Solid-State Redox Chemistry: Preparation of 1,4-Naphthoquinone, Hydroquinone, and the Corresponding Mixed Quinhydrone in the Solid State

Procedure for synthesizing a mixed quinhydrone using solid-state methods

Preparation, Solid-State Characterization, and Computational Study of a Crown Ether Attached to a Squaramide.

[eng] Crystals of a disecondary squaramide covalently linked to a crown ether presents a great variety of inter- and intramolecular nonbonded interactions including C-H/ð contacts, C-HâââO and N-HâââO hydrogen bonds, and ð-ð stacking between squaramide rings. Latter interaction, the stacking between squaramide rings, can be considered as an experimental evidence for the proposed aromaticity of squaramide when it is forming hydrogen bonds, either as acceptor or donor

Squaramide as a binding unit in molecular recognition

[eng] Urea and squaramide are used as building blocks of powerful hosts which are involved in the molecular recognition of quaternary ammonium guests. Complexes of urea and squaramide with ammonium cations were studied using both high level MP2r6-311qGUU ab initio and molecular interaction potential with polarization and MEP calculations, in order to explore the physical nature of the interactions. The same procedure was applied to ammonium complexes with water and benzene as prototype models of crown ethers and calixarenes. Our findings reveal that either urea or squaramide are better binding units for the recognition of ammonium cations than water or benzene

MP2 study of the dual sigma/pi anion-binding affinity of fluorinated phthallic acid anhydrides

[eng] Several complexes of fluorine-substituted phthallic acid anhydrides with chloride anion have been optimized at the RI-MP2(full)/6-31++G** level of theory. The presence of fluorine atoms attached to the aromatic ring increases the acidity of the aromatic hydrogen atoms. The dual ó/ð-binding affinity of title compounds have been studied by means of ab initio and molecular interaction potential with polarization (MIPp) calculations and Bader's theory of "atoms-in-molecules"

Squaramido-Based Receptors : Applicability of Molecular Interaction Potential to Molecular Recognition of Polyalkylammonium Compounds

[eng] A computational study of the mechanism of host±guest complexation between quaternary ammo- nium compounds and squaramido-based tripodal recep- tors has been carried out. Semiempirical molecular orbital calculations, which are in qualitative agreement with experimental results have been performed using the PM3 Hamiltonian. Molecular interaction potential (MIP) maps were used to analyze the suitability of both host and guest binding units for a high-a nity recogni- tion process. MIP calculations were computed from PM3 wavefunctions of the corresponding ammonium cations and dimethyl squaramide as a model compound for the hydrogen-bond-acceptor unit of the receptors. MIP analyses are helpful for understanding the host± guest process from the point of view of the double- complementarity principle

Rational Design, Synthesis and Application of a New Receptor for the Molecular Recognition of Tricarboxylate Salts in Aqueous Media

[eng] A rational design of a tripodal receptor for the molecular recognition of tricarboxylate salts in aqueous media, based on squaramide, has been performed using high-level DFT calculations (RI-BP86/SVP level of theory) in solution using the COSMO treatment, including some preliminary ab initio calculations at the higher RI-MP2/TZVP level of theory, comparing the ability of squaramide to bind carboxylate salts with two widely used guanidinium salts. The tripodal receptor has been synthesized using a new methodology that has been recently reported by some of us, and its capability of recognizing several mono-, di-, and tricarboxylate salts has been studied experimentally by means of microcalorimetry experiments in a very high competitive media, H2O:EtOH 1:3. These experiments give enthalpic and entropic data, which are unfortunately scarce in the literature of molecular recognition of anions. Finally, a fluorimetric ensemble of the receptor with fluorescein has been found to be useful for the fluorimetric determination of zinc citrate in a commercial toothpaste using competition assays