have been successfully tested for the hydroperoxidation of methyl linoleate, chosen as the PUFA model molecule.

Aerobic oxidation of alkylaromatics using a lipophilic N-hydroxyphthalimide: overcoming the industrial limit of catalyst solubility.

4,4'-(4,4'-Isopropylidenediphenoxy)bis(N-hydroxyphthalimide), which is a new lipophilic analogue of N-hydroxyphthalimide, can act as an effective catalyst in the aerobic oxidation of alkylaromatics under reduced amounts of polar cosolvent. The catalyst was selected on the basis of an in-depth study of the influence that substituents on the aromatic ring of N-hydroxyphthalimide exert on determining the NO-H bond dissociation energy (BDE). BDE values for a range of model molecules are calculated by DFT and measured by EPR spectroscopy. The new catalyst can be successfully employed in the aerobic oxidation of cumene, ethylbenzene, and cyclohexylbenzene, affording, in all cases, good conversions and high selectivity for the corresponding hydroperoxide. The effect of solvent, catalyst, and temperature has also been investigated.