A two-center three-electron 2c-3e bond (hemi-bond) is a non-classical chemical bond, and its existence has been supposed in radical cation clusters with lone pairs. Though the nature of the hemi-bond and its role in the reactivity of radical cations have attracted great interest, spectroscopic observations of hemi-bonded structures have been very scarce. In the present study, the presence of a ...

Silica-bonded n-propyldiethylenetriamine sulfamic acid (SBPDSA) was found as an efficient solid acid for the synthesis of coumarins. Coumarin derivatives were obtained via the Pechmann condensation reaction of phenols and β-keto-esters at 80 oC under solvent-free conditions. Also, biscoumarins were obtained via the condensation of aldehydes and 4-hydroxycoumarin in water at reflux conditions. T...

The aims of this study were to evaluate the shear bond strength (SBS) of metal and ceramic brackets bonded to two different all-ceramic crowns, IPS Empress 2 and In-Ceram Alumina, to compare the SBS between hydrofluoric acid (HFA), phosphoric acid etched, and sandblasted, non-etched all-ceramic surfaces. Ninety-six all-ceramic crowns were fabricated resembling a maxillary left first premolar. T...

The adsorption of nitric oxide as dinitrosyls and the deNOx proton-mediated reaction mechanism are assessed using electronic structure methods and transition state theory. Dinitrosyls bind to copper cations either via a N-atom or via an O-atom, with N-binding being more stable. In their ground states, dinitrosyls reach a planar configuration with the metal cation. The two nitric oxide molecules...

The 4-sulfophthalate trianion in the polymeric complex, {[Er(C(8)H(3)O(7)S)(C(12)H(8)N(2))(H(2)O)(2)]·2H(2)O}(n), bridges three water/phenanthroline-coordinated Er(III) ions to form a three-dimensional network architecture. The metal atom is further chelated by a carboxyl-ate group and is covalently bonded to a monodentate carboxyl-ate group as well as to a monodentate sulfonate group in a dist...

As a follow-up on a study of a family of boron-oxygen-nitrogen compounds composed of two datively bonded B-O-N backbones, we investigate a similar series of compounds that have similar fragments but are covalently bonded. B3LYP/6-31G(d,p) quantum mechanical calculations have been performed to determine the minimum-energy geometries, vibrational frequencies, and thermochemical properties of the ...

background: restoration of anterior primary teeth with severe caries lesion is a big challenge. the aim of this study was to compare the fracture resistance of three types of post, including composite resin, customized quartz fi ber and prefabricated glass fi ber in restoration of severely damaged primary anterior teeth. materials and methods: sixty extracted human primary maxillary incisors we...

The title compound, C(19)H(14)ClNO(3)·0.2H(2)O, crystallizes with five mol-ecules and a disordered water mol-ecule in the asymmetric unit. Four of the five mol-ecules form hydrogen-bonded dimers via N-H⋯O hydrogen bonds towards another symmetry-independent mol-ecule, whereas the fifth mol-ecule forms a hydrogen-bonded dimer with its symmetry equivalent, also via N-H⋯O hydrogen bonds. The dihedr...